Effects of limonin on oxidative stress and early apoptosis in oocytes during in vitro maturation

To investigate the effects of limonin (Lim) on oxidative stress and early apoptosis in bovine oocytes during in vitro maturation (IVM), different concentrations of Lim (0, 10, 20, 50 μmol/L) were added to bovine IVM medium. Oocyte maturation rates and development 24 h after in vitro fertilization (IVF) were examined to determine the optimal Lim concentration. The optimal Lim concentration was added to the IVM medium, and 0 μmol/L Lim was used as the control. Immunofluorescence staining was used to detect the abnormal rate of spindle assembly, reactive oxygen species (ROS), glutathione (GSH), mitochondrial membrane potential (MMP) levels, mitochondrial distribution, and the fluorescence intensity of cathepsin B (CB)-active LC3 protein. RT‒qPCR was used to detect the mRNA expression levels of antioxidant-, apoptosis- and autophagy-related genes in oocytes. The total number of blastocysts and the proportion of apoptotic cells among blastocysts were detected. The results showed that the PBI ejection rate, cleavage rate and blastocyst rate of bovine oocytes in the 20 μmol/L Lim group were significantly higher than those in the control group (P