Immune determinants of endometrial receptivity: a biological perspective

CCR8+ decidual regulatory T cells maintain maternal-fetal immune tolerance during early pregnancy

Regulatory T (Treg) cells play a vital role in maintaining maternal immune tolerance to the semiallogeneic fetus during pregnancy. Treg cell population heterogeneity and tissue-specific functions in the human decidua remain largely unknown. Here, using single-cell transcriptomic and T cell receptor sequencing of human CD4+ T cells from first-trimester deciduae and matched peripheral blood of pregnant women, we identified a highly activated, immunosuppressive CCR8+ Treg cell subset specifically enriched in the decidua (dTreg cells). CCR8+ dTreg cells were decreased in patients with recurrent pregnancy loss (RPL) and an abortion-prone mouse model. Depletion of CCR8+ dTreg cells increased susceptibility to fetal loss, with altered decidual immune profiles. Adoptive transfer of CCR8+ Treg cells rescued fetal loss in abortion-prone mice. The CCR8 ligand CCL1 was mainly produced by decidual CD49a+ natural killer cells and was significantly decreased in patients with RPL. Our data demonstrate that CCR8+ dTreg cells are required to maintain maternal-fetal tolerance and highlight potential avenues for RPL therapies.

Single-cell technology: the key to an improved understanding of the human endometrium in health and disease

Cyclic exposure of the endometrium to ovarian sex steroids during the menstrual cycle induces a transition between proliferative and receptive states involving a different variety of cell types (ie, epithelial, stromal, endothelial, and immune cells) in preparation for embryo implantation during the narrow window of implantation. The study of the female reproductive system cells across these different phases contributes to our understanding of the healthy endometrium at the cellular level, supporting comparisons with pathological conditions, such as endometriosis, endometrial cancer, or Asherman's syndrome. Single-cell RNA sequencing technology represents a powerful tool that can discern the gene expression profiles of each cell within a tissue sample and has recently revealed the complex collaborations taking place between diverse cell types during the distinct endometrial phases. This review aims to summarize those studies that have employed single-cell RNA sequencing to deepen our understanding of the endometrium at single-cell resolution during the menstrual cycle. We discuss the transitions taken by distinct cell populations across the proliferative and secretory phases and the general importance of these transitions to successful embryo implantation. Furthermore, we analyze the use of single-cell RNA sequencing technology to study in vitro models of healthy endometrium and endometrial carcinoma. We believe that future studies using single-cell RNA sequencing will be essential to understanding the behavior of the endometrium as a whole and identifying potential avenues for the improved management of endometrial diseases.

The maternal-fetal interface at single-cell resolution: uncovering the cellular anatomy of the placenta and decidua

The maternal-fetal interface represents a critical site of immunological interactions that can greatly influence pregnancy outcomes. The unique cellular composition and cell-cell interactions taking place within these tissues has spurred substantial research efforts focused on the maternal-fetal interface. With the recent advent of single-cell technologies, multiple investigators have applied such methods to gain an unprecedented level of insight into maternal-fetal communication. Here, we provide an overview of the dynamic cellular composition and cell-cell communications at the maternal-fetal interface as reported by single-cell investigations. By primarily focusing on data from pregnancies in the second and third trimesters, we aim to showcase how single-cell technologies have bolstered the foundational understanding of each cell's contribution to physiologic gestation. Indeed, single-cell technologies have enabled the examination of classical placental cells, such as the trophoblast, as well as uncovered new roles for structural cells now recognized as active participants in pregnancy and parturition, such as decidual and fetal stromal cells, which are reviewed herein. Furthermore, single-cell data investigating the ontogeny, function, differentiation, and interactions among immune cells present at the maternal-fetal interface, namely macrophages, T cells, dendritic cells, neutrophils, mast cells, innate lymphoid cells, natural killer cells, and B cells are discussed in this review. Moreover, a key output of single-cell investigations is the inference of cell-cell interactions, which has been leveraged to not only dissect the intercellular communications within specific tissues but also between compartments such as the decidua basalis and placental villi. Collectively, this review emphasizes the ways by which single-cell technologies have expanded the understanding of cell composition and cellular processes underlying pregnancy in mid-to-late gestation at the maternal-fetal interface, which can prompt their continued application to reveal new pathways and targets for the treatment of obstetrical disease.

Modulation of the Toll-like Receptor Pathway in Ovine Endometria During Early Pregnancy

Correct immunological dialogue between the maternal uterus and conceptus is essential during implantation, and Toll-like receptors (TLRs) participate in maternal immune tolerance during pregnancy. This study aimed to analyze the effect of early pregnancy on Toll-like receptor pathways in the ovine endometrium. Ovine endometria were obtained on day 16 of the estrous cycle (N16) and days 13, 16, and 25 of pregnancy (P13, P16, and P25), and expression profiles of TLR members, including TLRs, tumor necrosis factor receptor-associated factor 6 (TRAF6), interleukin 1 receptor-associated kinase 1 (IRAK1), and myeloid differentiation primary response gene 88 (MyD88), were detected by quantitative real-time PCR, Western blot analysis, and immunohistochemistry analysis. The data of this study showed that the expression of TLR2 and TLR5 was gradually increased during early pregnancy compared to N16, and TLR3 expression was greater at P16 and P25 than at N16 and P13. However, the expression levels of TLR4 and TRAF6 were weaker at P13 and P16, and the expression of MyD88 was inhibited by early pregnancy. Furthermore, early pregnancy regulated IRAK1 expression. These findings corroborated that the TLR pathway was modulated in the ovine endometrium during early pregnancy, which may be involved in maternal immunoregulation.

Enhancing understanding of endometrial function in patients with PCOS: clinical and immunological insights

OBJECTIVE

To evaluate the pregnancy and perinatal outcomes of different phenotypes of polycystic ovary syndrome (PCOS) patients during the frozen embryo transfer (FET) cycles. Additionally, to analyze the T cell balance in the endometrium of PCOS patients and explore its relationship with various PCOS phenotypes.

DESIGN

Retrospective cohort study.

SETTING

A single academically affiliated reproductive medicine center.

PATIENTS

21,074 FET cycles were included and divided into two groups based on the diagnosis of PCOS. Patients with PCOS were further categorized into four phenotypic groups: PCOM + HA + OA, PCOM + HA, PCOM + OA, and HA + OA. Endometrial biopsies from 21 PCOS patients and 26 controls were obtained to analyze T cell subsets.

METHODS

Pregnancy and perinatal outcomes, as well as T cell subset abundance were compared between women with and without PCOS. Multiple logistic regression models were employed to adjust for confounding factors impacting pregnancy-related outcomes. Flow cytometry was utilized to analyze the abundance of T cell subsets.

MAIN OUTCOME MEASURES

Pregnancy and perinatal outcomes were assessed. T cell subsets including CD4+CD8-T cells, CD4-CD8+T cells, Th1, Th2, Th17 and Treg cells in the endometrium were determined by flow cytometry.

RESULTS

There was a significantly increased incidence of miscarriage, hypertensive disorders of pregnancy (HDP), preterm birth (PTB), and even fetal malformations across different phenotypes of PCOS women, especially those with the hyperandrogenic phenotype. Th1 cells decreased while Th2 cells increased significantly in the PCOS endometrium.

CONCLUSIONS

The unfavorable pregnancy and perinatal outcomes in FET cycles and T cell imbalance both suggest the endometrial dysfunction of PCOS patients, especially those with the hyperandrogenic phenotype.

Impact of low-dose aspirin therapy initiation timing on pregnancy outcomes after frozen-thawed blastocyst transfer

Clinical effects of low-dose aspirin (LDA) on embryo implantation still remains controversial; therefore, we investigated the appropriate timing for starting LDA in frozen-thawed embryo transfer (ET) cycles. A cross-sectional study was conducted on 885 infertile women who underwent thrombophilia screening between 2020 and 2023. We recruited first frozen-thawed blastocyst transfer cycles in 553 consecutive women aged < 40 years. LDA was started on the day of ET from 2020 to 2021 in 79 women (day 0 group) and at 5 days after ET from 2021 to 2023 in 215 women (day 5 group). We also recruited 259 consecutive women who underwent first frozen-thawed blastocyst transfer without LDA treatment from 2020 to 2023 (control). We compared pregnancy outcomes after frozen-thawed ET between the three groups. In results, clinical pregnancy and livebirth rates after frozen-thawed ET in the day 0 group were significantly lower than those in the other two groups (clinical pregnancy rates: 57.5 %, 40.5 %, and 61.4 %, p = 0.005 and livebirth rates: 48.6 %, 34.2 %, and 54.0 %, p = 0.01 in the control, day 0, and day 5 groups, respectively). Multivariable logistic regression analysis showed that livebirth rate in the day 0 group was significantly lower than those in the other groups (odds ratio [OR]: 0.54, 95 % confidential interval [CI]: 0.31 -0.95); however, no significant difference in livebirth rates was found between the day 5 and control groups (OR: 1.13, 95 %CI: 0.70 -1.80). Starting LDA prior to implantation may decrease pregnancy and livebirth rates after frozen-thawed blastocyst transfer.

Analysis and identification of potential biomarkers for dysfunctional uterine bleeding

Clinical evidence increasingly suggests that traditional treatments for dysfunctional uterine bleeding (DUB) have limited success. In this study, blood samples from 10 DUB patients and 10 healthy controls were collected for transcriptome sequencing. Then, the differentially expressed genes (DEGs) were screened and crossed with the DUB-related module genes to obtain the target genes. These target genes were analyzed for functional enrichment. Further, the biomarkers were screened by protein-protein interaction (PPI) analysis and analyzed by the gene set enrichment analysis (GSEA) and ingenuity pathway analysis (IPA). To explore the pathogenesis of DUB, immune microenvironment analyses were also performed. Potential drugs targeting these biomarkers were predicted for clinical treatment. The expression of these biomarkers was validated using quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that, a total of 754 target genes were found to be related to cell proliferation and senescence. Five biomarkers-CENPE, KIF11, PIK3R1, SMC3, and SMC4-were identified, all of which were down-regulated in the DUB group, and most of these findings were confirmed by qRT-PCR. Notably, CENPE expression showed a negative association with activated NK cells and a positive association with resting NK cells. In addition, 44 potential drugs were predicted for DUB treatment. In conclusion, five DUB biomarkers were identified, enhancing understanding of gene regulation in DUB and providing a theoretical foundation for clinical diagnosis and treatment.

Seminal fluid effects on uterine receptivity to embryo implantation: transcriptomic strategies to define molecular mechanisms

Embryo implantation requires both a developmentally competent embryo and a receptive uterus. Impaired uterine receptivity is a common constraint on implantation success and reproductive outcome. Ovarian steroid hormones oestrogen and progesterone play a central role in establishing uterine receptivity, but other factors also contribute. One additional regulating factor is male partner seminal fluid. However, the full physiological impacts of seminal fluid on uterine receptivity and the specific molecular pathways involved are not yet completely defined. New advances in RNA-sequencing technologies provide a powerful means to examine how uterine tissues and cells respond to seminal fluid contact. Findings utilising sequencing technology provide strong cellular and molecular evidence in humans and mice that seminal fluid contact around the time of ovulation drives immune and vascular changes with potential to affect endometrial receptivity in the peri-implantation phase. This approach has led to the discovery of novel mediators and regulatory factors subsequently shown to facilitate embryo implantation in genetic mouse models, enabling functional validation. Here, we summarise the evidence from recent microarray and RNA-sequencing findings that seminal fluid contact can directly and indirectly impact the transcriptional state of endometrial tissue during the implantation window in mice and also in humans. Progress in elucidating the female reproductive tract response to seminal fluid will improve understanding of male partner effects on endometrial receptivity, and the knowledge gained will have practical applications for achieving healthy pregnancy and offspring outcomes.

Genetically predicted circulating immune cells and cytokines reveal the causal role of immune factors on female infertility: a two-sample mendelian randomization study

OBJECTIVES

Previous studies suggested that immune factors may play critical roles in female infertility, but their causal links remain unclear. To address this gap, this study employs the Mendelian randomization (MR) to delineate the causal association between circulating immune factors and female infertility.

METHODS

This study employed summary-level data from three genome-wide association studies (GWAS) encompassing 731 peripheral immune cell signatures, 41 circulating cytokines, and five female infertility phenotypes to reveal the causal relationship between immune factors and female infertility. Causalities of exposure-outcome pairs were explored mainly using two-sample MR, and comprehensive sensitivity analyses were deployed to validate the reliability of the results. Multi-variable Mendelian randomization (MVMR) was further employed to examine the potential mediating effects between significant exposures.

RESULTS

Following false discovery rate (FDR) correction and sensitivity analyses, univariable Mendelian randomization identified distinct causal immune signatures across infertility subtypes. Peripheral levels of Naive CD8br %CD8br, MIP1B and IL17 were causally associated with general female infertility, and higher circulating MIP1B level decreased the risk of ovarian infertility. Furthermore, peripheral levels of CD80 on monocyte and MIP1B were causally associated with a higher risk of tubal infertility, three peripheral immune cell features (CD86 + myeloid DC AC, HLA DR + NK %NK, CD16 on CD14- CD16 + monocyte) were causal for uterine factor infertility, and three cytokines (MIP1B, IL18, IL17) were genetic causes of cervical infertility, vaginal infertility, other or unspecified origin infertility (FIOTHNAS). MVMR further revealed that MIP1B's effects on general female infertility and FIOTHNAS were substantially attenuated upon adjusting for circulating levels of IL17 and IL18.

CONCLUSION

Our results highlight that immune response contributes to female infertility risk through subtype-specific mechanisms, providing clues for following clinical research and treatment.

Impaired fertility and perinatal outcomes in adenomyosis: insights from a novel murine model and uterine gene profile alterations during implantations

BACKGROUND

Adenomyosis is a uterine disorder closely linked to infertility and adverse pregnancy outcomes. Despite its clinical significance, the mechanisms by which adenomyosis impairs embryo implantation and perinatal outcomes remain incompletely defined. Previous studies have indicated that alterations in the uterine microenvironment may contribute to these reproductive challenges.

OBJECTIVE

To investigate the effects of adenomyosis on fertility and perinatal outcomes using a novel murine model and to identify molecular pathways involved in implantation failure and pregnancy loss.

STUDY DESIGN

A mechanically induced adenomyosis model was established in female Bagg Albino/c mice through endometrial-myometrial interface disruption to closely simulate the clinical condition observed in humans. Mice were randomly assigned to either the adenomyosis group or a sham-operated control group. Reproductive outcomes were systematically assessed at multiple gestational time points, focusing on embryo implantation site distribution, implantation rates, pregnancy loss, fetal growth parameters, and postnatal uterine recovery. In parallel, uterine tissues collected from implantation sites and interimplantation regions at 4.5 days postcoitus were subjected to RNA sequencing. Differential gene expression analyses were performed, and enriched pathways were identified using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment tools.

RESULTS

Mice in the adenomyosis group demonstrated significant disruptions in the uterine microenvironment compared to controls. Notably, the adenomyosis group exhibited irregular distribution of implantation sites with reduced interembryo distances, leading to compromised spatial organization of the developing conceptuses. Although the total number of embryos at early gestation did not differ significantly between groups, a marked increase in pregnancy loss was observed during mid-gestation, accompanied by a reduction in the size of surviving embryos. Histological evaluation revealed extensive architectural disruptions in the uterine muscle layers and increased local inflammatory responses in adenomyotic uteri. RNA sequencing further revealed that adenomyosis was associated with the dysregulation of multiple genes involved in immune modulation, apoptotic regulation, and metabolic processes. In particular, significant enrichment of the phosphoinositide 3-kinase-Akt pathway, mitogen-activated protein kinase, and tumor necrosis factor signaling pathways was observed, suggesting that variation in these cascades may underlie the impaired uterine receptivity and embryo development seen in adenomyosis.

CONCLUSION

Our findings indicate that adenomyosis exerts a adverse effect on fertility and perinatal outcomes by disrupting the uterine environment and interfering with critical molecular pathways essential for proper embryo implantation and development. The results of this study not only enhance our understanding of adenomyosis pathophysiology but also pinpoint potential molecular targets-such as the phosphoinositide 3-kinase-Akt pathway, mitogen-activated protein kinase, and tumor necrosis factor pathways-for therapeutic intervention. These insights offer promising targets for developing treatments aimed at reversing the adverse reproductive impacts associated with adenomyosis.

Shared diagnostic biomarkers and underlying mechanisms between endometriosis and recurrent implantation failure

BACKGROUND

Endometriosis (EMs) is a common condition that causes dysmenorrhea, chronic pelvic pain, and infertility, affecting millions of women worldwide. Despite the use of assisted reproductive technology, EMs patients often experience lower embryo implantation rates and recurrent implantation failure (RIF) due to impaired uterine endometrial receptivity. This study aims to identify shared diagnostic genes and underlying mechanisms between EMs and RIF using integrated transcriptomic analysis and machine learning with Gene Expression Omnibus (GEO) datasets.

METHODS

We analyzed GSE11691, GSE7305, GSE111974, and GSE103465 as training datasets for EMs and RIF, and GSE25628 and GSE92324 as validation datasets. Differentially expressed genes (DEGs) and Weighted Gene Co-Expression Network Analysis (WGCNA) identified key genes specific to and shared by EMs and RIF. Machine learning algorithms were used to determine the shared diagnostic gene, whose performance was validated in both training and validation datasets. Single-gene Gene Set Enrichment Analysis (GSEA) revealed shared biological processes in EMs and RIF, while CIBERSORT analysis highlighted similarities and differences in immune infiltration between the two conditions. Finally, endometrial samples from healthy controls, EMs, and RIF patients were collected, and qRT-PCR was performed to validate the diagnostic gene.

RESULTS

We identified 48 shared key genes between EMs and RIF. The diagnostic gene EHF was selected through machine learning algorithms, and its diagnostic performance was validated in both training and validation datasets. ROC curve analysis demonstrated excellent diagnostic accuracy of EHF for both diseases. Gene Set Enrichment Analysis (GSEA) revealed that both conditions shared biological processes, including dysregulated extracellular matrix remodeling and abnormal immune infiltration. Furthermore, we validated the expression of EHF in endometrial samples from healthy controls, EMs, and RIF patients. Additionally, we characterized the immune microenvironment in EMs and RIF, highlighting changes in immune cell components associated with EHF.

DISCUSSION

The diagnostic gene EHF identified in this study may serve as a key link between EMs and RIF. The shared pathological processes in both conditions involve alterations in the extracellular matrix and subsequent changes in the immune microenvironment. These findings provide novel insights into potential therapeutic strategies for improving infertility treatment in patients with EMs.

Exploring the Immunological Aspects and Treatments of Recurrent Pregnancy Loss and Recurrent Implantation Failure

Recurrent pregnancy loss (RPL) is defined as the occurrence of two or more consecutive pregnancy losses before 24 weeks of gestation. It affects 3-5% of women who are attempting to conceive. RPL can stem from a variety of causes and is frequently associated with psychological distress and a diminished quality of life. By contrast, recurrent implantation failure (RIF) refers to the inability to achieve a successful pregnancy after three or more high-quality embryo transfers or at least two instances of egg donation. RIF shares several causative factors with RPL. The immunological underpinnings of these conditions involve alterations in uterine NK cells, reductions in M2 macrophages and myeloid-derived suppressor cells, an increased Th1/Th2 ratio, a decreased Treg/Th17 ratio, the presence of shared ≥3 HLA alleles between partners, and autoimmune disorders. Various therapeutic approaches have been employed to address these immunological concerns, achieving varying degrees of success, although some therapies remain contentious within the medical community. This review intends to explore the immunological factors implicated in RPL and RIF and to analyze the immunological treatments employed for these conditions, which may include steroids, intravenous immunoglobulins, calcineurin inhibitors, anti-TNF antibodies, intralipid infusions, granulocyte colony-stimulating factor, and lymphocyte immunotherapy.

Cytokine modulation and immunoregulation of uterine NK cells in pregnancy disorders

Uterine natural killer (uNK) cells play a pivotal role in promoting placental development and supporting maternal-fetal immune tolerance, primarily through cytokine regulation and growth factor production. While the importance of uNK cells in pregnancy is well-established, the mechanisms of their interactions with trophoblasts and contributions to various pregnancy complications remain incompletely understood. This review highlights recent advancements in understanding uNK cell functions, with a focus on cytokine production, growth factor secretion, and receptor-ligand interactions, particularly involving killer immunoglobulin-like receptors (KIR) and human leukocyte antigen-C (HLA-C). We explore how uNK cell dysfunction contributes to pregnancy complications, including preeclampsia, recurrent pregnancy loss, and placenta accreta spectrum (PAS) disorders, emphasizing their roles in immune tolerance and placental health. By detailing the distinct cytokine signaling pathways and functional subtypes of uNK cells, this review provides insights into their regulatory mechanisms essential for pregnancy maintenance. Additionally, we discuss emerging therapeutic strategies targeting uNK-trophoblast interactions and propose future research directions, including the development of non-invasive biomarkers and personalized interventions. This comprehensive review addresses critical knowledge gaps, aiming to advance research in reproductive immunology and guide therapeutic innovations in maternal health.

Macrophages: a double-edged sword in female reproduction and disorders

Reproduction consists of sequential inflammation-like events, primarily within the endometrium, from ovulation to embryo implantation, decidualization and delivery. During the reproductive cycle, the endometrium repeatedly undergoes cyclic periods of proliferation, differentiation, tissue breakdown and repair without scarring. Owing to their phagocytic activity, macrophages, key players in innate immunity, are thought to play crucial roles in the endometrium. Endometrial macrophages actively participate in various stages of reproductive tissue remodeling, particularly during decidualization and pregnancy establishment. Traditionally considered simple bystanders that clear debris to prevent autoimmune responses in tissue homeostasis, macrophages are now recognized as main actors with broad functional plasticity that allows them to fine tune the balance between pro- and anti-inflammatory responses during tissue inflammation, remodeling and repair. Homeostatic balance is determined by the sum of various mediators produced by two distinctly polarized macrophage subpopulations. The biased polarization of tissue-resident macrophages may contribute to the pathogenesis of various diseases, such as inflammation and cancer. Thus, understanding how macrophages contribute to endometrial homeostasis is crucial for deciphering the underlying mechanisms of various reproductive disorders. Nanomedicines using extracellular vesicles, nanoparticles and noncoding RNAs have recently been applied to modulate macrophage polarization and alleviate disease phenotypes. Despite these advances, the functions of endometrial macrophages under physiological and pathophysiological conditions remain poorly understood, which complicates the development of targeted therapies. Here we update the current understanding of the homeostatic function of macrophages and the putative contribution of endometrial macrophage dysfunction to reproductive disorders in women, along with innovative molecular therapeutics to resolve this issue.

The Effect of Granulocyte Colony-Stimulating Factor on Endometrial Receptivity of Implantation Failure Mouse

The purpose of this study was to investigate the effect of G-CSF on the endometrial receptivity of implantation failure mice. Sixty female mice were treated mifepristone to establish an implant failure model. The treatment groups received different doses of G-CSF. Endometrial tissue and serum were collected on day 5 after mating. The abundance of pinopodes on the endometrium was observed by scanning electron microscopy. The expressions of LPAR3, COX2, and HOXA10 were detected by RT-qPCR and Western blotting. Serum levels of E2, P, VEGF, LIF, TNF-α and IL-10 were measured by ELISA. The expressions of VEGF, CD34, CD57, TNF-α, and IL-10 were assessed by immunohistochemistry. Immunofluorescence analysis was performed to determine the number of CD57, Treg, and Th17 cells. G-CSF increased implantation and pregnancy rates of mifepristone-induced implantation failure mice, with the most significant effect seen at the intermediate dose. G-CSF increased the serum levels of E2 and P, the abundance of endometrial pinopodes, and the level of LIF in the endometrium. It also promoted the expression of VEGF, HOXA10, LPAR3, and COX2. Moreover, G-CSF reduced the level of CD57 cells and the ratio of Th17/Treg cells in endometrium. G-CSF reduced the inflammatory factor TNF-α, but IL-10 did not change significantly. G-CSF can enhance embryo implantation rate and pregnancy rate and improve endometrial receptivity by attenuating degeneration of pinopodes, upregulating estrogen and progesterone, facilitating angiogenesis, maintaining immune cell homeostasis, and reducing the production of inflammatory cytokines in implantation failure mouse.

Effect of vitamin D adjuvant therapy on the proportion of regulatory T cells in peripheral blood and pregnancy outcome of patients with recurrent miscarriage

BACKGROUND

Recurrent miscarriage (RM) is influenced by immune factors, particularly regulatory T cells, which can impact immune function and miscarriage risk. Vitamin D (VD) is known to regulate the immune system, potentially improving pregnancy outcomes in RM patients. This study aims to assess the effect of VD adjuvant therapy on regulatory T cells and pregnancy outcomes in RM patients.

METHODS

Clinical data from 104 individuals with RM admitted to our hospital between March 2022 and February 2023 were allocated at random to either the VD group (VDG) or the control group (CG), with 52 patients in each group. Both groups received standard treatment; the CG was treated with aspirin, while the VDG received additional VD therapy. Outcomes measured included regulatory T cell proportion, metabolic factors, immune inflammatory markers, and pregnancy outcomes.

RESULTS

After treatment, the proportion of regulatory T cells in VDG was considerably higher (p < 0.05). Additionally, triglyceride levels, leptin, fasting blood glucose, and fasting insulin were lower in the VDG, whereas adiponectin levels were higher (p < 0.05). Levels of progesterone, luteinizing hormone, and 25-hydroxy VD were also higher in the VDG (p < 0.05). Furthermore, interleukin-17, gamma interferon, tumor necrosis factor-α, and C-reactive protein were lower in the VDG (p < 0.05). The pregnancy success rate in the VDG was higher, and the preterm birth rate was lower (p < 0.05).

CONCLUSION

Adjuvant treatment with VD can increase the proportion of regulatory T cells in peripheral blood of individuals with recurrent abortion, regulate metabolic disorder, alleviate immune inflammation, and improve pregnancy outcome.

Ovarian reserve modulates the impact of vitamin D deficiency on assisted reproductive outcomes in patients undergoing controlled ovarian hyperstimulation

Objective

The association between vitamin D deficiency and ovarian reserve-specific outcomes of assisted reproductive technology (ART) remains uncertain. This study aimed to investigate the role of ovarian reserve in the association between basal serum vitamin D levels and ART outcomes in patients undergoing controlled ovarian hyperstimulation (COH).

Methods

A total of 1,333 infertile women undergoing COH cycles were retrospectively analyzed. Patients were divided into a vitamin D deficiency group (serum vitamin D < 20 ng/mL) and a normal vitamin D group. Univariate and multivariate logistic regression analyses were performed to estimate the relationship between vitamin D deficiency and pregnancy outcomes including biochemical pregnancy rate, clinical pregnancy rate, miscarriage rate, and live birth rate in the overall cohort and subgroups with diminished ovarian reserve (DOR) or polycystic ovary syndrome (PCOS).

Results

In the entire participants' cohort, no correlation between vitamin D deficiency and pregnancy results was observed (p > 0.05). However, in the DOR subgroup, vitamin D deficiency was associated with a lower biochemical pregnancy rate (adjusted OR 0.27; 95% CI 0.08-0.90; p < 0.01) and clinical pregnancy rate (adjusted OR 0.36; 95% CI 0.14-0.90; p < 0.01). No significant differences were observed in pregnancy outcomes among patients with PCOS (p > 0.05).

Conclusion

Vitamin D deficiency does not affect pregnancy outcomes in the overall patient population, but it may negatively impact women with DOR potentially leading to poorer pregnancy outcomes. Further studies are needed to clarify the mechanisms involved and the potential use of vitamin D screening and supplementation in specific populations.

Intrauterine administration of peripheral blood mononuclear cells helps manage recurrent implantation failure by normalizing dysregulated gene expression including estrogen-responsive genes in mice

BACKGROUND

Intrauterine peripheral blood mononuclear cell (PBMC) therapy for recurrent implantation failure (RIF) has been reported to improve embryo implantation by acting on the endometrium. However, the exact mode of action of PBMC on the endometrium of patients with RIF remains unclear. In addition, the differences in the therapeutic effects of PBMC therapy with and without human chorionic gonadotropin (hCG) are unknown. Therefore, in this study, we investigated the changes in the endometrium during the implantation phase induced by PBMC administration and the differences in the efficacy of this therapy with and without hCG using a mouse model of implantation failure (IF).

METHODS

IF model was established by the subcutaneous administration of low-dose RU486. Pregnant mice were randomly divided into five groups: control, IF, culture medium, PBMC, and PBMC-hCG (the latter three groups were IF model mice with intrauterine administration). The pregnancy rate and the number and size of implantation sites were recorded during early pregnancy (day 7.5). Uteri from the preimplantation phase (evening of day 3.5) were collected and analyzed using RNA-sequencing (RNA-seq).

RESULTS

The pregnancy rate, the number of implantation sites, and the number of normal-sized implantation sites were significantly decreased in the IF model and were improved in the medium, PBMC, and PBMC-hCG groups. RNA-seq data showed that PBMC treatment normalized the expression of the majority of dysregulated genes in the endometrium during the preimplantation phase in the IF model, especially the overexpression of estrogen-activated genes. In addition, PBMC treatment increased the expression of local glucocorticoid receptors and suppressed the expression of inflammation-related genes, whereas no significant changes in blood estradiol and glucocorticoid levels were observed. These changes were more pronounced in the PBMC-hCG group and were consistent with the pregnancy outcomes.

CONCLUSIONS

Intrauterine administration of PBMC before embryo implantation promoted embryo implantation in the IF mouse model, and hCG enhanced pregnancy outcomes. PBMC modulated steroid receptor expression and suppressed inflammation and excessive estrogen action.

Mechanism of Endometrial Receptivity Affected by Fibroids

Fibroids are the most common benign tumors of the female reproductive system. Most patients with fibroids are asymptomatic, but the presence of fibroids can still cause some abnormal clinical symptoms, such as increased menstrual volume, abnormal uterine bleeding, pelvic pain, urinary tract and gastrointestinal tract compression symptoms, etc. The impact of fibroids on pregnancy is worth discussing. At present, it is believed that submucosal myoma and intramural myoma affecting uterine cavity shape affect the pregnancy outcome of patients, while the impact of type III intramural myoma on pregnancy is still controversial. A number of studies have found that in addition to direct contact with the endometrial compression, uterine myoma also affects the endometrial flexibility through other ways. In this review, we summarized the effects of fibroids on endometrial receptivity and discussed in depth the mechanisms of such effects, including secretion of cytokines, changes in endometrial blood flow and angiogenesis, effects on endometrial peristalsis and mechanical stress conduction, changes in uterine microecological environment, and abnormal signal transduction pathways. Understanding the mechanism of endometrial receptivity affected by fibroids is significant for exploring the treatment of fibroids, improving the pregnancy outcome of patients with fibroids and increasing the clinical pregnancy rate.

Understanding the heterogeneity of natural killer cells at the maternal-fetal interface: implications for pregnancy health and disease

Natural killer (NK) cells are the most abundant leukocytes located at the maternal-fetal interface; they respond to pregnancy-related hormones and play a pivotal role in maintaining the homeostatic micro-environment during pregnancy. However, due to the high heterogeneity of NK cell subsets, their categorization has been controversial. Here, we review previous studies on uterine NK cell subsets, including the classic categorization based on surface markers, functional molecules, and developmental stages, as well as single-cell RNA sequencing-based clustering approaches. In addition, we summarize the potential pathways by which endometrial NK cells differentiate into decidual NK (dNK) cells, as well as the differentiation pathways of various dNK subsets. Finally, we compared the alterations in the NK cell subsets in various pregnancy-associated diseases, emphasizing the possible contribution of specific subsets to the development of the disease.

Pharmacological and toxicological characteristics of baicalin in preventing spontaneous abortion and recurrent pregnancy loss: A multi-level critical review

Relevance

Spontaneous abortion (SAB) and recurrent pregnancy loss (RPL) occur alone or concurrently with increasing incidences recently. Scutellaria baicalensis Georgi (SBG) has been used to prevent pregnancy loss for thousands of years, which is recognized as a "pregnancy-stabilizing herb" in ancient China. Baicalin (BA) and its metabolite baicalein (BE) are the main bioactive flavonoids in the root of SBG.

Methods

In this study, we focused particularly on the metabolism, toxicology, and pharmacological effects of BA at the maternal-fetal interface based on the biological process prediction by network pharmacology. Focused on the systematic review of BA's regulatory mechanisms of immune homeostasis, cell proliferation and invasion, programmed cell death, inflammatory microenvironment, angiogenesis, oxidative stress and vascular remodeling at the maternal-fetal interface, it was found that BA exerts its biological effects to treat SAB and RPL through multiple perspectives and targets. We also critically elucidated the limitations of using BA from a clinical perspective.

Results

We explored the bioavailability, targeting and efficacy of BA from a new perspective (optimization of the BA delivery system, organoid studies based on BA, potential effects of BA on uterine flora and bioactive components). Finally, we propose a multimodal stereo sequencing study of biologically active components based on pathological dynamics incorporating single-cell RNA sequencing, spatially resolved transcriptomics, and single-cell multimodal omics to delve deeper into the fetal-preserving mechanism of BA and to promote the application of BA in clinical practice.

Altered Expressions of IL-15, IFNG, and HPRT1 Genes in the Thin Endometria of Patients with Reproductive Disorders: A Prospective Comparative Study

Reproductive disorders are common events in modern reproductive medicine, occurring both in spontaneous and assisted pregnancies. Studies on the molecular mechanisms of implantation disorders in thin endometria, including the study of gene transcriptional activities, have shed light on the identification of the potential biological markers of endometrial receptivity. Background/Objectives: The goal of this study was to reveal the significantly dysregulated selected gene expressions between RIF and RPL patients with thin endometria. Methods: Endometrial samples were collected from RIF patients (n = 20) and RPL patients (n = 19) during the implantation window days (LH + 7-LH + 10) of their natural menstrual cycles. Ten genes were chosen as the target genes regarding their possible relations with the implantation process. The total RNA was purified and reverse-transcribed, and gene expressions were quantified by RT-PCR. Results: The expressions of the IL-15, INFG, and HPRT1 genes were significantly decreased in the RIF patients with thin endometria compared to the RPL patients (log2 fold change = 0.92, p = 0.023 for IL-15; log2 fold change = 1.24, p = 0.046 for INFG; and log2 fold change = 0.579, p = 0.046 for HPRT1). There were no significant differences in the expressions of the CXCL8, CXCL1, MMP10, C4BPA, TNC, VEGFB, and HAND2 genes between the groups. Conclusions: Decreased expressions of the IL-15, INFG, and HPRT1 genes were found in patients with RIF with thin endometria compared to the endometria of women with RPL. This has practical significance for clinicians for the differentiated prescription of immunomodulatory therapy in patients undergoing ART programs.

B cells: roles in physiology and pathology of pregnancy

B cells constitute a diverse and adaptable immune cell population with functions that can vary according to the environment and circumstances. The involvement of B cells in pregnancy, as well as the associated molecular pathways, has yet to be investigated. This review consolidates current knowledge on B cell activities and regulation during pregnancy, with a particular focus on the roles of various B cell subsets and the effects of B cell-derived factors on pregnancy outcomes. Moreover, the review examines the significance of B cell-associated autoantibodies, cytokines, and signaling pathways in relation to pregnancy complications such as pregnancy loss, preeclampsia, and preterm birth.

Early pregnancy exposure to Microcystin-LR compromises endometrial decidualization in mice via the PI3K/AKT/FOXO1 signaling pathway

Previous experimental studies have found that exposure to Microcystin-leucine arginine can impact pregnancy outcomes in female mice. The impact of MC-LR on early pregnancy in mammals is not yet well understood. Both mice and humans need to undergo decidualization to maintain pregnancy. In this study, we tried to evaluate whether MC-LR affects decidualization process in mice. Our research showed that MC-LR decreased maternal weight gain, uterine weight, and implantation site weight. These findings suggested that MC-LR exerted adverse effects on decidualization. In mice, we examined decreased number of polyploid decidual cells, but marked proliferation of mouse endometrial stromal cells the expression levels of prolactin (PRL)and insulin-like growth factor binding protein 1 (IGFBP1) were significantly downregulated in the decidual tissue and primary endometrial stromal cells following MC-LR treatment. Furthermore, further in vitro experiments identified that MC-LR promoted endometrial stromal cell division and cycle transition. Lastly, our study demonstrated that MC-LR impaired decidualization through the PI3K/AKT/FOXO1 pathway. Collectively, these data suggested that exposure to MC-LR impaired decidualization during early pregnancy.

Integrated transcriptomic analysis reveals dysregulated immune infiltration and pro-inflammatory cytokines in the secretory endometrium of recurrent implantation failure patients

Recurrent implantation failure (RIF) is a leading impediment to assisted reproductive technology, yet the underlying pathogenesis of RIF remains elusive. Recent studies have sought to uncover novel biomarkers and etiological factors of RIF by profiling transcriptomes of endometrial samples. Nonetheless, the inherent heterogeneity among published studies and a scarcity of experimental validations hinder the identification of robust markers of RIF. Hence, we integrated six publicly accessible datasets with 209 samples, including microarray profiles of endometrial samples in the secretory phase. After removing batch effects, we identified 175 differentially expressed genes. Gene set enrichment analysis identified dysregulation of immunological pathways in RIF. We also observed altered immune infiltration and pro-inflammatory cytokines in RIF. Protein-protein interaction network analysis identified ten hub genes, representing two co-expression modules significantly related to RIF. Knockdown of ENTPD3, one of the hub genes, promoted the epithelial-mesenchymal transition process and resulted in elevated levels of pro-inflammatory cytokines. Collectively, our study reveals abnormal gene expressions involving the regulation of epithelial-mesenchymal transition and immune status in RIF, providing valuable insights into its pathogenesis.

Altered Expression of C4BPA and CXCL1 Genes in the Endometrium of Patients with Recurrent Implantation Failure after In Vitro Fertilization and Thin Endometrium

Currently, recurrent implantation failure (RIF) after in vitro fertilization is a problem that is commonly faced by reproductive specialists. The phenomenon of a thin endometrium in RIF patients is not yet completely understood or sufficiently treated. This study aimed to reveal the dysregulated expression of selected genes between RIF patients with a thin endometrium and fertile women. Endometrial samples were collected in the implantation window (21-24 days of the natural menstrual cycle) from RIF patients (n = 20) and fertile women (n = 14). Ten genes were chosen as target genes regarding their possible relations with the implantation process. The endometrial gene expression levels showed differences in RIF samples compared to fertile samples. Significant downregulation was observed for the CXCL1 (p = 0.005) and C4BPA (p = 0.03) genes. There was no statistically significant difference between the RIF group and the fertile group in the expression of eight genes: CXCL8, HPRT1, MMP10, INFG, VEGFB, HAND2, IL-15, and TNC (p > 0.05). The use of a combination of two markers (C4BPA + CXCL1) allows for the good discrimination of RIF patients from fertile women (AUC 0.806).

Activated THP-1 Macrophage-Derived Factors Increase the Cytokine, Fractalkine, and EGF Secretions, the Invasion-Related MMP Production, and Antioxidant Activity of HEC-1A Endometrium Cells

Endometrium receptivity is a multifactor-regulated process involving progesterone receptor-regulated signaling, cytokines and chemokines, and additional growth regulatory factors. In the female reproductive system, macrophages have distinct roles in the regulation of receptivity, embryo implantation, immune tolerance, and angiogenesis or oxidative stress. In the present study, we investigated the effects of PMA-activated THP-1 macrophages on the receptivity-related genes, cytokines and chemokines, growth regulators, and oxidative stress-related molecules of HEC-1A endometrium cells. We established a non-contact co-culture in which the culture medium of the PMA-activated macrophages exhibiting the pro-inflammatory phenotype was used for the treatment of the endometrial cells. In the endometrium cells, the expression of the growth-related factors activin and bone morphogenetic protein 2, the growth hormone EGF, and the activation of the downstream signaling molecules pERK1/2 and pAkt were analyzed by ELISA and Western blot. The secretions of cytokines and chemokines, which are involved in the establishment of endometrial receptivity, and the expression of matrix metalloproteinases implicated in invasion were also determined. Based on the results, the PMA-activated THP-1 macrophages exhibiting a pro-inflammatory phenotype may play a role in the regulation of HEC-1A endometrium cells. They alter the secretion of cytokines and chemokines, as well as the protein level of MMPs of HEC-1A cells. Moreover, activated THP-1 macrophages may elevate oxidative stress protection of HEC-1A endometrium cells. All these suggest that pro-inflammatory macrophages have a special role in the regulation of receptivity-related and implantation-related factors of HEC-1A cells.

Regional Analysis of the Immune Microenvironment in Human Endometrium

PROBLEM

Endometrial immune cells are essential for maintaining homeostasis and the endometrial receptivity to embryo implantation. Understanding regional variations in endometrial immune cell populations is crucial for comprehending normal endometrial function and the pathophysiology of endometrial disorders. Despite previous studies focusing on the overall immune cell composition and function in the endometrium, regional variations in premenopausal women remain unclear.

METHOD OF STUDY

Endometrial biopsies were obtained from four regions (anterior, posterior, left lateral, and right lateral) of premenopausal women undergoing hysteroscopy with no abnormalities. A 15-color human endometrial immune cell-focused flow cytometry panel was used for analysis. High-dimensional flow cytometry combined with a clustering algorithm was employed to unravel the complexity of endometrial immune cells. Additionally, multiplex immunofluorescent was performed for further validation.

RESULTS

Our findings revealed no significant variation in the distribution and abundance of immune cells across different regions under normal conditions during the proliferative phase. Each region harbored similar immune cell subtypes, indicating a consistent immune microenvironment. However, when comparing normal regions to areas with focal hemorrhage, significant differences were observed. An increase in CD8+ T cells highlights the impact of localized abnormalities on the immune microenvironment.

CONCLUSIONS

Our study demonstrates that the endometrial immune cell landscape is consistent across different anatomical regions during the proliferative phase in premenopausal women. This finding has important implications for understanding normal endometrial function and the pathophysiology of endometrial disorders.

The Causal Relationship Between Immune Cells and Infertility: A Mendelian Randomisation Study

OBJECTIVE

Infertility has emerged as a significant global public health concern, with a multitude of complex underlying causes. Epidemiological evidence indicates that immunological factors are significant contributors to the aetiology of infertility. However, previous studies on the relationship between immune inflammation and infertility have yielded inconclusive results.

METHODS

Mendelian randomisation (MR) is an emerging statistical method that employs exposure-related genetic variation as an instrumental variable (IV) to infer causal relationships between immune cells and infertility by modelling the principle of random assignment in Mendelian genetics. In this study, MR was employed to assess the causal relationship between 731 immune cell signatures and infertility. The data utilized in this study were obtained from publicly available genome-wide association studies (GWAS) and validated IVs, which were employed to fulfil the essential assumptions of MR analysis.

RESULTS

The Mendelian randomisation analysis revealed a total of 27 statistically significant immune cell phenotypes out of 731. The risk factor with the largest odds ratio (OR) was CD28- CD25++ CD8+ %T cell [OR, 1.21; 95% confidence interval (CI), 1.04-1.42], while the protective factor with the largest OR was activated and resting Treg AC (OR, 0.89; 95% CI, 0.82-0.97).

CONCLUSION

The present study has demonstrated a correlation between certain characteristics of immune cells and female infertility. These results provide clues for further research into the immune mechanisms of infertility and may inform the development of novel therapeutic strategies.

Reproductive and transcriptome characteristics of endometrium at the window of im-plantation in patients after fertility-sparing treatment of endometrial intraepithelial neoplasm or cancer

Background

Progestin therapy is an option for patients with endometrial carcinoma (EC) or endometrial intraepithelial neoplasm (EIN) who fit specific criteria of fertility-sparing treatment. However, the implantation rate remains low among females receiving in vitro fertilization (IVF) even after the complete reversal of endometrial lesions.

Methods

Here, ten patients with EC/EIN achieved complete regression (CR) in histology. Their relevant metabolic and IVF parameters were collected. An endometrial sampling at the window of implantation (WOI) and transcriptome analysis were conducted among them, and four healthy controls were analyzed to analyze endometrial receptivity.

Results

On average, it took ten patients five months to achieve CR after four curettage procedures. The interquartile range of endometrium thickness on trigger day was between 8.8 and 10.0 mm, while the range was 15.2-18.5 mm for controls. Five patients got pregnant after a frozen-embryo transfer. According to ERA analysis, the endometrial sampling at WOI showed pre-receptive status in four cases. In total, 1458 differential expression genes were identified, and 70 belonged to the ERA genes. ImmuneScore indicated decreased NK cells in the endometrium, affecting endometrial receptivity.

Conclusions

Even after EC/EIN reversal in histology, endometrial receptivity has already been compromised regarding altered WOI and immune microenvironment, leading to a low pregnancy rate.

Unraveling the H19/GAS1 axis in recurrent implantation failure: A potential biomarker for diagnosis and insight into immune microenvironment alteration

Recurrent implantation failure (RIF) presents a significant clinical challenge due to the lack of established diagnostic and therapeutic guidelines. Emerging evidence underscores the crucial role of competitive endogenous RNA (ceRNA) regulatory networks in non-cancerous female reproductive disorders, yet the intricacies and operational characteristics of these networks in RIF are not fully understood. This study aims to demystify the ceRNA regulatory network and identify potential biomarkers for its diagnosis. We analyzed expression profiles of three RNA types (long noncoding RNAs [lncRNAs], microRNAs [miRNAs], and mRNAs) sourced from the GEO database, leading to the identification of the H19-hsa-miR-301a-3p-GAS1 ceRNA network. This network demonstrates significant diagnostic relevance for RIF. Notably, the H19/GAS1 axis within this ceRNA network, identified through correlation analysis, emerged as a promising diagnostic marker, as evidenced by operating receiver operator characteristic (ROC) curve analysis. Further investigation into the binding potential of miR-301a-3p with H19 and GAS1 revealed a close association of these genes with endometrial disorders and embryo loss, as per the Comparative Toxicogenomics Database. Additionally, our immune infiltration analysis revealed a lower proportion of T cells gamma delta (γδ) in RIF, along with distinct differences in the expression of immune cell type-specific markers between fertile patients and those with RIF. We also observed a correlation between aberrant expression of H19/GAS1 and these immune markers, suggesting that the H19/GAS1 axis might play a role in modifying the immune microenvironment, contributing to the pathogenesis of RIF. In conclusion, the ceRNA-based H19/GAS1 axis holds promise as a novel diagnostic biomarker for RIF, potentially enhancing our understanding of its underlying mechanisms and improving the success rates of implantation.

Bioinformatic Analysis of the Significance of the KIR2DL4 Gene in Recurrent Implantation Failure

Related studies have pointed out that Killer immunoglobulin-like receptor 2DL4 (KIR2DL4) was associated with vascular remodeling in early pregnancy, and it might play an important role in immunity. In this study, recurrent implantation failure (RIF)-related GSE58144 dataset was extracted from the Gene Expression Omnibus (GEO) database. Firstly, the immune micro-environment analyses were conducted to analyze the pathogenesis of KIR2DL4 in RIF. Then, the gene set enrichment analysis (GSEA) was performed to investigate the function of KIR2DL4. Moreover, the TF-mRNA-miRNA and the co-expression networks were constructed to reveal the potential regulation of KIR2DL4. Furthermore, the genes that were associated with KIR2DL4 and differentially expressed in RIF were obtained and defined as key genes, and the functions of these genes were further explored. KIR2DL4 could be used for clinical diagnosis of RIF, and it was correlated with the changes in the immune micro-environment in RIF. From the perspective of function, KIR2DL4 was associated with complement and coagulation cascades, natural killer cell-mediated cytotoxicity, etc. Moreover, the TF-mRNA-miRNA regulatory network was constructed with KIR2DL4, 9 TFs, and 29 miRNAs. Furthermore, KIR2DL4, ACSM1, IL2RB, and PTPN11 were screened as key genes, which were associated with immune-related functions. This study deeply analyzed the function of KIR2DL4 and its role in RIF, and we found that STAT1 might up-regulate KIR2DL4 by INF-γ/JAK2/STAT1 signaling pathway. Besides, over-expressed KIR2DL4 in the mid-luteal endometrium might influence embryo implantation by affecting the embryo implantation microenvironment, which might help deepen the understanding of the molecular mechanism of RIF.

Beyond Immune Balance: The Pivotal Role of Decidual Regulatory T Cells in Unexplained Recurrent Spontaneous Abortion

Recurrent spontaneous abortion (RSA) is defined as two or more consecutive pregnancy failures, which brings tremendous stress to women of childbearing age and seriously affects family well-being. However, the reason in about 50% of cases remains unknown and is defined as unexplained recurrent spontaneous abortion (URSA). The immunological perspective in URSA has attracted widespread attention in recent years. The embryo is regarded as a semi-allogeneic graft to the mother. A successful pregnancy requires transition to an immune environment conducive to embryo survival at the maternal-fetal interface. As an important member of regulatory immunity, regulatory T (Treg) cells play a key role in regulating immune tolerance at the maternal-fetal interface. This review will focus on the phenotypic plasticity and lineage stability of Treg cells to illustrate its relationship with URSA.

Regulation of iron metabolism in HEC-1A endometrium cells by macrophage-derived factors and fractalkine

Macrophages in the endometrium promote receptivity and implantation by secreting proinflammatory cytokines and other factors like fractalkine (FKN). Macrophages are closely linked to regulating iron homeostasis and can modulate iron availability in the tissue microenvironment. It has been revealed that the iron metabolism of the mother is crucial in fertility. Iron metabolism is strictly controlled by hepcidin, the principal iron regulatory protein. The inflammatory cytokines can modulate hepcidin synthesis and, therefore, the iron metabolism of the endometrium. It was proven recently that FKN, a unique chemokine, is implicated in maternal-fetal communication and may contribute to endometrial receptivity and implantation. In the present study, we investigated the effect of activated THP-1 macrophages and FKN on the iron metabolism of the HEC-1A endometrial cells. We established a noncontact coculture with or without recombinant human FKN supplementation to study the impact of the macrophage-derived factors and FKN on the regulation of hepcidin synthesis and iron release and storage of endometrial cells. Based on our findings, the conditioned medium of the activated macrophages could modify hepcidin synthesis via the nuclear factor kappa-light-chain-enhancer of activated B cells, the signal transducer and activator of transcription 3, and the transferrin receptor 2/bone morphogenetic protein 6/suppressor of mothers against decapentaplegic 1/5/8 signaling pathways, and FKN could alter this effect on the endometrial cells. It was also revealed that the conditioned macrophage medium and FKN modulated the iron release and storage of HEC-1A cells. FKN signaling may be involved in the management of iron trafficking of the endometrium by the regulation of hepcidin. It can contribute to the iron supply for fetal development at the early stage of the pregnancy.

Intra-horn insemination in the alpaca Vicugna pacos: Copulatory wounding and deep sperm deposition

Alpacas (Vicugna pacos) are reported to be the rare mammal in which the penis enters the uterus in mating. To date, however, only circumstantial evidence supports this assertion. Using female alpacas culled for meat, we determined that the alpaca penis penetrates to the very tips of the uterine horns, abrading the tract and breaking fine blood vessels. All female alpacas sacrificed one hour or 24 hours after mating showed conspicuous bleeding in the epithelium of some region of their reproductive tract, including the hymen, cervix and the tips of each uterine horn, but typically not in the vagina. Unmated females showed no evidence of conspicuous bleeding. Histological examination of mated females revealed widespread abrasion of the cervical and endometrial epithelium, injuries absent in unmated females. Within one hour of mating, sperm were already present in the oviduct. The male alpaca's cartilaginous penis tip with a hardened urethral process is likely responsible for the copulatory abrasion. The entire female reproductive tract interacts with the penis, functioning like a vagina. Alpacas are induced ovulators, and wounding may hasten delivery of the seminal ovulation-inducing factor beta-NGF into the female's blood stream. There is no evidence of sexual conflict in copulation in alpaca, and thus wounding may also be one of a variety of mechanisms devised by mammals to induce a beneficial, short-term inflammatory response that stimulates blastocyst implantation, the uterine remodeling associated with placental development, and thus the success of early pregnancy.

Detection of Interleukin-1 β (IL-1β) in Single Human Blastocyst-Conditioned Medium Using Ultrasensitive Bead-Based Digital Microfluidic Chip and Its Relationship with Embryonic Implantation Potential

The implantation of human embryos is a complex process involving various cytokines and receptors expressed by both endometrium and embryos. However, the role of cytokines produced by a single embryo in successful implantation is largely unknown. This study aimed to investigate the role of IL-1β expressed in a single-embryo-conditioned medium (ECM) in embryo implantation. Seventy samples of single ECM were analyzed by a specially designed magnetic-beads-based microfluidic chip from 15 women. We discovered that IL-1β level increased as the embryo developed, and the difference was significant. In addition, receiver operator characteristic (ROC) curves analysis showed a higher chance of pregnancy when the IL-1β level on day 5 ECM was below 79.37 pg/mL and the difference between day 5 and day 3 was below 24.90 pg/mL. Our study discovered a possible association between embryonic proteomic expression and successful implantation, which might facilitate single-embryo transfer in the future by helping clinicians identify the embryo with the greatest implantation potential.

SARS-CoV-2 infection is detrimental to pregnancy outcomes after embryo transfer in IVF/ICSI: a prospective cohort study

BACKGROUND

To explore whether SARS-CoV-2 infection affects the pregnancy outcomes of assisted reproductive techniques (ART).

METHODS

A prospective cohort study recruited patients for embryo transfer from December 01, 2022, to December 31, 2022. All patients were closely followed up for SARS-CoV-2 infection after embryo transfer. The SARS-CoV-2 "diagnosed group" was defined as RNA or antigen-positive. The SARS-CoV-2 "suspected infection group" was defined as having apparent SARS-CoV-2 symptoms without an RNA or antigen test, while the "uninfected group" was defined as having a negative SARS-CoV-2 RNA or antigen test and no SARS-CoV-2 symptoms.

RESULTS

A total of 1330 patients participated in the study, 687 of whom were in the SARS-CoV-2 diagnosed group, 219 in the suspected infection group, and 424 in the uninfected group. There was no significant difference in basic characteristics among the three groups. The clinical pregnancy rate was 68% in the SARS-CoV-2 diagnosed group, 63% in the uninfected group, and 51% in the suspected infection group (P < 0.001). The ongoing pregnancy rate was 58% in the SARS-CoV-2 diagnosed group, 53% in the uninfected group, and 45% in the suspected infection group (P < 0.001). Upon analyzing the factors influencing clinical pregnancy, it was found that suspected infection (odds ratio [OR] 0.618, 95% CI 0.444-0.862, P = 0.005) and the short time (≤ 22 days) between embryo transfer and SARS-CoV-2 infection (OR 3.76, 95% CI 1.92-8.24, P < 0.001) were not conducive to clinical pregnancy. In addition, the concurrent presence of fever and dizziness/headache SARS-CoV-2 symptoms (OR 0.715, 95% CI 0.526-0.972, P = 0.032) decreased the clinical pregnancy rate. However, vaccination administered 2-3 times (OR 1.804, 95% CI 1.332-2.444, P < 0.001) was associated with an improvement in clinical pregnancy rate.

CONCLUSIONS

This prospective cohort study shows that SARS-CoV-2 infection in a short period of time after embryo transfer is not conducive to clinical pregnancy. Reproductive physicians should advise patients to avoid SARS-CoV-2 infection shortly after embryo transfer. Meanwhile, women should be encouraged to vaccinate at least 2-3 times before embryo transfer or pregnancy.

Exploring Natural Killer Cell Testing in Embryo Implantation and Reproductive Failure: An Overview of Techniques and Controversies

The blastocyst nidation is the most crucial stage to a successful pregnancy, as the white cells work to promote a favorable endometrial microenvironment for this process. Intriguingly, this implantation window lasts, on average, 6 days in most regular women, and its quality is affected by many pathological conditions. Since the grounds of reproductive failure in healthy couples are still uncharted, studies have widely suggested a potential hostile role of the immune system in the equilibrium of the maternal-fetal interface. In recent years, natural killer cells have been the highlight as they represent the greatest lymphocyte in the uterus and have immune surveillance through cytotoxicity during the implantation window. This review explored the main techniques used for natural killer (NK) cell testing in the implantation window over the last 13 years on the PubMed® database. Of 2167 published articles potentially relevant for the review, only thirty-three were about cell evaluation in healthy women, met the inclusion criteria, and had their methodology critically analyzed. Here, we bring a summary from the study group and sample collection to evidence comments about their findings and correlations. Meanwhile, we also summarize the current relationship between NK cells and endometrial receptivity with reproductive failure to help enhance the possibilities for future research. In conclusion, our overview points out that restricted and unstandardized methods support the controversy between the NK population and unsuccessful embryo implantation, which is an obstacle to studying why healthy eggs do not thrive and finding a solution for one of the most controversial topics in human reproduction.

Inflammatory markers are associated with infertility prevalence: a cross-sectional analysis of the NHANES 2013-2020

BACKGROUND

Inflammation exerts a critical role in the pathogenesis of infertility. The relationship between inflammatory parameters from peripheral blood and infertility remains unclear. Aim of this study was to investigate the association between inflammatory markers and infertility among women of reproductive age in the United States.

METHODS

Women aged 20-45 were included from the National Health and Nutrition Examination Survey (NHANES) 2013-2020 for the present cross-sectional study. Data of reproductive status was collected from the Reproductive Health Questionnaire. Six inflammatory markers, systemic immune inflammation index (SII), lymphocyte count (LC), product of platelet and neutrophil count (PPN), platelet-lymphocyte ratio (PLR), neutrophil-lymphocyte ratio (NLR) and lymphocyte-monocyte ratio (LMR) were calculated from complete blood counts in mobile examination center. Survey-weighted multivariable logistic regression was employed to assess the association between inflammatory markers and infertility in four different models, then restricted cubic spline (RCS) plot was used to explore non-linearity association between inflammatory markers and infertility. Subgroup analyses were performed to further clarify effects of other covariates on association between inflammatory markers and infertility.

RESULTS

A total of 3,105 women aged 20-45 was included in the final analysis, with 431 (13.88%) self-reported infertility. A negative association was found between log2-SII, log2-PLR and infertility, with an OR of 0.95 (95% CI: 0.78,1.15; p = 0.60), 0.80 (95% CI:0.60,1.05; p = 0.10), respectively. The results were similar in model 1, model 2, and model 3. Compared with the lowest quartile (Q1), the third quartile (Q3) of log2-SII was negatively correlation with infertility, with an OR (95% CI) of 0.56 (95% CI: 0.37,0.85; p = 0.01) in model 3. Similarly, the third quartile (Q3) of log2-PLR was negatively correlation with infertility, with an OR (95% CI) of 0.61 (95% CI: 0.43,0.88; p = 0.01) in model 3. No significant association was observed between log2-LC, log2-PPN, log2-NLR, log2-LMR and infertility in model 3. A similar U-shaped relationship between log2-SII and infertility was found (p for non-linear < 0.05). The results of subgroup analyses revealed that associations between the third quartile (Q3) of log2-SII, log2-PLR and infertility were nearly consistent.

CONCLUSION

The findings showed that SII and PLR were negatively associated with infertility. Further studies are needed to explore their association better and the underlying mechanisms.

Western-style diet in the presence of elevated circulating testosterone induces adipocyte hypertrophy without proinflammatory responses in rhesus macaques

PROBLEM

Anovulatory infertility is commonly associated with hyperandrogenemia (elevated testosterone, T), insulin resistance, obesity, and white adipose tissue (WAT) dysfunction associated with adipocyte hypertrophy. However, whether hyperandrogenemia and adipocyte hypertrophy per se induce a proinflammatory response is unknown.

METHOD OF STUDY

Young adult female rhesus macaques were exposed to an obesogenic Western-style diet (WSD) in the presence of elevated circulating testosterone (T+WSD) or a low-fat control diet with no exogenous T. Immune cells residing in visceral omental white adipose tissue (OM-WAT), corpus luteum and the contralateral ovary, endometrium, lymph nodes, bone marrow, and peripheral blood mononuclear cells were characterized by flow cytometry during the luteal phase of the reproductive cycle.

RESULTS

Following one year of treatment, T+WSD animals became more insulin-resistant and exhibited increased body fat and adipocyte hypertrophy compared to controls. T+WSD treatment did not induce macrophage polarization toward a proinflammatory phenotype in the tissues examined. Additionally, T+WSD treatment did not affect TNFα production by bone marrow macrophages in response to toll-like receptor agonists. While the major lymphoid subsets were not significantly affected by T+WSD treatment, we observed a significant reduction in the frequency of effector memory CD8+ T-cells (Tem) in OM-WAT, but not in other tissues. Notably, OM-WAT Tem frequencies were negatively correlated with insulin resistance as assessed by the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR).

CONCLUSION

This study shows that short-term T+WSD treatment induces weight gain, insulin resistance, and adipocyte hypertrophy, but does not have a significant effect on systemic and tissue-resident proinflammatory markers, suggesting that adipocyte hypertrophy and mild hyperandrogenemia alone are not sufficient to induce a proinflammatory response.

Effect of Chinese patent medicine Kunling Pill on endometrial receptivity: A clinical trial, network pharmacology, and animal-based study

Although pregnancy success rates are raised with assisted reproductive technology, it still cannot meet clinical demands. Kunling Pill (KLP), a traditional Chinese medicine, is widely used in various gynecological disorders, particularly in improving fertility and pregnancy rates. However, the underlying mechanism of how KLP affects pregnancy outcomes remains unclear. This study aimed to explore the effects and mechanisms of KLP on endometrial receptivity. Firstly, a retrospective trial was conducted to validate the efficacy of KLP on repeated implantation failure (RIF) patients. The result indicated a significant increase in the proportion of live birth in KLP group (30.56%) compared to the control group (16.89%). Secondly, network pharmacology methods predicted the active components and network targets of KLP. Endometrial receptivity is closely associated with the activation of inflammatory factors, predicting the function of KLP on the immune system. The estrogen and apoptotic signaling pathways were also highlighted in the gene ontology enrichment analysis. Thirdly, a decreased endometrial receptivity model was established by controlled ovarian hyperstimulation (COH) in female C57BL/6 mice, divided into the COH and KLP groups. Normal female mice are as control group. In vivo, KLP administration could increase endometrial thickness and the number of endometrial glands and pinopodes. In the endometrium, KLP supplementation upregulated the expressions of estrogen receptor α, progesterone receptor, endothelial nitric oxide synthase, and integrin αVβ3 in the murine uterus and reduced serum levels of estrogen and progesterone. KLP regulated the uterine immune cells and inhibited cell apoptosis in the ovary via Bcl-2/Bax/caspase-3 pathway. In conclusion, KLP administration raised the live birth rate in RIF patients to optimize medication regimens, mainly because KLP ameliorated impaired endometrial receptivity.

NK and T Cell Subtypes in the Endometrium of Patients with Recurrent Pregnancy Loss and Recurrent Implantation Failure: Implications for Pregnancy Success

BACKGROUND

RPL and RIF are challenges in reproductive medicine. The immune system plays a pivotal role in endometrial receptivity, successful implantation, and pregnancy complications. Immunological changes have been associated with RPL and RIF. Understanding immune dysregulation especially in NK and T cell subtypes may lead to better diagnostic concepts and treatments. From July 2019 to August 2020 patients with RPL and RIF underwent a standardized diagnostic procedure including endometrial biopsies. Immune cell analysis was performed using flow cytometry. Patients were contacted in March 2023 and interviewed concerning their pregnancy outcomes following diagnostics.

RESULTS

Out of 68 patients undergoing endometrial biopsies, 49 patients were finally included. Live birth rates were high with 72% in RPL and 86% in RIF. Immune cell analysis revealed that patients with RPL had more cytotoxic CD56dimCD16high cells, while RIF patients had more CD56+ uNK cells. RPL patients with pregnancy complications showed increased NKT cell percentages.

CONCLUSION

Our findings suggest specific immune changes in RPL and RIF patients, offering potential therapeutic targets. Tailored immunotherapy based on endometrial immunophenotyping might be an option, but further research is needed.

Using organoids to investigate human endometrial receptivity

The human endometrium is only receptive to an implanting blastocyst in the mid-secretory phase of each menstrual cycle. Such time-dependent alterations in function require intricate interplay of various factors, largely coordinated by estrogen and progesterone. Abnormal endometrial receptivity is thought to contribute to two-thirds of the implantation failure in humans and therefore significantly hindering IVF success. Despite the incontrovertible importance of endometrial receptivity in implantation, the precise mechanisms involved in the regulation of endometrial receptivity remain poorly defined. This is mainly due to a lack of proper in vitro models that recapitulate the in vivo environment of the receptive human endometrium. Organoids were recently established from human endometrium with promising features to better mimic the receptive phase. Endometrial organoids show long-term expandability and the capability to preserve the structural and functional characteristics of the endometrial tissue of origin. This three-dimensional model maintains a good responsiveness to steroid hormones in vitro and replicates key morphological features of the receptive endometrium in vivo, including pinopodes and pseudostratified epithelium. Here, we review the current findings of endometrial organoid studies that have been focused on investigating endometrial receptivity and place an emphasis on methods to further refine and improve this model.

Immune cell profiling of vaginal blood from patients with early pregnancy bleeding

PROBLEM

Vaginal bleeding during early pregnancy is estimated to occur in 20% of all pregnancies and it is often difficult to predict who will ultimately miscarry. The role of immune cells in early pregnancy loss is poorly understood.

METHOD OF STUDY

In this prospective cohort study, 28 pregnant women presenting with first-trimester vaginal bleeding donated vaginal blood, peripheral venous blood, and saliva during their initial emergency room visit, and at a follow-up. The composition, frequency, and phenotype of immune cells in the vaginal blood were determined using flow cytometry. The proteome of serum and saliva was analyzed with OLINK proximity extension assay and correlated to vaginal immune cell phenotype and outcome of pregnancy. The course and outcome of pregnancies were followed and recorded.

RESULTS

Vaginal blood contained all main immune cell lineages including B cells, NK cells, T cells, and monocytes/macrophages. Notably, vaginal blood immune cells expressed tissue residency markers including CD49a. Women who subsequently miscarried had a higher frequency of vaginal blood CD49a+ NK cells compared to those who did not miscarry, and this correlated with serum levels of granzyme A and H, as well as CSF1, CAIX, and TWEAK. Women in the miscarriage group also had a higher frequency of peripheral blood T cells expressing CD49a.

CONCLUSIONS

Our study provides novel insight into human reproductive immunology in relation to miscarriage. Tissue-resident NK cells in vaginal blood alone or in combination with serological biomarkers hold potential as prognostic factors in the prediction of pregnancy outcome in women with early pregnancy bleedings.

The effectiveness and safety of intrauterine infusion of autologous regulatory T cells (Tregs) in patients with recurrent pregnancy loss and low levels of endometrial FoxP3+ cells: A retrospective cohort study

PROBLEM

Regulatory T cells (Tregs) are a specialized type of T cells that help maintain immune tolerance and homeostasis. The potential of Tregs cell-based therapies in treating diseases has been demonstrated in several clinical trials, which have shown promising outcomes and high safety in autoimmune diseases, transplant rejection, and graft-versus-host disease. However, their effectiveness and safety in improving endometrial receptivity and reducing pregnancy loss in human reproduction are unknown.

METHOD OF STUDY

The study used a retrospective design and included patients with recurrent pregnancy loss (RPL) and lower levels of endometrial FoxP3⁺ Tregs. Patients in the Tregs group (n = 33) received intrauterine Tregs infusion three times during the follicular phase, while the control group (n = 28) did not receive any intrauterine infusion.

RESULTS

The intrauterine infusion of autologous Tregs increased the levels of FoxP3⁺ Tregs and CD56⁺ NK cells. Patients in the Treg group had higher live birth rates and lower miscarriage rates, especially early miscarriage rates. However, the two groups had no differences in the implantation rate, clinical pregnancy rate, and percentage of preterm delivery.

CONCLUSIONS

The findings suggest that intrauterine Tregs infusion may be a potential therapeutic approach for RPL. Further research in larger clinical trials is needed to confirm these findings.

Immune profiling and RNA-seq uncover the cause of partial unexplained recurrent implantation failure

BACKGROUND

Detailed knowledge of the changes in endometrial immune cells during the window of implantation in unexplained recurrent implantation failure (RIF) patients, the functions performed by immune cells, and the interactions between them is largely lacking. This study aimed to classify RIF patients and explore the mechanism through endometrial immune profiling and RNA-seq analysis.

METHODS

This study enrolled a total of 172 patients, comprising 144 women with unexplained RIF and 28 fertile women. Endometrial samples were collected using endometrial scratching at the mid-luteal phase before in vitro fertilization treatment or pregnancy. Transcriptome sequencing and immunohistochemical staining of endometrial immune cells including natural killer (NK) cells, macrophages, T cells, and B cells were performed.

MAIN OUTCOME MEASURE(S)

Comparison of the percentage of endometrial immune cells and the RNA-seq information between RIF patients and fertile control patients.

RESULT(S)

The proportions of uterine CD56⁺ uNK cells, CD57⁺ NKT cells, CD68⁺ macrophages, and CD19⁺ B cells were significantly elevated in RIF patients. In addition, the number of positive CD68 glandular lumens was significantly higher in RIF patients than in the fertile group. In addition, based on this result, we classified RIF patients into three categories.

CONCLUSION(S)

Hyperactivation of endometrial immune cells may be associated with reduced endometrial tolerance and recurrent implantation failure, affecting pregnancy outcomes in RIF patients.

Local Immune Biomarker Expression Depending on the Uterine Microbiota in Patients with Idiopathic Infertility

The endometrium has traditionally been considered sterile. Nowadays, active studies are performed on the female upper genital tract microbiota. Bacteria and/or viruses colonizing the endometrium are known to alter its functional properties, including receptivity and embryo implantation. Uterine cavity inflammation caused by microorganisms leads to disrupted cytokine expression, which, in turn, is mandatory for the successful implantation of the embryo. The present study assessed the vaginal and endometrial microbiota composition and its relation to the levels of cytokines produced by the endometrium in reproductive-aged women complaining of secondary infertility of unknown origin. The multiplex real-time PCR assay was applied for vaginal and endometrial microbiota analysis. The quantitative measurement of endometrial α-defensin (DEFa1), transforming growth factor (TGFβ1), and basic fibroblast growth factor (bFGF2) was carried out using the ELISA (Cloud-Clone Corporation (Katy, TX, USA; manufactured in Wuhan, China). A reliable decline in endometrial TGFβ1 and bFGF2 and an increase in DEFa1 were demonstrated in women with idiopathic infertility when compared to fertile patients. However, TGFβ1, bFGF2, and DEFa1 expression correlated reliably only with the presence of Peptostreptococcus spp. and HPV in the uterine cavity. The obtained results highlight the importance of local immune biomarker determination in the assessment of certain bacteria and viruses' significance as causative agents of infertility.

The Human Early Maternal–Embryonic Interactome

Background: Single cell transcriptomics offers an avenue for predicting, with improved accuracy, the gene networks that are involved in the establishment of the first direct cell–cell interactions between the blastocyst and the maternal luminal epithelium. We hypothesised that in silico modelling of the maternal–embryonic interface may provide a causal model of these interactions, leading to the identification of genes associated with a successful initiation of implantation. Methods: Bulk and single cell RNA-sequencing of endometrial epithelium and scRNAseq of day 6 and 7 trophectoderm (TE) were used to model the initial encounter between the blastocyst and the maternal uterine lining epithelium in silico. In silico modelling of the maternal–embryonic interface was performed using hypernetwork (HN) analysis of genes mediating endometrial–TE interactions and the wider endometrial epithelial transcriptome. A hypernetwork analysis identifies genes that co-ordinate the expression of many other genes to derive a higher order interaction likely to be causally linked to the function. Potential interactions of TE with non-ciliated luminal cells, ciliated cells, and glandular cells were examined. Results: Prominent epithelial activities include secretion, endocytosis, ion transport, adhesion, and immune modulation. Three highly correlated clusters of 25, 22 and 26 TE-interacting epithelial surface genes were identified, each with distinct properties. Genes in both ciliated and non-ciliated luminal epithelial cells and glandular cells exhibit significant functional associations. Ciliated cells are predicted to bind to TE via galectin–glycan interaction. Day 6 and day 7 embryonic–epithelial interactomes are largely similar. The removal of aneuploid TE-derived mRNA invoked only subtle differences. No direct interaction with the maternal gland epithelial cell surface is predicted. These functional differences validate the in silico segregation of phenotypes. Single cell analysis of the epithelium revealed significant change with the cycle phase, but differences in the cell phenotype between individual donors were also present. Conclusions: A hypernetwork analysis can identify epithelial gene clusters that show correlated change during the menstrual cycle and can be interfaced with TE genes to predict pathways and processes occurring during the initiation of embryo–epithelial interaction in the mid-secretory phase. The data are on a scale that is realistic for functional dissection using current ex vivo human implantation models. A focus on luminal epithelial cells may allow a resolution to the current bottleneck of endometrial receptivity testing based on tissue lysates, which is confounded by noise from multiple diverse cell populations.

Identification and validation of immune cells and hub genes alterations in recurrent implantation failure: A GEO data mining study

Introduction: Recurrent implantation failure (RIF) is a distressing problem in assisted reproductive technology (ART). Immunity plays a vital role in recurrent implantation failure (RIF) occurrence and development, but its underlying mechanism still needs to be fully elucidated. Through bioinformatics analysis, this study aims to identify the RIF-associated immune cell types and immune-related genes. Methods: The differentially expressed genes (DEGs) were screened based on RIF-associated Gene Expression Omnibus (GEO) datasets. Then, the enrichment analysis and protein-protein interaction (PPI) analysis were conducted with the DEGs. The RIF-associated immune cell types were clarified by combining single sample gene set enrichment analysis (ssGSEA) and CIBERSORT. Differentially expressed immune cell types-related modules were identified by weighted gene co-expression network analysis (WGCNA) and local maximal quasi-clique merger (lmQCM) analysis. The overlapping genes between DEGs and genes contained by modules mentioned above were delineated as candidate hub genes and validated in another two external datasets. Finally, the microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) that interacted with hub genes were predicted, and the competing endogenous RNA (ceRNA) regulatory network was structured. Results: In the present study, we collected 324 DEGs between RIF and the control group, which functions were mainly enriched in immune-related signaling pathways. Regarding differential cell types, the RIF group had a higher proportion of activated memory CD4 T cells and a lower proportion of γδ T cells in the endometrial tissue. Finally, three immune-related hub genes (ALOX5AP, SLC7A7, and PTGS2) were identified and verified to effectively discriminate RIF from control individuals with a specificity rate of 90.8% and a sensitivity rate of 90.8%. In addition, we constructed a key ceRNA network that is expected to mediate molecular mechanisms in RIF. Conclusion: Our study identified the intricate correlation between immune cell types and RIF and provided new immune-related hub genes that offer promising diagnostic and therapeutic targets for RIF.