Effects of Low Oxygen Condition on the Development of Mouse Embryos Cultured In Viro

Abstract

Objective: It is known that mouse embryos before implantation develop in a low oxygen environment of 3- 8% concentration and with antioxidant materials such as vitamins, antioxidant enzymes, ferrous binding proteins, and albumin in follicular and tubal fluids. However, the 20% oxygen culture condition with chemically defined media might be produce an abundance of ROS, and leads to developmental delay or developmental block in vitro. In this study, we attempt to elucidate the relationship between intracellular H2O2 production and embryo development in different oxygen culture conditions of mouse embryos. Methods: Prenuclear embryos from C57BL/CBA Fl hybrid and ICR mouse were cultured in incubators which provided 5% carbon dioxide, 20% oxygen and 5% carbon dioxide, 5% oxygen. Measurement of H2O2 level in a embryo was performed with DCHFDA(2,7 -dichlorodihydroflourescein diacetate)and analyzed with Quanti-cell 700, and the number of blastomeres was counted with DAPI( 4, 6'-diamidino-2-phenylindole). Results: Oxygen concentration of the culture medias was significantly higher in the 20% oxygen environment compared to that of 5% oxygen environment. Culture of mice embryos in high oxygen condition leads to high HO concentrations at 2 cell stage and developmental delay or "2-cell block" regardless of the strain. But in a 5% oxygen environment, which is similar to in-vivo conditions HO production was suppressed continuously through out culture and development of embryos was definitely improved. Conclusion: These results suggest that there is a difference in the production of ROS or protective mechanism according to the mouse strains and stage of development, and it is thought that in-vitro culture in 5% oxygen environment provides stable in vivo equilibrium but in a 20% oxygen environment there is production of ROS which overcome the protective mechanism which leads to cellular damage and embryo developmental delay.