Profile of Transforming Growth Factor-β Responses During the Murine Hair Cycle

Transforming growth factor-β (TGF-β) appears to promote the regression phase of the mammalian hair cycle, in vivo in mice and in organ culture of human hair follicles. To assess the relationship between TGF-β activity and apoptosis of epithelial cells during the murine hair cycle, we identified active TGF-β responses using phospho-Smad2/3-specific antibodies (PS2). Strong, nuclear PS2 staining was observed in the outer root sheath throughout the anagen growth phase. Some bulb matrix cells were positive for PS2 during late anagen. Extensive, but weak, staining was observed in this region at the anagen-catagen transition. We also examined expression of TGF-β-stimulated clone-22 (TSC-22), which is associated with TGF-β-induced apoptosis of some cell lines. Recombinant rat TSC-22 was used to generate a rabbit anti-TSC-22 antibody useful for immunohistochemistry. TSC-22 RNA accumulation and immunoreactivity were observed in follicles throughout the murine hair cycle, including the dermal papilla and lower epithelial strand of late-catagen hair follicles. Neither the expression pattern nor the presence of nuclear TSC-22 correlated with the sites of apoptosis, suggesting that TSC-22 is not an effector of apoptosis in mouse catagen hair follicles. These studies support a complex role for TGF-β in regulating the regression phase of the cycle, with potential for indirect promotion of apoptosis during the anagen–catagen transition