New stem cell method shows potential in every cell

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - James Thomson knew it the moment he learned that a sheep named Dolly had been cloned from an adult sheep in 1996 -- the process of cloning can re-program a cell, allowing it to be transformed into any other cell.

Two years later, Thomson became the first to isolate and grow human embryonic stem cells, the body's ultimate master cells. And on Tuesday, he led one of two teams that figured out how to transform ordinary cells into valued stem cells without using cloning technology or a human embryo.

"Dolly shows that, theoretically, any cell in your body can form a human being," Thomson, a cell biologist at the University of Wisconsin in Madison, told reporters in a telephone interview.

This is because inside the nucleus, every cell in the body has all the instructions to make any other cell, or a complete organism.

Scientists have been struggling to learn why, if all the DNA is there, a damaged heart cell cannot simply regenerate itself in the way a salamander can grow new limbs and lizards can sprout new tails.

Cloning offered a way to understand this. By scraping the nucleus out of an egg cell and replacing it with the nucleus from another cell, the egg could be programmed to start dividing as if it had been fertilized by sperm.

Dolly's birth, announced in 1997, sparked both wonder and revulsion. When scientists began trying to use this "somatic cell nuclear transfer" method in people, some politicians raced to block it.

But scientists wanted to understand what was going on inside these cells.