(Adds quote from Gurdon)
* Scientists find adult cells can turn back into stem cells * Stem cells turn into any tissue, may help repair injury * No need to harvest embryos, less risk of rejection By Anna Ringstrom
STOCKHOLM, Oct 8 (Reuters) - Scientists from Britain andJapan shared a Nobel Prize on Monday for the discovery thatadult cells can be transformed back into embryo-like stem cellsthat may one day regrow tissue in damaged brains, hearts orother 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 embryoniccells, without the need to collect the cells from embryos.
They share the $1.2 million Nobel Prize for Medicine, forwork Gurdon began 50 years ago and Yamanaka capped with a 2006experiment that transformed the field of "regenerative medicine"- the search for ways to cure disease by growing healthy tissue.
"These groundbreaking discoveries have completely changedour view of the development and specialisation of cells," theNobel Assembly at Stockholm's Karolinska Institute said.
All of the body starts as stem cells, before developing intotissue like skin, blood, nerves, muscle and bone. The big hopeis that stem cells can grow to replace damaged tissue in casesfrom spinal cord injuries to Parkinson's disease.
Scientists once thought it was impossible to turn adulttissue back into stem cells. That meant new stem cells couldonly be created by taking them from embryos, which raisedethical objections that led to research bans in some countries.
As far back as 1962 Gurdon became the first scientist toclone an animal, making a healthy tadpole from the egg of a frogwith DNA from another tadpole's intestinal cell. That showedthat developed cells carry the information to make every cell inthe body - decades before other scientists made world headlinesby cloning the first mammal from adult DNA, Dolly the sheep.
More than 40 years later, Yamanaka produced mouse stem cellsfrom adult mouse skin cells by inserting a small number ofgenes. His breakthrough effectively showed that the developmentthat takes place in adult tissue could be reversed, turningadult tissue back into cells that behave like embryos.
Stem cells created from adult tissue are known as "inducedpluripotency stem cells", or iPS cells. Because patients may oneday be treated with stem cells from their own tissue, theirbodies might be less likely to reject them.
"The eventual aim is to provide replacement cells of allkinds," Gurdon's institute explains on its website.
"We would like to be able to find a way of obtaining spareheart or brain cells from skin or blood cells. The importantpoint is that the replacement cells need to be from the sameindividual, to avoid problems of rejection and hence of the needfor immunosuppression."
In just six years, Yamanaka's paper has already been citedmore than 4,000 times in other scientists' work.
In a news conference in Japan, he thanked his team of youngresearchers: "My joy is very great. But I feel a grave sense ofresponsibility as well."
Gurdon spoke of his own unlikely career as a young man wholoved science but was steered away from it at school, only totake it up again at university.
He still keeps an old school report in a frame on his desk:"I believe he has ideas about becoming a scientist... This isquite ridiculous," his teacher wrote. "It would be a sheer wasteof time, both on his part and of those who have to teach him."
The science of iPS cells is still in early stages. Amongconcerns is the fear that implanted cells could grow out ofcontrol and develop into tumours.
Some scientists say stem cells from embryos may prove moreuseful against disease than iPS cells, and the ethics of workingwith embryos should be defended.
Nevertheless, since Yamanaka published his findings thediscoveries have already produced advances. The techniques arebeing used to grow cells in laboratories to study disease, thechairman of the awards committee, Urban Lendahl, told Reuters.
"You can't take out a large part of the heart or the brainor so to study this, but now you can take a cell from, forexample, the skin of the patient, reprogramme it, return it to apluripotent state, and then grow it in a laboratory," he said.
"The second thing is for further ahead. If you can growdifferent cell types from a cell from a human, you might - intheory for now but in future hopefully - be able to return cellswhere cells have been lost."
Thomas Perlmann, Nobel Committee member and professor ofMolecular Development Biology at the Karolinska Institute said:
"Thanks to these two scientists, we know now that developmentis not strictly a one-way street."
"There is lot of promise and excitement, and difficultdisorders such as neurodegenerative disorders, like perhapsAlzheimer's and, more likely, Parkinson's disease, are veryinteresting targets."
For now, both men said their scientific work continues.
Asked why he still keeps his schoolteacher's discouragingreport, Gurdon said: "When you're having problems, like when anexperiment doesn't work - which often happens - it's nice toremind yourself that perhaps after all you're not so good atthis job and the schoolmaster may have been right."
(Reporting by Patrick Lannin, Alistair Scrutton, Ben Hirschler,Kate Kelland, Kiyoshi Takenaka, Chris Wickham and Peter Graff;writing by Peter Graff; editing by Philippa Fletcher)
Keywords: NOBEL MEDICINE/