Dysfunctional Ovarian Stem Cells Due to Neonatal Endocrine Disruption Result in PCOS and Ovarian Insufficiency in Adult Mice

Polycystic ovarian syndrome (PCOS) is a common global cause of anovulatory infertility but underlying etiology leading to PCOS still remains elusive. Fetal and perinatal endocrine disruption reportedly affects germ cell nests (GCN) breakdown, meiosis, and primordial follicle (PF) assembly with unassembled oocytes in neonatal ovaries. We recently reported that very small embryonic-like stem cells (VSELs) and ovarian stem cells (OSCs) express ER alpha, ER beta and FSHR, undergo distinct cyclic changes and neo-oogenesis encompassing GCN formation, meiosis, and primordial follicle (PF) assembly on regular basis in adult mice ovaries and these GCN are arrested in pre-meiotic or early meiotic stage in aged ovaries. Present study was undertaken to evaluate whether neonatal exposure to endocrine disruption (estradiol E2 or diethylstilbestrol DES) affects ovarian stem cells and their differentiation (neo-oogenesis) and PF assembly in adult 100 days old ovaries. Neonatal exposure to E2 resulted in typical features of PCOS including hyperandrogenism, infertility, increased stromal compartment, absent corpus lutea, and cystic follicles whereas DES treated ovaries showed rapid recruitment of follicles in young ovaries and multi-ovular/cystic follicles. Ovary surface epithelial cells smears showed large numbers of growth-arrested GCN in zygotene/pachytene with increased expression of Mlh-1 and Scp-1 suggesting defects at synapsis and recombination stages during prophase-1 of meiosis. Being immortal and expression of ER alpha and ER beta makes VSELs directly vulnerable to carry developmental endocrine insults to adult life. Dysfunction of VSELs/OSCs possibly results in oocyte defects observed in our study in PCOS/POI besides the widely reported defects in granulosa cells.