P-33: The Effect of Vitrification on Integrity ofZona Pellucida and Blastocyst Surveillance

Background: In spite of the great advances in vitrification, the mechanism of embryo damage which occure in some cases and varies from one case to another case is not exactly understood. Since Zona pellucida has an important role on early embryonic development, the aim of the present study is to investigate the effect of vitrification on integrity of zona pellucida and surveillance of blastocysts in mice. Materials and Methods: For this purpose 30 balb-c mice superovulated and blastocysts were obtained by flushing and divided into control and experimental groups. In control group the blastocysts were transferred to DMEM media. 24 hours after the culture, morphological characteristics of zona pellucid and blastomers were studied by inverted microscope. In the experimental group, the blastocysts after collection were vitrified for one month. After thawing, the blastocysts were transferred to DMEM media and treated as in control group and compared with eachother. Results: The result showed that all of the blastocysts in control group (100%) had intact Zona pellucid and blastomeres appeared normal which were considered as live blastocysts. However, in experimental group, in 40% of blastocysts tne Zona pellucid were broken or separated from the blastocysts and blastomeres appeared shrunken and darkened which were considered as non alive blastocysts.Conclusion: Blastocysts damage during vitrification is accompanied with zona breakdown, and it could be concluded that vitrification induced embryonic damages is partly due to the zona breakdown.