MiR-31 enhances porcine oocyte maturation via MAPK8/JNK-mediated cumulus expansion and cytoplasmic maturation

This study elucidates the molecular mechanism by which porcine ovarian cumulus cell-derived miR-31 regulates oocyte IVM through the MAPK8/JNK signaling pathway, with particular emphasis on its biological roles in cumulus cell expansion and oocyte maturation quality. The experimental design comprised four treatment groups: miR-31 mimics group, mimics negative control (NC) group, miR-31 inhibition group, and inhibition NC group. The results showed: (1) miR-31 overexpression significantly enhanced cumulus cell expansion processes, upregulating PTGS2 (P < 0.05) and PTX3 (P < 0.01) gene expression, while concurrently increasing oocyte maturation rates (P < 0.05). (2) Oocyte quality analysis revealed that miR-31 overexpression induced: Elevated mitochondrial membrane potential (P < 0.05); Increased ATP production (P < 0.05); Reduced lipid droplet size (P < 0.05) with concurrent quantity increased (P < 0.05); Improved redox homeostasis (P < 0.05). Conversely, miR-31 inhibition demonstrated opposing effects: Elevated cortical granule misdistribution rate (P < 0.05); Significant activation of MAPK8/JNK pathway activity (P < 0.01). In conclusion, this study demonstrates that miR-31 coordinates cumulus cell expansion with oocyte metabolic reprogramming by targeting MAPK8, thereby enhancing nuclear-cytoplasmic maturation synchrony.