DHT and E2 Synthesis-Related Proteins and Receptors Expression in Male Yak Skin During Different Hair Follicle Stages.

Dihydrotestosterone (DHT) and 17β-estradiol (E2) are sex hormones that regulate human hair follicle (HF) growth and are produced by peripheral reduction and aromatization of testosterone. However, the expression patterns of DHT and E2 synthesis-related proteins and their receptors in male yak skin during different HF stages (telogen, anagen, and catagen) are unknown. In this study, we found that both 5α-red and androgen receptor (AR) were expressed in epithelial cells and AR was expressed in the dermal papilla. Additionally, the transcription level of 5α-red1 at different HF stages was significantly higher than that of 5α-red2 mRNA at the same stage; 5α-red1 and 5α-red2 proteins peaked during the anagen and telogen periods of HF, respectively. However, AR protein was only expressed in the skin during the anagen phase of HF. Aromatase and estrogen receptors (ERα and ERβ) were expressed in cutaneous epithelial cells, whereas ERα and ERβ were expressed in the dermal papilla; the transcription level of ERα in HFs at each stage was much higher than that of ERβ. From the catagen to telogen phase, aromatase protein expression was down-regulated, while ERα protein expression was up-regulated. Based on our results, we speculate that 5α-red1 is essential for the synthesis of DHT in male yak skin epithelial cells and promotes the growth of HFs through AR. E2 synthesized by male yak skin epithelial cells may inhibit the growth of male yak skin HFs by ERα. These results provide a foundation for further study on the mechanism of hormone-regulated male yak skin HFs.