miRNA-125a regulates porcine oocyte maturation in vitro by targeting ADAR

Follicular fluid extracellular vesicles are beneficial for in vitro oocyte maturation and development; however, their effect on the expression profiles of oocyte microRNAs (miRNAs) and the roles of related miRNAs are unknown. In this study, we aimed to investigate miRNA expression in mature oocytes cultured in follicular fluid extracellular vesicles and the effect of miRNA-125a (miR-125a) on oocyte maturation. The expression profiles of the miRNAs were determined by microRNA sequencing, followed by target gene prediction analysis. We transfected miR-125a mimics and an miR-125a inhibitor to evaluate the effect of modulated miRNA-125a on cumulus expansion, oocyte maturation rate, changes in cytoplasmic maturation-related indicators, and changes in the expression of oocyte maturation-related, cumulus expansion-related, and predicted target genes. We found that miR-125a overexpression decreased the levels of cumulus expansion-related, oocyte maturation-related, and predicted target genes, adenosine deaminase RNA specific (ADAR), and lipid droplet number, and it increased the percentage of oocytes with abnormal cortical granule distribution. Inhibiting miR-125a increased the expression levels of oocyte maturation-related and target genes, number of lipid droplets, and endoplasmic reticulum function, and it decreased lipid droplet size. Mitochondrial membrane potential and reactive oxygen species levels were not significantly different between groups. In conclusion, our results suggest that extracellular vesicles may improve oocyte quality by modulating ADAR through regulating miR-125a.