Culture medium and embryo density influence on developmental competence and gene expression of cat embryos

Morphology and gene expression are the currently preferred methods for assessing the effect of culture medium and density on embryos of several species. To define their effects on domestic cat embryos, groups of 8-10 embryos were cultured in SOF, modified Tyrode's solution or MK-1 medium in a fixed volume (50 μL) and in different volumes (20, 50 and 100 μL). SOF supplemented with different concentrations of glucose (1.5, 3.0 and 6.0 mM) was used to examine the effect of glucose level on embryo development. Real-time reverse transcriptase polymerase chain reaction was used to determine the relative transcripts of BAX, BCL-2 and GLUT-1 genes in blastocysts derived from various concentrations of glucose. SOF and MK-1 supported feline embryo development better than modified Tyrode's solution. Embryos cultured in 20 μL droplets showed decreased development in all three media (P < 0.05). Increasing the glucose concentration in SOF to 6.0 mM adversely affected embryo development and tended to increase the BCL-2 transcript in blastocysts. In conclusion, type of culture medium, embryo density and glucose concentration affected the development of domestic cat embryos. High culture density and glucose concentration negatively affected embryo development. The increase of anti-apoptotic BCL-2 expression found in blastocysts cultured in 6.0 mM glucose may have prevented an increase in the incidence of apoptosis. In the present study, it was clearly demonstrated that differential gene expression occurred in embryos with similar morphology.