miR-18b regulates the function of rabbit ovary granulosa cells

MicroRNAs (miRNAs) have been determined to participate in the process of oestradiol production. Generally, there are two pathways by which oestradiol levels change, one being the state of cells (i.e. the status of enzymes involved in the synthesis of hormones such as oestradiol) and the other being the number of cells that secrete oestradiol. It is known that oestrogens are the main steroids produced by granulosa cells (GCs) of mature ovarian follicles. In this study we explored the function of miR-18b in rabbit GCs by overexpressing or inhibiting its activity. We found that miR-18b silencing promoted the secretion of oestradiol by significantly affecting the expression of steroidogenesis-related genes. Thus, miR-18b may act as a negative regulator of the production of enzymes related to oestradiol synthesis and affect oestradiol production. Furthermore, the effects of miR-18b on the proliferation, cell cycle and apoptosis of GCs were investigated using a cell counting kit (CCK-8) proliferation assay, detection of annexin V-fluorescein isothiocyanate apoptosis, flow cytometry and quantitative polymerase chain reaction. The results showed that miR-18b upregulated GC apoptosis (miR-18b overexpression decreases cell growth and stimulates apoptosis). These findings suggest that miR-18b and the oestrogen receptor 1 (ESR1) gene may be attractive targets to further explore the molecular regulation of GCs. The miR-18b may also explain, in part, the abnormal folliculogenesis in mammals caused by conditions such as polycystic ovary syndrome, primary ovarian insufficiency, and others.