2-Mercaptoethanol promotes porcine oocyte maturation in vitro by maintaining autophagy homeostasis

2-Mercaptoethanol (2-ME) is often used as an antioxidant to optimize culture systems for in vitro oocyte maturation in livestock. However, the relationship between 2-ME and Autophagy has not yet been elucidated. In this study, we hypothesized that 2-ME can promote porcine oocyte maturation in vitro by maintaining Autophagy homeostasis. To test this hypothesis, we explored the effects of 2-ME on the maturation of porcine oocytes exposed to an Autophagy activator (rapamycin) or an Autophagy inhibitor (3-methyladenine, i.e., 3-MA) in vitro. Rapamycin-induced Autophagy over-activation significantly increased autophagy- and apoptosis-related gene expression, oxidative stress, Apoptosis rates, abnormal mitochondrial redistribution, and significantly decreased oocyte first polar body extrusion (PBE) rates, spindle/chromosome integrity and developmental competence. 3-MA-mediated Autophagy inhibition exerted similar effects on all these parameters except the expression of genes that promote Autophagy and inhibit Apoptosis. Importantly, 2-ME supplementation significantly attenuated the detrimental effects of rapamycin and 3-MA. Interestingly, we observed that 44 h of coincubation with rapamycin/3-MA and 2-ME restored Autophagy homeostasis in vitro. In conclusion, our study confirmed that 2-ME promotes porcine oocyte maturation and embryo development in vitro by maintaining Autophagy homeostasis and lays a foundation for further research on the underlying mechanism.