A New Delhi clinic that has claimed to help paralyzed Canadians walk again by injecting them with stem cells now says it can use the same treatment to make children with Down syndrome almost near normal.

Nutech Mediworld says it has treated up to 16 newborns, toddlers and older children with Down syndrome. According to its medical director, Geeta Shroff, we have seen that patients actually start improving clinically they become almost at par for their age.

Canadian experts say the bold claim risks raising false expectations and public confusion, much like the now-discredited Liberation therapy for multiple sclerosis, and that its playing off the over-hyped belief stem cells have the potential to cure almost anything.

Its also the latest controversy over stem cell tourism, and the growing number of clinics worldwide marketing pricey, unregulated and unproven treatments.

Nutech Mediworld charges US$5,000 to $6,000 per week for its stem cell-based therapies. The clinic says it has treated such incurable conditions as spinal cord injury and cerebral palsy. Around 20 Canadians have sought treatment at the clinic for paralyzing spinal cord injuries, spending upwards of $US48,000 each. Shroff says some of her patients have regained the ability to walk with walkers.

More recently, she began working with Down syndrome, one of the most common chromosomal disorders worldwide.

Most cases are caused by a random error in cell division. The child ends up with three copies of chromosome 21, instead of the usual two.

That extra copy causes abnormal neuronal development and changes in the central nervous system, Shroff says, leading to persistent developmental delays.

Human embryonic stem cells injected into a childs muscles and bloodstreamcan regenerate and repair that damaged brain, she says. They also work at the genetic level, she claims.

In a single case published last year, Shroff reported treating a two-month-old baby boy in September 2014 diagnosed with Down syndrome at birth. The infant had delayed milestones, lack of speech, subnormal understanding and subnormal motor skills, she wrote.

After two stem cell therapy sessions, the baby started babbling and crawling, she reported. He had improved muscle tone. He was social and was able to recognize near ones.

The child became almost as near normal as possible cognitively

The child became almost as near normal as possible cognitively, Shroff told the Post in an interview. Today, hes talking; hes walking. He was at par with normal children on analysis.

The former infertility specialist uses embryonic stem cells developed from a single fertilized egg donated by an IVF patient 17 years ago. According to Shroff, We have witnessed no adverse events at all.

The Down syndrome treatments, reported by New Scientist, have raised skepticism and alarm. Its not at all clear what cells shes actually putting in patients, says renowned developmental biologist Janet Rossant, senior scientist at the Hospital for Sick Children Research Institute in Toronto.

By just putting them into the bloodstream theres no way to imagine they could contribute to the right tissues.

Embryonic stem cells can also form teratomas benign tumours and masses composed of lung cells, tufts of hair, teeth, bone and other tissues.

The gold standard for any therapy would be a clinical trial comparing treated with untreated children and vetted through proper regulatory systems that clearly she is not going through, Rossant says.

The Ottawa Hospitals Dr. Duncan Stewart, who is leading the first trial in the world of a genetically enhanced stem cell therapy for heart attack, says theres a remote chance embryonic stem cells could help with Down syndrome. But its a stretch. The injected cells would also likely be rejected and die off with days, he believes. If the cells are disappearing within days, how are they working?

This is a very vulnerable population Theyre very vulnerable to people who are selling hope and have no basis for it

This is a very vulnerable population, Stewart adds. Theyre very vulnerable to people who are selling hope and have no basis for it.

But stem cells have taken on almost mystical appeal.

Theyve become a pop culture phenomenon, says healthy policy expert Timothy Caulfield, of the University of Alberta. The field itself is guilty of making breathless announcements about breakthroughs and cutting edge, he says. And people can market that kind of language.

This kind of nonsense doesnt help.

Email: jskirkey@postmedia.com | Twitter:

Go here to see the original:
From Down syndrome to 'near normal'? New Delhi clinic makes stem cell claims that worry experts - National Post

Spinal Cord Stem Cells Comments Off on From Down syndrome to ‘near normal’? New Delhi clinic makes stem cell claims that worry experts – National Post | February 7th, 2017

A new revolutionary stem cell technique is being used to treat those suffering from damaged muscles without the cancer risk that was previously present. This was the first time that researchers had successfully implanted synthetic stem cardiac cells that managed to repair the muscle that a previous heart attack has weakened. Cancer was previously a risk with traditional stem cell therapy as scientists were unable to stop formertumors as the cells continued to replicate.

This procedure is mostly performed on those suffering from blood or bone marrow cancers such as leukemia. But, researchers are also working on developing effective stem cell treatments for those diagnosed with neurodegenerative diseases such as Parkinsons and heart disease too.

Synthetic stem cells are very handy because unlike natural stem cells, theyre easy to preserve and can be adapted to be used in various parts of the body. Ke Cheng, associate professor of molecular biomedical sciences at North Carolina State University, said, We are hoping that this may be the first step towards a truly off-the-shelf cell product that would enable people to receive beneficial stem cell therapies when theyre needed, without costly delays.

[The study can be found here.]

The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion, and analysis. Read full, original post:Pioneering Stem Cell Technique Promise Muscle Regeneration Without Cancer Risk

See original here:
Regrowing heart muscles without cancer risk, using synthetic stem cells - Genetic Literacy Project

Cardiac Stem Cells Comments Off on Regrowing heart muscles without cancer risk, using synthetic stem cells – Genetic Literacy Project | February 7th, 2017

Globalnews.ca

Quebec family hopes to raise awareness for patients in need with stem cell registry drive Globalnews.ca Natasha Camacho-Gomes (middle right, standing) organized a bone marrow registry drive Saturday, Feb. 4, 2017 to raise awareness for patients in need. Her Fianc Kevin Butterfill is one of those patients. He was diagnosed with leukemia in January.

View original post here:
Quebec family hopes to raise awareness for patients in need with stem cell registry drive - Globalnews.ca

Bone Marrow Stem Cells Comments Off on Quebec family hopes to raise awareness for patients in need with stem cell registry drive – Globalnews.ca | February 7th, 2017

By filling out a form, and swabbing his mouth, Harlee O'Watch could save a life.

"To find a match, because the list of donors is so low, is really unlikely," said the 22-year-old.

O'Watch is one of four young adults from Carry the Kettle First Nation who registered with the OneMatch program, which connects donors with people in need of bone marrow or stem cell transplants.

A problem for the 14 indigenous people currently waiting for a match is that, out of the 17,000 people on the Canadian registry, fewer than one per cent are indigenous.

"It doesn't give me much hope if I ever get sick and need a blood transfusion or bone marrow transplant, said OWatch.

It doesn't give me much hope because, if there's no potential matches, I'm going to die, bottom line, and I don't want to die."

Robyn Henwood works for Canadian Blood Services, which runs OneMatch. She covers Alberta to Northern Ontario and the Northwest Territories, including the Prairies, and visited Carry the Kettle to recruit. A match requires a genetic twin and indigenous people are only in Canada.

"It does get more complicated [with] these different ethnic backgrounds. . . even within First Nations that get brought into it, said Henwood.

The chances of finding a match becomes that much more difficult."

This means someone who is Cree cannot donate to someone who is Mohawk, she said.

In the past year, Canadian Blood Services has visited less than 12 reserves to help find matches for indigenous people. Carry the Kettle is Henwoods third community.

"We have been leaving messages and voicemails, not getting a lot of response back, she said.

I'm hoping a new technique will work. Things like this, this is so important to spread our message."

According to Indigenous and Northern Affairs Canada, more than 50 per cent of indigenous people live in urban centres. And yet, Henwood says finding indigenous donors in cities is also a struggle.

"Trying to get someone to sign up and commit for the next 30 to 40 years, to potentially save a stranger's life is not an easy thing to do," she said.

Henwood says informing indigenous people about one match will empower more to donate. Until then, the chance of survival for those waiting on the registry is low.

Excerpt from:
Program seeks to boost bone marrow, stem cell donations from indigenous people - CTV News

Bone Marrow Stem Cells Comments Off on Program seeks to boost bone marrow, stem cell donations from indigenous people – CTV News | February 7th, 2017

BUCKEYE, AZ - As the saying goes: "blood is thicker than water." But when it comes to bone marrow, it is truer than ever especially because family is usually the only people to turn to for a match.

But, one Buckeye family is finding that the phrase could not be more perfectfor them because a brother has been serving as the lifeline for his sibling over the last few years.

Gloria Mesquias calls her 11-year-old son, Shaun, "the warrior."

"He takes every jab he gets and just rolls through," said Mesquias.

Shaun's 13-year-old brother Malik is called "the hero."

"They are actually like night and day, "Mesquias said. "They're brothers."

The three of them, and other supportive family members, have spent months at Phoenix Children's Hospital. Shaun has a condition where his body isn't producing new blood cells.

"He was diagnosed with severe aplastic anemia," Mesquias said.

That happened when he was just about 1 year old. Ever since then, he's been in and out of the hospital.

But, Malikhas served as a bone marrow and stem cell donor to his b brother not once, not twice but, three different times.

And the fight for this little warrior, is not over yet. If his treatment goes well over the next few days, he will have a fourth surgery on Wednesday; another stem cell transplant.

Mesquias doing this all as a single mother. She also has a 5-year-old daughter, who has not seen Shaun since before Christmas.

"She understand;she gets it," Mesquias explained. "She knows brother is sick and she knows mom is here with Shaun."

But, while she tries to keep it together, all of the stress and days away from home are weighing on Mesquias. But, it's something she will never let her family see.

"At night time, I can go in the restroom and cry my eyes out or ball my face out in the pillow," Mesquias said. "But, I just don't do it in front of him."

So, the boys' Buckeye teacher, Carrie Brown, has also taken action to try and do something special for the family.

"She would never ask for help," Brown said. "She's not that kind of person. So, I just thought that this was one thing that I could do to relieve some of the worry that she has and to give her a little bit of comfort."

Brown started a GoFundMe page to try and help the family who has given so much to each other.

And Mesquias said she is making sure all of them get out of that hospital together.

"He has his moments too where he says he wants to go home," Mesquias explained. "And... I'm like, 'I'm not going home until you're going home. So, we're good."

More:
Buckeye boy donates bone marrow to sick brother - ABC15 Arizona - ABC15 Arizona

Bone Marrow Stem Cells Comments Off on Buckeye boy donates bone marrow to sick brother – ABC15 Arizona – ABC15 Arizona | February 7th, 2017

The 2017 Australian of the Year award went to Professor Alan Mackay-Sim for his significant career in stem cell science.

The prize was linked to barbeque-stopping headlines equating his achievements to the scientific equivalent of the moon landing and paving the road to recovery for people with spinal cord injuries.

Such claims in the media imply that there is now a scientifically proven stem cell treatment for spinal cord injury. This is not the case.

For now, any clinic or headline claiming miracle cures should be viewed with caution, as they are likely to be trading on peoples hope.

Put simply, injury to the spinal cord causes damage to the nerve cells that transmit information between the brain and the rest of the body.

Depending on which part of the spine is involved, the injury can affect the nerves that control the muscles in our legs and arms; those that control bowel and bladder function and how we regulate body temperature and blood pressure; and those that carry the sensation of being touched. This occurs in part because injury and subsequent scarring affect not just the nerves but also the insulation that surrounds and protects them. The insulation the myelin sheath is damaged and the body cannot usually completely replace or regenerate this covering.

Stem cells can self-reproduce and grow into hundreds of different cell types, including nerves and the cells that make myelin. So the blue-sky vision is that stem cells could restore some nerve function by replacing missing or faulty cells, or prevent further damage caused by scarring.

Studies in animals have applied stem cells derived from sources including brain tissue, the lining of the nasal cavity, tooth pulp, and embryos (known as embryonic stem cells).

Dramatic improvements have been shown on some occasions, such as rats and mice regaining bladder control or the ability to walk after injury. While striking, such improvement often represents only a partial recovery. It holds significant promise, but is not direct evidence that such an approach will work in people, particularly those with more complex injuries.

The translation of findings from basic laboratory stem cell research to effective and safe treatments in the clinic involves many steps and challenges. It needs a firm scientific basis from animal studies and then careful evaluation in humans.

Many clinical studies examining stem cells for spinal repair are currently underway. The approaches fit broadly into two categories:

using stem cells as a source of cells to replace those damaged as a result of injury

applying cells to act on the bodys own cells to accelerate repair or prevent further damage.

One study that has attracted significant interest involves the injection of myelin-producing cells made from human embryonic stem cells. Researchers hoped that these cells, once injected into the spinal cord, would mature and form a new coating on the nerve cells, restoring the ability of signals to cross the spinal cord injury site. Preliminary results seem to show that the cells are safe; studies are ongoing.

Other clinical trials use cells from patients own bone marrow or adipose tissue (fat), or from donated cord blood or nerves from fetal tissue. The scientific rationale is based on the possibility that when transplanted into the injured spinal cord, these cells may provide surrounding tissue with protective factors which help to re-establish some of the connections important for the network of nerves that carry information around the body.

The field as it stands combines years of research, and tens of millions of dollars of investment. However, the development of stem cell therapies for spinal cord injury remains a long way from translating laboratory promise into proven and effective bedside treatments.

Each case is unique in people with spinal cord injury: the level of paralysis, and loss of sensation and function relate to the type of injury and its location. Injuries as a result of stab wounds or infection may result in different outcomes from those incurred as a result of trauma from a car accident or serious fall. The previous health of those injured, the care received at the time of injury, and the type of rehabilitation they access can all impact on subsequent health and mobility.

Such variability means caution needs to accompany claims of man walking again particularly when reports relate to a single individual.

In the case that was linked to the Australian of the Year award, the actual 2013 study focused on whether it was safe to take the patients own nerves and other cells from the nose and place these into the damaged region of the spine. While the researchers themselves recommended caution in interpreting the results, accompanying media reports focused on the outcome from just one of the six participants.

While the outcome was significant for the gentleman involved, we simply do not know whether recovery may have occurred for this individual even without stem cells, given the type of injury (stab wounds), the level of injury, the accompanying rehabilitation that he received or a combination of these factors. It cannot be assumed a similar outcome would be the case for all people with spinal injury.

Finding a way to alleviate the suffering of those with spinal cord injury, and many other conditions, drives the work of thousands of researchers and doctors around the globe. But stem cells are not a silver bullet and should not be immune from careful evaluation in clinical trials.

Failure to proceed with caution could actually cause harm. For example, a paraplegic woman who was also treated with nasal stem cells showed no clinical improvement, and developed a large mucus-secreting tumour in her spine. This case highlights the need for further refinement and assessment in properly conducted clinical trials before nasal stem cells can become part of mainstream medicine.

Its also worth noting that for spinal cord injury, trials for recovery of function are not limited to the use of stem cells but include approaches focused on promoting health of surviving nerves (neuroprotection), surgery following injury, nerve transfers, electrical stimulation, external physical supports known as exoskeletons, nanotechnology and brain-machine interfaces.

Ultimately, determining which of these approaches will improve the lives of people with spinal injury can only be done through rigorous, ethical research.

See the original post:
Yes there's hope, but treating spinal injuries with stem cells is not a reality yet - The Conversation AU

Bone Marrow Stem Cells Comments Off on Yes there’s hope, but treating spinal injuries with stem cells is not a reality yet – The Conversation AU | February 7th, 2017

ANDREW and Judy Kim are still searching the globe for a donor for their two-year-old son after he was diagnosed with a rare genetic condition.

The couple's son Alastair was diagnosed with chronic granulomatous disorder (CGD) in February last year.

Mr and Mrs Kim launched an appeal for help in September but the search is still on for a matching donor and their son still needs hospital treatment.

The life-threatening condition wipes out his immune system, meaning even the most minor infections leave him seriously ill.

A course of genetic therapy treatment to help him fight infections has been launched and Alastair has been treated at Oxford Children's Hospital and Great Ormond Street Hospital in London.

The only hope of a permanent cure lies in a bone marrow stem cell donor but it needs to be a 90 per cent genetic match and the family is calling for more East Asians to sign up as donors.

Mr Kim, 37, a medical research engineer, said: "It is not easy to find a match and we pray every day that it will work out.

"We have to make sure that Alastair does not get a cut because it could get infected and he does not have the ability to fight off bacteria.

"That could cascade down the line to something very dangerous for him.

"If we get ill then we have to stay away from him he loves our dog Choco Pie but he is not allowed to stroke her.

"We are doing our best to stay positive and raise awareness about his condition."

Mr and Mrs Kim, who live near Longworth with their other son Micah, five, have already searched the international register of more than four million donors but without success.

They are both of Korean descent so a matching donor will most likely be of Korean, Japanese or Chinese heritage.

The number of East Asians on international donor registers is very limited of the 617,000 registered donors in the UK just 0.5 per cent are east Asian.

The couple, who moved to Oxfordshire from Chicago nine years ago, are now appealing for people around the world, particularly East Asians, to order a free kit through a website they have set up, and take a two-minute home test to see if they could help.

Alastair has had numerous infections since he was born in September 2014.

He spent the first year-and-a-half of his life in and out of hospital but CGD is so rare, doctors never thought to test him for it but eventually a doctor at the John Radcliffe Hospital in Oxford decided to test Alastair for the condition.

The couple desperately want to find a matching donor, but also want to increase the number of East Asians on the donor register.

The couple have run several blood drives at Mrs Kim's office at Oxford University and at Harwell Oxford.

More than 90 people came forward and of those, five were able to donate blood that helped Alastair to fight infections.

Mr Kim added: "At a couple of blood drives we have found matches for other people and hopefully one day a match will found for Alastair."

To join the register go to allysfight.com

See the rest here:
Search goes on for bone marrow match for little Longworth lad ... - Oxford Mail

Bone Marrow Stem Cells Comments Off on Search goes on for bone marrow match for little Longworth lad … – Oxford Mail | February 7th, 2017

Human skin can be morphed into genetically modified, cancer-killing brain stem cells, according to a new study. This latest advance has only been tested in mice but eventually, its possible that it could be translated into a personalized treatment for people with a deadly form of brain cancer.

The study builds on an earlier discovery that brain stem cells have a weird affinity for cancers. So researchers, led by Shawn Hingtgen, a professor at University of North Carolina at Chapel Hill, created genetically engineered brain stem cells out of human skin. Then they armed the stem cells with drugs to squirt directly onto the tumors of mice that had been given a human form of brain cancer. The treatment shrank the tumors and extended survival of the mice, according to results recently published in the journal Science Translational Medicine.

The treatment shrank the tumors and extended survival

Usually we think about stem cell therapy in the context of rebuilding or regrowing a broken body part like a spinal cord. But if they could be modified to become cancer-fighting homing missiles, it would give patients with a deadly and incurable brain cancer called glioblastoma a better chance at survival. Glioblastomas typically affect adults, and are highly fatal because they send out a web of cancerous threads. Even when the main mass is removed, those threads remain despite chemotherapy and radiation treatment. This cancer has caused a number of high-profile deaths including Senator Edward (Ted) Kennedy in 2009, and possibly Beau Biden more recently. Approximately 12,000 new cases of glioblastoma are estimated to be diagnosed in 2017.

We really have no drugs, no new treatment options in years to even decades, Hingtgen says. [We] just really want to create new therapy that can stand a chance against this disease.

But theres a problem: brain stem cells arent exactly easy to get. Brain stem cells, more properly known as neural stem cells, hang out in the walls of the brains irrigation canals areas filled with cerebrospinal fluid, called ventricles. They generate the cells of the nervous system, like neurons and glial cells, throughout our lives.

They could be modified to become cancer-fighting homing missiles

A research group at the City of Hope in California conducted a clinical trial to make sure it was safe to treat glioblastoma patients with genetically engineered neural stem cells. But they used a neural stem cell line that theyd obtained from fetal tissue. Since the stem cells werent the patients own, people who were genetically more likely to reject the cells couldnt receive the treatment at all. For the people who could, treatment with the neural stem cells turned out to be relatively safe although at this phase of clinical trials, it hasnt been particularly effective.

More personalized treatments have been held up by the challenge of getting enough stem cells out of the patients own brains, which is virtually impossible, says stem cell scientist Frank Marini at the Wake Forest School of Medicine, who was not involved in this study. You cant really generate a bank of neural stem cells from anybody because you have to go in and resect the brain.

So instead, Hingtgen and his colleagues figured out a way to generate neural stem cells from skin which in the future, could let them make neural stem cells personalized to each patient. For this study, though, Hingtgen and his colleagues extracted the skin cells from chunks of human flesh leftover as surgical waste. That really is the magic piece here, Marini says. Now, all of a sudden we have a neural stem cell that can be used as a tumor-homing vehicle.

That really is the magic piece here.

Using a disarmed virus to infect the cells with a cocktail of new genes, the researchers morphed the skin cells into something in between a skin cell and a neural stem cell. People have turned skin cells back into a more generalized type of stem cell before. But then turning those basic stem cells into stem cells for a certain organ like the brain takes another couple of steps, which takes more time. Thats something that people with glioblastoma dont have.

The breakthrough here is that Hingtgens team figured out how to go straight from skin cells to something resembling a neural stem cell in just four days. The researchers then genetically engineered these induced neural stem cells to arm them with one of two different weapons: One group was equipped with an enzyme that could convert an anti-fungal drug into chemotherapy, right at the cancers location. The other was armed with a protein that binds to the cancer cells and makes them commit suicide in an orderly process called apoptosis.

The researchers tested these engineered neural stem cells in mice that had been injected with human glioblastoma cells, which multiplied out of control to create a human cancer in a mouse body. Both of the weaponized stem cell groups were able to significantly shrink the tumors and keep the mice alive by about an extra 30 days (for scale, mice usually live an average of two years).

Were working as fast as we can.

But injecting the cells directly into the tumor doesnt really reflect how the therapy would be used in humans. Its more likely that a person with glioblastoma would get the bulk of the tumor surgically removed. Then, the idea is that these neural stem cells, generated from the patients own skin, will be inserted into the hole left in the brain. So, the researchers tried this out in mice, and the tumors that regrew after surgery were more than three times smaller in the mice treated with the neural stem cells.

Its a promising start, but it could take a few years still before its in the clinic, Hingtgen says. He and his colleagues started a company called Falcon Therapeutics to drive this new therapy forward. Were working as fast as we can, Hingtgen says. We probably cant help the patients today. Hopefully in a year or two, well be able to help those patients.

One of the things theyll have to figure out first is whether the neural stem cells can travel the much bigger distances in human brains, and whether theyll be able to eliminate every remaining cancer cell. The caveats on this are that, of course, its a mouse study, and whether or not that directly converts to humans is unclear, Marini says. Still, he adds, Theres a very high probability in this case.

Read the original post:
The next weapon against brain cancer may be human skin - The Verge

Skin Stem Cells Comments Off on The next weapon against brain cancer may be human skin – The Verge | February 7th, 2017

Mouse and human skin cells can be reprogrammed to hunt down tumors and deliver anticancer therapies.

Imagine cells that can move through your brain, hunting down cancer and destroying it before they themselves disappear without a trace. Scientists have just achieved that in mice, creating personalized tumor-homing cells from adult skin cells that can shrink brain tumors to 2% to 5% of their original size. Althoughthe strategy has yet to be fully tested in people, the new method could one day give doctors a quick way to develop a custom treatment for aggressive cancers like glioblastoma, which kills most human patients in 1215 months. It only took 4 days to create the tumor-homing cells for the mice.

Glioblastomas are nasty: They spread roots and tendrils of cancerous cells through the brain, making them impossible to remove surgically. They, and other cancers, also exude a chemical signal that attracts stem cellsspecialized cells that can produce multiple cell types in the body. Scientists think stem cells might detect tumors as a wound that needs healing and migrate to help fix the damage. But that gives scientists a secret weaponif they can harness stem cells natural ability to home toward tumor cells, the stem cells could be manipulated to deliver cancer-killing drugs precisely where they are needed.

Other research has already exploited this methodusing neural stem cellswhich give rise to neurons and other brain cellsto hunt down brain cancer in mice and deliver tumor-eradicating drugs. But few have tried this in people, in part because getting those neural stem cells is hard, says Shawn Hingtgen, a stem cell biologist at the University of North Carolina inChapel Hill. Right now, there are three main ways. Scientists can either harvest the cells directly from the patient, harvest them from another patient, or they can genetically reprogram adult cells. But harvesting requires invasive surgery, and bestowing stem cell properties on adult cells takes a two-step process that can increase the risk of the final cells becoming cancerous. And using cells from someone other than the cancer patient being treated might trigger an immune response against the foreign cells.

To solve these problems, Hingtgens group wanted to see whetherthey could skip a step in the genetic reprogramming process, which first transforms adult skin cells into standard stem cells and then turns those into neural stem cells. Treating the skin cells with a biochemical cocktail to promote neural stem cell characteristics seemed to do the trick, turning it into a one-step process, he and his colleague report today in Science Translational Medicine.

But the next big question was whether these cells could home in on tumors in lab dishes, and in animals, like neural stem cells. We were really holding our breath, Hingtgen says. The day we saw the cells crawling across the [Petri] dish toward the tumors, we knew we had something special. The tumor-homing cells moved 500 micronsthe same width as five human hairsin 22 hours, and they could burrow into lab-grown glioblastomas. This is a great start, says Frank Marini, a cancer biologist at the Wake Forest Institute forRegenerative Medicine in Winston-Salem, North Carolina,who was not involved with the study. Incredibly quick and relatively efficient.

The team also engineered the cells to deliver common cancer treatments to glioblastomas in mice. Mouse tumors injected directly with the reprogrammed stem cells shrank 20- to 50-fold in 2428 days compared withnontreated mice. In addition, the survival times of treated rodents nearly doubled. In some mice, the scientists removed tumors after they were established, and injected treatment cells into the cavity. Residual tumors, spawned from the remaining cancer cells, were 3.5 times smaller in the treated mice than in untreated mice.

Marini notes that more rigorous testing is needed to demonstrate just how far the tumor-targeting cells can migrate. In a human brain, the cells would need to travel a matter of millimeters or centimeters, up to 20 times farther than the 500 microns tested here, he says. And other researchers question the need to use cells from the patients own skin. An immune response, triggered by foreign neural stem cells, could actually help attack tumors, says Evan Snyder, a stem cell biologist at Sanford Burnham Prebys Medical Discovery Institute in San Diego, California, and one of the early pioneers of the idea of using stem cells to attack tumors.

Hingtgens group is already testing how far their tumor-homing cells can migrate using larger animal models. They are also getting skin cells from glioblastoma patients to make sure the new method works for the people they hope to help, he says. Everything were doing is to get this to the patient as quickly as we can.

Please note that, in an effort to combat spam, comments with hyperlinks will not be published.

See the article here:
Reprogrammed skin cells shrink brain tumors in mice | Science | AAAS - Science Magazine

Skin Stem Cells Comments Off on Reprogrammed skin cells shrink brain tumors in mice | Science | AAAS – Science Magazine | February 7th, 2017

Glioblastoma is an aggressive form of brain cancer that kills most patients within two years of diagnosis. In tests on mice last year, a team at the University of North Carolina at Chapel Hill showed that adult skin cells could be transformed into stem cells and used to hunt down the tumors. Building on that, they've now found that the process works with human cells, and can be administered quickly enough to beat the ticking time-bombs.

Treatments for glioblastoma include the usual options of surgery, radiation therapy and chemotherapy, but none of them are particularly effective. The tumors are capable of spreading tendrils out into the brain and it can grow back in a matter of months after being removed. As a result, the median survival rate of sufferers is under 18 months, and there's only a 30 percent chance of living more than two years.

"We desperately need something better," says Shawn Hingtgen, the lead researcher on the study.

To find that something better, last year the scientists took fibroblasts a type of skin cell that generates collagen and connective tissue from mice and reprogrammed them into neural stem cells. These stem cells seek out and latch onto cancer cells in the brain, but alone are powerless to fight the tumor. To give them that ability, the scientists engineered them to express a particular cancer-killing protein. The result was mice that lived between 160 and 220 percent longer.

The next step was to test the process with human cells, and in the year since, the team has found that the results are just as promising. The technique differs slightly when scaled up to humans. The patient would be administered with a substance called a prodrug, which by itself does nothing, until it's triggered. The stem cells are engineered to carry a protein that acts as that trigger, activating the prodrug only in a small halo around itself instead of affecting the entire body. That allows the drug to target only a small desired area, ideally reducing the ill side effects that treatments like chemotherapy can induce.

Importantly, the technique can be administered quickly, to give the patients the best chance at survival.

"Speed is essential," says Hingtgen. "It used to take weeks to convert human skin cells to stem cells. But brain cancer patients don't have weeks and months to wait for us to generate these therapies. The new process we developed to create these stem cells is fast enough and simple enough to be used to treat a patient."

The treatment is an important step, but there's still a long way to go.

"We're one to two years away from clinical trials, but for the first time, we showed that our strategy for treating glioblastoma works with human stem cells and human cancers," says Hingtgen. "This is a big step toward a real treatment and making a real difference."

The research was published in the journal Science Translational Medicine.

See the rest here:
Stem cells beat the clock for brain cancer - New Atlas

Skin Stem Cells Comments Off on Stem cells beat the clock for brain cancer – New Atlas | February 7th, 2017

Brain cancers can be really tricky to treat. Some, such as glioblastomas, spread roots through the brain tissue, meaning they are often impossible to remove surgically, leading to tragically low survival rates. But researchers are working on a way touse stem cells to track down the cancer, kill it, and then melt it away. By doing this, theyve managed to shrink brain tumors in mice to2 to 5 percent of their original size.

The trick has already been tried before using neural stem cells to hunt down and deliver cancer-killing drugs to tumors in mice. But there is a problem: It's tricky to getneural stem cells from humans. The safest way of doing this would be to take adult cells and then induce them in a two-step process to become neural stem cells. This, however, takes time.

Speed is essential, saysShawn Hingtgen, who led the research published in Science Translational Medicine. It used to take weeks to convert human skin cells to stem cells. But brain cancer patients dont have weeks and months to wait for us to generate these therapies. The new process we developed to create these stem cells is fast enough and simple enough to be used to treat a patient.

The researchers found a way to speed the process up byremoving one of the steps entirely, allowing them to produce the neural stem cells from adult skin cells in just four days. Usually, researchers would need to take the skin cell, induce it to become a generic stem cell, and then push it towards becoming a neural stem cell.

But by treating the skin cells with a cocktail of biochemicals, they were able to get the cells to turn straight into neural stem cells. They then tested these to see if they still had the same properties as original neutral stem cells and home in on tumors both in a petri dish and in animals models. They found they behaved exactly the same.

The final step was to see if they could somehow engineer these newly created cells to deliver drugs that are targeted at the cancer. They therefore got the stem cells to carry a particular protein that activates what is called a prodrug, which the researchers describe as forming a halo of drugs around the stem cell.

Were one to two years away from clinical trials, but for the first time, we showed that our strategy for treating glioblastoma works with human stem cells and human cancers, says Hingtgen. This is a big step toward a real treatment and making a real difference.

Excerpt from:
Scientists Reprogram Skin Cells To Hunt Down And Shrink Brain Tumors - IFLScience

Skin Stem Cells Comments Off on Scientists Reprogram Skin Cells To Hunt Down And Shrink Brain Tumors – IFLScience | February 7th, 2017

The Scientist

Regulators OK Clinical Trials Using Donor Stem Cells The Scientist WIKIPEDIA, TMHLEEResearchers in Japan who have been developing a cell therapy for macular degeneration received support from health authorities this week (February 1) to begin a clinical trial using donor-derived induced pluripotent stem (IPS) cells ...

The rest is here:
Regulators OK Clinical Trials Using Donor Stem Cells - The Scientist

IPS Cell Therapy Comments Off on Regulators OK Clinical Trials Using Donor Stem Cells – The Scientist | February 7th, 2017

The red shows rat cells in the developing heart of a mouse embryo.

A team of scientists from the Salk Institute in the United States created a stir last week with the announcement that they had created hybrid human-pig foetuses.

The story was widely reported, although some outlets took a more hyperbolic or alarmed tone than others.

One might wonder why scientists are even creating human-animal hybrids often referred to as chimeras after the Greek mythological creature with features of lion, goat and snake.

The intention is not to create new and bizarre creatures. Chimeras are incredibly useful for understanding how animals grow and develop. They might one day be used to grow life-saving organs that can be transplanted into humans.

The chimeric pig foetuses produced by Juan Izpisua Belmonte, Jun Wu and their team at the Salk Institute were not allowed to develop to term, and contained human cells in multiple tissues.

The actual proportion of human cells in the chimeras was quite low and their presence appeared to interfere with development. Even so, the study represents a first step in a new avenue of stem cell research which has great promise. But it also raises serious ethical concerns.

A chimera is an organism containing cells from two or more individuals and they do occur in nature, albeit rarely.

Marmoset monkeys often display chimerism in their blood and other tissues as a result of transfer of cells between twins while still in the womb. Following a successful bone marrow transplantation to treat leukaemia, patients have cells in their bone marrow from the donor as well as themselves.

Chimeras can be generated artificially in the laboratory through combining the cells from early embryos of the same or different species. The creation of chimeric mice has been essential for research in developmental biology, genetics, physiology and pathology.

This has been made possible by advances in gene targeting in mouse embryonic stem cells, allowing scientists to alter the cells to express or silence certain genes. Along with the ability to use those cells in the development of chimeras, this has enabled researchers to produce animals that can be used to study how genes influence health and disease.

The pioneers of this technology are Oliver Smithies, Mario Cappechi and Martin Evans, who received a Nobel Prize in Physiology or Medicine in 2007 for their work.

More recently, researchers have become interested in investigating the ability of human pluripotent stem cells master cells obtained from human embryos or created in the laboratory from body cells, to contribute to the tissues of chimeric animals.

Human pluripotent stem cells can be grown indefinitely in the laboratory, and like their mouse counterparts, they can form all the tissues of the body.

Many researchers have now shown they can make functional human tissues of medical significance from human pluripotent cells, such as nerve, heart, liver and kidney cells.

Indeed, cellular therapeutics derived from human pluripotent stem cells are already in clinical trials for spinal cord injury, diabetes and macular degeneration.

However, since 2007 it has been clear that there is not one type of pluripotent stem cell. Rather, a range of different types of pluripotent stem cells have been generated in mice and humans using different techniques.

These cells appear to correspond to cells at different stages of embryonic development, and therefore are likely to have different properties, raising the question about which source of cells is best.

Creating a chimeras has long been the gold standard used by researchers to determine the potential of pluripotent stem cells. While used extensively in animal stem cell research, chimeric studies using human pluripotent stem cells have proved challenging as few human cells survive in human-animal chimeras.

Although the number of human cells in the chimera was low, the findings by the Salk Institute researchers provide a new avenue to address two important goals. The first is the possibility of creating humanised animals for use in biomedical research.

While it is already possible to produce mice with human blood, providing an invaluable insight into how our blood and immune system functions, these animals rely on the use of human fetal tissue and are difficult to make.

The use of pluripotent stem cells in human-animal chimeras might facilitate the efficient production of mice with human blood cells, or other tissues such as liver or heart, on a larger scale. This could greatly enhance our ability to study the development of diseases and to develop new drugs to treat them.

The second potential application of human-animal chimeras comes from some enticing studies performed in Japan in 2010. These studies were able to generate interspecies chimeras following the introduction of rat pluripotent stem cells into a mouse embryo that lacked a key gene for pancreas development.

As a result, the live born mice had a fully functional pancreas comprised entirely of rat cells. If a similar outcome could be achieved with human stem cells in a pig chimera, this would represent a new source of human organs for transplantation.

While scientifically achieving such goals remains a long way off, it is almost certain that progress in pluripotent stem cell biology will enable successful experimentation along these lines. But how much of this work is ethically acceptable, and where do the boundaries lie?

Many people condone the use of pigs for food or as a source of replacement heart valves. They might also be content to use pig embryos and foetuses as incubators to manufacture human pancreas or hearts for those waiting on the transplant list. But the use of human-monkey chimeras may be more contested.

Studies have shown that early cells of the central nervous system made from human embryonic stem cells can engraft and colonise the brain of a newborn mouse. This provides a proof of concept for possible cellular therapies.

But what if human cells were injected into monkey embryos? What would be the ethical and cognitive status of a newborn rhesus monkey whose brain consists of predominantly human nerves?

It may be possible to genetically engineer the cells so that human cells can effectively grow into replacement parts. But what safeguards do we need to ensure that the human cells dont also contribute to other organs of the host, such as the reproductive organs?

While the announcement of a human-pig chimera may have taken many by surprise, regulators and medical researchers well recognise that chimeric research may raise issues in addition to the those already posed by animal research.

However, rather than call for a blanket ban or restricting funding for this area of medical research, it requires careful case-by-case consideration by independent oversight committees fully aware of animal welfare considerations and recognising existing standards.

For example, The 2016 Guidelines for Clinical Research and Translation from the International Society for Stem Cell Research call for research where human gametes could be generated from human-animal chimeras to be prohibited, but supports research using human-animal chimeras conducted under appropriate review and oversight.

Chimeric research will and needs to continue. But equally scientists involved in this field need to continue to discuss and consider the implications of their research with the broader community. Chimeras can all too readily be dismissed as mythological monsters engendering fear.

Visit link:
What's the benefit in making human-animal hybrids? - The Conversation AU

IPS Cell Therapy Comments Off on What’s the benefit in making human-animal hybrids? – The Conversation AU | February 7th, 2017

Induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed to an embryonic stem celllike state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells. Although these cells meet the defining criteria for pluripotent stem cells, it is not known if iPSCs and embryonic stem cells differ in clinically significant ways. Mouse iPSCs were first reported in 2006, and human iPSCs were first reported in late 2007. Mouse iPSCs demonstrate important characteristics of pluripotent stem cells, including expressing stem cell markers, forming tumors containing cells from all three germ layers, and being able to contribute to many different tissues when injected into mouse embryos at a very early stage in development. Human iPSCs also express stem cell markers and are capable of generating cells characteristic of all three germ layers.

Although additional research is needed, iPSCs are already useful tools for drug development and modeling of diseases, and scientists hope to use them in transplantation medicine. Viruses are currently used to introduce the reprogramming factors into adult cells, and this process must be carefully controlled and tested before the technique can lead to useful treatment for humans. In animal studies, the virus used to introduce the stem cell factors sometimes causes cancers. Researchers are currently investigating non-viral delivery strategies. In any case, this breakthrough discovery has created a powerful new way to "de-differentiate" cells whose developmental fates had been previously assumed to be determined. In addition, tissues derived from iPSCs will be a nearly identical match to the cell donor and thus probably avoid rejection by the immune system. The iPSC strategy creates pluripotent stem cells that, together with studies of other types of pluripotent stem cells, will help researchers learn how to reprogram cells to repair damaged tissues in the human body.

Previous|VI. What are induced pluripotent stem cells?|Next

Read more:
Stem Cell Basics VI. | stemcells.nih.gov

Cardiac Stem Cells Comments Off on Stem Cell Basics VI. | stemcells.nih.gov | February 3rd, 2017

Cardiac muscle cells or cardiomyocytes (also known as myocardiocytes[1] or cardiac myocytes[2]) are the muscle cells (myocytes) that make up the cardiac muscle. Each myocardial cell contains myofibrils, which are specialized organelles consisting of long chains of sarcomeres, the fundamental contractile units of muscle cells. Cardiomyocytes show striations similar to those on skeletal muscle cells. Unlike multinucleated skeletal cells, the majority of cardiomyocytes contain only one nucleus, although they may have as many as four.[3] Cardiomyocytes have a high mitochondrial density, which allows them to produce adenosine triphosphate (ATP) quickly, making them highly resistant to fatigue.

There are two types of cells within the heart: the cardiomyocytes and the cardiac pacemaker cells. Cardiomyocytes make up the atria (the chambers in which blood enters the heart) and the ventricles (the chambers where blood is collected and pumped out of the heart). These cells must be able to shorten and lengthen their fibers and the fibers must be flexible enough to stretch. These functions are critical to the proper form during the beating of the heart.[4]

Cardiac pacemaker cells carry the impulses that are responsible for the beating of the heart. They are distributed throughout the heart and are responsible for several functions. First, they are responsible for being able to spontaneously generate and send out electrical impulses. They also must be able to receive and respond to electrical impulses from the brain. Lastly, they must be able to transfer electrical impulses from cell to cell.[5]

All of these cells are connected by cellular bridges. Porous junctions called intercalated discs form junctions between the cells. They permit sodium, potassium and calcium to easily diffuse from cell to cell. This makes it easier for depolarization and repolarization in the myocardium. Because of these junctions and bridges the heart muscle is able to act as a single coordinated unit.[6][7]

The cardiomyocytes are about 100 to 150 micrometers long and 15 to 20 micrometers in diameter.[citation needed]

Humans are born with a set number of heart muscle cells, or cardiomyocytes, which increase in size as heart grows larger during childhood development. Recent evidence suggests that cardiomyocytes are actually slowly turned over as we age, but that less than 50% of the cardiomyocytes we are born with are replaced during a normal life span.[8] The growth of individual cardiomyocytes not only occurs during normal heart development, it also occurs in response to extensive exercise (athletic heart syndrome), heart disease, or heart muscle injury such as after a myocardial infarction. A healthy adult cardiomyocyte has a cylindrical shape that is approximately 100m long and 10-25m in diameter. Cardiomyocyte hypertrophy occurs through sarcomerogenesis, the creation of new sarcomere units in the cell. During heart volume overload, cardiomyocytes grow through eccentric hypertrophy.[9] The cardiomyocytes extend lengthwise but have the same diameter, resulting in ventricular dilation. During heart pressure overload, cardiomyocytes grow through concentric hypertrophy.[9] The cardiomyocytes grow larger in diameter but have the same length, resulting in heart wall thickening.

Cardiac action potential consists of two cycles, a rest phase and an active phase. These two phases are commonly understood as systole and diastole. The rest phase is considered polarized. The resting potential during this phase of the beat separates the ions such as sodium, potassium and calcium. Myocardial cells possess the property of automaticity or spontaneous depolarization. This is the direct result of a membrane which allows sodium ions to slowly enter the cell until the threshold is reached for depolarization. Calcium ions follow and extend the depolarization even further. Once calcium stops moving inward, potassium ions move out slowly to produce repolarization. The very slow repolarization of the CMC membrane is responsible for the long refractory period.[10][11]

Myocardial infarction, commonly known as a heart attack, occurs when the heart's supplementary blood vessels are obstructed by an unstable build-up of white blood cells, cholesterol, and fat. With no blood flow, the cells die, causing whole portions of cardiac tissue to die. Once these tissues are lost, they cannot be replaced, thus causing permanent damage. Current research indicates, however, that it may be possible to repair damaged cardiac tissue with stem cells,[12] as human embryonic stem cells can differentiate into cardiomyocytes under appropriate conditions.[13]

The cardiomyopathies are a group of diseases characterized by disruptions to cardiac muscle cell growth and / or organization. Presentation can range from asymptomatic to sudden cardiac death.

Cardiomyopathy can be caused by genetic, endocrine, environmental, or other factors.

View original post here:
Cardiac muscle cell - Wikipedia

Cardiac Stem Cells Comments Off on Cardiac muscle cell – Wikipedia | February 3rd, 2017

Stem cells have tremendous promise to help us understand and treat a range of diseases, injuries and other health-related conditions. Their potential is evident in the use of blood stem cells to treat diseases of the blood, a therapy that has saved the lives of thousands of children with leukemia; and can be seen in the use of stem cells for tissue grafts to treat diseases or injury to the bone, skin and surface of the eye. Important clinical trials involving stem cells are underway for many other conditions and researchers continue to explore new avenues using stem cells in medicine.

There is still a lot to learn about stem cells, however, and their current applications as treatments are sometimes exaggerated by the media and other parties who do not fully understand the science and current limitations, and also by clinics looking to capitalize on the hype by selling treatments to chronically ill or seriously injured patients. The information on this page is intended to help you understand both the potential and the limitations of stem cells at this point in time, and to help you spot some of the misinformation that is widely circulated by clinics offering unproven treatments.

It is important to discuss these Nine Things to Know and any research or information you gather with your primary care physician and other trusted members of your healthcare team in deciding what is right for you.

Read the original here:
Nine Things to Know About Stem Cell Treatments

Skin Stem Cells Comments Off on Nine Things to Know About Stem Cell Treatments | February 3rd, 2017

While a number of companies have dabbled in this space, the following players are facilitating the development of iPS cell therapies: Cellular Dynamics International (CDI), RIKEN, Cynata Therapeutics, and Astellas (previously Ocata Therapeutics).

While each iPS cell therapy group is considered in detail below, Cellular Dynamics International (CDI) is featured first, because it dominates the iPSC industry. CDI also recently split into two business units, a Life Science Unit and a Therapeutics Unit, demonstrating a commercial strategy for its iPS cell therapy development.

Cellular Dynamics International (CDI) is headquartered in Madison, Wisconsin, although it provides technical support and sales information from both the United States and Japan. CDI was founded in 2004 and listed on NASDAQ in July 2013. The company had global revenues of $16.7 million in 2014 and currently has 150+ employees. It also has an extremely robust patent portfolio containing more than 800 patents, of which 130 pertain to iPSCs.

According to the company, CDI is the worlds largest producer of fully functional human cells derived from induced pluripotent stem (iPS) cells.[1] Their trademarked, iCell Cardiomyocytes, derived from iPSCs, are human cardiac cells used to aid drug discovery, improve the predictability of a drugs worth, and screen for toxicity. In addition, CDI provides: iCell Endothelial Cells for use in vascular-targeted drug discovery and tissue regeneration, iCell Hepatocytes, and iCell Neurons for pre-clinical drug discovery, toxicity testing, disease prediction, and cellular research.[2] As such, CDIs main role with regard to iPCS therapy development is the production of industrial-scale, clinical-grade iPSCs.

As mentioned previously, induced pluripotent stem cells were first produced in 2006 from mouse cells and in 2007 from human cells, by Shinya Yamanaka at Kyoto University,[3] who also won the Nobel Prize in Medicine or Physiology for his work on iPSCs.[4] Yamanaka has ties toCellular Dynamics International as a member of the scientific advisory board of iPS Academia Japan.

IPS Academia Japan was originally established to manage the patents and technology of Yamanakas work, and is now the distributor of several of Cellular Dynamics products, including iCell Neurons, iCell Cardiomyocytes, and iCell Endothelial Cells.[5] Importantly, in 2010 Cellular Dynamics became the first foreign company to be granted rights to use Yamanakas iPSC patent portfolio.Not only has CDI licensed rights to Yamanakas patents, but it also has a license to use Otsu, Japan-based Takara Bios RetroNectin product, which it uses as a tool to produce its iCell and MyCell products.[6] Through its licenses and intellectual property, CDI currently uses induced pluripotent stem cells to produce human heart cells (cardiomyocytes), brain cells (neurons), blood vessel cells (endothelial cells), and liver cells (hepatocytes), manufacturing them in high quantity, quality, and purity.

These human cells produced by the company are used for both in vitro and in vivo applications that range from basic and applied research to drug discovery research that includes target identification and validation, toxicity testing, safety and efficacy testing, and more. As such, CDI has emerged as a global leader with the ability to generate iPSCs that have the potential to be used for a wide range of research and possibly therapeutic purposes.

In a landmark event with the iPSC market, the company had an initial public offering (IPO) in July of 2013, in which it sold 38,460,000 shares of common stock to the public at $12.00 per share, to raise proceeds of approximately $43 million.[7] This event secured the companys position as the global leader in producing high-quality human iPSCs and differentiated cells in industrial quantities.

In addition, in March of 2013, Celullar Dynamics International and the Coriell Institute for Medical Research announced receiving multi-million dollars grants from the California Institute for Regenerative Medicine (CIRM) for the creation of iPSC lines from 3,000 healthy and diseased donors, a result that will create the worlds largest human iPSC bank.

Not surprisingly, Cellular Dynamics International has continued its innovation, announcing in February of 2015 that it would be manufacturing cGMP HLA Superdonor stem cell lines that will support cellular therapy applications through genetic matching.[8] Currently, CDI has two HLA superdonor cell lines that provide a partial HLA match to approximately 19% of the population within the U.S., and it aims to expand its master stem cell bank by collecting more donor cell lines that will cover 95% of the U.S. population.[9]

The HLA superdonor cell lines were manufactured using blood samples, and used to produce pluripotent iPSC lines, giving the cells the capacity to differentiate into nearly any cell within the human body.

CDI also leads the iPSC market in terms of supporting drug development and discovery. For example, CDIs MyCell products are created using custom iPSC reprogramming and differentiation methods, thereby providing biologically relevant human cells from patients with unique disease-associated genotypes and phenotypes.[10] The companys iCell and MyCell cells can also be adapted to screening platforms and are matched to function with common readout technologies.[11] CDIs products are also used for high-throughput screening,[12] and have been used as supporting data for Investigational New Drug (IND) applications submitted to the Federal Drug Administration (FDA).[13]

On March 30, 2015, Fujifilm Holdings Corporation announced that it was acquiring CDI, in which Fujifilm will acquire CDI through all-cash offer followed by a second step merger. Specifically, Fujifilm will acquire all issued and outstanding shares of CDIs common stock for $16.5 per share or approximately $ 307 million, after which CDI will continue to run its operations in Madison, Wisconsin, and Novato, California as a consolidated subsidiary of Fujifilm.[14]

CDIs technology platform enables the production of high-quality fully functioning iPSCs (and other human cells) on an industrial scale, while Fujifilm has developed highly-biocompatible recombinant peptidesthat can be shaped into a variety of forms for use as a cellular scaffoldin regenerative medicinewhen used in conjunction with CDIs products.[15] Fujifilm has been strengthening its presence in the regenerative medicine field over several years, including by acquiring a majority of shares of Japan Tissue Engineering Co. in December 2014, so while the acquisition was unexpected, it as not fully suprising.

In summary, the acquisition of CDI will allow Fujifilm to gaindominance in the areaof iPS cell-based drug discovery services and will position it to strategically combine CDIs iPS cell technologywithFujifilms expertise in material science and engineering systems, creating a powerhouse within the iPSC market. It is yet to be seen whether Fujifilm will try to commercialize CDIs iPS cell production technologies by making the cells available for clinical use or whether they will choose to focus their attention on iPS cell-based drug discovery services.

In November 2015 Astellas Pharma announced it was acquiring Ocata Therapeutics for $379M. Ocata Therapeutics is a biotechnology company that specializes in the development of cellular therapies, using both adult and human embryonic stem cells to develop patient-specific therapies. The companys main laboratory and GMP facility is in Marlborough, Massachusetts, and its corporate offices are in Santa Monica, California.

When a number of private companies began to explore the possibility of using artificially re-manufactured iPSCs for therapeutic purposes, one such company that was ready to capitalize on the breakthrough technology was Ocata Therapeutics (at the time called Advanced Cell Technology or ACT). In 2010, the company announced that it had discovered several problematic issues while conducting experiments for the purpose of applying for U.S. Food and Drug Administration approval to use iPSCs in therapeutic applications. Concerns such as premature cell death, mutation into cancer cells, and low proliferation rates were some of the problems that surfaced. [16]

As a result, the company has since shifted its induced pluripotent stem cell approach to producingiPS cell-derived human platelets, as one of the benefits of a platelet-based product is that platelets do not contain nuclei, and therefore, cannot divide or carry genetic information. Although nothing is completely safe, iPS cell-derived platelets are likely to be much safer than other iPSC therapies, in which uncontrolled proliferation is a major concern.

While the companys Induced Pluripotent Stem Cell-Derived Human Platelet Program received a great deal of media coverage in late 2012, including being awarded the December 2012 honor of being named one of the 10 Ideas that Will Shape the Yearby New Scientist Magazine,[17] unfortunately the company did not succeed in moving the concept through to clinical testing in 2013.

Nonetheless, in a November 2015 presentation by Astellas President and CEO, Yoshihiko Hatanaka, he indicated that the company will aim to develop an Ophthalmic Disease Cell Therapy Franchise based around its embryonic stem cells (ESCs) and induced pluripotent stem cell (iPS cells) technology. [18]

On June 22, 2016, RIKEN announced that it is resuming its retinal induced pluripotent stem cell (iPSC) study in partnership with Kyoto University.

2013 was the first time in which clinical research involving transplant of iPSCs into humans was initiated, led by Masayo Takahashi of the RIKEN Center for Developmental Biology (CDB)in Kobe, Japan. Dr. Takahashi and her team wereinvestigating the safety of iPSC-derived cell sheets in patients with wet-type age-related macular degeneration. Althoughthe trial was initiated in 2013 and production of iPSCs from patients began at that time, it was not until August of 2014 that the first patient, a Japanese woman, was implanted with retinal tissue generated using iPSCs derived from her own skin cells.

A team of three eye specialists, led by Yasuo Kurimoto of the Kobe City Medical Center General Hospital, implanted a 1.3 by 3.0mm sheet of iPSC-derived retinal pigment epithelium cells into the patients retina.[19]Unfortunately, the study was suspended in 2015 due to safety concerns. As the lab prepared to treat the second trial participant, Yamanakas team identified two small genetic changes in the patients iPSCs and the retinal pigment epithelium (RPE) cells derived from them. Therefore, it is major news that theRIKEN Institute will now be resuming the worlds first clinical study involving the use of iPSC-derived cells in humans.

According to the Japan Times, this attempt at the clinical studywill involve allogeneic rather than autologous iPSC-derived cells for purposes of cost and time efficiency.Specifically,the researchers will be developing retinal tissues from iPS cells supplied by Kyoto Universitys Center for iPS Cell Research and Application, an institution headed by Nobel prize winner Shinya Yamanaka. To learn about this announcement, view this article fromAsahi Shimbun, aTokyo- based newspaper.

Australian stem cell company Cynata Therapeutics (ASX:CYP) is taking a unique approach. It is creating allogeneic iPS cell derived mesenchyal stem cell (MSCs).Cynatas Cymerus technology utilizes iPSCs originating from an adult donor as the starting material for generating mesenchymoangioblasts (MCAs), and subsequently, for manufacturing clinical-gradeMSCs.

One of the key inventors of the approach is Igor Slukvin, who has released more than 70 publications about stem cell topics, including the landmark article in Cell describing the now patented Cymerus technique. Dr. Slukvins co-inventor is James Thomson, the first person to isolate an embryonic stem cell (ESC) and one of the first people to create a human-induced, pluripotent stem cell (hiPSC).

Recently, Cynata received advice from the UK Medicines and Healthcare products Regulatory Agency (MHRA) that its Phase I clinical trial application has been approved, titledAn Open-Label Phase 1 Study to Investigate the Safety and Efficacy of CYP-001 for the Treatment of Adults With Steroid-Resistant Acute Graft Versus Host Disease. It will be the worlds first clinical trial involving a therapeutic product derived from allogeneic (unrelated to the patient) induced pluripotent stem cells (iPSCs).

Participants for Cynatas upcoming Phase I clinical trial will be adults who have undergone an allogeneic haematopoietic stem cell transplant (HSCT) to treat a haematological disorder and subsequently been diagnosed with steroid-resistant Grade II-IV GvHD.The primary objective of the trial is to assess safety and tolerability, while the secondary objective is to evaluate the efficacy of two infusions of CYP-001 in adults with steroid-resistant GvHD.

There are four key advantages of Cynatas proprietary Cymerus MSC manufacturing platform, as described below.

Unlimited Quantities Cynatas Cymerus technology utilizes iPSCs originating from an adult donor as the starting material for generating mesenchymoangioblasts (MCAs), and subsequently, for manufacturing clinical-gradeMSCs. According to Cynatas Executive Chairman Stewart Washer who was recently interviewed by The Life Sciences Report, The Cymerus technology gets around the loss of potency with the unlimited iPS cellor induced pluripotent stem cellwhich is basically immortal.

Uniform Batches Because the proprietary Cymerus technology allows nearly unlimited production of MSCs from a single iPSC donor, there is batch-to-batch uniformity. Utilizing a consistent starting material allows for a standardized cell manufacturing process and a consistent cell therapy product.

Single Donor As described previously, Cynatas Cymerus technology creates iPSC-derived mesenchymoangioblasts (MCAs), which are differentiated into MSCs. Unlike other companies involved with MSC manufacturing, Cynata does not require a constant stream of new donors in order to source fresh stem cells for its cell manufacturing process, nor does it require the massive expansion of MSCs necessitated by reliance on freshly isolated donations.

Economic Manufacture at Commercial Scale (Low Cost) Finally, Cynata has achieved a cost-savings advantage through its uniqueapproach to MSCmanufacturing. Its proprietary Cymerus technology addresses a critical shortcoming in existing methods of production of MSCs for therapeutic use, which is the ability to achieve economic manufacture at commercial scale.

Footnotes [1] CellularDynamics.com (2014). About CDI. Available at: http://www.cellulardynamics.com/about/index.html. Web. 1 Apr. 2015. [2] Ibid. [3] Takahashi K, Yamanaka S (August 2006).Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.Cell126(4): 66376. [4] 2012 Nobel Prize in Physiology or Medicine Press Release. Nobelprize.org. Nobel Media AB 2013. Web. 7 Feb 2014. Available at: http://www.nobelprize.org/nobel_prizes/medicine/laureates/2012/press.html. Web. 1 Apr. 2015. [5] Striklin, D (Jan 13, 2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet. Retrieved Feb 1, 2014 from, http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. [6] Striklin, D (2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet [Online]. Available at: http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. Web. 1 Apr. 2015. [7] Cellular Dynamics International (July 30, 2013). Cellular Dynamics International Announces Closing of Initial Public Offering [Press Release]. Retrieved from http://www.cellulardynamics.com/news/pr/2013_07_30.html. [8] Investors.cellulardynamics.com,. Cellular Dynamics Manufactures Cgmp HLA Superdonor Stem Cell Lines To Enable Cell Therapy With Genetic Matching (NASDAQ:ICEL). N.p., 2015. Web. 7 Mar. 2015. [9] Ibid. [10] Cellulardynamics.com,. Cellular Dynamics | Mycell Products. N.p., 2015. Web. 7 Mar. 2015. [11]Sirenko, O. et al. Multiparameter In Vitro Assessment Of Compound Effects On Cardiomyocyte Physiology Using Ipsc Cells.Journal of Biomolecular Screening18.1 (2012): 39-53. Web. 7 Mar. 2015. [12] Sciencedirect.com,. Prevention Of -Amyloid Induced Toxicity In Human Ips Cell-Derived Neurons By Inhibition Of Cyclin-Dependent Kinases And Associated Cell Cycle Events. N.p., 2015. Web. 7 Mar. 2015. [13] Sciencedirect.com,. HER2-Targeted Liposomal Doxorubicin Displays Enhanced Anti-Tumorigenic Effects Without Associated Cardiotoxicity. N.p., 2015. Web. 7 Mar. 2015. [14] Cellular Dynamics International, Inc. Fujifilm Holdings To Acquire Cellular Dynamics International, Inc.. GlobeNewswire News Room. N.p., 2015. Web. 7 Apr. 2015. [15] Ibid. [16] Advanced Cell Technologies (Feb 11, 2011). Advanced Cell and Colleagues Report Therapeutic Cells Derived From iPS Cells Display Early Aging [Press Release]. Available at: http://www.advancedcell.com/news-and-media/press-releases/advanced-cell-and-colleagues-report-therapeutic-cells-derived-from-ips-cells-display-early-aging/. [17] Advanced Cell Technology (Dec 20, 2012). New Scientist Magazine Selects ACTs Induced Pluripotent Stem (iPS) Cell-Derived Human Platelet Program As One of 10 Ideas That Will Shape The Year [Press Release]. Available at: http://articles.latimes.com/2009/mar/06/science/sci-stemcell6. Web. 9 Apr. 2015. [18] Astellas Pharma (2015). Acquisition of Ocata Therapeutics New Step Forward in Ophthalmology with Cell Therapy Approach. Available at: https://www.astellas.com/en/corporate/news/pdf/151110_2_Eg.pdf. Web. 29 Jan. 2017. [19]Cyranoski, David. Japanese Woman Is First Recipient Of Next-Generation Stem Cells. Nature (2014): n. pag. Web. 6 Mar. 2015.

See the rest here:
Companies Developing Induced Pluripotent Stem Cell (iPS ...

IPS Cell Therapy Comments Off on Companies Developing Induced Pluripotent Stem Cell (iPS … | January 30th, 2017

One of the current challenges for stem cell researchers is to understand how all the skin appendages are regenerated. This could lead to improved treatments for burn patients, or others with severe skin damage.

Researchers are also working to identify new ways to grow skin cells in the lab. Epidermal stem cells are currently cultivated on a layer of cells from rodents, called murine cells. These cell culture conditions have been proved safe, but it would be preferable to avoid using animal products when cultivating cells that will be transplanted into patients. So, researchers are searching for effective cell culture conditions that will not require the use of murine cells.

Scientists are also working to treat genetic diseases affecting the skin. Since skin stem cells can be cultivated in laboratories, researchers can genetically modify the cells, for example by inserting a missing gene. The correctly modified cells can be selected, grown and multiplied in the lab, then transplanted back onto the patient. Epidermolysis Bullosa is one example of a genetic skin disease that might benefit from this approach. Work is underway to test the technique.

Read more from the original source:
Skin stem cells: where do they live and what can they do ...

Skin Stem Cells Comments Off on Skin stem cells: where do they live and what can they do … | January 26th, 2017

Actin is a family of globular multi-functional proteins that form microfilaments. It is found in essentially all eukaryotic cells (the only known exception being nematode sperm), where it may be present at a concentration of over 100 M. An actin protein's mass is roughly 42-kDa, with a diameter of 4 to 7nm, and it is the monomeric subunit of two types of filaments in cells: microfilaments, one of the three major components of the cytoskeleton, and thin filaments, part of the contractile apparatus in muscle cells. It can be present as either a free monomer called G-actin (globular) or as part of a linear polymer microfilament called F-actin (filamentous), both of which are essential for such important cellular functions as the mobility and contraction of cells during cell division.

Actin participates in many important cellular processes, including muscle contraction, cell motility, cell division and cytokinesis, vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape. Many of these processes are mediated by extensive and intimate interactions of actin with cellular membranes.[2] In vertebrates, three main groups of actin isoforms, alpha, beta, and gamma have been identified. The alpha actins, found in muscle tissues, are a major constituent of the contractile apparatus. The beta and gamma actins coexist in most cell types as components of the cytoskeleton, and as mediators of internal cell motility. It is believed that the diverse range of structures formed by actin enabling it to fulfill such a large range of functions is regulated through the binding of tropomyosin along the filaments.[3]

A cells ability to dynamically form microfilaments provides the scaffolding that allows it to rapidly remodel itself in response to its environment or to the organisms internal signals, for example, to increase cell membrane absorption or increase cell adhesion in order to form cell tissue. Other enzymes or organelles such as cilia can be anchored to this scaffolding in order to control the deformation of the external cell membrane, which allows endocytosis and cytokinesis. It can also produce movement either by itself or with the help of molecular motors. Actin therefore contributes to processes such as the intracellular transport of vesicles and organelles as well as muscular contraction and cellular migration. It therefore plays an important role in embryogenesis, the healing of wounds and the invasivity of cancer cells. The evolutionary origin of actin can be traced to prokaryotic cells, which have equivalent proteins.[4] Actin homologs from prokaryotes and archaea polymerize into different helical or linear filaments consisting of one or multiple strands. However the in-strand contacts and nucleotide binding sites are preserved in prokaryotes and in archaea.[5] Lastly, actin plays an important role in the control of gene expression.

A large number of illnesses and diseases are caused by mutations in alleles of the genes that regulate the production of actin or of its associated proteins. The production of actin is also key to the process of infection by some pathogenic microorganisms. Mutations in the different genes that regulate actin production in humans can cause muscular diseases, variations in the size and function of the heart as well as deafness. The make-up of the cytoskeleton is also related to the pathogenicity of intracellular bacteria and viruses, particularly in the processes related to evading the actions of the immune system.[6]

Actin was first observed experimentally in 1887 by W.D. Halliburton, who extracted a protein from muscle that 'coagulated' preparations of myosin that he called "myosin-ferment".[7] However, Halliburton was unable to further refine his findings, and the discovery of actin is credited instead to Brun Ferenc Straub, a young biochemist working in Albert Szent-Gyrgyi's laboratory at the Institute of Medical Chemistry at the University of Szeged, Hungary.

In 1942, Straub developed a novel technique for extracting muscle protein that allowed him to isolate substantial amounts of relatively pure actin. Straub's method is essentially the same as that used in laboratories today. Szent-Gyorgyi had previously described the more viscous form of myosin produced by slow muscle extractions as 'activated' myosin, and, since Straub's protein produced the activating effect, it was dubbed actin. Adding ATP to a mixture of both proteins (called actomyosin) causes a decrease in viscosity. The hostilities of World War II meant Szent-Gyorgyi and Straub were unable to publish the work in Western scientific journals. Actin therefore only became well known in the West in 1945, when their paper was published as a supplement to the Acta Physiologica Scandinavica.[8] Straub continued to work on actin, and in 1950 reported that actin contains bound ATP[9] and that, during polymerization of the protein into microfilaments, the nucleotide is hydrolyzed to ADP and inorganic phosphate (which remain bound to the microfilament). Straub suggested that the transformation of ATP-bound actin to ADP-bound actin played a role in muscular contraction. In fact, this is true only in smooth muscle, and was not supported through experimentation until 2001.[9][10]

The amino acid sequencing of actin was completed by M. Elzinga and co-workers in 1973.[11] The crystal structure of G-actin was solved in 1990 by Kabsch and colleagues.[12] In the same year, a model for F-actin was proposed by Holmes and colleagues following experiments using co-crystallization with different proteins.[13] The procedure of co-crystallization with different proteins was used repeatedly during the following years, until in 2001 the isolated protein was crystallized along with ADP. However, there is still no high-resolution X-ray structure of F-actin. The crystallization of F-actin was possible due to the use of a rhodamine conjugate that impedes polymerization by blocking the amino acid cys-374.[1] Christine Oriol-Audit died in the same year that actin was first crystallized but she was the researcher that in 1977 first crystallized actin in the absence of Actin Binding Proteins (ABPs). However, the resulting crystals were too small for the available technology of the time.[14]

Although no high-resolution model of actins filamentous form currently exists, in 2008 Sawayas team were able to produce a more exact model of its structure based on multiple crystals of actin dimers that bind in different places.[15] This model has subsequently been further refined by Sawaya and Lorenz. Other approaches such as the use of cryo-electron microscopy and synchrotron radiation have recently allowed increasing resolution and better understanding of the nature of the interactions and conformational changes implicated in the formation of actin filaments.[16][17][18]

Its amino acid sequence is also one of the most highly conserved of the proteins as it has changed little over the course of evolution, differing by no more than 20% in species as diverse as algae and humans. It is therefore considered to have an optimised structure.[4] It has two distinguishing features: it is an enzyme that slowly hydrolizes ATP, the "universal energy currency" of biological processes. However, the ATP is required in order to maintain its structural integrity. Its efficient structure is formed by an almost unique folding process. In addition, it is able to carry out more interactions than any other protein, which allows it to perform a wider variety of functions than other proteins at almost every level of cellular life.[4]Myosin is an example of a protein that bonds with actin. Another example is villin, which can weave actin into bundles or cut the filaments depending on the concentration of calcium cations in the surrounding medium.[19]

Actin is one of the most abundant proteins in eukaryotes, where it is found throughout the cytoplasm.[19] In fact, in muscle fibres it comprises 20% of total cellular protein by weight and between 1% and 5% in other cells. However, there is not only one type of actin, the genes that code for actin are defined as a gene family (a family that in plants contains more than 60 elements, including genes and pseudogenes and in humans more than 30 elements).[4][20] This means that the genetic information of each individual contains instructions that generate actin variants (called isoforms) that possess slightly different functions. This, in turn, means that eukaryotic organisms express different genes that give rise to: -actin, which is found in contractile structures; -actin, found at the expanding edge of cells that use the projection of their cellular structures as their means of mobility; and -actin, which is found in the filaments of stress fibres.[21] In addition to the similarities that exist between an organisms isoforms there is also an evolutionary conservation in the structure and function even between organisms contained in different eukaryotic domains: in bacteria the actin homologue MreB has been identified, which is a protein that is capable of polymerizing into microfilaments;[4][17] and in archaea the homologue Ta0583 is even more similar to the eukaryotic actins.[22]

Cellular actin has two forms: monomeric globules called G-actin and polymeric filaments called F-actin (that is, as filaments made up of many G-actin monomers). F-actin can also be described as a microfilament. Two parallel F-actin strands must rotate 166 degrees to lie correctly on top of each other. This creates the double helix structure of the microfilaments found in the cytoskeleton. Microfilaments measure approximately 7 nm in diameter with the helix repeating every 37nm. Each molecule of actin is bound to a molecule of adenosine triphosphate (ATP) or adenosine diphosphate (ADP) that is associated with a Mg2+ cation. The most commonly found forms of actin, compared to all the possible combinations, are ATP-G-Actin and ADP-F-actin.[23][24]

Scanning electron microscope images indicate that G-actin has a globular structure; however, X-ray crystallography shows that each of these globules consists of two lobes separated by a cleft. This structure represents the ATPase fold, which is a centre of enzymatic catalysis that binds ATP and Mg2+ and hydrolyzes the former to ADP plus phosphate. This fold is a conserved structural motif that is also found in other proteins that interact with triphosphate nucleotides such as hexokinase (an enzyme used in energy metabolism) or in Hsp70 proteins (a protein family that play an important part in protein folding).[25] G-actin is only functional when it contains either ADP or ATP in its cleft but the form that is bound to ATP predominates in cells when actin is present in its free state.[23]

The X-ray crystallography model of actin that was produced by Kabsch from the striated muscle tissue of rabbits is the most commonly used in structural studies as it was the first to be purified. The G-actin crystallized by Kabsch is approximately 67 x 40 x 37 in size, has a molecular mass of 41,785 Da and an estimated isoelectric point of 4.8. Its net charge at pH = 7 is -7.[11][26]

Elzinga and co-workers first determined the complete peptide sequence for this type of actin in 1973, with later work by the same author adding further detail to the model. It contains 374 amino acid residues. Its N-terminus is highly acidic and starts with an acetyled aspartate in its amino group. While its C-terminus is alkaline and is formed by a phenylalanine preceded by a cysteine, which has a degree of functional importance. Both extremes are in close proximity within the I-subdomain. An anomalous N-methylhistidine is located at position 73.[26]

The tertiary structure is formed by two domains known as the large and the small, which are separated by a cleft centred around the location of the bond with ATP-ADP+Pi. Below this there is a deeper notch called a groove. In the native state, despite their names, both have a comparable depth.[11]

The normal convention in topological studies means that a protein is shown with the biggest domain on the left-hand side and the smallest domain on the right-hand side. In this position the smaller domain is in turn divided into two: subdomain I (lower position, residues 1-32, 70-144 and 338-374) and subdomain II (upper position, residues 33-69). The larger domain is also divided in two: subdomain III (lower, residues 145-180 and 270-337) and subdomain IV (higher, residues 181-269). The exposed areas of subdomains I and III are referred to as the barbed ends, while the exposed areas of domains II and IV are termed the pointed" ends. This nomenclature refers to the fact that, due to the small mass of subdomain II actin is polar; the importance of this will be discussed below in the discussion on assembly dynamics. Some authors call the subdomains Ia, Ib, IIa and IIb, respectively.[27]

The most notable supersecondary structure is a five chain beta sheet that is composed of a -meander and a -- clockwise unit. It is present in both domains suggesting that the protein arose from gene duplication.[12]

The classical description of F-actin states that it has a filamentous structure that can be considered to be a single stranded levorotatory helix with a rotation of 166 around the helical axis and an axial translation of 27.5 , or a single stranded dextrorotatory helix with a cross over spacing of 350-380 , with each actin surrounded by four more.[29] The symmetry of the actin polymer at 2.17 subunits per turn of a helix is incompatible with the formation of crystals, which is only possible with a symmetry of exactly 2, 3, 4 or 6 subunits per turn. Therefore, models have to be constructed that explain these anomalies using data from electron microscopy, cryo-electron microscopy, crystallization of dimers in different positions and diffraction of X-rays.[17][18] It should be pointed out that it is not correct to talk of a structure for a molecule as dynamic as the actin filament. In reality we talk of distinct structural states, in these the measurement of axial translation remains constant at 27.5 while the subunit rotation data shows considerable variability, with displacements of up to 10% from its optimum position commonly seen. Some proteins, such as cofilin appear to increase the angle of turn, but again this could be interpreted as the establishment of different "structural states". These could be important in the polymerization process.[30]

There is less agreement regarding measurements of the turn radius and filament thickness: while the first models assigned a longitude of 25 , current X-ray diffraction data, backed up by cryo-electron microscopy suggests a longitude of 23.7 . These studies have shown the precise contact points between monomers. Some are formed with units of the same chain, between the "barbed" end on one monomer and the "pointed" end of the next one. While the monomers in adjacent chains make lateral contact through projections from subdomain IV, with the most important projections being those formed by the C-terminus and the hydrophobic link formed by three bodies involving residues 39-42, 201-203 and 286. This model suggests that a filament is formed by monomers in a "sheet" formation, in which the subdomains turn about themselves, this form is also found in the bacterial actin homologue MreB.[17]

The F-actin polymer is considered to have structural polarity due to the fact that all the microfilaments subunits point towards the same end. This gives rise to a naming convention: the end that possesses an actin subunit that has its ATP binding site exposed is called the "(-) end", while the opposite end where the cleft is directed at a different adjacent monomer is called the "(+) end".[21] The terms "pointed" and "barbed" referring to the two ends of the microfilaments derive from their appearance under transmission electron microscopy when samples are examined following a preparation technique called "decoration". This method consists of the addition of myosin S1 fragments to tissue that has been fixed with tannic acid. This myosin forms polar bonds with actin monomers, giving rise to a configuration that looks like arrows with feather fletchings along its shaft, where the shaft is the actin and the fletchings are the myosin. Following this logic, the end of the microfilament that does not have any protruding myosin is called the point of the arrow (- end) and the other end is called the barbed end (+ end).[31] A S1 fragment is composed of the head and neck domains of myosin II. Under physiological conditions, G-actin (the monomer form) is transformed to F-actin (the polymer form) by ATP, where the role of ATP is essential.[32]

The helical F-actin filament found in muscles also contains a tropomyosin molecule, which is a 40 nanometre long protein that is wrapped around the F-actin helix.[18] During the resting phase the tropomyosin covers the actins active sites so that the actin-myosin interaction cannot take place and produce muscular contraction. There are other protein molecules bound to the tropomyosin thread, these are the troponins that have three polymers: troponin I, troponin T and troponin C.[33]

Actin can spontaneously acquire a large part of its tertiary structure.[35] However, the way it acquires its fully functional form from its newly synthesized native form is special and almost unique in protein chemistry. The reason for this special route could be the need to avoid the presence of incorrectly folded actin monomers, which could be toxic as they can act as inefficient polymerization terminators. Nevertheless, it is key to establishing the stability of the cytoskeleton, and additionally, it is an essential process for coordinating the cell cycle.[36][37]

CCT is required in order to ensure that folding takes place correctly. CCT is a group II cytosolic molecular chaperone (or chaperonin, a protein that assists in the folding of other macromolecular structures). CCT is formed of a double ring of eight different subunits (hetero-octameric) and it differs from other molecular chaperones, particularly from its homologue GroEL which is found in the Archaea, as it does not require a co-chaperone to act as a lid over the central catalytic cavity. Substrates bind to CCT through specific domains. It was initially thought that it only bound with actin and tubulin, although recent immunoprecipitation studies have shown that it interacts with a large number of polypeptides, which possibly function as substrates. It acts through ATP-dependent conformational changes that on occasion require several rounds of liberation and catalysis in order to complete a reaction.[38]

In order to successfully complete their folding, both actin and tubulin need to interact with another protein called prefoldin, which is a heterohexameric complex (formed by six distinct subunits), in an interaction that is so specific that the molecules have coevolved[citation needed]. Actin complexes with prefoldin while it is still being formed, when it is approximately 145 amino acids long, specifically those at the N-terminal.[39]

Different recognition sub-units are used for actin or tubulin although there is some overlap. In actin the subunits that bind with prefoldin are probably PFD3 and PFD4, which bind in two places one between residues 60-79 and the other between residues 170-198. The actin is recognized, loaded and delivered to the cytosolic chaperonin (CCT) in an open conformation by the inner end of prefoldins "tentacles (see the image and note).[35] The contact when actin is delivered is so brief that a tertiary complex is not formed, immediately freeing the prefoldin.[34]

The CCT then causes actin's sequential folding by forming bonds with its subunits rather than simply enclosing it in its cavity.[40] This is why it possesses specific recognition areas in its apical -domain. The first stage in the folding consists of the recognition of residues 245-249. Next, other determinants establish contact.[41] Both actin and tubulin bind to CCT in open conformations in the absence of ATP. In actins case, two subunits are bound during each conformational change, whereas for tubulin binding takes place with four subunits. Actin has specific binding sequences, which interact with the and -CCT subunits or with -CCT and -CCT. After AMP-PNP is bound to CCT the substrates move within the chaperonins cavity. It also seems that in the case of actin, the CAP protein is required as a possible cofactor in actin's final folding states.[37]

The exact manner by which this process is regulated is still not fully understood, but it is known that the protein PhLP3 (a protein similar to phosducin) inhibits its activity through the formation of a tertiary complex.[38]

Actin is an ATPase, which means that it is an enzyme that hydrolyzes ATP. This group of enzymes is characterised by their slow reaction rates. It is known that this ATPase is active, that is, its speed increases by some 40,000 times when the actin forms part of a filament.[30] A reference value for this rate of hydrolysis under ideal conditions is around 0.3 s1. Then, the Pi remains bound to the actin next to the ADP for a long time, until it is liberated next to the end of the filament.[42]

The exact molecular details of the catalytic mechanism are still not fully understood. Although there is much debate on this issue, it seems certain that a "closed" conformation is required for the hydrolysis of ATP, and it is thought that the residues that are involved in the process move to the appropriate distance.[30] The glutamic acid Glu137 is one of the key residues, which is located in subdomain 1. Its function is to bind the water molecule that produces a nucleophilic attack on the ATPs -phosphate bond, while the nucleotide is strongly bound to subdomains 3 and 4. The slowness of the catalytic process is due to the large distance and skewed position of the water molecule in relation to the reactant. It is highly likely that the conformational change produced by the rotation of the domains between actins G and F forms moves the Glu137 closer allowing its hydrolysis. This model suggests that the polymerization and ATPases function would be decoupled straight away.[17][18]

Principal interactions of structural proteins are at cadherin-based adherens junction. Actin filaments are linked to -actinin and to the membrane through vinculin. The head domain of vinculin associates to E-cadherin via -catenin, -catenin, and -catenin. The tail domain of vinculin binds to membrane lipids and to actin filaments.

Actin has been one of the most highly conserved proteins throughout evolution because it interacts with a large number of other proteins. It has 80.2% sequence conservation at the gene level between Homo sapiens and Saccharomyces cerevisiae (a species of yeast), and 95% conservation of the primary structure of the protein product.[4]

Although most yeasts have only a single actin gene, higher eukaryotes, in general, express several isoforms of actin encoded by a family of related genes. Mammals have at least six actin isoforms coded by separate genes,[43] which are divided into three classes (alpha, beta and gamma) according to their isoelectric points. In general, alpha actins are found in muscle (-skeletal, -aortic smooth, -cardiac, and 2-enteric smooth), whereas beta and gamma isoforms are prominent in non-muscle cells (- and 1-cytoplasmic). Although the amino acid sequences and in vitro properties of the isoforms are highly similar, these isoforms cannot completely substitute for one another in vivo.[44]

The typical actin gene has an approximately 100-nucleotide 5' UTR, a 1200-nucleotide translated region, and a 200-nucleotide 3' UTR. The majority of actin genes are interrupted by introns, with up to six introns in any of 19 well-characterised locations. The high conservation of the family makes actin the favoured model for studies comparing the introns-early and introns-late models of intron evolution.

All non-spherical prokaryotes appear to possess genes such as MreB, which encode homologues of actin; these genes are required for the cell's shape to be maintained. The plasmid-derived gene ParM encodes an actin-like protein whose polymerized form is dynamically unstable, and appears to partition the plasmid DNA into its daughter cells during cell division by a mechanism analogous to that employed by microtubules in eukaryotic mitosis.[45] Actin is found in both smooth and rough endoplasmic reticulums.

Actin polymerization and depolymerization is necessary in chemotaxis and cytokinesis. Nucleating factors are necessary to stimulate actin polymerization. One such nucleating factor is the Arp2/3 complex, which mimics a G-actin dimer in order to stimulate the nucleation (or formation of the first trimer) of monomeric G-actin. The Arp2/3 complex binds to actin filaments at 70 degrees to form new actin branches off existing actin filaments. Also, actin filaments themselves bind ATP, and hydrolysis of this ATP stimulates destabilization of the polymer.

The growth of actin filaments can be regulated by thymosin and profilin. Thymosin binds to G-actin to buffer the polymerizing process, while profilin binds to G-actin to exchange ADP for ATP, promoting the monomeric addition to the barbed, plus end of F-actin filaments.

F-actin is both strong and dynamic. Unlike other polymers, such as DNA, whose constituent elements are bound together with covalent bonds, the monomers of actin filaments are assembled by weaker bonds. The lateral bonds with neighbouring monomers resolve this anomaly, which in theory should weaken the structure as they can be broken by thermal agitation. In addition, the weak bonds give the advantage that the filament ends can easily release or incorporate monomers. This means that the filaments can be rapidly remodelled and can change cellular structure in response to an environmental stimulus. Which, along with the biochemical mechanism by which it is brought about is known as the "assembly dynamic".[6]

Studies focusing on the accumulation and loss of subunits by microfilaments are carried out in vitro (that is, in the laboratory and not on cellular systems) as the polymerization of the resulting actin gives rise to the same F-actin as produced in vivo. The in vivo process is controlled by a multitude of proteins in order to make it responsive to cellular demands, this makes it difficult to observe its basic conditions.[46]

In vitro production takes place in a sequential manner: first, there is the "activation phase", when the bonding and exchange of divalent cations occurs in specific places on the G-actin, which is bound to ATP. This produces a conformational change, sometimes called G*-actin or F-actin monomer as it is very similar to the units that are located on the filament.[27] This prepares it for the "nucleation phase", in which the G-actin gives rise to small unstable fragments of F-actin that are able to polymerize. Unstable dimers and trimers are initially formed. The "elongation phase" begins when there are a sufficiently large number of these short polymers. In this phase the filament forms and rapidly grows through the reversible addition of new monomers at both extremes.[47] Finally, a "stationary equilibrium" is achieved where the G-actin monomers are exchanged at both ends of the microfilament without any change to its total length.[19] In this last phase the "critical concentration Cc" is defined as the ratio between the assembly constant and the dissociation constant for G-actin, where the dynamic for the addition and elimination of dimers and trimers does not produce a change in the microfilament's length. Under normal in vitro conditions Cc is 0.1 M,[48] which means that at higher values polymerization occurs and at lower values depolymerization occurs.[49]

As indicated above, although actin hydrolyzes ATP, everything points to the fact that ATP is not required for actin to be assembled, given that, on one hand, the hydrolysis mainly takes place inside the filament, and on the other hand the ADP could also instigate polymerization. This poses the question of understanding which thermodynamically unfavourable process requires such a prodigious expenditure of energy. The so-called actin cycle, which couples ATP hydrolysis to actin polymerization, consists of the preferential addition of G-actin-ATP monomers to a filaments barbed end, and the simultaneous disassembly of F-actin-ADP monomers at the pointed end where the ADP is subsequently changed into ATP, thereby closing the cycle, this aspect of actin filament formation is known as treadmilling.

ATP is hydrolysed relatively rapidly just after the addition of a G-actin monomer to the filament. There are two hypotheses regarding how this occurs; the stochastic, which suggests that hydrolysis randomly occurs in a manner that is in some way influenced by the neighbouring molecules; and the vectoral, which suggests that hydrolysis only occurs adjacent to other molecules whose ATP has already been hydrolysed. In either case, the resulting Pi is not released, it remains for some time noncovalently bound to actins ADP, in this way there are three species of actin in a filament: ATP-Actin, ADP+Pi-Actin and ADP-Actin.[42][50] The amount of each one of these species present in a filament depends on its length and state: as elongation commences the filament has an approximately equal amount of actin monomers bound with ATP and ADP+Pi and a small amount of ADP-Actin at the (-) end. As the stationary state is reached the situation reverses, with ADP present along the majority of the filament and only the area nearest the (+) end containing ADP+Pi and with ATP only present at the tip.[51]

If we compare the filaments that only contain ADP-Actin with those that include ATP, in the former the critical constants are similar at both ends, while Cc for the other two nucleotides is different: At the (+) end Cc+=0.1 M, while at the (-) end Cc=0.8 M, which gives rise to the following situations:[21]

It is therefore possible to deduce that the energy produced by hydrolysis is used to create a true stationary state, that is a flux, instead of a simple equilibrium, one that is dynamic, polar and attached to the filament. This justifies the expenditure of energy as it promotes essential biological functions.[42] In addition, the configuration of the different monomer types is detected by actin binding proteins, which also control this dynamism, as will be described in the following section.

Microfilament formation by treadmilling has been found to be atypical in stereocilia. In this case the control of the structure's size is totally apical and it is controlled in some way by gene expression, that is, by the total quantity of protein monomer synthesized in any given moment.[52]

The actin cytoskeleton in vivo is not exclusively composed of actin, other proteins are required for its formation, continuance and function. These proteins are called actin-binding proteins (ABP) and they are involved in actins polymerization, depolymerization, stability, organisation in bundles or networks, fragmentation and destruction.[19] The diversity of these proteins is such that actin is thought to be the protein that takes part in the greatest number of protein-protein interactions.[54] For example, G-actin sequestering elements exist that impede its incorporation into microfilaments. There are also proteins that stimulate its polymerization or that give complexity to the synthesizing networks.[21]

Other proteins that bind to actin regulate the length of the microfilaments by cutting them, which gives rise to new active ends for polymerization. For example, if a microfilament with two ends is cut twice, there will be three new microfilaments with six ends. This new situation favors the dynamics of assembly and disassembly. The most notable of these proteins are gelsolin and cofilin. These proteins first achieve a cut by binding to an actin monomer located in the polymer they then change the actin monomers conformation while remaining bound to the newly generated (+) end. This has the effect of impeding the addition or exchange of new G-actin subunits. Depolymerization is encouraged as the (-) ends are not linked to any other molecule.[60]

Other proteins that bind with actin cover the ends of F-actin in order to stabilize them, but they are unable to break them. Examples of this type of protein are CapZ (that binds the (+) ends depending on a cells levels of Ca2+/calmodulin. These levels depend on the cells internal and external signals and are involved in the regulation of its biological functions).[61] Another example is tropomodulin (that binds to the (-) end). Tropomodulin basically acts to stabilize the F-actin present in the myofibrils present in muscle sarcomeres, which are structures characterized by their great stability.[62]

The Arp2/3 complex is widely found in all eukaryotic organisms.[64] It is composed of seven subunits, some of which possess a topology that is clearly related to their biological function: two of the subunits, "ARP2 and "ARP3, have a structure similar to that of actin monomers. This homology allows both units to act as nucleation agents in the polymerization of G-actin and F-actin. This complex is also required in more complicated processes such as in establishing dendritic structures and also in anastomosis (the reconnection of two branching structures that had previously been joined, such as in blood vessels).[65]

There are a number of toxins that interfere with actins dynamics, either by preventing it from polymerizing (latrunculin and cytochalasin D) or by stabilizing it (phalloidin):

Actin forms filaments ('F-actin' or microfilaments) that are essential elements of the eukaryotic cytoskeleton, able to undergo very fast polymerization and depolymerization dynamics. In most cells actin filaments form larger-scale networks which are essential for many key functions in cells:[69]

The actin protein is found in both the cytoplasm and the cell nucleus.[70] Its location is regulated by cell membrane signal transduction pathways that integrate the stimuli that a cell receives stimulating the restructuring of the actin networks in response. In Dictyostelium, phospholipase D has been found to intervene in inositol phosphate pathways.[71] Actin filaments are particularly stable and abundant in muscle fibres. Within the sarcomere (the basic morphological and physiological unit of muscle fibres) actin is present in both the I and A bands; myosin is also present in the latter.[72]

Microfilaments are involved in the movement of all mobile cells, including non-muscular types, and drugs that disrupt F-actin organization (such as the cytochalasins) affect the activity of these cells. Actin comprises 2% of the total amount of proteins in hepatocytes, 10% in fibroblasts, 15% in amoebas and up to 50-80% in activated platelets.[73] There are a number of different types of actin with slightly different structures and functions. This means that -actin is found exclusively in muscle fibres, while types and are found in other cells. In addition, as the latter types have a high turnover rate the majority of them are found outside permanent structures. This means that the microfilaments found in cells other than muscle cells are present in two forms:[74]

Actins cytoskeleton is key to the processes of endocytosis, cytokinesis, determination of cell polarity and morphogenesis in yeasts. In addition to relying on actin these processes involve 20 or 30 associated proteins, which all have a high degree of evolutionary conservation, along with many signalling molecules. Together these elements allow a spatially and temporally modulated assembly that defines a cells response to both internal and external stimuli.[76]

Yeasts contain three main elements that are associated with actin: patches, cables and rings that, despite being present for long, are subject to a dynamic equilibrium due to continual polymerization and depolymerization. They possess a number of accessory proteins including ADF/cofilin, which has a molecular weight of 16kDa and is coded for by a single gene, called COF1; Aip1, a cofilin cofactor that promotes the disassembly of microfilaments; Srv2/CAP, a process regulator related to adenylate cyclase proteins; a profilin with a molecular weight of approximately 14 kDa that is associated with actin monomers; and twinfilin, a 40 kDa protein involved in the organization of patches.[76]

Plant genome studies have revealed the existence of protein isovariants within the actin family of genes. Within Arabidopsis thaliana, a dicotyledon used as a model organism, there are ten types of actin, nine types of -tubulins, six -tubulins, six profilins and dozens of myosins. This diversity is explained by the evolutionary necessity of possessing variants that slightly differ in their temporal and spatial expression.[4] The majority of these proteins were jointly expressed in the tissue analysed. Actin networks are distributed throughout the cytoplasm of cells that have been cultivated in vitro. There is a concentration of the network around the nucleus that is connected via spokes to the cellular cortex, this network is highly dynamic, with a continuous polymerization and depolymerization.[77]

Even though the majority of plant cells have a cell wall that defines their morphology and impedes their movement, their microfilaments can generate sufficient force to achieve a number of cellular activities, such as, the cytoplasmic currents generated by the microfilaments and myosin. Actin is also involved in the movement of organelles and in cellular morphogenesis, which involve cell division as well as the elongation and differentiation of the cell.[79]

The most notable proteins associated with the actin cytoskeleton in plants include:[79]villin, which belongs to the same family as gelsolin/severin and is able to cut microfilaments and bind actin monomers in the presence of calcium cations; fimbrin, which is able to recognize and unite actin monomers and which is involved in the formation of networks (by a different regulation process from that of animals and yeasts);[80]formins, which are able to act as an F-actin polymerization nucleating agent; myosin, a typical molecular motor that is specific to eukaryotes and which in Arabidopsis thaliana is coded for by 17 genes in two distinct classes; CHUP1, which can bind actin and is implicated in the spatial distribution of chloroplasts in the cell; KAM1/MUR3 that define the morphology of the Golgi apparatus as well as the composition of xyloglucans in the cell wall; NtWLIM1, which facilitates the emergence of actin cell structures; and ERD10, which is involved in the association of organelles within membranes and microfilaments and which seems to play a role that is involved in an organisms reaction to stress.

Nuclear actin was first noticed and described in 1977 by Clark and Merriam.[81] Authors describe a protein present in the nuclear fraction, obtained from Xenopus laevis oocytes, which shows the same features such skeletal muscle actin. Since that time there have been many scientific reports about the structure and functions of actin in the nucleus (for review see: Hofmann 2009.[82]) The controlled level of actin in the nucleus, its interaction with actin-binding proteins (ABP) and the presence of different isoforms allows actin to play an important role in many important nuclear processes.

The actin sequence does not contain a nuclear localization signal. The small size of actin (about 43 kDa) allows it to enter the nucleus by passive diffusion.[83] Actin however shuttles between cytoplasm and nucleus quite quickly, which indicates the existence of active transport. The import of actin into the nucleus (probably in a complex with cofilin) is facilitated by the import protein importin 9.[84]

Low level of actin in the nucleus seems to be very important, because actin has two nuclear export signals (NES) into its sequence. Microinjected actin is quickly removed from the nucleus to the cytoplasm. Actin is exported at least in two ways, through exportin 1 (EXP1) and exportin 6 (Exp6).[85][86]

Specific modifications, such as SUMOylation, allows for nuclear actin retention. It was demonstrated that a mutation preventing SUMOylation causes rapid export of beta actin from the nucleus.[87]

Based on the experimental results a general mechanism of nuclear actin transport can be proposed:[87][88]

Nuclear actin exists mainly as a monomer, but can also form dynamic oligomers and short polymers.[89][90][91] Nuclear actin organization varies in different cell types. For example, in Xenopus oocytes (with higher nuclear actin level in comparison to somatic cells) actin forms filaments, which stabilize nucleus architecture. These filaments can be observed under the microscope thanks to fluorophore-conjugated phalloidin staining.[81][83]

In somatic cell nucleus however we cannot observe any actin filaments using this technique.[92] The DNase I inhibition assay, so far the only test which allows the quantification of the polymerized actin directly in biological samples, have revealed that endogenous nuclear actin occurs indeed mainly in a monomeric form.[91]

Precisely controlled level of actin in the cell nucleus, lower than in the cytoplasm, prevents the formation of filaments. The polymerization is also reduced by the limited access to actin monomers, which are bound in complexes with ABPs, mainly cofilin.[88]

Little attention is paid to actin isoforms, however it has been shown that different isoforms of actin are present in the cell nucleus. Actin isoforms, despite of their high sequence similarity, have different biochemical properties such as polymerization and depolymerization kinetic.[93] They also shows different localization and functions.

The level of actin isoforms, both in the cytoplasm and the nucleus, may change for example in response to stimulation of cell growth or arrest of proliferation and transcriptional activity.[94]

Research concerns on nuclear actin are usually focused on isoform beta.[95][96][97][98] However the use of antibodies directed against different actin isoforms allows identifying not only the cytoplasmic beta in the cell nucleus, but also:

The presence of different isoforms of actin may have a significant effect on its function in nuclear processes, especially because the level of individual isoforms can be controlled independently.[91]

Functions of actin in the nucleus are associated with its ability to polymerization, interaction with variety of ABPs and with structural elements of the nucleus. Nuclear actin is involved in:

Due to its ability to conformational changes and interaction with many proteins actin acts as a regulator of formation and activity of protein complexes such as transcriptional complex.[105]

In muscle cells, actomyosin myofibrils makeup much of the cytoplasmic material. These myofibrils are made of thin filaments of actin (typically around 7nm in diameter), and thick filaments of the motor-protein myosin (typically around 15nm in diameter).[121] These myofibrils use energy derived from ATP to create movements of cells, such as muscle contraction.[121] Using the hydrolysis of ATP for energy, myosin heads undergo a cycle during which they attach to thin filaments, exert a tension, and then, depending on the load, perform a power stroke that causes the thin filaments to slide past, shortening the muscle.

In contractile bundles, the actin-bundling protein alpha-actinin separates each thin filament by ~35nm. This increase in distance allows thick filaments to fit in between and interact, enabling deformation or contraction. In deformation, one end of myosin is bound to the plasma membrane, while the other end "walks" toward the plus end of the actin filament. This pulls the membrane into a different shape relative to the cell cortex. For contraction, the myosin molecule is usually bound to two separate filaments and both ends simultaneously "walk" toward their filament's plus end, sliding the actin filaments closer to each other. This results in the shortening, or contraction, of the actin bundle (but not the filament). This mechanism is responsible for muscle contraction and cytokinesis, the division of one cell into two.

The helical F-actin filament found in muscles also contains a tropomyosin molecule, a 40-nanometre protein that is wrapped around the F-actin helix. During the resting phase the tropomyosin covers the actins active sites so that the actin-myosin interaction cannot take place and produce muscular contraction (the interaction gives rise to a movement between the two proteins that, because it is repeated many times, produces a contraction). There are other protein molecules bound to the tropomyosin thread, these include the troponins that have three polymers: troponin I, troponin T, and troponin C.[33] Tropomyosins regulatory function depends on its interaction with troponin in the presence of Ca2+ ions.[122]

Both actin and myosin are involved in muscle contraction and relaxation and they make up 90% of muscle protein.[123] The overall process is initiated by an external signal, typically through an action potential stimulating the muscle, which contains specialized cells whose interiors are rich in actin and myosin filaments. The contraction-relaxation cycle comprises the following steps:[72]

The traditional image of actins function relates it to the maintenance of the cytoskeleton and, therefore, the organization and movement of organelles, as well as the determination of a cells shape.[74] However, actin has a wider role in eukaryotic cell physiology, in addition to similar functions in prokaryotes.

The majority of mammals possess six different actin genes. Of these, two code for the cytoskeleton (ACTB and ACTG1) while the other four are involved in skeletal striated muscle (ACTA1), smooth muscle tissue (ACTA2), intestinal muscles (ACTG2) and cardiac muscle (ACTC1). The actin in the cytoskeleton is involved in the pathogenic mechanisms of many infectious agents, including HIV. The vast majority of the mutations that affect actin are point mutations that have a dominant effect, with the exception of six mutations involved in nemaline myopathy. This is because in many cases the mutant of the actin monomer acts as a cap by preventing the elongation of F-actin.[27]

ACTA1 is the gene that codes for the -isoform of actin that is predominant in human skeletal striated muscles, although it is also expressed in heart muscle and in the thyroid gland.[141] Its DNA sequence consists of seven exons that produce five known transcripts.[142] The majority of these consist of point mutations causing substitution of amino acids. The mutations are in many cases associated with a phenotype that determines the severity and the course of the affliction.[27][142]

The mutation alters the structure and function of skeletal muscles producing one of three forms of myopathy: type 3 nemaline myopathy, congenital myopathy with an excess of thin myofilaments (CM) and Congenital myopathy with fibre type disproportion (CMFTD). Mutations have also been found that produce core myopathies).[144] Although their phenotypes are similar, in addition to typical nemaline myopathy some specialists distinguish another type of myopathy called actinic nemaline myopathy. In the former, clumps of actin form instead of the typical rods. It is important to state that a patient can show more than one of these phenotypes in a biopsy.[145] The most common symptoms consist of a typical facial morphology (myopathic faces), muscular weakness, a delay in motor development and respiratory difficulties. The course of the illness, its gravity and the age at which it appears are all variable and overlapping forms of myopathy are also found. A symptom of nemalinic myopathy is that Nemaline rods appear in differing places in Type 1 muscle fibres. These rods are non-pathognomonic structures that have a similar composition to the Z disks found in the sarcomere.[146]

The pathogenesis of this myopathy is very varied. Many mutations occur in the region of actins indentation near to its nucleotide binding sites, while others occur in Domain 2, or in the areas where interaction occurs with associated proteins. This goes some way to explain the great variety of clumps that form in these cases, such as Nemaline or Intranuclear Bodies or Zebra Bodies.[27] Changes in actins folding occur in nemaline myopathy as well as changes in its aggregation and there are also changes in the expression of other associated proteins. In some variants where intranuclear bodies are found the changes in the folding masks the nucleuss protein exportation signal so that the accumulation of actin's mutated form occurs in the cell nucleus.[147] On the other hand, it appears that mutations to ACTA1 that give rise to a CFTDM have a greater effect on sarcomeric function than on its structure.[148] Recent investigations have tried to understand this apparent paradox, which suggests there is no clear correlation between the number of rods and muscular weakness. It appears that some mutations are able to induce a greater apoptosis rate in type II muscular fibres.[36]

There are two isoforms that code for actins in the smooth muscle tissue:

ACTG2 codes for the largest actin isoform, which has nine exons, one of which, the one located at the 5' end, is not translated.[149] It is an -actin that is expressed in the enteric smooth muscle. No mutations to this gene have been found that correspond to pathologies, although microarrays have shown that this protein is more often expressed in cases that are resistant to chemotherapy using cisplatin.[150]

ACTA2 codes for an -actin located in the smooth muscle, and also in vascular smooth muscle. It has been noted that the MYH11 mutation could be responsible for at least 14% of hereditary thoracic aortic aneurisms particularly Type 6. This is because the mutated variant produces an incorrect filamentary assembly and a reduced capacity for vascular smooth muscle contraction. Degradation of the aortic media has been recorded in these individuals, with areas of disorganization and hyperplasia as well as stenosis of the aortas vasa vasorum.[151] The number of afflictions that the gene is implicated in is increasing. It has been related to Moyamoya disease and it seems likely that certain mutations in heterozygosis could confer a predisposition to many vascular pathologies, such as thoracic aortic aneurysm and ischaemic heart disease.[152] The -actin found in smooth muscles is also an interesting marker for evaluating the progress of liver cirrhosis.[153]

The ACTC1 gene codes for the -actin isoform present in heart muscle. It was first sequenced by Hamada and co-workers in 1982, when it was found that it is interrupted by five introns.[154] It was the first of the six genes where alleles were found that were implicated in pathological processes.[155]

A number of structural disorders associated with point mutations of this gene have been described that cause malfunctioning of the heart, such as Type 1R dilated cardiomyopathy and Type 11 hypertrophic cardiomyopathy. Certain defects of the atrial septum have been described recently that could also be related to these mutations.[157][158]

Two cases of dilated cardiomyopathy have been studied involving a substitution of highly conserved amino acids belonging to the protein domains that bind and intersperse with the Z discs. This has led to the theory that the dilation is produced by a defect in the transmission of contractile force in the myocytes.[29][155]

The mutations inACTC1 are responsible for at least 5% of hypertrophic cardiomyopathies.[159] The existence of a number of point mutations have also been found:[160]

Pathogenesis appears to involve a compensatory mechanism: the mutated proteins act like toxins with a dominant effect, decreasing the hearts ability to contract causing abnormal mechanical behaviour such that the hypertrophy, that is usually delayed, is a consequence of the cardiac muscles normal response to stress.[161]

Recent studies have discovered ACTC1 mutations that are implicated in two other pathological processes: Infantile idiopathic restrictive cardiomyopathy,[162] and noncompaction of the left ventricular myocardium.[163]

ACTB is a highly complex locus. A number of pseudogenes exist that are distributed throughout the genome, and its sequence contains six exons that can give rise to up to 21 different transcriptions by alternative splicing, which are known as the -actins. Consistent with this complexity, its products are also found in a number of locations and they form part of a wide variety of processes (cytoskeleton, NuA4 histone-acyltransferase complex, cell nucleus) and in addition they are associated with the mechanisms of a great number of pathological processes (carcinomas, juvenile dystonia, infection mechanisms, nervous system malformations and tumour invasion, among others).[164] A new form of actin has been discovered, kappa actin, which appears to substitute for -actin in processes relating to tumours.[165]

Three pathological processes have so far been discovered that are caused by a direct alteration in gene sequence:

The ACTG1 locus codes for the cytosolic -actin protein that is responsible for the formation of cytoskeletal microfilaments. It contains six exons, giving rise to 22 different mRNAs, which produce four complete isoforms whose form of expression is probably dependent on the type of tissue they are found in. It also has two different DNA promoters.[170] It has been noted that the sequences translated from this locus and from that of -actin are very similar to the predicted ones, suggesting a common ancestral sequence that suffered duplication and genetic conversion.[171]

In terms of pathology, it has been associated with processes such as amyloidosis, retinitis pigmentosa, infection mechanisms, kidney diseases and various types of congenital hearing loss.[170]

Six autosomal-dominant point mutations in the sequence have been found to cause various types of hearing loss, particularly sensorineural hearing loss linked to the DFNA 20/26 locus. It seems that they affect the stereocilia of the ciliated cells present in the inner ears Organ of Corti. -actin is the most abundant protein found in human tissue, but it is not very abundant in ciliated cells, which explains the location of the pathology. On the other hand, it appears that the majority of these mutations affect the areas involved in linking with other proteins, particularly actomyosin.[27] Some experiments have suggested that the pathological mechanism for this type of hearing loss relates to the F-actin in the mutations being more sensitive to cofilin than normal.[172]

However, although there is no record of any case, it is known that -actin is also expressed in skeletal muscles, and although it is present in small quantities, model organisms have shown that its absence can give rise to myopathies.[173]

Some infectious agents use actin, especially cytoplasmic actin, in their life cycle. Two basic forms are present in bacteria:

In addition to the previously cited example, actin polymerization is stimulated in the initial steps of the internalization of some viruses, notably HIV, by, for example, inactivating the cofilin complex.[178]

The role that actin plays in the invasion process of cancer cells has still not been determined.[179]

The eukaryotic cytoskeleton of organisms among all taxonomic groups have similar components to actin and tubulin. For example, the protein that is coded by the ACTG2 gene in humans is completely equivalent to the homologues present in rats and mice, even though at a nucleotide level the similarity decreases to 92%.[149] However, there are major differences with the equivalents in prokaryotes (FtsZ and MreB), where the similarity between nucleotide sequences is between 4050% among different bacteria and archaea species. Some authors suggest that the ancestral protein that gave rise to the model eukaryotic actin resembles the proteins present in modern bacterial cytoskeletons.[4][180]

Some authors point out that the behaviour of actin, tubulin and histone, a protein involved in the stabilization and regulation of DNA, are similar in their ability to bind nucleotides and in their ability of take advantage of Brownian motion. It has also been suggested that they all have a common ancestor.[181] Therefore, evolutionary processes resulted in the diversification of ancestral proteins into the varieties present today, conserving, among others, actins as efficient molecules that were able to tackle essential ancestral biological processes, such as endocytosis.[182]

See more here:
Actin - Wikipedia

Skin Stem Cells Comments Off on Actin – Wikipedia | January 23rd, 2017

The primary focus of the Disabled World web site is to provide up to date information via our informative articles, disability news and educational videos. In addition to stories by our in-house writers and news items by disability organizations and Government Departments, each day we manually select relevant items that we consider will be of interest to persons with disabilities, carers, and the general public. Submission of disability related information, press releases and events are welcome.

The word "disabled" is defined as having a physical or mental disability : unable to perform one or more natural activities (such as walking or seeing) because of illness, injury, etc.

The word disabled came to be used as the standard term in referring to people with physical or mental disabilities in the second half of the 20th century - and it remains the most generally accepted term in both British and US English. Lately, "Disability" and "Disabled" are terms that are undergoing change due to the disability rights movement in the U.S. and U.K. - Disability or Disabled - Which Term is Right?

"People with disabilities are the largest minority group, the only one any person can join at any time."

Disability is a subject you may read about online, or in a newspaper, but not think of as something that might actually happen to you. But your chances of becoming disabled are greater than you realize. Today more people live with a disability than ever before due to our aging societies as well as improved medical treatments helping manage long-term health problems.

Some people are born with a disability, others become disabled as a result of an illness or injury, and some people develop them as they age. At some point in our lives almost all of us will have some type of disability.

More World Disability Facts & Statistics

One of the key challenges for a person with a disability is to be seen by the public, to be portrayed in media outlets, and treated by health care professionals, as an individual with their own abilities, not just stereotyped as a "disabled person".

More Disability & Health News

Visit link:
Disabled World - Disability News & Information

Spinal Cord Stem Cells Comments Off on Disabled World – Disability News & Information | January 19th, 2017