Involvement of MicroRNAs in the Regulation of Porcine Follicle Maturation

In preparation for the release of a fertilizable egg, mural granulosa cells that form the follicle wall and cumulus granulosa cells that encircle the oocyte are essential in supporting the growth and maturation of the oocyte. The complex molecular changes that occur within follicular cells in response to hormone signaling have been overlaid with a network of non-coding microRNAs (miRNAs) that post-transcriptionally regulate gene expression. The somatic components of the ovary have an intricate network of miRNAs that fine tune cell behavior. The overall objective of my Ph.D. research was to study the involvement of miRNAs in regulating the target genes necessary for oocyte maturation in vitro. To begin with, it was found that miR-378 suppressed E2 production via targeting aromatase in the cumulus cell, thus regulating oocyte maturation. Additionally, to explore whether miRNAs are involved in regulating cumulus extracellular matrix (ECM) remodeling, we identified that miR-574 impacts cumulus expansion and oocyte maturation by directly targeting a key enzyme in the production of extracellular matrix, HAS2. Moreover, our research showed one of the most abundant ovarian microRNAs, miR-21, targets TIMP3 in cumulus cells and influences the cumulus cells matrix remodeling via TIMP3-ADAMTS1-VERSICAN cascade. To conclude, our findings suggest a mechanism of post-transcriptional regulation by key microRNAs in the mammalian ovary. Our work supports the important role of microRNA during ovarian follicular development and oocyte maturation.