Effects of oxygen tension on gene expression in preimplantation mouse embryos

Objective: To compare the effects of atmospheric and physiologic oxygen concentrations on the global patterns of gene expression during mouse preimplantation development. Design: Comparative analysis of in vivo-produced and in vitro-produced embryos. Setting: Research laboratory. Patient(s): None. Intervention(s): Control embryos at the blastocyst stage that developed in vivo were collected from uteri. Experimental embryos were obtained at the zygote stage and cultured to the blastocyst stage in Whitten's medium or KSOM medium with amino acids under 20% oxygen (atmospheric) or 5% oxygen (physiologic). Main Outcome Measure(s): Embryo development, cell number, and gene expression assayed by microarray technology. Result(s): Low (physiologic) oxygen concentration is associated with faster embryo development and increased cell number. In addition, there are marked perturbations in the global pattern of gene expression, as assessed by oligonucleotide microarray, after culture in 20% oxygen as compared with 5% oxygen. Conclusion(s): Culture in low oxygen is associated with fewer perturbations in the global pattern of gene expression and more closely resembles that of the in vivo control embryos. These findings provide rationale for culturing human embryos in the presence of 5%, rather than 20% oxygen.