Abstract

The purpose of this study was to investigate the effects of 2 vitrification procedures on the developmental capacity and ultrastructural changes of matured swamp buffalo (Bubalus bubalis) oocytes. In vitro-matured (IVM) oocytes were vitrified by using 35% and 40% ethylene glycol (EG) as vitrification solution (VS) for solid surface vitrification (SSV) and in-straw vitrification (ISV), respectively. Survival rate of vitrified–warmed oocytes was evaluated on the basis of homogeneous cytoplasm, membrane integrity, and complete zona pellucida. All developmental data were analyzed using chi-square analysis. P < 0.05 was considered significant. The blastocyst rates of parthenogenetic vitrified–warmed oocytes were significantly higher with SSV (89.3% and 13.6%, respectively) than with ISV (81.8% and 5.5%, respectively). However, they were still significantly lower than those of control (100% and 34.2%, respectively). For examining the ultrastructural changes, fresh VS-exposed (ISV and SSV), and vitrified–warmed oocytes were processed for transmission electron microscopy. In VS-exposed oocytes, reduction of microvilli abundance and damage of mitochondrial membrane were found only in the ISV group. In vitrified–warmed oocytes, however, it was clear that both methods of vitrification induced profound ultrastructural modifications to microvilli, mitochondria, oolemma, and cortical granules as well as to the size and position of vesicles. Damaged mitochondria were, however, more abundant in ISV vitrified oocytes than in SSV vitrified oocytes, which correlated with the developmental data, showing the superiority of the SSV method. This study demonstrated for the first time the feasibility of vitrification of IVM swamp buffalo oocytes.