Potential Biomarkers and Endometrial Immune Microenvironment in Recurrent Implantation Failure

Abstract

The molecular mechanisms underlying unexplained recurrent implantation failure (RIF) remain unclear. This study aimed at identifying potential biomarkers, exploring relevant signaling pathways, and analyzing the contribution of immune cell infiltration in RIF. Microarray expression datasets were extracted from the Gene Expression Omnibus database to perform bioinformatic analyses. The results showed that ten hub genes may predict RIF with high specificity and sensitivity (area under the curve = 1.000). Protein–protein interaction analysis revealed close interactions between the hub genes and the endometrial receptivity array. The real-time quantitative polymerase chain reaction further validated three potential biomarkers (RAB32, TRIB2, and FAM155B). Functional enrichment analyses indicated that immune pathways were significantly downregulated and lipid metabolism pathways were significantly upregulated in RIF compared with the controls. Significant negative correlations were observed between fatty acid biosynthesis and the immune pathways. Immune cell infiltration, including those in CD56dim natural killer, dendritic, Th1, Th2, and regulatory T cells, as well as macrophages, was significantly reduced in RIF compared with the controls used herein. This study may provide a novel perspective on the diagnosis and treatment of RIF.

Assessment of immune cells in the uterine fluid at the time of the embryo transfer

“…40 Altered presence of CD8 and CD4 T cells have been associated with pregnancy outcomes after fresh and frozen embryo transfer, idiopathic infertility, and RIF. 14,26,27 We found 3:1 ratio of CD8 to CD4 T cells in the lower, and 2:1 in the upper uterus (Figure 5), which is in line with the reported data about first-trimester human decidual CD8 cells that constitute approximately 45% of total T cells. [41][42][43] Within the nonpregnant human uterus, CD8+ T cells have cytotoxic capabilities with fluctuating activity throughout the menstrual cycle.…”

“…CD8 T cells are necessary to establish a healthy pregnancy via optimal immune regulation to provide protection again infections while avoiding a harmful response to allogeneic fetal cells 40 . Altered presence of CD8 and CD4 T cells have been associated with pregnancy outcomes after fresh and frozen embryo transfer, idiopathic infertility, and RIF 14,26,27 . We found 3:1 ratio of CD8 to CD4 T cells in the lower, and 2:1 in the upper uterus (Figure 5), which is in line with the reported data about first‐trimester human decidual CD8 cells that constitute approximately 45% of total T cells 41–43 .…”

“…[7][8][9][10][11] Recently, Kasvandik et al, showed that protein content of uterine fluid differs in recurrent implantation failure (RIF) patients 12 correlation of immune cell activity with RIF. [13][14][15][16] Molecular mechanisms that control leukocyte migration across epithelial cells in the gut and lungs have been characterized in vivo. [17][18][19] Furthermore, dysregulated neutrophil recruitment across epithelial surfaces was linked to pathophysiology of numerous inflammatory diseases, such as inflammatory bowel disease (IBD).…”

“…Cellular composition of uterine fluid has never been addressed before, so our study gives a deeper biological insight to better understand the function of uterine fluid in facilitating pregnancy. The presence of immune cells in the pre/peri‐implantation and pregnant endometrium tissue has long been established as well as a correlation of immune cell activity with RIF 13–16 . Molecular mechanisms that control leukocyte migration across epithelial cells in the gut and lungs have been characterized in vivo 17–19 .…”