TGF-β and HSP70 Profiles During Transformation of Yak Hair Follicles from Anagen to Catagen Stage

The study investigated the roles of TGF-β, TGF-βRII, and HSP70 in the transition of yak hair follicles (HFs) from the anagen to catagen stage. It was found that TGF-β2 transcription was significantly higher than TGF-β1 and TGF-β3 during the same periods. TGF-β2, TGF-βRII, and caspase-3 expressions were elevated in the catagen phase compared to mid-anagen, with some TGF-βRII-positive HF cells also being TUNEL-positive, indicating apoptosis. HSP70 protein levels were higher in mid-anagen than in late-anagen and catagen. The results suggested that TGF-β2 promotes catagen induction through TGF-βRII-mediated apoptosis in HF epithelial cells, while HSP70 protects epithelial cells from apoptosis, inhibiting HF regression. Thus, TGF-β2 had positive effects, and HSP70 had negative effects on catagen induction.