Stem cells: How stress affects hair growth

Stress hormones suppress hair growth in mice through the regulation of hair follicle stem cells, reports a paper published in Nature this week. The study identifies the mechanism in mice that underlies this effect and suggests how we might reverse it.

Hair follicles cycle between growth and rest phases. Research in rodents and humans has indicated that stress may affect hair growth, but precisely how the two may be linked has been poorly understood. To determine the effects of stress on hair growth, Ya-Chieh Hsu and colleagues investigated how corticosterone (a hormone in mice released during chronic stress) regulates the activity of hair follicles in mice.

When corticosterone levels are elevated, hair follicles stay in an extended rest phase and fail to regenerate, experiments in mice reveal. Conversely, if corticosterone is depleted, hair follicle stem cells become activated and new hair growth occurs. The authors report that corticosterone inhibits the activation of hair follicle stem cells by suppressing the production of a protein called GAS6, which is shown to promote the proliferation of hair follicle stem cells in the absence of corticosterone. Their results suggest that restoring the expression of GAS6 could overcome stress-induced inhibition of hair follicle stem cells and might encourage regeneration of hair growth.

“These exciting findings establish a foundation for exploring treatments for hair loss caused by chronic stress,” writes Rui Yi in an accompanying News & Views. However, Yi adds that several issues need to be addressed before the findings can be translated to humans. For example, corticosterone is considered to be the rodent equivalent of human cortisol, but we do not know whether cortisol produces identical effects in humans to those observed here. Moreover, hair-growth phases differ between mice and humans, which might influence the effectiveness of approaches to reverse stress-induced inhibition of hair follicle stem cells.

After the embargo ends, the full paper will be available at: https://www.nature.com/articles/s41586-021-03417-2