When Stem Cells Decide to Leave the Bulge: A New Mechanism of Stem Cell Depletion During Hair Follicle Aging

New Research Suggests Some Hair Follicle Stem Cells Choose to Leave the Hair Follicle

A landmark new study is changing the way we think about stem cells and what happens to them during the aging process.

Stem cells are cells with the potential to produce a vast array of new cell types. Hair follicle stem cells live quietly in the hair follicle bulge region and get called upon every now and then to produce new hairs.

The current view of stem cells is that over time they reduce in number as the organism gets older. Some get used up and some just die. In scientific terms, this is called “stem cell exhaustion.” The process of getting older, of course, is commonly called “aging.”

New studies by Zhang and colleagues suggest a surprising new mechanism for how stem cell exhaustion comes about: some stem cells simply get up and leave the bulge region. They hop out and free themselves into the nearby dermis and by doing so are no longer able to be called upon in the future to participate in hair follicle regeneration. This stem cell depletion was shown to also lead to hair follicle miniaturization.

This study was done in mice so we don’t know if it perfectly applies to humans quite yet. Likely there are some important similarities and a variety of mechanisms of “stem cell exhaustion” are already proving to be true in humans.

The authors went on to show that two genes - FOXC1 and NFATC1 - play a key role in making sure the stem cells don’t leave. Mice generated that lack these proteins develop progressively miniaturized hair and then lose all their hair.

This study opens new doors to understanding the aging process of hair follicles and stem cells in general.

Reference

Zhang, C., Wang, D., Wang, J. et al. Escape of hair follicle stem cells causes stem cell exhaustion during aging. Nat Aging 1, 889–903