LAUSR

Transforming growth factor‐β (TGF‐β) and heat shock protein 70 (HSP70) are important for the hair follicle (HF) cycle, but it is unclear whether they participate in HF regression in yak skin. In this study, we investigated the role of TGF‐β, TGF‐βRII, and HSP70 in the transition from anagen to catagen of HFs. The results showed that TGF‐β2 transcription was significantly higher than that of TGF‐β1 and TGF‐β3 in the same periods. Meanwhile, the expressions of TGF‐β2, TGF‐βRII, and caspase‐3 were higher in the catagen phase than that in mid‐anagen, and some TGF‐βRII‐positive HF cells were terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate‐biotin nick end labeling (TUNEL)‐positive. Moreover, the HSP70 protein levels in mid‐anagen were higher than those in late‐anagen and catagen. These results suggested that TGF‐β2 plays a major role in catagen induction in yak HFs, which might be achieved via TGF‐βRII‐mediated apoptosis in HF epithelial cells. In contrast, HSP70 might protect epithelial cells from apoptosis and ultimately inhibit HF regression. In conclusion, TGF‐β2 has positive effects, whereas HSP70 has negative effects, on catagen induction.