MICHELE NORRIS, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

ANDREA SEABROOK, host:

And I'm Andrea Seabrook.

Scientists may have found a way to help Fuzzy Wuzzy. You remember poor Fuzzy Wuzzy's plight. Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair. Fuzzy Wuzzy wasn't fuzzy, was he?

NORRIS: So far, researchers have only established that they can encourage new hair growth in mice. But they're hoping something similar could be done with bears, and even humans.

NPR's Joe Palca has that story.

JOE PALCA: First, a bit of hair dogma. Hair comes from a complex mini-organ in the skin called a hair follicle. And according to traditional thinking, new hair follicles only form in junior mammals. Once you're an adult, and you lose some hair follicles, you're out of luck in the hair department.

Now it's a funny thing about dogma, it tends to color the way you look at the world. Jonathan Vogel is a dermatologist at the National Institutes of Health. He says scientists who study how wounds heal relied on dogma to explain something they always see.

Dr. JONATHAN VOGEL (Dermatologist, National Institutes of Health): We know when we make wounds in mice that eventually that area is replaced with hair. And it's not like the mice typically go around with large patches of skin without hair. But I guess we assumed that that was not new hair, it was just the areas that previously had hair kind of migrated in as the wound healed.

PALCA: But as George Cotsarelis reports in the current issue of the journal Nature, that explanation appears to be wrong. Cotsarelis is a stem-cell biologist at the University of Pennsylvania. He, too, noticed that hair appeared in a wounded area. But he also knew from his stem-cell work that hair follicles typically come from something called a bulge stem cell. And the hair forming after wounds was not coming from bulge stem cells. Something else was happening.

Dr. GEORGE COTSARELIS (Stem-cell Biologist, University of Pennsylvania): It really tells us that the skin is sort of reprogramming cells that normally don't make hair follicles to make hair follicles.

PALCA: In other words, not only were these hair follicles new, they were forming in a totally new way.

Now, you might think it a bit surprising that scientists had overlooked the fact that these new hair follicles were forming in response to a wound.

Dr. CHENG-MING CHUONG (Pathologist, University of Southern California): Fifty years ago, some doctors did observe this in the rabbit as well as in the human.

PALCA: Cheng-Ming Chuong is a pathologist at the University of Southern California.

But even 50 years ago, dogma was so strong that they dismissed the results.

But Chuong says there's another factor. In order to see the new hair, Cotsarelis had to make a fairly large wound and leave it open. The new hair didn't grow when the wound was smaller. Chuong says that may explain why doctors don't see new hair growing in patients with large wounds.

Dr. CHUONG: People would try to get the wound to close, as fast as you can. So that in a way, make the condition not ideal for hair regeneration.

PALCA: So you have to keep the wound open long enough for these hair follicles to appear.

Dr. CHUOUNG: Exactly. You got that right.

PALCA: So the bad news for Fuzzy Wuzzy the bear and his human counterparts who might like to grow a little hair is that for the moment, at least, a substantial wound appears to be necessary. But the good news, says George Cotsarelis, is that it may be possible to figure out how to switch on this molecular pathway that triggers hair growth without inflicting an injury.

And there's an even more promising outcome.

Dr. COTSARELIS: If you look at the molecular pathways during hair follicle development, many of them overlap with limb development.

PALCA: So maybe one day, in addition to new hair, people could grow new fingers or arms.

Dr. COTSARELIS: That's a kind of a really pie in the sky, but, you know, you never know where these advances come from, and that we're always thinking about things like that.

PALCA: After all, dogma says growing new limbs is impossible too.

Joe Palca, NPR News, Washington.

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