Divergent Proliferation Patterns of Distinct Human Hair Follicle Epithelial Progenitor Niches In Situ and Their Differential Responsiveness to Prostaglandin D2

In the 2017 study, researchers examined the cell cycle activity of various epithelial stem and progenitor cell populations within human scalp hair follicles and their response to prostaglandin D2 (PGD2), a compound associated with balding. They discovered that the CD200+/K15+ bulge region had lower cell cycle activity compared to other progenitor compartments. Treatment with PGD2 led to a reduction in proliferation of K15+ cells in the bulge but not in other regions, suggesting PGD2 selectively affects different stem cell populations. The study also found that both PGD2 and its metabolite 15d-PGJ2 suppressed proliferation in the bulge region, but not in the proximal bulb outer root sheath, and induced a G1 arrest in the sub-bulge region. The research involved ex vivo hair follicle organ culture experiments with 9-16 hair follicles from 4-6 patients for each analysis. These findings underscore the unique proliferation patterns of hair follicle stem cell niches and their varied responses to PGD2, which may contribute to hair loss in conditions like androgenetic alopecia.