Characterization of the Endometrial Transcriptome in Early Diestrus Influencing Pregnancy Establishment in Dairy Cattle after Transfer of In-Vitro Produced Embryos

Modifications of the endometrial transcriptome at day 7 of the estrus cycle are crucial to maintain gestation after transfer of in-vitro produced (IVP) embryos. The aim of this study was to identify genes, and their related biological mechanisms, in the endometria of recipient lactating dairy cows that become pregnant in the subsequent estrus cycle upon transfer of IVP embryos. Endometrial biopsies were taken from lactating Holstein Friesian cows on day 6-8 of the estrus cycle followed by embryo transfer in the following cycle. Animals were classified retrospectively as pregnant (PR, n=8) or non-pregnant (non-PR, n=11) cows, according to pregnancy status at 26-47 days. Extracted mRNAs from endometrial samples were sequenced with an Illumina platform to determine differentially expressed genes (DEG) between the endometrial transcriptome from PR and non-PR cows. There were 111 DEG (FDR<0.05), which were mainly related to extracellular matrix interaction, histotroph metabolic composition, prostaglandin synthesis, TGF-{beta} signaling as well as inflammation and leukocyte activation. Comparison of these DEG with DEG identified in two public external datasets confirmed the more fertile endometrial molecular profile of PR cows. In conclusion, this study provides insights into the key early endometrial mechanisms for pregnancy establishment, after IVP embryo transfer in dairy cows.