Bald no longer. Wound healing pathways have given dermatologists clues to curing baldness.

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PARIS: Few things strike fear into the human heart like a receding hairline. Now researchers may have hit on a gene-therapy remedy for hair loss.

The finding might also lead to regenerative treatments for healing wounds, say experts.

In experiments on mice, scientists at the University of Pennsylvania in the U.S. showed that the skin of wounded animals can naturally regenerate the follicles from which individual hairs grow.

They also identified a gene that is essential for normal hair development, and were able to stimulate or stop hair growth by boosting or inhibiting the protein's activity at a molecular level, opening the way to non-invasive therapies.

Stunned scientists

The results have stunned many scientists, who have long assumed that mammalian hair follicles were a non-renewable resource. The human head comes equipped with approximately 100,000 of these tiny, hair-generating organs, and once they stop working, it was thought, the scalp was doomed to gradual exposure.

The study, published today in the U.K. journal Nature, is all the more surprising because it reproduces results observed 50 years ago in rabbits, mice and humans that were widely dismissed at the time and have been ignored ever since.

Creeping baldness is a source of distress to millions of people all over the world. Hair-challenged adults spend upward of a billion dollars every year on mostly bogus remedies in the United States alone, according to the Federal Drug Administration. They also lavish at least as much on sometimes painful hair implants and other forms of more or less convincing hair substitutes.

Lead author of the new study, dermatologist George Cotsarelis, is also co-founder of a spin-off company, Follica, that has licensed technology to develop hair-restoration treatments.

"Stem cells awakened"

In the experiments on mice, his team found that the removal of a patch of the outer skin layer – the epidermis – one to two and a half centimetres in diameter "awakened stems cells" with the capacity to generate new hair follicles. Once the healing was complete, the skin returned to its normal adult form.

"The new hair follicles grew, passed through the hair cycle, and eventually became indistinguishable from neighbouring hair," explained Cheng-Ming Chuong, a pathologist at the University of Southern California, in a commentary, also published in Nature.

"These unexpected findings could change our current understanding of repair and regeneration in adult mammals," said Chuong, not one of the study authors. But he also cautions that human and mouse skin heal differently.

This finding "provides convincing evidence that the skin has remarkable powers of regeneration, not just repair as previously known. It was long thought that hair follicle development, under physiological conditions, was limited to early developmental process in the embryo," commented cell biologist Desmond Tobin of the University of Bradford in England.

"Now [we know] that under the conditions peculiar to the wound-healing environment, the highly complex hair follicle can be created anew from apparently unremarkable cells of the healing epidermis and its underlying dermis," he said.

Regenerative medicine

To find out what was happening at a molecular level during the process, Cotsarelis and his team used mice in which the bulge cells that generate hair were genetically-labelled before the wounds were inflicted so that they could be traced.

Wounding activated the signalling pathway of a gene, called Wnt, which is essential for normal hair development. When the scientists inhibiting this pathway, it led to a substantial decrease in the number of new hairs.

But in mice whose Wnt activity had been artificially boosted, there was a "significant increase" in new hair follicles compared to normal mice, the study showed.

"This provides a window for manipulation of hair follicle neogenesis ... and treatments for wounds, hair loss and other degenerative diseases," wrote the researchers.

Chuong sees even broader implications of the study though. "Regenerative medicine promises to identify natural healing powers and a shift from repair to regeneration," he wrote. "By simply altering the environment of stem cells during wound healing, future wounds might heal with appendages reformed."