miRNA expression analysis of the sheep follicle during the prerecruitment, dominant, and mature stages of development under FSH stimulation.

Follicle stimulating hormone (FSH) has been widely reported to influence ovarian follicular development, and miRNAs play a significant role in mammalian follicular development by regulating their target genes. Therefore, it is of interest to explore the roles of miRNAs in sheep follicular development during FSH stimulation. In the current study, we constructed miRNA expression profiles of small follicles (SFs, prerecruitment stage), medium follicles (MFs, dominance stage), and large follicles (LFs, maturation stage). Three and 50 significant differentially expressed miRNAs (DEMs) were identified in the MF vs. SF and LF vs. SF comparisons, respectively, and none were identified in the LF vs. MF comparison. Oar-miR-10a was significantly downregulated in MFs compared with SFs. In LFs compared with SFs, miR-212-3p, miR-212-5p and miR-202-5p were significantly upregulated, and miR-27a-3p, miR-181a-5p, miR-204-5p, and miR-182-5p were significantly downregulated. Furthermore, we predicted the target genes of significant DEMs and performed functional enrichment analyses of these target genes. Analyses of KEGG pathways and GO terms showed that the putative target genes were significantly enriched in ovarian steroidogenesis, glutathione metabolism, positive regulation of cell differentiation, positive regulation of cell development, and cellular response to oxygen-containing compounds. Analyses of miRNA-gene regulatory networks suggested that miR-181a-5p-CYP11A1, (miR-27a-3p and miR-129-5p)-LDLR, (miR-212-3p and miR-212-5p)-EFNA5, (miR-181a-5p, miR-182-5p, and miR-27a-3p)-INHBA, and miR-182-5p-SOD2 might be involved in follicular development. The present study provides basic data and suggests research directions for further exploration of the roles of miRNAs in sheep follicular development under FSH stimulation.