Functional complexity of hair follicle stem cell niche and therapeutic targeting of niche dysfunction for hair regeneration

摘要

Hair follicle structure, hair follicle stem cell and hair cycle. Quiescent HFSCs reside in the bulge region and primed HFSCs are located in the secondary hair germ. They are transiently activated in early anagen, giving rise to progeny that grow down to form the lower portion of HFs. HFs progress through catagen (regressing phase), telogen (resting phase) and anagen (growing phase) cyclically. Matrix cells in the hair bulb actively proliferate and differentiate to support the continued elongation of the hair shaft in anagen. In catagen, the hair bulb shrinks and the lower portion of the HF regresses through a progressively shortened epithelial strand into the telogen HF. In telogen, HFSCs in the secondary hair germ and bulge remain inactivated