Why do so many men go bald? What exactly changes on their heads? Hot off the lab bench: Men go bald because the follicles from which their hairs sprout run out of special progenitor cells with which to make the hair.
Normally, inside hair follicles a region called “the bulge” contains a packet of adult stem cells from which the hair is replenished. Scientists have theorized that these stem cells might simply run out in those prone to male-pattern baldness.
To test this, a team of researchers at the University of Pennsylvania (and, it seems, a few other places) looked at hair follicles from discarded bits of scalp from 54 men seeking hair transplants. Comparing the follicles from still-hairy samples of these scalps with non-hairy samples, the researchers found:
1) The hair follicle stem cells were still there
2) Another set of cells — known as hair progenitor stem cells — were depleted.
The scientists concluded that somehow, for some reason, the stem cells don’t transform into progenitor cells anymore. That makes male-pattern baldness similar to alopecia areata, a reversible kind of hair loss.