"This is what I've been shooting for over 14 years now," says George Cotsarelis of the University of Pennsylvania School of Medicine in Philadelphia. "I'm just in nirvana ."

Cotsarelis' team relied on genetic tricks to mark the stem cells, which allowed the cells to be purified and also for the researchers to catalogue their patterns of gene activation. Earlier in 2004, Elaine Fuchs' group at the Rockefeller University in New York City independently reported a different strategy to label the cells and probe their genetic secrets.

"Here you have two very talented groups taking different approaches and coming to similar conclusions," says Anthony Oro, a dermatology researcher at Stanford University in California. "That changes the field and gives us a lot of confidence in these results."

The project marks the first time that ``blank slate'' stem cells were able to induce hair growth, said Dr. George Cotsarelis, a University of Pennsylvania dermatologist and co-author of the study. The study was released Sunday on the Web site of the journal Nature Technology in advance of its April publication date.

``We've shown for the first time these cells have the ability to generate hair when taken from one animal and put into another,'' Cotsarelis said in a telephone interview. ``You can envision a process of isolating existing stem cells and re-implanting them in the areas where guys are bald.''

The study confirms what scientists suspected for years: hair follicles contain ``blank slate'' stem cells that give most humans a full head of hair for life.

Although they are called stem cells, they differ from embryonic stem cells, the research on which has sparked a political debate because embryos are destroyed in the process. Embryonic stem cells are created in the first days after conception and give rise to the human body and its more than 200 different types of cells.

Probing the bulge

For years, biologists knew that the cells that give rise to hair and can heal skin wounds lying in an area of the follicle known as the bulge. But no one had devised a way to separate the cells from the surrounding tissue to characterise them further.

The two teams used different genetic tricks to mark the bulge stem cells by getting them to produce a green fluorescent protein (GFP) that the surrounding cells did not have. Standard cell sorting machines were then able to separate out the glowing cells from the others.

Cotsarelis and his colleagues then transplanted some of the cells onto new mice and showed that they produced hair and all its associated structures: follicles, epidermis and sebaceous glands.

After purifying a sufficient amount of these cells, both groups used gene chips to find which genes were switched on in the stem cells. For the first time, this provides a signature that researchers can use to identify the same cells in humans.

Tiny colorless hairs

It also suggests many new genes that might control hair production. Male pattern baldnesses, for example, results when follicles start producing tiny, colourless hairs that are nearly invisible. But the underlying cause for this switch from thick to thin hair production is not known. Cotsarelis says that with these cells in hand, it might eventually be possible to screen for drugs that will reverse this balding process.

Oro says the work could also yield insights into other diseases. These same stem cells are the suspected targets of the ultraviolet damage that triggers common forms of skin cancer. "We've known where these cells are for a while, but now we finally have the prospect of getting our hands on a lot of them," he says.

Biologists who study hair because of its regenerative qualities said the new study is an important breakthrough. But they cautioned that a baldness cure is still some years away. ``Like with any stem cells, the amount of information needed to get us from a stem to a fully developed organ is a lot,'' said Stanford University biologist Anthony Oro. ``It will require a lot of things to go right and we are still along way off.''

Two drugs now on the market, known commercially as Rogaine and Propecia, were first designed to treat hypertension and enlarged prostates but later were discovered to have hair growth as a side effect. Each drug has about $100 million in sales annually.

It's estimated that more than $1 billion is spent each year in the United States combatting baldness, mostly through hair transplants.

Journal references: Cotsarelis paper, Nature Biotechnology (DOI: 10.1038/nbt950); Fuchs paper, Science, (vol 303, p 359)

HLT