A protective role of cumulus cells after short-term exposure of rat cumulus cell-oocyte complexes to lifestyle or environmental contaminants

- Expression levels of cumulus cell, but rarely oocyte, genes are modulated after in vitro culture of COC.
- Reagent transfer from cumulus cells to oocyte increases up to 13 h in culture, but decrease thereafter.
- There is disparity between gap junction transfer rate, protein (GJA1) and gene (Gja1) levels in rcultured rat COC.
- Exogenous compounds tested in this study altered some aspect of gap junction function in rat COCs in culture.
- Cumulus cells protect oocytes from exogenous compounds in regards to gene expression modulation.

Ovarian follicular fluid provides a potential reservoir for exogenous compounds that may adversely affect oocyte quality. This study examined the effects of common lifestyle and environmental contaminants, namely bisphenol-A (BPA), caffeine, 3,4-methylenedioxymethamphetamine (MDMA), nicotine and Δ9-tetrahydrocannabinol (THC) on gap junction genes (Gja1, Gja4) and proteins (GJA1), glucose metabolism genes (Gfpt1, Pfkp) and oocyte growth factor genes (Bmp15, Gdf9), as well as gap junction transfer rate, in rat cumulus-oocyte complexes (COCs). In vitro exposure to MDMA and THC accelerated the timing of meiotic resumption and all contaminants altered either gap junction gene expression (BPA, caffeine, MDMA and THC) or transfer rate (BPA and nicotine). In vitro exposure of COCs to MDMA also altered glucose metabolism genes. Overall, oocyte-derived genes were largely unaffected following exposure to any contaminant. In summary, the impact of short-term exposure to lifestyle and environmental contaminants on oocyte function may be diminished due to protective properties of cumulus cells.