P-90: Effect of Phosphodiesterase Type3 Inhibitor, Cilostamide, on The Developmental Competence of Ovine OocytesIsolated by Glucose 6-Phosphate Dehydrogenase Activity

Background: The developmental competence of oocytes matured in vitro (IVM) is yet far below than in vivo counterparts. Recent studies suggest that the asynchrony between nuclear/cytoplasmic maturation and the initial low/heterogeneous quality of oocytes are the most important factors affecting IVM success. We investigated whether selection of growing oocytes (based on their glucose 6- phosphate dehydrogenase (G6PDH) activity) and chemical induction of nuclear/cytoplasmic synchrony (through transient inhibition of meiosis resumption with cilostamide) can improve developmental competence of sheep oocytes Materials and Methods: Abattoir-derived oocytes were stained with 26μM BCB for 45 minutes to isolate growing (high G6PDH activity) and fully grown (low G6PDH) oocytes according to their differential capacities in breaking BCB and retaining colorless (BCB-) or blue (BCB+) ooplasm, respectively. Then, BCB- and BCB+ oocytes were incubated with 1 μM cilostamide for 6h before culture in normal IVM medium. Then, matured oocytes were used for embryo development assessment using parthenogenetic activation Results: Cilostamide delayed meiotic progression in BCB- ovine oocytes. The cleavage,blastocyst and hatching rates in BCB- oocytes that treated by cilostamide were higher than that of control group, although these increases were not statistically significant Conclusion: We concluded that increase of ovine oocyte cAMP concentration during two-step culture partially improves yield and quality of in vitro embryo. This also may suggest that phosphodiesterase type 3-mediated inhibition of cAMP activity is not the only mechanism that controls the process of nuclear maturation in ovine oocyte.