Hair-Raising Mice Point to Cure for Baldness

Few things strike fear into the human heart like a receding hairline, but a path-breaking study released Wednesday points for the first time to a genetically-based remedy for hair loss.

In experiments on mice, scientists at the University of Pennsylvania 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.

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 in the British 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.

The lead author of the study, dermatologist George Cotsarelis, is also cofounder of a company, Follica, that has licensed technology to develop hair-restoration treatments.

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.

In the experiments on mice, the researchers found that the removal of a patch of outer skin, called epidermis, 1-2.5 centimeters 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 neighboring 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,” he said, while cautioning that human and mouse skin heal differently.

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 labeled before the wounds were inflicted so that they could be traced.

Wounding activated the signaling pathway of a gene, called Wnt, which is essential for normal hair development. When the scientists inhibited 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,” the researchers concluded.

Chuong sees even broader implications of the study. “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.”

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