Scientists find way to grow hair in mice

PHILADELPHIA – Unlike salamanders, humans and other mammals are generally thought to be incapable of true regeneration – growing a new organ or limb when it has been lost entirely.

But Wednesday, University of Pennsylvania dermatologists announced they had indeed performed this feat of biological renewal, regrowing complex “mini-organs” that are of pressing interest to millions of older men: the follicles that produce hair.

The researchers, who published their findings today in the journal Nature, said that by carefully cutting out patches of skin in mice, they awakened a genetic pathway that normally remains dormant after embryonic development.

The shallow wounds stimulated new hair growth even though the follicles had been removed; the process worked especially well when researchers artificially boosted levels of a special signaling protein, said senior author George Cotsarelis.

They have not yet experimented on people, but already the wheels of commerce are churning: A startup company has licensed a patent based on the research. And the findings are of interest beyond the multibillion-dollar hair-loss industry, perhaps pointing to how doctors could do a better job healing burns and other wounds.

Bruce Morgan, an associate professor of dermatology at Harvard Medical School who was not involved with the research, called it “striking.”

The authors “reprogrammed the cells to regenerate those organs from scratch,” Morgan said.

Cotsarelis holds a stake in the startup company, aptly named Follica Inc., and is listed on the patent application with lead author and post-doctoral fellow Mayumi Ito.

Why has this phenomenon not been widely recognized before now?

In a review accompanying today’s report in Nature, the University of Southern California’s Cheng-Ming Chuong offers a possible reason: Generating new follicles may require fairly large wounds, which in people are normally sutured or bandaged, perhaps impeding hair regrowth.

Cotsarelis urged people not to try this on themselves. Without the application of some substance formulated to boost the special protein pathway, he said, hair growth likely would not be robust.

“I’m kind of afraid of people misinterpreting this and incising the scalp,” said Cotsarelis, an associate professor at Penn’s School of Medicine. “Don’t try this at home.”

The cosmetics industry has been doing a robust business in transplanting hair follicles for years. Some companies, including one for which Cotsarelis is a board member, have begun trials that involve injecting cells to stimulate hair growth.

But the new approach – seemingly reconditioning skin cells to develop hair, much as they did in infancy – may one day make the most sense, said Harvard’s Morgan.

“Far more desirable in the end would be to let them do what they know how to do in the first place,” he said.