Introduction: Polycystic ovarian syndrome (PCOS) is a common endocrinopathy in women. MicroRNAs (miRNAs) have been proven to play a crucial role in balancing the proliferation and apoptosis of granulosa cells (GCs) in PCOS.
Material and methods: The miRNA of PCOS was screened by bioinformatics analysis, and microRNA 646 (miR-646) was found to be involved in insulin-related pathways by enrichment analysis. The cell counting kit-8 (CCK-8), cell colony formation, and the 5-ethynyl-2'-deoxyuridine (EdU) assays were used to explore the effect of miR-646 on proliferation of GCs, flow cytometry was used to measure the cell cycle and apoptosis, and Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were used to explore the biological mechanism of miR-646. The human ovarian granulosa cells KGN were selected by measuring the miR-646 and via insulin-like growth factor 1 (IGF-1) levels and used for cell transfection.
Results: Overexpressed miR-646 inhibited KGN cell proliferation, and silenced miR-646 advanced it. Most cells were arrested in the S phase of cell cycle with overexpressed-miR-646, while after silencing miR-646, cells were arrested in the G2/M phase. And the miR-646 mimic raised apoptosis in KGN cells. Also, a dual-luciferase reporter proved the regulation effect of miR-646 on IGF-1, miR-646 mimic inhibited IGF-1, and miR-646 inhibitor advanced IGF-1. The cyclin D1, cyclin-dependent kinase 2 (CDK2), and B-cell CLL/lymphoma 2 (Bcl-2) levels were inhibited with overexpressed-miR-646, while silenced-miR-646 promoted their expression, and the bcl-2-like protein 4 (Bax) level was the opposite. This study found that silenced-IGF1 antagonized the promotive effect of the miR-646 inhibitor on cell proliferation.
Conclusions: MiR-646 inhibitor treatment can promote the proliferation of GCs by regulating the cell cycle and inhibiting apoptosis, while silenced-IGF-1 antagonizes it.
Keywords: IGF1; KGN cells; granulosa cells; miR-646; microRNA; polycystic ovarian syndrome.