Control of murine hair follicle regression (catagen) by TGF- b 1 in vivo hair follicle

The regression phase of the hair cycle (catagen) is an apoptosis-driven process accompanied by terminal differentiation, proteolysis, and matrix remodeling. As an inhibitor of keratinocyte proliferation and inductor of keratinocyte apoptosis, transforming growth factor b 1 (TGF- b 1) has been proposed to play an important role in catagen regulation. This is suggested, for example, by maximal expression of TGF- b 1 and its receptors during late anagen and the onset of catagen of the hair cycle. We examined the potential involvement of TGF- b 1 in catagen control. We compared the first spontaneous entry of hair follicles into catagen between TGF- b 1 null mice and age-matched wild-type littermates, and assessed the effects of TGF- b 1 injection on murine anagen hair follicles in vivo . At day 18 p.p., hair follicles in TGF- b 1 2 / 2 mice were still in early -RII-IR To double visualize apoptotic cells and TGF b -RII-IR, we used a previously established protocol (4). Briefly, TUNEL-positive cells were detected using commercially available kit (Ap-opTag, Oncor) with antidigoxigenin FITC-conjugated F(ab) 2 fragments, and TGF b -RII-IR was visualized with the applica-tion of corresponding primary rabbit antiserum overnight at room temperature (1:100, followed by secondary goat anti-rabbit TRITC-conjugated anti- body (Jackson Immuno-Research 1:200, 37°C) following previously developed basic protocols (36). Sections were for staining were omitting according