Roscovitine Improved the Cytoplasmic Maturation of Bovine Oocytes and Subsequent Embryo Quality

This study examined the effects of different concentrations of roscovitine (ROSC) on cytoplasmic maturation in bovine oocytes and subsequent embryo development. Oocytes were prematured with ROSC at concentrations of 0, 25, 37.5, 50 and 75 µM for 6 h. A significant increase in the number of oocytes at GV stage was observed in the treatment groups compared to the control group, indicating an inhibitory effect of ROSC on meiosis. After continued culture in a maturation solution without ROSC for 18 h, oocytes did not exhibit significant difference in maturation rates between the treatment and control groups, suggesting that the inhibitory effect of ROSC is reversible. Further analysis revealed that a 37.5 µM ROSC treatment significantly enhanced homogeneous mitochondrial distribution, mitochondrial membrane potential, and glutathione levels in mature oocytes, while reducing reactive oxygen radical content. IVF blastocysts from oocytes treated with 37.5 μM ROSC had a significant increase in the total cell number, and inner cell mass/total cell number ratio, and a reduction in apoptosis rate, despite no significant differences in cleavage or blastocyst rates compared to controls. These findings suggested that prematuration with 37.5 µM ROSC promoted cytoplasmic maturation in bovine oocytes and improved embryo quality. This study analyzed comprehensively the impacts of meiosis arrest induced by ROSC on cytoplasmic maturation in oocyte and embryo quality from various perspectives for the first time.