miRNA-335-5p negatively regulates granulosa cell proliferation via SGK3 in PCOS

Abstract

Polycystic ovary syndrome (PCOS) is a major cause of infertility in women of reproductive age. However, its exact etiology remains unknown. In this study, we sequenced microRNAs (miRNAs) in human follicular fluid and identified 16 downregulated and 3 upregulated miRNAs in PCOS group compared with non-PCOS group. Among the differential expressed miRNAs, miR-335-5p was verified lower abundance in PCOS than non-PCOS group using quantitative real-time polymerase chain reaction. Besides, miR-335-5p negatively correlated with antral follicle count, anti-Müllerian hormone, and total testosterone. Bioinformatics analysis identified serum/glucocorticoid regulated kinase family member 3 (SGK3) as a potential target gene of miR-335-5p. SGK3 is involved in protein kinase B-mammalian target of rapamycin kinase (AKT-mTOR) signaling pathway and cell proliferation. Western blotting and cell counting kit-8 assays demonstrated that miR-335-5p mimic reduced, while miR-335-5p inhibitor increased, SGK3 abundance, AKT-mTOR pathway and cell proliferation in human granulosa-like tumor KGN cells. Dual-luciferase reporter assays showed that miR-335-5p binds to the 3 untranslated region of SGK3 mRNA. Furthermore, miR-335-5p was decreased and SGK3 was elevated in human granulosa cells obtained from PCOS patients as compared with non-PCOS controls. These findings suggested that miR-335-5p is involved in granulosa cells proliferation via reducing SGK3 expression, which might provide a molecular target to improve dysfunctional granulosa cells in patients with PCOS.