Effect of vitrification using the Cryotop method on the gene expression profile of in vitro-produced bovine embryos

The present study analyzed the changes in gene expression induced by the Cryotop vitrification technique in bovine blastocyst-stage embryos, using Agilent EmbryoGENE microarray slides. Bovine in vitro-produced embryos were vitrified and compared with nonvitrified (control) embryos. After vitrification, embryos were warmed and cultured for an additional 4 hours. Survived embryos were used for microarray analysis and quantitative polymerase chain reaction (qPCR) quantification. Survival rates were higher (P < 0.05) in the control embryos (100%) than in the vitrified embryos (87%). Global gene expression analysis revealed that only 43 out of 21,139 genes exhibited significantly altered expression in the vitrified embryos compared to the control embryos, with a very limited fold change (P < 0.05). A total of 10 genes were assessed by qPCR. Only the FOS-like antigen 1 (FOSL1) gene presented differential expression (P < 0.05) according to both the array and qPCR methods, and it was overexpressed in vitrified embryos. Although, the major consequence of vitrification seems to be the activation of the apoptosis pathway in some cells. Indeed, FOSL1 is part of the activating protein 1 transcription factor complex and is implicated in a variety of cellular processes, including proliferation, differentiation, and apoptosis. Therefore, our results suggest that a limited increase in the rate of apoptosis was the only detectable response of the embryos to vitrification stress.