Regenerating Hair Follicle Stem Cells

Researchers at Harvard University have confirmed a long assumed, but until now, not scientifically-proven fact: stress causes hair loss. 

In a study on mice published in Nature, the team at the Harvard Stem Cell Institute have identified the stress hormone that causes hair follicle stem cells to stay in an extended Telegen (resting) phase. This hormone, corticosterone, is received by skin cells that surround the hair follicle, preventing them from releasing Gas6, a key molecule that activates stem cells. 

“So even the baseline level of stress hormone that’s normally circulating in the body is an important regulator of the resting phase. Stress essentially just elevates this preexisting ‘adrenal gland–hair follicle axis,’ making it even more difficult for hair follicle stem cells to enter the growth phase to regenerate new hair follicles,” said said Ya-Chieh Hsu, Ph.D., the Alvin and Esta Star Associate Professor of Stem Cell and Regenerative Biology at Harvard and HSCI Principal Faculty member. 

Perhaps most exciting, the findings showed that by adding Gas6 back this hair growth pathway can be restored and stems cells are reactivated. "Under both normal and stress conditions, adding Gas6 was sufficient to activate hair follicle stem cells that were in the resting phase and to promote hair growth," said Sekyu Choi, Ph.D., the lead author of the study. "In the future, the Gas6 pathway could be exploited for its potential in activating stem cells to promote hair growth. It will also be very interesting to explore if other stress-related tissue changes are related to the stress hormone's impact on regulating Gas6."

While additional work needs to be completed, this is a promising initial finding that finally sheds light on the “why” of stress-related hair loss. 

Sources: Harvard Gazette, Choi, S. et al. (2021). Corticosterone inhibits GAS6 to govern hair follicle stem cell quiescence