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 O2], 5% [low O2] and 5% decreased to 2% [dynamic O2]) 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-O2 and low-O2 groups were cultured from the one-cell to the blastocyst stage under 20% and 5% oxygen concentrations, respectively. In the dynamic-O2 group, mouse embryos were cultured from the one-cell to the morula stage under 5% O2 for 3 days, followed by culture under 2% O2 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-O2 and dynamic-O2 groups than in the high-O2 group. The total cell number was significantly higher in the dynamic-O2 group than in the low-O2 and high-O2 groups. Additionally, the apoptotic index was significantly lower in the low-O2 and dynamic-O2 groups than in the high-O2 group. The trophoblast outgrowth rate and spread area were significantly higher in the low-O2 and dynamic-O2 groups than in the high-O2 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.