Apoptosis Coordinates With Proliferation And Differentiation During Human Hair Follicle Morphogenesis

The study investigated the role of apoptosis in human hair follicle morphogenesis, highlighting its coordination with proliferation and differentiation. Using TUNEL and immuno-localization techniques, it was found that apoptosis occurred in specific areas of the developing hair follicle, such as the outer root sheath and hair follicle sheath, while sparing regions with high bcl-2 expression like the dermal papilla and bulge area. Apoptosis facilitated the formation of the epidermal and subepidermal hair canal, with filaggrin and involucrin expressed in the canal lining cells. Additionally, CD1a+ Langerhans cells were present along the hair canal before its opening. The study concluded that apoptosis not only shapes the growth zone and frees the hair shaft from the follicular wall but also prepares the epidermal barrier for hair emergence.