The effect of bisphenol A on the Notch (Notch2 and Jagged2) signaling pathway in the follicular development of the neonatal rat ovary

The formation of primordial follicles determines the pool size of follicles in the ovary, and is crucial for female reproductivity. Oocyte nest breakdown, and the formation of primordial follicles, largely depend upon the communication between oocytes and the surrounding pregranulosa cells. The neurogenic locus notch homolog protein (Notch) signaling pathway is the key player for this cell-to-cell communication, and is responsible for primordial folliculogenesis. However, different endocrine disruptors, including bisphenol A (BPA; a plasticizer and a constituent of reusable plastic containers) may affect the Notch signaling pathway, and might induce ovary dysfunction via Notch signaling. Consequently, we investigated the possible influence of BPA treatment on the proportional distribution of the follicular stages, follicle numbers, levels of apoptosis, and on Notch2 and Jagged2 expressions in the ovary. BPA was administered at doses of either 50 µg/kg/day or 50 mg/kg/day, at different time intervals, during neonatal and fetal periods in vivo. After collecting the ovaries from the various experimental groups, follicles were counted, and frequency of apoptosis was determined by TUNEL assay. In addition, Notch2 and Jagged2 expressions were assessed by immunohistochemical staining and qPCR. In summary, BPA treatment affected the follicle numbers and apoptosis level, and Notch2 and Jagged2 expressions varied with follicular stage. It was also observed that these parameters were dose and time dependent with respect to BPA exposure.