The effect of vitrification on pluripotency specific genes, Oct4 and Nanog in mouse blastocysts

From the first vitrification of mouse embryos in 1985, considerable efforts have been made to develop and improve cryopreservation techniques, but still biochemical and fetal chromosomal abnormalities caused by vitrification can cause changes in the pattern of genes expression involved in embryonic development and function, reduced implantation and fetal death. The purpose of this study was to investigate the effects of vitrification on survival and the expression of pluripotency specific genes like Oct4 and Nanog in the vitrified-warmed mouse blastocysts.
Methods & Materials: Harvested blastocysts from superovulated female mice were vitrified in the presence of dimethyl sulfoxide 15%, ethylene glycol 15% and sucrose 0.5 M as cryoprotectants and vitrified in liquid nitrogen after loading on Cryotop. Thawing process was performed by immersing the blastocysts in thawing solution prepared using sucrose 1 M. Survival and hatching rates were evaluated and also the Oct4 and Nanog genes expression in vitrified- thawed and fresh blastocysts (control group) were assessed by real time-PCR method.
Survival and hatching rates decreased significantly in vitrified blastocysts compared with control group (94.43± 5.81% vs. 100% for survival and 57.78± 11.76% vs. 86.88± 5.80% for hatching). Also increased expression of Nanog and Oct4 genes were observed in vitrified- warmed blastocysts.
Considering the results of this study, it can be said that vitrification of mouse embryo at the blastocyst stage can change gene expression and quality of the embryo.