Single-cell transcriptome analysis reveals endometrial immune microenvironment in minimal/mild endometriosis

Abstract

Endometriosis is a common inflammatory disorder in women of reproductive age due to an abnormal endometrial immune environment and is associated with infertility. This study aimed to systematically understand the endometrial leukocyte types, inflammatory environment, and impaired receptivity at single-cell resolution. We profiled single-cell RNA transcriptomes of 138,057 endometrial cells from endometriosis patients (n=6) and control (n=7), respectively, using 10x Genomics platform. We found that one cluster of epithelial cells that expressed PAEP and CXCL14 was mostly from the control during the window of implantation (WOI). This epithelial cell type is absent in the eutopic endometrium during the secretory phase. The proportion of endometrial immune cells decreased in the secretory phase in the control group, whereas the cycle variation of total immune cells, NK cells, and T cells was absent in endometriosis. Endometrial immune cells secreted more IL-10 in the secretory phase than in the proliferative phase in the control group; the opposite trend was observed in endometriosis. Proinflammatory cytokines levels in the endometrial immune cells were higher in endometriosis than in the control group. Trajectory analysis revealed that the secretory phase epithelial cells decreased in endometriosis. Ligand–receptor analysis revealed that 11 ligand-receptor pairs were upregulated between endometrial immune and epithelial cells during WOI. These results provide new insights into the endometrial immune microenvironment and impaired endometrial receptivity in infertile women with minimal/mild endometriosis.

An integrated single-cell reference atlas of the human endometrium

“…We started by creating a single-cell reference atlas, which we termed the HECA ( Figure 1c ). To create the HECA, we integrated six publicly available single-cell RNA sequencing (scRNA-seq) datasets (Wang et al 14 , Garcia-Alonso et al 15 , Tan et al 16 , Lai et al 19 , Fonseca et al 17 , Huang et al 18 ) with our newly generated dataset (termed Mareckova (cells) dataset) ( Figure 1b ). Harmonisation of metadata across the studies and application of strict data quality control filters ( see Methods ) was essential for the integration.…”

“…the eutopic endometrium) differs between those with and without endometriosis 26,27 . Recently, single-cell studies analysing small sample sizes, reported dysregulation of the stromal and immune compartments in the endometrium of women with endometriosis to various degrees 16,18,20,28,29 . Larger sample sets are now needed if we are to unpick whether and how the endometrium differs in those with and without the condition.…”

Endometriosis in the era of precision medicine and impact on sexual and reproductive health across the lifespan and in diverse populations

“…Menstrual endometrium scRNAseq in endometriosis patients reveals decreased decidualization markers in stromal fibroblasts, reduced frequencies of uNK cells, and enrichment of B cells, demonstrating that menstrual endometrium reflects secretory endometrium abnormalities as possible biomarkers of disease 89 . Another study on mid‐secretory endometrium (i.e., the window of implantation, (WOI)) of stage I/II subjects revealed that in one epithelial cell cluster PAEP and CXCL14 expression was absent, immune cells had higher pro‐inflammatory cytokine expression, and no cycle variation of uNK and T cell frequencies was observed versus controls 91 . Lower epithelial receptivity markers, abnormal immune cell frequencies, and a pro‐inflammatory WOI likely adversely affect implantation and pregnancy outcomes in patients with stage I/II disease.…”

“…[84][85][86][87] These studies underscore heterogeneity of specific cell types and altered features in different hormonal states across the menstrual cycle and provide a key backdrop to studies on endometrium and endometriosis lesions at the single-cell level. Recently, scRNAseq [88][89][90][91][92] have complemented bulk tissue, blood, peritoneal fluid, and in vitro cellular and tissue organoid analyses of endometriosis lesions and endometrium from cases versus controls without disease (Table 2). These have provided further insights into the heterogeneity of cell types/subtypes, unique clusters, and signatures informing mechanisms and pathways involved in cellular dysfunctions relevant to pain and fertility compromise in patients with disease.…”

“…89 Another study on mid-secretory endometrium (i.e., the window of implantation, (WOI)) of stage I/II subjects revealed that in one epithelial cell cluster PAEP and CXCL14 expression was absent, immune cells had higher pro-inflammatory cytokine expression, and no cycle variation of uNK and T cell frequencies was observed versus controls. 91 Lower epithelial receptivity markers, abnormal immune cell frequencies, and a pro-inflammatory WOI likely adversely affect implantation and pregnancy outcomes in patients with stage I/II disease.…”