308 VERBASCOSIDE TREATMENT DURING IN VITRO MATURATION IMPROVES THE EMBRYO DEVELOPMENT OF PREPUBERTAL OVINE OOCYTES

Verbascoside (VB), a bioactive polyphenol from olive mill wastewater with known antioxidant activity, was shown to act as a pro-oxidant molecule, by impairing energy/redox status and embryo developmental competence of prepubertal ovine oocytes when added at micromolar concentrations in a continuative 24-h in vitro maturation (IVM) exposure protocol (1). The aim of the present study was to determine whether a lower (nanomolar) VB concentration and a shorter exposure time (2 v. 24 h) during IVM may improve the maturation rates of prepubertal ovine oocytes and their subsequent embryonic development in vitro. Cumulus-oocyte complexes derived from the ovaries of slaughtered 1-mo-old prepubertal sheep oocytes underwent IVM in TCM 199 with 10% oestrus sheep serum, 0.1 IU mL–1 of FSH/LH, and 100 µM cysteamine, in 5% CO2 in air at 38.5°C for 24 h. Based on our previous results (Dell'Aquila et al. 2014 Biomed. Res. Int. 2014, 878062), VB was added in the IVM medium at 1.03 nM, and 2 incubation times (24 and 2 h) were tested. In the 2-h exposure group, after 2 h of exposure to VB, oocytes were washed and cultured up to 24 h without VB. A group of oocytes were cultured in absence of VB, as controls. Matured oocytes were fertilized with frozen-thawed ram semen in SOF medium for 22 h and zygotes were cultured in vitro for 8 days. Metaphase II (MII) cleavage and blastocyst rates were analysed by Chi-squared test. Embryo quality was evaluated by staining and total cell count of the blastocyst and analysis of variance (ANOVA) was applied. Differences were considered to be significant when P 0.05). However, this treatment allowed to obtain significantly higher rates of cleaved embryos/MII oocytes (156/196, 80% v. 165/226, 73%; respectively; P