Oxygen-regulated expression of GLUT-1, GLUT-3, and VEGF in the mouse blastocyst.

The oxygen concentration used in the incubation atmosphere during embryo culture influences embryo development rates and embryo quality. In somatic cells, oxygen levels can influence the expression of a range of genes, including glucose transporters, glycolytic enzymes, and angiogenic growth factors. Many of these oxygen-regulated genes have important roles in embryonic development and metabolism. The aim of this study was to determine whether oxygen regulates gene expression in the preimplantation mouse blastocyst. Mouse embryos were cultured from the 1-cell to morula stage under 7% oxygen, followed by culture under 20, 7, or 2% oxygen to the blastocyst stage. Expression of glucose transporter (GLUT)-1, GLUT-3, and vascular endothelial growth factor (VEGF) in blastocysts was measured by real-time reverse transcription PCR. Development from morula to blastocyst was not altered by culture under different oxygen conditions. Expression of GLUT-1, GLUT-3, and vascular endothelial growth (VEGF) was increased by 2- to 4-fold in embryos cultured under 2% oxygen, when compared to embryos cultured under 20 or 7% oxygen, and when compared to embryos developed in vivo (all P < 0.001). These results suggest that the preimplantation mouse embryo has the capacity to detect and respond to low oxygen availability with changes in expression of oxygen-regulated genes.