MiR-214-3p promotes proliferation and inhibits estradiol synthesis in porcine granulosa cells

Background: Granulosa cells（GCs） proliferation and estradiol synthesis significantly affect follicular development.The miR-214-3p expression in the ovarian tissues of high-yielding sows is higher than that in low-yielding sows,indicating that miR-214-3p may be involved in sow fertility. However, the functions and mechanisms of miR-214-3p on GCs are unclear. This study focuses on miR-214-3p in terms of the effects on GCs proliferation and estradiol synthesis.Results: Our findings revealed that miR-214-3p promotes proliferation and inhibits estradiol synthesis in porcine GCs. MiR-214-3p can increase the percentage of S-phase cells, the number of EdU labeled positive cells, and cell viability. However, E2 concentration was reduced after miR-214-3p agomir treatment. We also found that miR-214-3p up-regulates the expression of cell cycle genes including cell cycle protein B（Cyclin B）, cell cycle protein D（Cyclin D）, cell cycle protein E（Cyclin E）, and cyclin-dependent kinase 4（CDK4） at the transcription and translation levels, but down-regulates the mRNA and protein levels of cytochrome P450 family 11 subfamily A member 1（CYP11A1）, cytochrome P450 family 19 subfamily A member 1（CYP19A1）, and steroidogenic acute regulatory protein（StAR）（i.e., the key enzymes in estradiol synthesis）. On-line prediction, bioinformatics analysis, a luciferase reporter assay, RT-qPCR, and Western blot results showed that the target genes of miR-214-3p in proliferation and estradiol synthesis are Mfn2 and NR5A1, respectively.Conclusions: Our findings suggest that miR-214-3 p plays an important role in the functional regulation of porcine GCs and therefore may be a target gene for regulating follicular development.