Gene Expression Profiling of Viable IVF Blastocysts

The vast majority of embryos generated by assisted reproduction technology fail to implant. This failure must be ascribed to the embryo rather than the uterus as it is not uncommon to attain a single implantation following the transfer of more than one embryo of good morphological quality. Current embryo selection criteria are inadequate and confounded by the practice of transferring more than one embryo so that identification of the origin of subsequent offspring is usually not possible. The aim of the present study was to test the hypothesis that a viable embryo has a different gene expression profile to that of a non-viable embryo. Retrospective institutional ethics committee approved study of gene expression in human blastocyst biopsy samples with respect to implantation competence following blastocyst transfer. Forty-eight patients undergoing assisted reproduction treatment consented to blastocyst biopsy followed by blastocyst transfer. Ten to twenty trophectoderm (TE) cells were biopsied from each blastocyst. Seven patients had transfers where all embryos implanted (defined as viable embryos, group 1). In contrast, 18 patients had transfers where none of the embryos implanted (defined as non-viable embryos, group 2). TE biopsy samples were washed and placed in lysis buffer to preserve cellular RNA then snap frozen. cRNA was generated from samples using the Picopure RNA isolation and RiboAmpHS RNA Amplification Kits (Arcturus). Microarray analysis was performed using human whole genome gene chips (GE Healthcare) containing 54,840 transcript probes. Analysis of expression data was performed using Codelink and Genesprings software. The cRNA from a pool of group1 embryos (n=8) and a pool of group 2 embryos (n=8) were subjected to separate microarray analysis. Collectively, 44406 and 43142 transcripts were expressed by viable and non-viable embryos and of these, 35238 were present in both samples. A small subset of genes within the commonly expressed pool were differentially expressed (>5-fold difference). Of note there were 9,230 genes uniquely expressed by viable embryos. The majority of these genes were confirmed to be present in a second pool of cRNA from embryos known to implant. Comparison of gene expression profiles from viable and non-viable embryos using microarrays has identified and confirmed genes associated with viability. This data provides a platform for designing new assays to determine embryo viability in an IVF setting.