The Thinning Top: Why Old People Have Less Hair

The document discusses age-related alopecia and the decline in regenerative capacity of hair follicles as people age. Chen et al. (2014) conducted experiments that suggest an imbalance between stem cell-activating and inhibitory signals is a key factor in the regenerative decline of hair follicles in older mice. They found that both young and old mice have similar numbers of stem cells in the bulge region of hair follicles, indicating that the decrease in hair regeneration with age is not due to a decrease in stem cell number but rather a decrease in stem cell activation. The study also identified follistatin, a secreted protein, as a potential therapeutic target because it can enhance hair follicle cycling. The authors conclude that factors extrinsic to hair follicles can reactivate hair cycling in dormant older skin and that follistatin may be responsible for the reactivation of hair cycling in older mice when grafted onto younger recipients. The findings point to a potential therapeutic strategy for alopecia involving the modulation of the hair follicle environment.