Analysis of Apoptotic Cell Death in Human Hair Follicles In Vivo and In Vitro

The study analyzed apoptotic cell death in human hair follicles during the anagen and catagen phases, both in vivo and in vitro. It found that apoptosis occurred in specific zones during anagen, while it was more widespread in catagen, particularly around the dermal papilla and outer root sheath. Caspases, including caspase-3, were expressed in anagen follicles. Transforming growth factor-β (TGF-β) induced catagen-like changes, while tumor necrosis factor-α (TNF-α) inhibited hair shaft elongation and increased cell death. The study suggested two types of apoptosis: one related to terminal differentiation in anagen and another driving epithelial component elimination in catagen. TGF-β was indicated as a potential initiator of the catagen phase, although its mechanism remained unclear.