Effect of the meiotic inhibitor cilostamide on resumption of meiosis and cytoskeletal distribution in buffalo oocytes

•Addition of cilostamide to the pre-maturation culture arrests the resumption of meiosis.•Prolonging the maturation culture period improves oocyte development in IVM.•Dynamic changes in microtubules and microfilaments were similar to the control.•Cilostamide didn't adversely affect the in vitro maturation of oocytes and their subsequent embryo development.

Improving the quality of in vitro maturated buffalo oocytes is essential for embryo production. We report here the effects on microtubules and microfilaments in oocytes and embryo development that result from treating buffalo oocytes with the phosphodiesterase 3 (PDE3) inhibitor cilostamide. Addition of 20 μM or 50 μM cilostamide for 24 h during in vitro maturation showed no differences in the percentage of oocytes arrested at the germinal vesicle (GV) stage. When 20 μM cilostamide was added to the pre-maturation culture for 6 h, 12 h or 24 h and continued for another 24 h without cilostamide, oocytes resumed meiosis, but with significantly lower (P < 0.01) maturation rates in the 24 h group than that in the other two groups. During oocyte maturation in vitro, no microtubules were detected before GV breakdown (GVBD). After GVBD, microtubules combined with condensed chromatin to form the meiotic metaphase spindle. Microfilaments covered a thick area around the cellular cortex and overlying chromosomes. Cilostamide had no effects on microtubules and microfilaments in metaphase II oocytes, and there were no significant differences in the rates of cleavage, blastocyst formation and number of blastocyst cells between oocytes treated pre-maturation with inhibitor for 6 h and those of the control group (P > 0.05). In summary, cilostamide reversibly arrested the resumption of meiosis without any adverse impact on the dynamic changes in microtubules and microfilaments in buffalo oocytes and their in vitro developmental capacity.