Dysfunction of Human Estrogen Signaling as a Novel Molecular Signature of Polycystic Ovary Syndrome.

Estradiol (E2) is a major hormone-controlling folliculogenesis whose dysfunction may participate in polycystic ovary syndrome (PCOS) infertility. To determine whether both the concentration and action of E2 could be impaired in non-hyperandrogenic overweight PCOS women, we isolated granulosa cells (GCs) and follicular fluid (FF) from follicles of women undergoing ovarian stimulation (27 with PCOS, and 54 without PCOS). An analysis of the transcript abundance of 16 genes in GCs showed that androgen and progesterone receptor expressions were significantly increased in GCs of PCOS (by 2.7-fold and 1.5-fold, respectively), while those of the steroidogenic enzymes CYP11A1 and HSD3B2 were down-regulated (by 56% and 38%, respectively). Remarkably, treatment of GC cultures with E2 revealed its ineffectiveness in regulating the expression of several key endocrine genes (e.g., GREB1 or BCL2) in PCOS. Additionally, a comparison of the steroid concentrations (measured by GC/MS) in GCs with those in FF of matched follicles demonstrated that the significant decline in the E2 concentration (by 23%) in PCOS FF was not the result of the E2 biosynthesis reduction. Overall, our study provides novel hallmarks of PCOS by highlighting the ineffective E2 signaling in GCs as well as the dysregulation in the expression of genes involved in follicular growth, which may contribute to aberrant folliculogenesis in non-hyperandrogenic women with PCOS.

Estradiol Regulates mRNA Levels of Estrogen Receptor Beta 4 and Beta 5 Isoforms and Modulates Human Granulosa Cell Apoptosis.

Estrogen receptor beta (ERß) plays a critical role in granulosa cell (GC) functions. The existence of four human ERß splice isoforms in the ovary suggests their differential implication in 17ß-estradiol (E2) actions on GC apoptosis causing follicular atresia. In this study, we investigated whether E2 can regulate ERß isoforms expression to fine tune its apoptotic activities in human GC. For this purpose, we measured by RT-qPCR the expression of ERß isoforms in primary culture of human granulosa cells (hGCs) collected from patients undergoing in vitro fertilization, before and after E2 exposure. Besides, we assessed the potential role of ERß isoforms on cell growth and apoptosis after their overexpression in a human GC line (HGrC1 cells). We confirmed that ERß1, ERß2, ERß4, and ERß5 isoform mRNAs were predominant over that of ERα in hGCs, and found that E2 selectively regulates mRNA levels of ERß4 and ERß5 isoforms in these cells. In addition, we demonstrated that overexpression of ERß1 and ERß4 in HGrC1 cells increased cell apoptosis by 225% while ERß5 or ERß2 had no effect. Altogether, our study revealed that E2 may influence GC fate by specifically regulating the relative abundance of ERß isoforms mRNA to modulate the balance between pro-apoptotic and non-apoptotic ERß isoforms.