The Relevance of the Deer as an Animal Model for Studying the Contaminant Effect on Early Embryo Development

Abstract

Nowadays, environmental contaminants are a ubiquitous part of the ecological scenario, as is the ability of many of these chemicals to alter embryo development. There is therefore a need for researching and clarifying the effects of contaminants during different phases of early embryo development in humans. The use of alternative animal models may provide new insights into research on human embryo development, and the Iberian red deer may be a viable option. The main advantage of this animal model is the availability of samples which have not been sacrificed for this purpose, as we have access to samples (mature spermatozoa and oocytes) from animals killed during hunting activities. Therefore, our aim was to optimize the system that allows us to carry out in vitro fertilization (IVF) in deer, to then assess the effect of different contaminants on embryonic development. The aim of this work was to test two different oxygen concentrations (5 percent or 20 percent) on the in vitro fertilization. We have also assessed the addition, or not, of fetal calf serum (FCS) during embryo culture after IVF. Ovaries and testicles were transported to the laboratory at 20 ºC. Oocytes were matured in TCM 199 supplemented with 10 percent foetal calf serum, 100 mM cysteamine and 10 µgmL-1 FSH and LH during 24 h with 20 percent CO2. Matured oocytes were inseminated with thawed epididymal spermatozoa during 18 h at 38.5ºC with 5 percent or 20 percent O2.The presumptive embryos were cultured with synthetic oviductal fluid (SOF) supplemented with FCS at 0 hour, at 2 days post insemination (d.p.i.), 4 d.p.i. and without FCS at 38.5ºC with 5 percent CO2. Our results showed that treatment rendering best results for cleavage and blastocyst rates included five percent oxygen and embryo culture without fetal calf serum, as these conditions are quite similar to those used in human IVF. In conclusion, the optimization of the in vitro embryo development system in deer might prove useful information for the role of contaminants during this critical physiological period. Alternative animal models may contribute to advance our understanding of the effect of contaminants on early embryo development in humans.