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UPDATE 3-UK, Japan scientists win Nobel for stem cell breakthroughs

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* 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 harvest 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 field of curing disease by regrowing 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's tissue starts as stem cells, beforedeveloping into skin, blood, nerves, muscle and bone. The bighope for stem cells is that they can be used to replace damagedtissue in everything from spinal cord injuries to Parkinson'sdisease.

Scientists once thought it was impossible to turn adulttissue back into stem cells, which meant that new stem cellscould only be created by harvesting embryos - a practice thatraised ethical qualms in some countries and also means thatimplanted cells might be rejected by the body.

In 1958, Gurdon was the first scientist to clone an animal,producing a healthy tadpole from the egg of a frog with DNA fromanother tadpole's intestinal cell. That showed developed cellsstill carry the information needed to make every cell in thebody, decades before other scientists made headlines around theworld by cloning the first mammal, Dolly the sheep.

More than 40 years later, Yamanaka produced mouse stem cellsfrom adult mouse skin cells, by inserting a few genes. Hisbreakthrough effectively showed that the development that takesplace in adult tissue could be reversed, turning adult cellsback into cells that behave like embryos. The new stem cells areknown as "induced pluripotency stem cells", or iPS cells.

"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."

The science is still in its early stages, and amongimportant concerns is the fear that iPS cells could grow out ofcontrol and develop into tumours.

Nevertheless, in the six years since Yamanaka published hisfindings the discoveries have already produced dramatic advancesin medical research, with none of the political and ethicalissues raised by embryo harvesting.

"NOT A ONE-WAY STREET"

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."

The techniques are already being used to grow specialisedcells in laboratories to study disease, the chairman of theawards 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."

Yamanaka's paper has already been cited more than 4,000times in other scientists' work. He has compared research torunning marathons, and ran one in just over four hours in Marchto raise money for his lab.

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 has spoken of an unlikely career for a young man wholoved science but was steered away from it at school. He stillkeeps a discouraging school report on his office wall.

"I believe he has ideas about becoming a scientist... Thisis quite ridiculous," his teacher wrote. "It would be a sheerwaste of time, both on his part and of those who have to teachhim." The young John "will not listen, but will insist on doinghis work in his own way."

(Reporting by Patrick Lannin, Alistair Scrutton, Ben Hirschler,Kate Helland, Kiyoshi Takenaka, Chris Wickham and Peter Graff;writing by Peter Graff; editing by Philippa Fletcher)

((peter.graff@thomsonreuters.com))

Keywords: NOBEL MEDICINE/