Dimethyl sulfoxide inhibits spontaneous oocyte fragmentation and delays inactivation of maturation promoting factor (MPF) during the prolonged culture of ovulated murine oocytes in vitro

Abstract

In this study, the effects of dimethyl sulfoxide (DMSO) on the spontaneous aging of ovulated murine oocyte were evaluated in vitro. When ovulated oocytes were cultured continuously in vitro without fertilization stimulation, they underwent several phenotypic changes, including non-activation, activation, fragmentation, and lysis. To investigate the effects of DMSO on these changes, I cultured ovulated oocytes with various concentrations of DMSO and evaluated the phenotypic changes for up to 3days. After 3days of culture, the frequency of oocyte fragmentation was significantly lower in oocytes treated with 2 and 4% DMSO (7 and 5%, respectively) than in control oocytes (80%). All control oocytes were activated or fragmented after 3days of culture in vitro. However, more than 80% of the oocytes cultured with 4% DMSO for 3days contained spindles and condensed chromosomes, although they displayed abnormal spindle structures. Next Cdk1 activity in DMSO-treated oocytes was examined. The results showed that DMSO treatment prevented the reduction in Cdk1 activity during prolonged culture. Moreover, DMSO inhibited the degradation of cyclin B. These results suggest that DMSO inhibits spontaneous oocyte fragmentation and maintains Cdk1 activity in ovulated murine oocytes during prolonged culture in vitro, possibly by inhibiting cyclin B degradation.