Enhancing the Oocyte Ultrastructure and Antioxidant Defence System of In Vitro Matured Buffalo Oocytes via...

Despite buffalo's ability to thrive in challenging climates, the scarcity of superior germplasm remains a significant barrier to enhancing the global buffalo industry. Resveratrol (RE) is a potent antioxidant known to improve oocyte maturation and developmental competence in several mammalian species. Yet, its specific impact on the ultrastructural integrity and antioxidant defence systems of buffalo oocytes remain to be fully elucidated. Cumulus-oocyte complexes (COCs) were cultured during In Vitro maturation (IVM) with varying concentrations of resveratrol (0, 0.5, 0.75, or 1 μM) and designated as the CON, RE0.5, RE0.75, and RE1.0 groups, respectively. Following IVM, maturation rates and ultrastructural integrity were assessed, and the levels of reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) were quantified. The results indicated that the RE0.5 group exhibited a significantly higher metaphase II (MII) rate than the CON group (p < 0.05), whereas the RE0.75 and RE1.0 groups did not differ significantly compared with other groups (p > 0.05). Furthermore, supplementing the maturation media with RE (0.5, 0.75, or 1 μM) significantly increased the percentage of fully expanded cumulus complexes (p < 0.05). This was accompanied by a significant reduction in the rates of partially expanded, slightly expanded, and non- expanded cumulus complexes compared with the control treatment (p < 0.05). The RE0.5 group showed the lowest MDA levels and the highest CAT levels compared with the other groups (p < 0.05). Additionally, the RE0.5 group exhibited significantly higher GSH levels than the other treatment groups (p < 0.05). The SOD levels were decreased in all RE groups (p < 0.05) compared with control group. Ultrastructural analysis revealed that supplementation with 0.5 or 0.75 μM RE preserved the morphological integrity of the mitochondria, the zona pellucida, a dense ooplasm, and a well-organized distribution of cortical granules and short microvilli. These improvements were characterized by a normal perivitelline space and the successful extrusion of the first polar body, in contrast to the structural alterations observed in the CON group. In conclusion, supplementation with RE (0.5 or 0.75 μM) maintained the ultrastructural integrity of buffalo oocytes during IVM. This preservation is likely attributable to the potent antioxidant activity of resveratrol, which effectively mitigates oxidative stress, thereby enhancing both the cytoplasmic and nuclear maturation of buffalo oocytes In Vitro.