Effects of dynamic oxygen concentrations on the development of mouse pre- and peri-implantation embryos using a double-channel gas supply incubator system

OBJECTIVE: We aimed to evaluate the effects of different oxygen conditions (20% [high O(2)], 5% [low O(2)] and 5% decreased to 2% [dynamic O(2)]) on mouse pre- and peri-implantation development using a novel double-channel gas supply (DCGS) incubator (CNC Biotech Inc.) to alter the oxygen concentration during in vitro culture. METHODS: The high-O(2) and low-O(2) groups were cultured from the one-cell to the blastocyst stage under 20% and 5% oxygen concentrations, respectively. In the dynamic-O(2) group, mouse embryos were cultured from the one-cell to the morula stage under 5% O(2) for 3 days, followed by culture under 2% O(2) to the blastocyst stage. To evaluate peri-implantation development, the blastocysts from the three groups were individually transferred to a fibronectin-coated dish and cultured to the outgrowth stage in droplets. RESULTS: The blastocyst formation rate was significantly higher in the low-O(2) and dynamic-O(2) groups than in the high-O(2) group. The total cell number was significantly higher in the dynamic-O(2) group than in the low-O(2) and high-O(2) groups. Additionally, the apoptotic index was significantly lower in the low-O(2) and dynamic-O(2) groups than in the high-O(2) group. The trophoblast outgrowth rate and spread area were significantly higher in the low-O(2) and dynamic-O(2) groups than in the high-O(2) group. CONCLUSION: Our results showed that a dynamic oxygen concentration (decreasing from 5% to 2%) had beneficial effects on mouse pre- and peri-implantation development. Optimized, dynamic changing of oxygen concentrations using the novel DCGS incubator could improve the developmental competence of in vitro cultured embryos in a human in vitro fertilization and embryo transfer program.