A team of scientists has successfully repaired the broken bones of lab animals without invasive surgery, by using microbubbles and ultrasound to stimulate the growth of stem cells.

In a study published in the journal Science Translational Medicine on Wednesday, Maxim Bez and a team of Cedars Sinai-led scientists were able to facilitate the natural growth of stem cells to create more bone marrow in broken bones that cannot heal on their own, known as nonunion fractures.

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While certain bone injuries only require a few weeks in a cast to heal, more severe injuries can cause large gaps between the edges of a fracture that cannot be healed without invasive surgery or bone grafting.

There are currently two methods for bone grafting, either using autografts that transfer bone marrow from a different part of the patients own body, or allografts that use donated bone marrow from another patient. Artificial transplants are often rejected by the body, making another bone graft necessary.

There are more than 2 million bone grafting procedures performed around the world each year, with roughly 100,000 cases in the US alone.

Nonunion bone fractures can cause great damage to the body, leaving patients crippled or with other severe complications.

In a first of its kind study, Bez and his team developed an alternative that uses microbubbles and ultrasound to facilitate the bodys natural stem-cell growth.

"This study is the first to demonstrate that ultrasound-mediated gene delivery to an animal's own stem cells can effectively be used to treat nonhealing bone fractures," said Gadi Pelled, assistant professor of surgery at Cedars-Sinai and co-author of the study, according to Medical XPress. "It addresses a major orthopedic unmet need and offers new possibilities for clinical translation."

In the study, Bez and his team first created severe bone fractures the tibiae bones of large pigs. Then, they inserted a biodegradable collagen scaffold in the fracture, which supported stem cell growth. Two weeks later, after the stem cells grew around the scaffold, the scientists injected microbubbles containing growth-promoting genes. Finally, they used an ultrasound pulse, which causes the stems cells to become bone cells, healing the fracture.

The technique was able to completely heal nonunion fractures in eight weeks. Bez and his team found their method healed bones to the point that they were just as strong as those treated with bone grafts.

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The technique is minimally invasive and does not have the side effects associated with bone grafts. If the method is found to be safe for humans, it would provide patients with an alternative to replace bone grafting.

Bez and his team say that their method could potentially be used in tissue engineering applications in the future.

"We are just at the beginning of a revolution in orthopedics," said Dan Gazit, co-director of the Skeletal Regeneration and Stem Cell Therapy Program in the Department of Surgery and the Cedars-Sinai Board of Governors Regenerative Medicine Institute and co-author of the study, according to Medical XPress. "We're combining an engineering approach with a biological approach to advance regenerative engineering, which we believe is the future of medicine."

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'Future of medicine': Broken pig bones healed using tiny bubbles & ultrasound - RT