MiRNA-125b-5p Disrupts Follicle Steroidogenesis Through Targeting Pak3/ERK Signalling In Polycystic Ovary Syndrome

Background:Disrupted androgen and estrogen synthesis are considered the most common characteristics in polycystic ovary syndrome(PCOS).Micro RNA is an endogenous non-coding RNA,which plays an important role in many biological processes.We recently discovered that mi R-125b-5p was significantly downregulated in PCOS patients with high androgen and low estrogen levels,but the molecular mechanism underlying mi R-125b-5p regulating steroidogenesis in preantral follicles remains elusive.Method:Clinical serum samples from PCOS patients were collected to detect the levels of various hormone secretion and mi R-125b-5p expression.Using a mouse preantral follicle culture model,we further investigated the expression of Pak3,ERK phosphorylation,steroidogenesis-related gene,testosterone and estradiol after the follicles treated with mi R-125b-5p mimics and inhibitor.Luciferase reporter assay was used to confirm that the Pak3 gene is a direct target of mi R-125b-5p.Rescue experiments were performed in follicles by treating with the two inhibitors together.To further confirm whether mi R-125b-5p could affect follicle hormone secretion through directly targeting Pak3,the expression of Pak3 in ovarian tissues of POCS patients and control group was also detected.Result:Mi R-125b-5p expression was significantly down-regulated in HA-PCOS patients.In mouse preantral follicles,inhibiting mi R-125b-5p upregulated the expression of androgen synthesis-related genes and stimulated the secretion of testosterone,while downregulating estrogen synthesis-related genes and decreasing estradiol release.In contrast,overexpression of mi R-125b-5p reversed steroidogenesis-related gene expression and hormone release.Mechanistic studies identified Pak3 as a direct target of mi R-125b-5p.Furthermore,inhibiting mi R-125b-5p facilitated the activation of ERK1/2 in mouse preantral follicles,while inhibiting Pak3 abrogated this activating effect.Conclusion:Due to the decreased mi R-125b-5p expression,Pak3 expression was markedly increased in the ovaries of PCOS patients,leading to activation of ERK signaling,thus stimulating the expression of androgen synthesis-related enzymes and testosterone secretion in hyperandrogenic PCOS(HA-PCOS)patients.