Bisphenol A and Expression of Cell Cycle Regulators and Apoptotic Factors in Cultured Mouse Ovarian Antral Follicles.

Abstract

Bisphenol A (BPA) is a plasticizer that is widely used in polycarbonate plastics. BPA is a known endocrine disrupting chemical that has been reported to have some toxic effects on female reproductive system. For example, BPA exposure has been inversely associated with the number and quality of oocytes retrieved from women undergoing in-vitro fertilization. Our previous studies indicated that a 100 μg/ml dose of BPA inhibits mouse antral follicle growth in culture. However, the effects of lower dose BPA exposure on mouse antral follicles are not known. Thus, we hypothesized that low doses of BPA (0.001-1 μg/ml) inhibit follicle growth by altering expression levels of key cell cycle regulators and/or apoptotic factors. To test this hypothesis, we mechanically isolated antral follicles from mouse ovaries (C57Bl/6; aged 50-54 days; n=3) and cultured them in dimethylsulfoxide (DMSO) or BPA (0.001-100 μg/ml) for 96 hours. Every 24 hours, follicle growth was measured in perpendicular axes. At the end of the cultures, follicles were snap-frozen and further processed for real-time polymerase chain reactions for expression levels of the following genes: transformation related protein (Trp53), B-cell leukemia/lymphoma 2 (Bcl2), Bcl-2–associated X protein (Bax), Bcl-2-associated agonist of cell death (Bad), cyclin-D2 (Ccnd2), Cyclin-dependent kinase 4 (Cdk4), and cyclin-E1 (Ccne1). The data indicate that low doses of BPA (0.001-1μg/ml) do not inhibit follicle growth, but that the higher dose of BPA (100 μg/ml) significantly inhibits follicle growth compared to DMSO control. Further, low doses of BPA did not alter expression levels of the selected genes compared to DMSO control. These data suggest that treatment of mouse antral follicles with relatively low doses of BPA does not affect the growth or levels of selected cell cycle regulators or apoptotic factors in mouse antral follicles. Supported by: NIH ES019178 (JAF) and Billie Field Fellowships (ZRC and WW).