Hypoxia promotes steroidogenic competence of buffalo (Bubalus bubalis) theca cells.

Theca cells (TCs) play an important role in follicular development and atresia. TCs synthesize androgens that act as substrate for granulosa cells aromatization to estrogens needed for follicular growth. However, the effects of hypoxia on steroidogenesis in buffalo TCs remain unclear. In the present study, the impacts of hypoxic conditions (5% oxygen) on androgen synthesis in buffalo TCs were examined. The results showed that hypoxia improved both the expression levels of androgen synthesis-related genes (CYP11A1, CYP17A1, and 3β-HSD) and the secretion levels of testosterone in buffalo TCs. Hypoxic conditions promoted the sensitivity of buffalo TCs to LH. Furthermore, inhibition of PI3K/AKT signaling pathway reduced both the expression levels of androgen synthesis-related genes (CYP11A1, CYP17A1, and 3β-HSD) and the secretion levels of testosterone in hypoxia-cultured buffalo TCs. Besides, inhibition of PI3K/AKT signaling pathway lowered the sensitivity of buffalo TCs to LH under hypoxic conditions. This study indicated that hypoxia enhanced the steroidogenic competence of buffalo TCs main through activating PI3K/AKT signaling pathway and subsequently facilitating the responsiveness of TCs to LH. This study provides a basis for further exploration of ovarian endocrine mechanism for steroidogenesis.