Effect of Antioxidant Procyanidin B2 (PCB2) on Ovine Oocyte Developmental Potential in Response to in Vitro Maturation (IVM) and Vitrification Stress

BACKGROUND: It was demonstrated that external stress, such as in vitro maturation (IVM) and vitrification process can induce significantly reduced development capacity in oocytes. Previous studies indicated that antioxidants play a pivotal part in the acquisition of adaptation in changed conditions. At present, the role of the natural potent antioxidant PCB2 in response to IVM and vitrification during ovine oocyte manipulation has not been explored. OBJECTIVE: To investigate whether PCB2 treatment could improve the developmental potential of ovine oocytes under IVM and vitrification stimuli. MATERIALS AND METHODS: The experiment was divided into two parts. Firstly, the effect of PCB2 on the development of oocytes during IVM was evaluated. Unsupplem ented and 5 μg/mL PCB2 -supplemented in the IVM solution were considered as control and experimental groups (C + 5 μg/mL PCB2). The polar body extrusion (PBE) rate, mitochondrial membrane potential (MMP), ATP, reactive oxygen species (ROS) levels and early apoptosis of oocytes were measured after IVM. Secondly, we further determine whether PCB2 could improve oocyte quality under vitrification stress. The survival rate, PBE rate and early apoptosis of oocytes were compared between fresh group, vitrified group and 5 μg/mL PCB2 -supplemented in the IVM solution after vitrification (V + 5μg/mL PCB2). RESULTS: Compared to the control group, adding PCB2 significantly increased PBE rate (79.4% vs. 62.8%, P < 0.01) and MMP level (1.9 ± 0.08 vs. 1.3 ± 0.04, P < 0.01), and decreased ROS level (47.1 ± 6.3 vs. 145.3 ± 8.9, P < 0.01). However, there was no significant difference in ATP content and early apoptosis. Compared to the fresh group, vitrification significantly reduced oocytes viability (43.0% vs. 90.8%, P < 0.01) as well as PBE rate (24.2% vs. 60.6%, P < 0.05). However, 5 μg/mL PCB2-supplemention during maturation had no effect on survival, PBE or early apoptosis in vitrified oocytes. CONCLUSION: PCB2 could effectively antagonise the oxidative stress during IVM and promote oocyte development.