Transcriptional analyses of endometrial caruncles in sheep with in vivo / in vitro produced embryos during the peri-implantation period.

In vitro fertilization (IVF) for ovine embryos is strongly associated with low pregnancy rates and negative effects on embryonic and postnatal development, but the mechanisms remain unclear. We aimed to identify genes essential for successful implantation of IVF embryos in sheep by species-specific microarray analysis. Differential gene expression analysis between caruncles and intercaruncle sites of the ovine uterus with in vivo (IVV) -produced embryos on day 10 of pregnancy found 43 differentially expressed genes (DEGs) with at least a 2-fold change, such as coiled-coil domain-containing 152 (CCDC152) and pregnancy-associated plasma protein A (PAPPA). Gene ontology analysis revealed these DEGs were related to cell proliferation, the immune system process, localization and response to stimulus. Moreover, we identified 93 DEGs in endometrial caruncles with IVV- versus in vitro (IVT)-produced embryos on days 12, 14 and 16 of pregnancy, including prostaglandin-endoperoxide synthase 2 (PTGS2) and cubilin (CUBN). GO analysis revealed that these DEGs were related to cell adhesion, cell proliferation, embryo implantation, embryonic morphogenesis, the immune system process and localization. Two DEGs (PAPPA and RSAD2) in caruncle versus intercaruncle sites at day 10 were also differentially expressed between the IVV and IVT groups at the three implantation stages. Self-organizing feature map cluster analysis of transcript profiles during embryo implantation revealed different gene expression patterns between the IVV and IVT groups. In conclusion, this study identified many genes that may be associated with mechanisms underlying IVF-induced ovine embryo implantation failure during the peri-implantation period, and such genes provide potential candidates for further study.