Androgenetic alopecia (AGA) is a frequent form of hair loss in both men and women. However, it is more common in men, in whom it is also known as male-pattern baldness. Through the analysis of bald and non-bald scalp samples from men with AGA, a team of researchers, led by George Cotsarelis, at the University of Pennsylvania School of Medicine, Philadelphia, has gained new insight into the underlying causes of AGA. Specifically, the data indicate that a defect in the conversion of hair follicle stem cells to progenitor cells has an important role in AGA. The authors therefore suggest that further studies defining the signals responsible for the transition of stem cells to progenitor cells could provide new therapeutic targets for the treatment of AGA.

TITLE: Bald scalp in men with androgenetic alopecia retains hair follicle stem cells but lacks CD200-rich and CD34-positive hair follicle progenitor cells

Source: Journal of Clinical Investigation

Bald scalp in men with androgenetic alopecia retains hair follicle stem cells but lacks CD200-rich and CD34-positive hair follicle progenitor cells

U.S. study found that stem cell deficiency may lead to a major cause of hair loss. This discovery will help scientists find a new method of treating hair loss.

Researchers at the University of Pennsylvania in the new issue of the U.S. “Journal of clinical examination,” the report said defects in hair follicle stem cells to hair growth makes it impossible to produce the source of cells, leading to hair loss. For men, a phenomenon known as male baldness, the symptoms started out as a head of hair, the hairline back, eventually leading to alopecia totalis; for women, the symptoms of hair is getting thin, but rarely cause alopecia to talis.

The researchers analyzed 54 men aged 40 to 65 years in the hair and scalp tissue was found, whether or not hair loss, hair loss, scalp tissue, the number of hair follicle stem cells are the same, the difference is, hair loss and scalp tissue The hair follicle stem cells did not produce the source of cells for hair growth, suggesting that the defect of hair follicle stem cells, so that the scalp can not grow hair.

Fix Qiaozhi Ke led the study, said Liss, previous studies that lead to hair loss because hair follicle stem cells no longer exists, but the latest study found that hair follicle stem cells are still only appeared flawed.

In other new research, the kinds of stem cells in question are the adult variety, not the more versatile embryonic stem cells that have stirred controversy.

Still, many scientists think these adult cells are a promising area of study, holding the potential to regenerate certain organs or heal wounds without scars. And what better laboratory to study them than the scalp, where hair stem cells are accessible and plentiful?

"Many of us think we can gain clues about how to regenerate other organs by understanding how to regenerate the hair," says Stanford University dermatologist Anthony Oro.

Oro, who was not involved with the new research, said it provided "one additional step along the way to better understanding the disease" of male baldness.

Andrzej Dlugosz, a University of Michigan dermatologist who also was not involved with the study, said it was promising but cautioned "there is no guarantee that the stem cells in this setting would still be responsive to stimuli that effectively activate normal follicle stem cells."

Luis A. Garza, the paper's lead author, agreed that more work was needed, adding that for some, the wait would be hard. Eager for treatment, bald people have been known to scour patent websites for promising treatments before coming in to Penn for an appointment, Garza said.

"It's a big part of people's self-image," said Garza, who is now at Johns Hopkins University. "It's a big part of who people think they are."

For the new study, Garza, Cotsarelis, and colleagues studied scalp samples left over from men who underwent hair transplants. Bald scalp was found to have just as many stem cells as scalp with hair.

Where the scalp samples differed, however, was in their levels of two other kinds of so-called progenitor cells that appear to be descendants of follicle stem cells. Samples of bald scalp contained one-tenth as many of these progenitor cells, on average, when compared to "haired" scalp.

Progenitor cells are created by the division of stem cells; the progenitors then divide further to produce hair and other kinds of cells. So in bald men, stem cells seem to have slowed way down in the process of dividing to form progenitor cells, and the answer may be simply to reactivate this process, the researchers wrote.

To further test their theory, the scientists transplanted progenitor cells from one mouse to another, where the cells led to the creation of new hair follicles. This experiment could not be done in people because such donor cells would be rejected; the mice that received donated cells were immunodeficient.

Cotsarelis said he now wants to determine the chemical signal that tells stem cells to divide into progenitors, in hopes that someday such an agent could be put in a product and applied to the scalp. He also plans to look for the chemical signals that drive hair loss in women, which are likely to be different.

Instead of a topical treatment, another possible solution for baldness would be to remove some of a person's hair-generating cells, grow them outside the body, and reimplant them, the authors said.

Yet if some other deficiency is also to blame for hair loss, then replenishing the depleted supply of hair-generating cells might not be enough, Garza said.