Research update for the immune microenvironment of chronic endometritis

Causal association of immune cells and endometritis: a Mendelian randomization study

Research exploring the link between immune cell profiles and the development of endometritis remains scant. This gap necessitates further study to decode the complex interrelations influencing this condition. In this analysis, we leveraged two-sample Mendelian randomization to examine the causal ties between the phenotypes of immune cells and the incidence of endometritis. Our evaluation hinged on data from 3757 participants hailing from Sardinia, focusing on a diverse array of 731 immune phenotypes, and cross-referenced with endometritis data sourced from the UK Biobank. To ensure rigor, we performed sensitivity analyses, utilized MR-Egger and MR-Presso to check for pleiotropy, and applied Cochran's Q test for assessing the heterogeneity of our findings. Our investigation identified numerous immune characteristics associated with endometritis. For certain immune traits, a lower risk of endometritis was observed, including: Absolute Counts of CD39 + CD4 + T cells, CD25 + CD39 + CD4 regulatory T cells, and CD25 + + CD8 + T cells; Absolute Counts of Switched Memory B cells; CD19 expression on IgD + CD38dim and Switched Memory B cells; CD20 expression on IgD + CD38- Unswitched Memory B cells; percentage of Switched Memory B cells among lymphocytes; CD16-CD56 expression on HLA DR + Natural Killer cells; percentage of CD11c + CD62L- monocytes; CD86 expression on monocytes; CCR2 expression on CD14 + CD16 + monocytes; and CD14 expression on Monocytic Myeloid-Derived Suppressor Cells, with Odds Ratios (ORs) between 0.413 and 0.703. On the contrary, increased risks of endometritis were linked with: the percentage of Effector Memory CD4 + T cells within the CD4 + T cell population; percentages of HLA DR + T cells and HLA DR + CD8 + T cells among T cells; CD4 expression on CD28 + CD4 + T cells; CD20 expression on CD20- CD38- B cells; percentage of IgD + CD24 + B cells within the B cell population; CD62L expression on CD62L + myeloid Dendritic Cells; and Absolute Counts of Plasmacytoid Dendritic Cells, with ORs from 1.473 to 2.677, indicating these traits potentially elevate the risk of developing endometritis. Our research delineates distinct causal links between specific immune cell phenotypes and endometritis, offering new perspectives that could contribute to the pinpointing of new therapeutic avenues for this condition.

Analysis of the Predictive Factors for Chronic Endometritis Recurrence in Infertile Women

PROBLEM

To identify the predictive factors for the recurrence of chronic endometritis (CE) in infertile women.

METHOD OF STUDY

In this case-control study, 1170 infertile women recovered from CE and underwent fertility treatment between December 2018 and August 2021. Among the 146 women (12.5%) who did not conceive or experienced pregnancy loss in 18 months after CE recovery, 105 consecutive women who underwent repeat endometrial biopsy for CD138 immunostaining and endometrial bacterial culturing were recruited. Thereafter, patients with and without CE recurrence were compared.

RESULTS

The total recurrence rate of CE was 29.5% (31 women). Multivariable logistic regression analysis to determine predictive factors for CE recurrence revealed that hysteroscopic surgery (odds ratio [OR], 0.10; 95% confidence interval [CI], 0.02-0.56; p = 0.0009) and pregnancy loss (OR, 4.13; 95% CI, 1.31-13.05; p = 0.016) were significantly associated with decreased and increased CE recurrence rates, respectively. Also, reexamination with CD138 immunostaining after 16-18 months (OR, 9.75; 95% CI, 1.47-64.64; p = 0.024) was significantly associated with increased CE recurrence rates. Among 49 patients without a history of pregnancy loss, the cumulative CE recurrence rates after 6, 12, and 18 months were 5.6%, 13.5%, and 20.4%, respectively.

CONCLUSIONS

We recommend reexamination with endometrial CD138 immunostaining in patients with pregnancy loss or long-term infertility during fertility treatment. Hysteroscopic surgery without antibiotic therapy for CE associated with intrauterine abnormalities is also recommended.

Chronic endometritis multiplies the recurrence risk of endometrial polyps after transcervical resection of endometrial polyps: a prospective study

BACKGROUND

To investigate the impact of chronic endometritis (CE) on the recurrence of endometrial polyps (EPs) in premenopausal women after transcervical resection of endometrial polyps (TCRP).

METHODS

This prospective study enrolled 507 women who underwent TCRP between January 1, 2022 and December 31, 2022. The patients were divided into a CE group (n = 133) and non-CE group (n = 374) based on the expression of CD138 in the endometrium. The EP recurrence rate at 1 year after TCRP was compared between the CE and non-CE groups and between groups with mild CE and severe CE. The impact of CD138 expression by resected EPs on EP recurrence also was investigated.

RESULTS

The EP recurrence rate at 1 year post-TCRP was higher in the CE group than in the non-CE group (25.6% vs. 10.4%) and also higher in the severe CE group than in the mild CE group (34.5% vs. 18.7%). Additionally, the EP recurrence rate was higher among patients with CD138-expressing EPs than among those with EPs lacking CD138 expression (30.5% vs. 6.5%). The odds ratio (OR) for EP recurrence in the CE cohort compared with the non-CE cohort was 3.10 (95% confidence interval [CI] 1.84-5.23) after adjustment for EP number and precautions against EP recurrence. The ORs for EP recurrence in patients with mild CE and severe CE were 2.21 (95%CI 1.11-4.40) and 4.32 (95%CI 2.26-8.26), respectively. Similarly, the OR for EP recurrence in cases with CD138-expressing EPs relative to cases with EPs lacking CD138 expression was 6.22 (95%CI 3.59-10.80) after adjustment for EP number and precautions against EP recurrence.

CONCLUSIONS

CE multiplied the recurrence rate of EPs in premenopausal women after TCRP, and this effect positively correlated with CE severity. CD138 expression by EPs also was associated with a higher risk for EP recurrence.

Microbiome dysbiosis in patients with chronic endometritis and Clostridium tyrobutyricum ameliorates chronic endometritis in mice

Chronic endometritis is associated with the imbalance of female reproductive tract microbiota and pathogenic microbial infection. This study aimed to identify the specific changes in the endometrial microbiome in patients with endometritis and to explore how Clostridium tyrobutyricum (C.t) influences the progression of endometritis in mice for further elucidating endometritis pathogenesis. For this purpose, endometrial tissues from 100 participants were collected and divided into positive, weakly positive, and negative groups based on CD138 levels, while endometrial microbiome differences were detected and analyzed using 16S rRNA gene sequencing. Staphylococcus aureus (S. aureus)-induced endometritis mouse model was established, followed by treatment with C.t, and inflammatory response, epithelial barrier, and TLR4/NF-κB pathway were evaluated. Results showed that α- and β-diversity was significantly lower in the positive group compared with the weakly positive or negative groups, where the negative group had more unique operational taxonomic units. The abundance of Proteobacteria was found to be increased, while that of Actinobacteria, Firmicutes, and Bacteroidetes was found to be reduced in the positive group, while the area under the curve value was found to be 0.664. Furthermore, C.t treatment resulted in the alleviation of S. aureus-induced inflammatory response, epithelial barrier damage, and activation of the TLR4/NF-κB pathway in mice. Clinical samples analysis revealed that the diversity and abundance of microbiota were altered in patients with endometritis having positive CD138 levels, while mechanistic investigations revealed C.t alleviated S. aureus-induced endometritis by inactivating TLR4/NF-κB pathway. The findings of this study are envisaged to provide a diagnostic and therapeutic potential of microbiota in endometritis.

Hashimoto's Thyroiditis Negatively Influences Intracytoplasmic Sperm Injection Outcome in Euthyroid Women on T4 Substitution Therapy: A Retrospective Study

OBJECTIVE

The objective of this study was to analyze the impact of thyroid autoimmunity (TAI) on reproductive outcome parameters of intracytoplasmic sperm injection (ICSI) cycles as compared to TAI-negative ICSI cycles.

DESIGN

In this single in vitro fertilization (IVF) center retrospective study, 86 infertile women with elevated thyroid peroxidase or TGAb levels, but euthyroid after thyroxine replacement (study group), were compared to 69 female patients with no thyroid abnormalities (controls). Following ICSI treatment fertilization rate (FR), clinical pregnancy rate (CPR), miscarriage rate (MR), and live birth rate (LBR) were analyzed.

MATERIALS, SETTING, METHODS

All subjects with various infertility factors were treated with ICSI in university-based IVF center. Patients in the study group received thyroxine replacement and were euthyroid at IVF treatment. Before the IVF cycles, endocrinological parameters were uniformly assessed: thyroid function and antibodies, reproductive hormones (anti-Müllerian hormone [AMH], follicular stimulating hormone [FSH], luteinizing hormone, E2, PRL, testosterone, DHEAS, 17-OHP, AD) and OGTT (0-60-120 min glucose and insulin). Following descriptive comparison of laboratory parameters, age-adjusted analyses of FR, CPR, MR, and LBR were performed.

RESULTS

TAI-positive women were older (mean age 35.31 ± 4.95 vs. 32.15 ± 4.87 years; p = 0.002), had higher FSH (8.4 ± 3.4 vs. 7.4 ± 2.32 U/L; p = 0.024), higher E2 (53.94 ± 47.61 vs. 42.93 ± 18.92 pg/mL; p = 0.025) levels, while AMH (2.88 ± 2.62 vs. 3.61 ± 1.69 ng/mL; p = 0.0002) was lower. There were no differences in TSH levels (1.64 ± 0.96 vs. 1.66 ± 0.65 µIU/mL; p = 0.652) between the two groups. FT3 (2.63 ± 0.58 vs. 2.98 ± 0.55 pg/mL; p = 0.002) was lower and FT4 (1.3 ± 0.29 vs. 1.13 ± 0.21 ng/dL; p = 0.0002) was higher in the TAI-positive group, reflecting clinically irrelevant differences. Egg cell counts (6 ± 3.8 vs. 7.5 ± 3.95; p = 0.015) were lower in TAI and remained so following age adjustment. Although the overall ICSI FR did not differ (62.9% vs. 69.1%, p = 0.12), it was lower for patients under 35 with TAI showing decreasing differences in line with age. The CPR (36.04% vs. 69.56%; p < 0.001) and LBR (23.25% vs. 60.86%; p < 0.001) were lower, the MR (35.48% vs. 12.5%; p = 0.024) was higher in the TAI group, and these differences remained after age adjustment.

LIMITATIONS

Since the higher age of the study group may interfere with the effect of TAI, age adjustment calculations were necessary to perform to eliminate this confounding factor.

CONCLUSION

Despite optimal thyroid supplementation in clinical or subclinical hypothyroidism, the presence of TAI negatively influences CPR and is connected to a higher MR, thus resulting in a lower LBR after ICSI. Decreased FR with ICSI in TAI patients may also contribute to poorer outcomes, especially in younger women.

Antibiotic cured chronic endometritis remains a risk factor for early pregnancy loss in the subsequent frozen euploid embryo transfer

RESEARCH QUESTION

Do patients with antibiotic-cured chronic endometritis (CCE) have a comparable pregnancy outcome to those with non-chronic endometritis (NCE) in the subsequent frozen embryo transfer (FET) cycle?

DESIGN

A retrospective cohort analysis included 833 patients in their first FET cycles with single euploid embryo transfer. Chronic endometritis (≥5 CD138+ plasma cells per high-power field [CD138+/HPF]) was treated with standard antibiotic therapy. Patients were classified into two groups: the NCE group (n = 611, <5 CD138+/HPF) and the CCE group (n = 222, ≥5 CD138+/HPF and cured after antibiotic treatment). Pregnancy outcomes were compared. NCE group was divided into subgroup 1 (CD138+/HPF = 0) and subgroup 2 (CD138+/HPF = 1-4) for further analysis.

RESULTS

The rate of early pregnancy loss (EPL), incorporating all losses before 10 weeks' gestation, was significantly higher in the CCE group than the NCE group (21.2% versus 14.2%, P = 0.016), and the difference was statistically significant (adjusted odds ratio [AOR] 1.68, 95% confidence interval [CI] 1.11-2.55). No significant differences were observed between the two groups with regard to other pregnancy outcomes. In the subgroup analysis, the EPL rate and biochemical pregnancy rate were significantly higher in subgroup 2 than subgroup 1 (17.2% versus 9.4%, AOR 2.21, 95% CI 1.30-3.74; 12.2% versus 6.9%, AOR 2.01, 95% CI 1.09-3.68).

CONCLUSIONS

Chronic endometritis cured by standard antibiotic therapy remains a risk factor for EPL in FET cycles, although no differences were found in live birth rates between patients with CCE or with NCE.

Increasing expression of STING by ERα antagonizes LCN2 downregulation during chronic endometritis

Chronic endometritis has a high incidence in infertile women, which is caused by endometrial microbiome infection. In response to microbial infection, the role of defensins during chronic endometritis need explored. Besides, the expression of estrogen and its receptors vary in different menstrual cycles, but their roles in chronic endometritis are still unclear. In this study, we used the human endometrial tissues to examine the expression of antimicrobial peptides (AMPs) α-defensin hNP-1 and β-defensins hBD-1, hBD-2, hBD-3, hBD-4 and LCN2. We found the expression of hBD-1 and LCN2 were downregulated in endometritis tissues, while the expressions of hBD-2, hBD-3, hBD-4, hNP-1, and estrogen and ERα were upregulated in chronic endometritis tissues compared to normal tissues. The expression and phosphorylation of STING, which is a crucial mediator of mammalian innate immunity in response to pathogens, was regulated with the treatment of ERα inhibitor raloxifene (Rx). Furthermore, using with the estrogen receptor inhibitor Rx and STING inhibitor H-151 significantly decreases the LCN2 expression. Taken together, these results suggested ERα was upregulated to modulate STING expression inducing LCN2 antimicrobial peptide expression to modulate the mucosal immunity during chronic endometritis.

HMGB1 induces macrophage pyroptosis in chronic endometritis

BACKGROUND

Chronic endometritis (CE) reflects the local imbalance in the endometrial immune microenvironment after inflammation. High mobility group box 1 (HMGB1) is highly involved in both immunity and inflammation. In this study, we aimed to explore the roles of HMGB1 in the endometrium of patients with CE.

METHODS

Endometrium and uterine fluid HMGB1 were tested in a cohort of infertile patients with or without CE. Expression levels of the pyroptosis marker, gasdermin D (GSDMD)-N-terminal (NT), in the human endometrium of patients with CE and controls were determined. Next, the role of HMGB1 as a driver of macrophage pyroptosis was investigated using human THP-1 cells in vitro and a CE mouse model in vivo.

RESULTS

High expression levels of HMGB1 in biopsied endometrial tissue and uterine fluid were confirmed in a cohort of patients with CE. Positive correlation between the number of CD138+ cells and HMGB1 mRNA expression level were detected (rs = 0.592, P < 0.001). Meanwhile, we found that GSDMD-NT expression was significantly increased in the CE endometrium at both the transcriptional and translational levels. Moreover, co-localization of GSDMD-NT and macrophages was confirmed via the double immunostaining of GSDMD-NT and CD68. In vitro experiments revealed that macrophage pyroptosis was induced by HMGB1 in human THP-1-derived macrophages. Treatment with glycyrrhizic acid, an inhibitor of HMGB1, significantly suppressed endometrial pyroptosis and inflammation in the CE mouse model.

CONCLUSIONS

HMGB1 effectively induced macrophage pyroptosis in the human endometrium, suggesting that its inhibition may serve as a novel treatment option for CE.

Current perspectives on endometrial receptivity: A comprehensive overview of etiology and treatment

Recurrent implantation failure (RIF) remains a challenging problem in assisted reproductive technology (ART). Further insights into uterine abnormalities that can disturb embryo implantation should be obtained. This review provides an overview of the effects of organic and non-organic uterine disorders on endometrial receptivity. The results suggest that various uterine pathologies can lead to defective embryo implantation via multiple mechanisms. In particular, uterine adenomyosis dysregulates molecular and cellular interactions that are vital for successful embryo implantation with a background of chronic inflammation, which may be alleviated by pretreatment with a gonadotropin-releasing hormone agonist. Uterine myomas can cause endometrial deformation and adverse alterations in uterine contractility. Nonetheless, the effectiveness of myomectomy remains debated, and endometrial polyp removal may be considered, particularly in patients with RIF. Chronic endometritis abrogates the appropriate uterine immunological environment critical for embryo implantation. Abnormal endometrial microbiota have been suggested to influence endometrial receptivity; however, supporting evidence is currently scarce. Platelet-rich plasma therapy may be a potential treatment for thin endometria; nevertheless, further validation is required. Endometrial receptivity analysis can detect dysregulation of the window of implantation, and new non-invasive methods for predicting endometrial receptivity have recently been proposed. However, numerous issues still need to be fully clarified. Further clinical and basic studies are necessary to investigate the pathophysiology of defective endometrial receptivity and identify optimal treatments for patients undergoing ART, especially those with RIF.

High prevalence of chronic endometritis is associated with metabolic abnormality and reduced live birth rate among IVF women with non-uniform endometrial echogenicity

OBJECTIVE

To assess the prevalence of chronic endometritis (CE) among women with non-uniform endometrial echogenicity, and to evaluate the association between CE and metabolic characteristics as well as pregnancy outcomes in the subsequent frozen-thawed embryo transfer (FET) cycles.

DESIGN

Retrospective cohort study.

SETTING

University-based hospitals and an academic medical center.

PATIENTS

A total of 315 patients included in this research underwent hysteroscopy and endometrial biopsy before the first FET cycle after whole embryos freezing. Patients were divided into CE (histopathologic CE or hysteroscopic CE) and non-CE groups.

INTERVENTION(S)

Freeze-all strategy, hysteroscopy and endometrial biopsy.

MAIN OUTCOME MEASURES

Baseline and cycle characteristics, hysteroscopic, and histopathological profile, as well as pregnancy outcomes.

RESULTS

The prevalence of histopathologic CE and hysteroscopic CE were 78.1% and 34.9%, respectively. CE was associated with higher homocysteine level and BMI, independent of insulin response and dyslipidemia. High homocysteine level and BMI were risk factors for histopathologic CE (OR: 1.182; 95% CI: 1.01-1.384; p = .037) and hysteroscopic CE (OR: 1.117; 95% CI: 1.041-1.199; p = .002), respectively. Histopathologic CE was a risk factor for live birth (OR:2.167; 95% CI: 1.037-4.525; p = .04), and hysteroscopic CE was an independent risk factor for both live birth (OR: 4.239; 95% CI: 1.929-9.313; p = .001) and cumulative live birth (OR: 3.963; 95% CI: 1.875-8.376; p = .001).

CONCLUSIONS

Infertile women with non-uniform endometrial echogenicity have a high prevalence of CE which significantly reduces the live birth rate. Diagnosing CE by hysteroscopy is important to assess the cumulative probability of pregnancy in IVF patients.

Impact of antibiotic cured chronic endometritis on perinatal outcomes: Re-evaluation of a cohort study with a detailed follow-up

PROBLEM

The impact of antibiotic-cured chronic endometritis (CE) on perinatal outcomes of patients conceived with frozen embryo transfer (FET) was unclear.

METHOD

This study was to re-evaluate the perinatal outcomes of a cohort of infertile patients who had undergone endometrial biopsy for CE detection from February 2018 to December 2019 and successfully delivered babies after FET. The study population was divided into two groups: the non-CE (NCE) group (0-4/HPF CD138) and the cured-CE (CCE) group (CD138+/HPF≥5 and has been cured after one or two rounds of antibiotic treatment). For subgroup analysis, the NCE group was further divided into subgroup 1 (CD138+/HPF = 0), subgroup 2 (CD138+/HPF = 1-4 with antibiotic treatment), and subgroup 3 (CD138+/HPF = 1-4 without antibiotic treatment) RESULTS: A total of 321 live births, including 210 in the NCE group and 111 in the CCE group were analyzed. The prevalence rates of premature rupture of the membrane and preterm birth were comparable between NCE and CCE (6.2% vs. 7.1% and 10.8% vs. 10.1%, respectively) groups. In addition, no differences were detected in the rates of placenta-mediated complications, such as preeclampsia, placenta abruption, or low birthweight. Multiple logistic analyses confirmed that CCE was not associated with an increased risk of any adverse perinatal outcomes. Subgroup analysis in NCE failed to find any significant differences in the incidences of obstetrical and neonatal complications.

CONCLUSIONS

CCE might not increase the risks of adverse perinatal outcomes after antibiotic treatment.

Combined oral antibiotics and intrauterine perfusion can improve in vitro fertilization and embryo transfer pregnancy outcomes in patients with chronic endometritis and repeated embryo implantation failure

BACKGROUND

The aim of this retrospective study was to investigate whether oral antibiotics (doxycycline and metronidazole) combined with intrauterine perfusion (gentamicin and dexamethasone) are beneficial for patients with repeated implantation failure (RIF) and chronic endometritis (CE) to improve clinical pregnancy outcomes.

METHODS

Patients with RIF and CE were diagnosed using hysteroscopy and histology together. A total of 42 patients were enrolled in the study. All patients received oral antibiotics (doxycycline combined with metronidazole) and 22 patients underwent intrauterine perfusion (gentamicin combined with dexamethasone) immediately after the end of oral antibiotic therapy. Pregnancy outcomes were evaluated during the first in vitro fertilization (IVF) and embryo transfer (ET) cycle.

RESULTS

For the first D3 ET after treatment with oral antibiotics (doxycycline and metronidazole) combined with intrauterine perfusion (gentamicin and dexamethasone), higher embryo implantation rate (30.95% vs. 26.67%, P = 0.0308), clinical pregnancy rate (30% vs. 50%, P < 0.001), live birth rate (33.33% vs. 45.45%, P < 0.0001). No fetal malformations or ectopic pregnancies were observed.

CONCLUSION

We report oral antibiotics (doxycycline and metronidazole) combined with intrauterine perfusion (gentamicin and dexamethasone) as a novel treatment for CE to improve the outcomes of successful pregnancy compared with those of oral antibiotics alone.