Antioxidative effect of carboxyethylgermanium sesquioxide (Ge-132) on IVM of porcine oocytes and subsequent embryonic development after parthenogenetic activation and IVF

Abstract

Carboxyethylgermanium sesquioxide (Ge-132) is an organogermanium compound known to exert biological activities, such as antioxidant and anticancer effects. In this study, we investigated the effect of Ge-132 on the IVM of porcine oocytes via analysis of nuclear maturation, intracellular glutathione (GSH) and reactive oxygen species (ROS) levels, and subsequent embryonic development after parthenogenetic activation (PA) and IVF. After 40 hours of IVM, no significant difference in nuclear maturation was observed in the 100, 200, and 400 μg/mL of Ge-132 treatment groups (89.9%, 91.3%, and 90.4%, respectively) compared with the control group (89.0%). However, intracellular GSH levels in oocytes treated with 200 μg/mL of Ge-132 increased significantly (P < 0.05), and the 200 and 400 μg/mL of Ge-132 treatment groups exhibited a significant (P < 0.05) decrease in intracellular ROS levels compared with the control group. Oocytes matured with 200 and 400 μg/mL of Ge-132 during IVM displayed significantly higher cleavage rates (78.7% and 82.7% vs. 67.5%, respectively), and the 200 μg/mL of Ge-132 treatment group displayed higher blastocyst formation rates and greater total cell numbers after PA (59.5% and 67.8 vs. 38.2% and 55.3, respectively) than the control group. Furthermore, oocytes matured with 200 μg/mL of Ge-132 during IVM failed to display significantly higher blastocyst formation rates (31.6% vs. 36.7%) but exhibited greater total cell numbers after IVF (71.5 vs. 101.3, respectively) than the control group. We also found that the Ge-132-treated oocytes showed significantly higher messenger RNA (mRNA) expression levels of the oxidative-related gene Nrf-2 and lower mRNA expression levels of the proapoptotic gene Bax than the control group (P < 0.05). In conclusion, our results suggest that treatment with Ge-132 during IVM improves the developmental potential of PA and IVF porcine embryos by increasing the intracellular GSH levels, thereby decreasing the intracellular ROS levels and reducing oxidative stress-induced apoptosis, thereby regulating the mRNA expression of oocytes during oocyte maturation.

Keywords: Carboxyethylgermanium sesquioxide; Glutathione; Porcine oocyte; Preimplantation embryonic development; Reactive oxygen species.