Circulating and Endometrial Regulatory T Cell and Related Populations in Endometriosis and Infertility: Endometriosis Is Associated with Blunting of Endometrial Cyclical Effects and Reduced Proportions in Moderate-Severe Disease

The role of regulatory T-cells in the development of endometriosis

Endometriosis is a benign disease of the female reproductive tract, characterized by the process of chronic inflammation and alterations in immune response. It is estimated to affect 2-19% of women in the general population and is commonly associated with symptoms of chronic pelvic pain and infertility. Regulatory T cells (Treg) are a subpopulation of T lymphocytes that are potent suppressors of inflammatory immune response, essential in preventing destructive immunity in all tissues. In endometriosis, several studies have investigated the possible role of Treg cells in the development of the disease. Most studies to date are heterogeneous in methodology and are based on a small number of cases, which means that it is impossible to define their exact role at present. Based on current knowledge, it seems that disturbed Treg homeostasis, leading to increased systemic and local inflammation within ectopic and eutopic endometrium, is present in women who eventually develop endometriosis. It is also evident that different subsets of human Treg cells have different roles in suppressing the immune response. Recent studies in patients with endometriosis have investigated naive/resting FOXP3lowCD45RA+ Treg cells, which upon T cell receptor stimulation, differentiate into activated/effector FOXP3highCD45RA- Treg cells, characterized by a strong immunosuppressive activity. In addition, critical factors controlling expression of Treg/effector genes, including reactive oxygen species and heme-responsive master transcription factor BACH2, were found to be upregulated in endometriotic lesions. As shown recently for cancer microenvironments, microbial inflammation may also contribute to the local composition of FOXP3+ subpopulations in endometriotic lesions. Furthermore, cytokines, such as IL-7, which control the homeostasis of Treg subsets through the tyrosine phosphorylation STAT5 signalling pathway, have also been shown to be dysregulated. To better understand the role of Treg in the development of endometriosis, future studies should use clear definitions of Tregs along with specific characterization of the non-Treg (FOXP3lowCD45RA-) fraction, which itself is a mixture of follicular Tregs and cells producing inflammatory cytokines.

Disrupted Tuzzerella abundance and impaired L-glutamine levels induce Treg accumulation in ovarian endometriosis: a comprehensive multi-omics analysis

INTRODUCTION

The microbial community plays a crucial role in the pathological microenvironment. However, the structure of the microbial community within endometriotic lesions and its impact on the microenvironment is still limited.

METHODS

All 55 tissue samples, including ovarian ectopic (OEMs) and normal (NE) endometrium, were subjected to 16S rRNA sequencing, metabolomic and proteomic analysis.

RESULTS

We found the abundance of Tuzzerella is significantly lower in OEMs compared to NE tissue (p < 0.01). We selected samples from these two groups that exhibited the most pronounced difference in Tuzzerella abundance for further metabolomic and proteomic analysis. Our findings indicated that endometriotic lesions were associated with a decrease in L-Glutamine levels. However, proteomic analysis revealed a significant upregulation of proteins related to the complement pathway, including C3, C7, C1S, CLU, and A2M. Subsequent metabolic and protein correlation predictions demonstrated a negative regulation between L-Glutamine and C7. In vitro experiments further confirmed that high concentrations of Glutamine significantly inhibit C7 protein expression. Additionally, immune cell infiltration analysis, multiplex immunofluorescence, and multifactorial testing demonstrated a positive correlation between C7 expression and the infiltration of regulatory T cells (Tregs) in ectopic lesions, while L-Glutamine was found to negatively regulate the expression of chemotactic factors for Tregs.

CONCLUSION

In this study, we found a clear multi-omics pathway alteration, "Tuzzerella (microbe)-L-Glutamine (metabolite)-C7 (protein)," which affects the infiltration of Tregs in endometriotic lesions. Our findings provide insights into endometriosis classification and personalized treatment strategies based on microbial structures.

The effects of menstrual cycle phases on immune function and inflammation at rest and after acute exercise: A systematic review and meta-analysis

The immune system plays an important role in mediating exercise responses and adaptations. However, whether fluctuating hormone concentrations across the menstrual cycle may impact these processes remains unknown. The aim of this systematic review with meta-analysis was to compare baseline concentrations as well as exercise-induced changes in immune and inflammatory parameters between menstrual cycle phases. A systematic literature search was conducted according to the PRISMA guidelines using Pubmed/MEDLINE, ISI Web of Science, and SPORTDiscus. Of the 159 studies included in the qualitative synthesis, 110 studies were used for meta-analysis. Due to the designs of the included studies, only the follicular and luteal phase could be compared. The estimated standardized mean differences based on the random-effects model revealed higher numbers of leukocytes (-0.48 [-0.73; -0.23], p < 0.001), monocytes (-0.73 [-1.37; -0.10], p = 0.023), granulocytes (-0.85 [-0.1.48; -0.21], p = 0.009), neutrophils (-0.32 [-0.52; -0.12], p = 0.001), and leptin concentrations (-0.37 [-0.5; -0.23], p = 0.003) in the luteal compared to the follicular phase at rest. Other parameters (adaptive immune cells, cytokines, chemokines, and cell adhesion molecules) showed no systematic baseline differences. Seventeen studies investigated the exercise-induced response of these parameters, providing some indications for a higher pro-inflammatory response in the luteal phase. In conclusion, parameters of innate immunity showed cycle-dependent regulation at rest, while little is known on the exercise responses. Due to a large heterogeneity and a lack of cycle phase standardization among the included studies, future research should focus on comparing at least three distinct hormonal profiles to derive more specific recommendations for exercise prescription.

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

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.

Decrease in activated regulatory T cell populations in the endometrium during ovulation in endometriosis

Endometriosis is a serious disorder that can lead to infertility. The immune system, particularly regulatory T cells (Tregs), is involved in endometriosis and infertility; however, endometriosis-associated infertility is poorly understood. Tregs, which have an immunosuppressive function, fluctuate during the menstrual cycle. They are functionally heterogeneous and can be divided into subsets, with only activated Tregs (aTregs) having a true immunosuppressive function. The purpose of this study is to investigate the role of aTregs in endometriosis and how they contribute to endometriosis-associated infertility. We enrolled 72 women with (n = 39) and without (n = 33) endometriosis. Subpopulations of Tregs were examined in normal endometrium (NE), eutopic endometrium from women with endometriosis (EE), normal peritoneal fluid (N-PF), and peritoneal fluid from women with endometriosis (E-PF) via flow cytometry. The proportion of aTregs during the ovulatory phase was higher in NE than in EE (P < 0.05), and that during ovulatory and secretory phases was significantly higher in NE than in N-PF (P < 0.01 and 0.05, respectively). aTreg populations did not significantly differ between EE and E-PF. During the ovulatory phase, the proportion of resting Treg (rTreg) in the N-PF was significantly higher than during the proliferative phase (P < 0.05). The E-PF of rTreg populations did not differ significantly throughout the menstrual cycle. We found that Treg subsets were altered in the endometrium and PF of patients with endometriosis during the menstrual cycle. Our findings, particularly the reduction of aTregs in the EE, may provide an insight into the mechanism of endometriosis-associated infertility.

Towards a Better Understanding of Endometriosis-Related Infertility: A Review on How Endometriosis Affects Endometrial Receptivity

Endometriosis is the most common cause of infertility. Endometrial receptivity has been suggested to contribute to infertility and poor reproductive outcomes in affected women. Even though experimental and clinical data suggest that the endometrium differs in women with endometriosis, the pathogenesis of impaired endometrial receptivity remains incomplete. Therefore, this review summarizes the potential mechanisms that affect endometrial function and contribute to implantation failure. Contemporary data regarding hormone imbalance, inflammation, and immunoregulatory dysfunction will be reviewed here. In addition, genetic, epigenetic, glycosylation, metabolism and microRNA in endometriosis-related infertility/subfertility will be summarized. We provide a brief discussion and perspectives on their future clinical implications in the diagnosis and therapy to improve endometrial function in affected women.

Endometriosis-associated infertility: From pathophysiology to tailored treatment

Despite the clinically recognized association between endometriosis and infertility, the mechanisms implicated in endometriosis-associated infertility are not fully understood. Endometriosis is a multifactorial and systemic disease that has pleiotropic direct and indirect effects on reproduction. A complex interaction between endometriosis subtype, pain, inflammation, altered pelvic anatomy, adhesions, disrupted ovarian reserve/function, and compromised endometrial receptivity as well as systemic effects of the disease define endometriosis-associated infertility. The population of infertile women with endometriosis is heterogeneous, and diverse patients' phenotypes can be observed in the clinical setting, thus making difficult to establish a precise diagnosis and a single mechanism of endometriosis related infertility. Moreover, clinical management of infertility associated with endometriosis can be challenging due to this heterogeneity. Innovative non-invasive diagnostic tools are on the horizon that may allow us to target the specific dysfunctional alteration in the reproduction process. Currently the treatment should be individualized according to the clinical situation and to the suspected level of impairment. Here we review the etiology of endometriosis related infertility as well as current treatment options, including the roles of surgery and assisted reproductive technologies.

Integrated bioinformatics analysis uncovers characteristic genes and molecular subtyping system for endometriosis

Objective: Endometriosis is a chronic inflammatory estrogen-dependent disease with the growth of endometrial tissues outside the uterine cavity. Nevertheless, the etiology of endometriosis is still unclear. Integrated bioinformatics analysis was implemented to reveal the molecular mechanisms underlying this disease.

Methods: A total of four gene expression datasets (GSE7305, GSE11691, GSE23339, and GSE25628) were retrieved from the GEO, which were merged into a meta-dataset, followed by the removal of batch effects via the sva package. Weighted gene co-expression network analysis (WGCNA) was implemented, and endometriosis-related genes were screened under normal and endometriosis conditions. Thereafter, characteristic genes were determined via Lasso analysis. The diagnostic performance was estimated via receiver operating characteristic curves, and epigenetic and post-transcriptional modifications were analyzed. Small molecular compounds were predicted. Unsupervised clustering analysis was conducted via non-negative matrix factorization algorithm. The enriched pathways were analyzed via gene set enrichment analysis or GSVA. Immune features were evaluated according to immune-checkpoints, HLA, receptors, chemokines, and immune cells.

Results: In total, four characteristic genes (BGN, AQP1, ELMO1, and DDR2) were determined for endometriosis, all of which exhibited the favorable efficacy in diagnosing endometriosis. Their aberrant levels were modulated by epigenetic and post-transcriptional modifications. In total, 51 potential drugs were predicted against endometriosis. The characteristic genes exhibited remarkable associations with immunological function. Three subtypes were classified across endometriosis, with different mechanisms and immune features.

Conclusion: Our study reveals the characteristic genes and novel molecular subtyping of endometriosis, contributing to the early diagnosis and intervention in endometriosis.

Whole-Tissue Deconvolution and scRNAseq Analysis Identify Altered Endometrial Cellular Compositions and Functionality Associated With Endometriosis

The uterine lining (endometrium) exhibits a pro-inflammatory phenotype in women with endometriosis, resulting in pain, infertility, and poor pregnancy outcomes. The full complement of cell types contributing to this phenotype has yet to be identified, as most studies have focused on bulk tissue or select cell populations. Herein, through integrating whole-tissue deconvolution and single-cell RNAseq, we comprehensively characterized immune and nonimmune cell types in the endometrium of women with or without disease and their dynamic changes across the menstrual cycle. We designed metrics to evaluate specificity of deconvolution signatures that resulted in single-cell identification of 13 novel signatures for immune cell subtypes in healthy endometrium. Guided by statistical metrics, we identified contributions of endometrial epithelial, endothelial, plasmacytoid dendritic cells, classical dendritic cells, monocytes, macrophages, and granulocytes to the endometrial pro-inflammatory phenotype, underscoring roles for nonimmune as well as immune cells to the dysfunctionality of this tissue.