Establishment of a Single-Oocyte Culture System for Pigs and Its Validation Using Curcumin as a Model Antioxidant for Oocyte Maturation

Since individual embryos cannot be evaluated in group culture, establishing a single culture from in vitro maturation to in vitro culture may provide new insights into oocyte and embryo quality. This study aimed to develop a single culture system for individual oocytes, from in vitro maturation through fertilization to embryo development. The effects of curcumin supplementation during in vitro maturation on oocyte maturation, embryo development, and embryo quality were examined in single and group culture systems. Porcine oocytes were cultured individually in 20 µL microdroplets, with one oocyte per droplet, or in groups of 50 oocytes per 500 µL. The maturation medium contained curcumin at concentrations of 20 µM or less. Supplementation with 10 µM curcumin increased oocyte maturation in both systems compared to the controls. The fertilization rates and oocyte/embryo quality did not differ among the treatment groups. Oocytes matured with 10 µM curcumin in a single culture showed a higher blastocyst formation rate (7.0%) than the control (2.3%). In the group culture, 10 µM curcumin increased cleavage rates compared to the control (75.2% vs. 63.0%), but blastocyst formation rates did not differ. Blastocyst formation rates were similar between single and group cultures under control (2.3% and 4.3%, respectively) or 10 µM curcumin (7.0% and 11.4%, respectively) conditions. Therefore, porcine oocytes can develop to the blastocyst stage in a single culture system. Incorporating antioxidants during in vitro maturation may be an effective condition for in vitro embryo culture that can be implemented in a single oocyte.