Transcriptomic analysis of mid‐secretory endometrium reveals essential immune factors associated with pregnancy after single euploid blastocyst transfer.

Purpose: Implantation is a limiting factor for treatment success in assisted reproduction. Both embryonic and endometrial factors contribute to implantation. Embryonic factors have often been ignored in previous studies about the role of endometrium in implantation. In this study, we sought to identify the endometrial genes associated with negative pregnancy outcomes following the transfer of a single euploid blastocyst. Methods: Computational analyses of the transcriptomes of mid‐secretory endometria from nine pregnant and seven non‐pregnant patients in a cycle preceding the transfer of a single euploid blastocyst in a vitrified‐warmed cycle were performed. Results: Principal component analysis of two reported endometrial receptivity gene sets showed close clustering of the pregnant and non‐pregnant samples. Differential gene expression analysis and co‐expression module analysis identified 131 genes associated with the pregnancy status. The endometrial signatures identified highlight the importance of immune and metabolic regulation in pregnancy outcome. Network analysis identified 20 hub genes that could predict pregnancy outcomes with 88.9% sensitivity and 85.7% specificity. Single‐cell gene expression analysis highlighted the regulation of endometrial natural killer (NK) cells, T cells, and macrophages during embryo implantation. Immune cell abundance analysis supported the dysregulation of cytotoxic immune cells in the endometria of non‐pregnant women. Conclusions: We reported the first endometrial gene signature associated with pregnancy after elimination of embryo aneuploidy and highlighted the importance of the endometrial immune microenvironment and metabolic status in pregnancy outcomes. [ABSTRACT FROM AUTHOR]