STOCKHOLM (Reuters) - Scientists from Britain and Japan shared a Nobel Prize on Monday for the discovery that adult cells can be transformed back into embryo-like stem cells that may one day regrow tissue in damaged brains, hearts or other organs.

John Gurdon, 79, of the Gurdon Institute in Cambridge, Britain and Shinya Yamanaka, 50, of Kyoto University in Japan, discovered ways to create tissue that would act like embryonic cells, without the need to collect the cells from embryos.

They share the $1.2 million Nobel Prize for Medicine, for work Gurdon began 50 years ago and Yamanaka capped with a 2006 experiment that transformed the field of "regenerative medicine" - the search for ways to cure disease by growing healthy tissue.

"These groundbreaking discoveries have completely changed our view of the development and specialisation of cells," the Nobel Assembly at Stockholm's Karolinska Institute said.

All of the body starts as stem cells, before developing into tissue like skin, blood, nerves, muscle and bone. The big hope is that stem cells can grow to replace damaged tissue in cases from spinal cord injuries to Parkinson's disease.

Scientists once thought it was impossible to turn adult tissue back into stem cells. That meant new stem cells could only be created by taking them from embryos, which raised ethical objections that led to research bans in some countries.

As far back as 1962 Gurdon became the first scientist to clone an animal, making a healthy tadpole from the egg of a frog with DNA from another tadpole's intestinal cell. That showed that developed cells carry the information to make every cell in the body - decades before other scientists made world headlines by cloning the first mammal from adult DNA, Dolly the sheep.

More than 40 years later, Yamanaka produced mouse stem cells from adult mouse skin cells by inserting a small number of genes. His breakthrough effectively showed that the development that takes place in adult tissue could be reversed, turning adult tissue back into cells that behave like embryos.

Stem cells created from adult tissue are known as "induced pluripotency stem cells", or iPS cells. Because patients may one day be treated with stem cells from their own tissue, their bodies might be less likely to reject them.

"The eventual aim is to provide replacement cells of all kinds," Gurdon's institute explains on its website.

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UK, Japan scientists win Nobel for adult stem cell discovery