Developmental Programming: Gestational Bisphenol-A Treatment Alters Trajectory of Fetal Ovarian Gene Expression

Bisphenol-A (BPA), a ubiquitous environmental endocrine disrupting chemical, is a component of polycarbonate plastic and epoxy resins. Because of its estrogenic properties, there is increasing concern relative to risks from exposures during critical periods of early organ differentiation. Prenatal BPA treatment in sheep results in low birth weight, hypergonadotropism, and ovarian cycle disruptions. This study tested the hypothesis that gestational exposure to bisphenol A, at an environmentally relevant dose, induces early perturbations in the ovarian transcriptome (mRNA and microRNA). Pregnant Suffolk ewes were treated with bisphenol A (0.5 mg/kg, sc, daily, produced ∼2.6 ng/mL of unconjugated BPA in umbilical arterial samples of BPA treated fetuses approaching median levels of BPA measured in maternal circulation) from days 30 to 90 of gestation. Expression of steroidogenic enzymes, steroid/gonadotropin receptors, key ovarian regulators, and microRNA biogenesis components were measured by RT-PCR using RNA derived from fetal ovaries collected on gestational days 65 and 90. An age-dependent effect was evident in most steroidogenic enzymes, steroid receptors, and key ovarian regulators. Prenatal BPA increased Cyp19 and 5α-reductase expression in day 65, but not day 90, ovaries. Fetal ovarian microRNA expression was altered by prenatal BPA with 45 down-regulated (>1.5-fold) at day 65 and 11 down-regulated at day 90 of gestation. These included microRNAs targeting Sry-related high-mobility-group box (SOX) family genes, kit ligand, and insulin-related genes. The results of this study demonstrate that exposure to BPA at an environmentally relevant dose alters fetal ovarian steroidogenic gene and microRNA expression of relevance to gonadal differentiation, folliculogenesis, and insulin homeostasis.