"Our results are not directly applicable to children conceived through assisted reproductive technology," said Richard M. Schultz, a professor in Penn's Department of Biology and a co-author of the study. "Nevertheless, the results highlight the need for further research to optimize culture conditions for human embryos."
In a test that measures anxiety, male mice developed from cultured embryos spent more time in open spaces, a behavior that runs counter to a mouse's fear of being in the open and suggests a decrease in anxiety. Another test that measures learning and memory demonstrated that, although there was no difference in learning for culture-derived mice of either sex, small, but significant, decreases in memory were observed. No differences in development or motor skills were found.
According to the researchers, their findings suggest a broader need to examine carefully practices associated with assisted reproductive technologies. Their study notes an increasing trend to culture human embryos longer to choose the "best" embryos for transfer and to minimize multiple pregnancies. In mice, previous studies have shown that many genes are mis-expressed in the developing embryo in response to culture and the magnitude of this mis-expression is influenced by the composition of the culture medium. Similar studies on the effect of embryo culture on gene expression in humans are lacking.
"Overall, our findings suggest that a special effort should be made to minimize the effect of culture on pre-implantation embryos," said Ted Abel, an assistant professor in Penn's Department of Biology and co-author of the study. "Decreasing the length of time between fertilization and implantation and further refining the composition of the culture medium are two ways that may mitigate risk."