Scalp Stem Cell Deactivation May Be Cause of Male Pattern Baldness


Balding can cause a tremendous amount of anxiety for both men and women. Current treatments available may help to maintain the hair already present on the scalp, but aren’t effective in re-growing hair. Researchers from the University of Pennsylvania may have found a cause of male pattern baldness that may someday lead to treatments to reverse hair loss.

Stem Cells Do Not Mature Into Progenitor Cells in Androgenetic Alopecia

Dr. George Cotsarelis, professor of dermatology at the University’s School of Medicine, and colleagues have discovered a cellular malfunction that may be a reason why hair-producing progenitor cells cause hair loss. The team compared the scalps of 54 while males, aged 40 to 65, some of which had androgenetic alopecia, the clinical name for male-pattern baldness.

Scalp cells were tagged with a marker to distinguish the different types - stem cells or progenitor cells – so that the researchers could count the number of each.

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Stem cells are naïve cells that can go on to become other cells, such as progenitor cells that become hair follicles. In men who are bald, the hair follicles have shrunken and become microscopic. So scientists have long thought that bald people may have a depletion of hair follicle stem cells. But this didn’t turn out to be true.


Men with bald scalps have the same number of stem cells on their heads as men with hair, however those experiencing hair loss had fewer progenitor cells, meaning the naïve cells had been somehow blocked or deactivated prior to becoming mature.

The question now is “once you find something is deactivated, the target there in terms of therapy is, can you turn it on,” says CBS News Medical Correspondent Dr. Jennifer Ashton.

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Dr. Cotsarelis suggests that if they could coax the stem cells into producing more progenitor cells, then it would be possible to generate bigger hair follicles that could grow hair. “It’s not impossible. It gives you hope,” he says.

But the cure won’t come for several years, if not decades, warns Dr. Cotsarelis. “There’s no treatment around the corner. It’s really going to take quite a while to figure this out.”

Currently, Rogaine and Propecia are the only two treatments for baldness approved by the Food and Drug Administration. Both medications may slow hair loss, but cannot re-grow hair.

Source Reference:
Garza L, Yang CC, et al. “Bald scalp in men with androgenetic alopecia retains hair follicle stem cells but lacks CD200-rich and CD34-positive hair follicle progenitor cells”, J Clin Invest. doi:10.1172/JCI44478