Developmental programming: mechanisms of early exposure to real-life chemicals in biosolids on offspring ovarian dynamics†.

Female reproductive capacity is shaped by ovarian reserve and patterns of follicle development. Ovarian reserve depletion occurs by follicle activation and atresia, which are affected by environmental chemicals (ECs). Because humans are simultaneously exposed to hundreds of ECs, real-life exposure models are essential to assess patterns of atresia after EC exposure. Previous findings demonstrate maternal preconceptional and gestational EC exposure via biosolids increases activation rate and reduces primordial follicle pool in juvenile, but not adult sheep. We hypothesized that this shift involves changes in death and proliferative pathways that impact follicle atresia from juvenile to adult life. Ovaries were collected from juvenile (9.5 weeks) and adult (2.5 years) offspring from ewes grazed on biosolids-treated pasture (BTP) or inorganic fertilizer-treated pasture (Control). Follicular atresia was assessed through morphological characteristics and molecular death pathways, including expression of markers for apoptosis (CASP3), autophagy (LC3), ferroptosis (GPX4), and proliferation (Ki67). There were higher levels of apoptosis and autophagy, and lower proliferation, in juvenile BTP offspring compared to controls. In adult BTP offspring, apoptosis and proliferation were similar, autophagy was lower, and ferroptosis was higher compared to controls. Apoptosis was lower and ferroptosis was higher in adults than juveniles, regardless of treatment. Adult BTP offspring had lower autophagy and similar proliferation levels than juvenile BTP offspring. These findings suggest that lower autophagy and lack of decrease in proliferation contribute to normalization of activation rate and ovarian pool in BTP adult offspring and supportive of lasting impacts of gestational EC exposure on offspring follicular health.