Direct and Indirect endocrine-mediated suppression of human endometrial CD8+T cell cytotoxicity

Impact of aging on the frequency, phenotype, and function of CD4+ T cells in the human female reproductive tract

Since CD4+ T cells are essential for regulating adaptive immune responses and for long lasting mucosal protection, changes in CD4+ T cell numbers and function are likely to affect protective immunity. What remains unclear is whether CD4+ T cell composition and function in the female reproductive tract (FRT) changes as women age. Here we investigated the changes in the composition and function of CD4+ T cells in the endometrium (EM), endocervix (CX), and ectocervix (ECX) with aging. We observed a significant decrease in both the total number and percentage of CD4+ T cells in the EM with increasing age, particularly in the years following menopause. CD4+ T cells within the FRT predominantly expressed CD69. The proportion of CD69+CD4+ T cells increased significantly with increasing age in the EM, CX and ECX. The composition of T helper cell subsets within the EM CD4+ T cell population also showed age-related changes. Specifically, there was a significant increase in the proportion of Th1 cells and a significant decrease in Th17 and Treg cells with increasing age. Furthermore, the production of IFNγ by CD4+ T cells in the EM, CX, and ECX significantly decreased with increasing age upon activation. Our findings highlight the complex changes occurring in CD4+ T cell frequency, phenotype, and function within the FRT as women age. Understanding these age-related immune changes in the FRT is crucial for enhancing our knowledge of reproductive health and immune responses in women.

The impact of reproductive hormones on T cell immunity; normal and assisted reproductive cycles

During pregnancy, a unique immune milieu is established systemically and locally at the maternal-fetal interface. While preparing for embryonic implantation, endometrial effectors significantly change their proportions and function, which are synchronized with hormonal changes. During assisted reproductive technology cycles, various cytokines, chemokines, and immune factors dynamically change with the altered receptor expressions on the immune effectors. Thus, the hormonal regulation of immune effectors is critical to maintaining the immune milieu. In this review, hormonal effects on T cell subsets are reviewed. Sex hormones affect T cell ontogeny and development, consequently affecting their functions. Like other T cell subsets, CD4+ T helper (Th) cells are modulated by estrogen, where low estrogen concentration promotes Th1-driven cell-mediated immunity in the uterus and in vitro by enhancing IFN-γ production, while a high estrogen level decreases it. The abundance and differentiation of T regulatory (Treg) cells are controlled by estrogen, inducing Treg expansion. Conversely, progesterone maintains immune homeostasis by balancing Th1/Th2 and Th17/Treg immunity, leading to maternal-fetal tolerance. Therefore, the understanding of the hormonal impact on various T cell subsets during the reproductive cycles is critical to improving reproductive outcomes in women with recurrent pregnancy losses, repeated implantation failures, and undergoing assisted reproductive cycles.

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.

Sub-Optimal Paternal Diet at the Time of Mating Disrupts Maternal Adaptations to Pregnancy in the Late Gestation Mouse

Pregnancy represents a stage during which maternal physiology and homeostatic regulation undergo dramatic change and adaptation. The fundamental purpose of these adaptations is to ensure the survival of her offspring through adequate nutrient provision and an environment that is tolerant to the semi-allogenic foetus. While poor maternal diet during pregnancy is associated with perturbed maternal adaptations during pregnancy, the influence of paternal diet on maternal well-being is less clearly defined. We fed C57BL/6 male mice either a control (CD), low protein diet (LPD), a high fat/sugar Western diet (WD) or the LPD or WD supplemented with methyl donors (MD-LPD and MD-WD, respectively) for a minimum of 8 weeks prior to mating with C57BL/6 females. Mated females were culled at day 17 of gestation for the analysis of maternal metabolic, gut, cardiac and bone health. Paternal diet had minimal influences on maternal serum and hepatic metabolite levels or gut microbiota diversity. However, analysis of the maternal hepatic transcriptome revealed distinct profiles of differential gene expression in response to the diet of the father. Paternal LPD and MD-LPD resulted in differential expression of genes associated with lipid metabolism, transcription, ubiquitin conjugation and immunity in dams, while paternal WD and MD-WD modified the expression of genes associated with ubiquitin conjugation and cardiac morphology. Finally, we observed changes in maternal femur length, volume of trabecular bone, trabecular connectivity, volume of the cortical medullar cavity and thickness of the cortical bone in response to the father's diets. Our current study demonstrates that poor paternal diet at the time of mating can influence the patterns of maternal metabolism and gestation-associated adaptations to her physiology.

Endometrial Proliferative Phase-Centered View of Transcriptome Dynamics across the Menstrual Cycle

The endometrium, the inner mucosal lining of the uterus, undergoes complex molecular and cellular changes across the menstrual cycle in preparation for embryo implantation. Transcriptome-wide analyses have mainly been utilized to study endometrial receptivity, the prerequisite for successful implantation, with most studies, so far, comparing the endometrial transcriptomes between (i) secretory and proliferative endometrium or (ii) mid-secretory and early secretory endometrium. In the current study, we provide a complete transcriptome description of the endometrium across the entire menstrual cycle and, for the first time, comprehensively characterize the proliferative phase of the endometrium. Our temporal transcriptome analysis includes five time points including the mid-proliferative, late proliferative (peri-ovulatory phase), early secretory, mid-secretory, and late secretory phases. Thus, we unveil exhaustively the transitions between the consecutive proliferative and secretory phases, highlighting their unique gene expression profiles and possible distinct biological functions. The transcriptome analysis reveals many differentially expressed genes (DEGs) across the menstrual cycle, most of which are phase-specific. As an example of coordinated gene activity, the expression profile of histone-encoding genes within the HIST cluster on chromosome 6 shows an increase in cluster activity during the late proliferative and a decline during the mid-secretory phase. Moreover, numerous DEGs are shared among all phases. In conclusion, in the current study, we delineate the endometrial proliferative phase-centered view of transcriptome dynamics across the menstrual cycle. Our data analysis highlights significant transcriptomic and functional changes occurring during the late proliferative phase-an essential transition point from the proliferative phase to the secretory phase. Future studies should explore how the biology of the late proliferative phase endometrium impacts the achievement of mid-secretory endometrial receptivity or contributes to molecular aberrations leading to embryo implantation failure.

Endometrial receptivity in women of advanced age: an underrated factor in infertility

BACKGROUND

Modern lifestyle has led to an increase in the age at conception. Advanced age is one of the critical risk factors for female-related infertility. It is well known that maternal age positively correlates with the deterioration of oocyte quality and chromosomal abnormalities in oocytes and embryos. The effect of age on endometrial function may be an equally important factor influencing implantation rate, pregnancy rate, and overall female fertility. However, there are only a few published studies on this topic, suggesting that this area has been under-explored. Improving our knowledge of endometrial aging from the biological (cellular, molecular, histological) and clinical perspectives would broaden our understanding of the risks of age-related female infertility.

OBJECTIVE AND RATIONALE

The objective of this narrative review is to critically evaluate the existing literature on endometrial aging with a focus on synthesizing the evidence for the impact of endometrial aging on conception and pregnancy success. This would provide insights into existing gaps in the clinical application of research findings and promote the development of treatment options in this field.

SEARCH METHODS

The review was prepared using PubMed (Medline) until February 2023 with the keywords such as 'endometrial aging', 'receptivity', 'decidualization', 'hormone', 'senescence', 'cellular', 'molecular', 'methylation', 'biological age', 'epigenetic', 'oocyte recipient', 'oocyte donation', 'embryo transfer', and 'pregnancy rate'. Articles in a language other than English were excluded.

OUTCOMES

In the aging endometrium, alterations occur at the molecular, cellular, and histological levels suggesting that aging has a negative effect on endometrial biology and may impair endometrial receptivity. Additionally, advanced age influences cellular senescence, which plays an important role during the initial phase of implantation and is a major obstacle in the development of suitable senolytic agents for endometrial aging. Aging is also accountable for chronic conditions associated with inflammaging, which eventually can lead to increased pro-inflammation and tissue fibrosis. Furthermore, advanced age influences epigenetic regulation in the endometrium, thus altering the relation between its epigenetic and chronological age. The studies in oocyte donation cycles to determine the effect of age on endometrial receptivity with respect to the rates of implantation, clinical pregnancy, miscarriage, and live birth have revealed contradictory inferences indicating the need for future research on the mechanisms and corresponding causal effects of women's age on endometrial receptivity.

WIDER IMPLICATIONS

Increasing age can be accountable for female infertility and IVF failures. Based on the complied observations and synthesized conclusions in this review, advanced age has been shown to have a negative impact on endometrial functioning. This information can provide recommendations for future research focusing on molecular mechanisms of age-related cellular senescence, cellular composition, and transcriptomic changes in relation to endometrial aging. Additionally, further prospective research is needed to explore newly emerging therapeutic options, such as the senolytic agents that can target endometrial aging without affecting decidualization. Moreover, clinical trial protocols, focusing on oocyte donation cycles, would be beneficial in understanding the direct clinical implications of endometrial aging on pregnancy outcomes.

Antigen-specific decidual CD8+ T cells include distinct effector memory and tissue-resident memory cells

Maternal decidual CD8+ T cells must integrate the antithetical demands of providing immunity to infection while maintaining immune tolerance for fetal and placental antigens. Human decidual CD8+ T cells were shown to be highly differentiated memory T cells with mixed signatures of dysfunction, activation, and effector function. However, no information is present on how specificity for microbial or fetal antigens relates to their function or dysfunction. In addition, a key question, whether decidual CD8+ T cells include unique tissue-resident memory T cells (Trm) or also effector memory T cell (Tem) types shared with peripheral blood populations, is unknown. Here, high-dimensional flow cytometry of decidual and blood CD8+ T cells identified 2 Tem populations shared in blood and decidua and 9 functionally distinct Trm clusters uniquely found in decidua. Interestingly, fetus- and virus-specific decidual CD8+ Trm cells had similar features of inhibition and cytotoxicity, with no significant differences in their expression of activation, inhibitory, and cytotoxic molecules, suggesting that not all fetus-specific CD8+ T cell responses are suppressed at the maternal-fetal interface. Understanding how decidual CD8+ T cell specificity relates to their function and tissue residency is crucial in advancing understanding of their contribution to placental inflammation and control of congenital infections.

Aging modifies endometrial dendritic cell function and unconventional double negative T cells in the human genital mucosa

BACKGROUND

Immune function in the genital mucosa balances reproduction with protection against pathogens. As women age, genital infections, and gynecological cancer risk increase, however, the mechanisms that regulate cell-mediated immune protection in the female genital tract and how they change with aging remain poorly understood. Unconventional double negative (DN) T cells (TCRαβ + CD4-CD8-) are thought to play important roles in reproduction in mice but have yet to be characterized in the human female genital tract. Using genital tissues from women (27-77 years old), here we investigated the impact of aging on the induction, distribution, and function of DN T cells throughout the female genital tract.

RESULTS

We discovered a novel site-specific regulation of dendritic cells (DCs) and unconventional DN T cells in the genital tract that changes with age. Human genital DCs, particularly CD1a + DCs, induced proliferation of DN T cells in a TFGβ dependent manner. Importantly, induction of DN T cell proliferation, as well as specific changes in cytokine production, was enhanced in DCs from older women, indicating subset-specific regulation of DC function with increasing age. In human genital tissues, DN T cells represented a discrete T cell subset with distinct phenotypical and transcriptional profiles compared to CD4 + and CD8 + T cells. Single-cell RNA and oligo-tag antibody sequencing studies revealed that DN T cells represented a heterogeneous population with unique homeostatic, regulatory, cytotoxic, and antiviral functions. DN T cells showed relative to CD4 + and CD8 + T cells, enhanced expression of inhibitory checkpoint molecules and genes related to immune regulatory as well as innate-like anti-viral pathways. Flow cytometry analysis demonstrated that DN T cells express tissue residency markers and intracellular content of cytotoxic molecules. Interestingly, we demonstrate age-dependent and site-dependent redistribution and functional changes of genital DN T cells, with increased cytotoxic potential of endometrial DN T cells, but decreased cytotoxicity in the ectocervix as women age, with implications for reproductive failure and enhanced susceptibility to infections respectively.

CONCLUSIONS

Our deep characterization of DN T cell induction and function in the female genital tract provides novel mechanistic avenues to improve reproductive outcomes, protection against infections and gynecological cancers as women age.

The role of CD8+ T cells in endometriosis: a systematic review

Background

Endometriosis is a chronic disease affecting 6-10% of women of reproductive age. It is an important cause of infertility and chronic pelvic pain with poorly understood aetiology. CD8+ T (CD8 T) cells were shown to be linked to infertility and chronic pain and play a significant role in lesion clearance in other pathologies, yet their function in endometriosis is unknown. We systematically evaluated the literature on the CD8 T in peripheral blood and endometriosis-associated tissues to determine the current understanding of their pathophysiological and clinical relevance in the disease and associated conditions (e.g. infertility and pelvic pain).

Methods

Four databases were searched (MEDLINE, EMBASE, Web of Science, CINAHL), from database inception until September 2022, for papers written in the English language with database-specific relevant terms/free-text terms from two categories: CD8 T cells and endometriosis. We included peer-reviewed papers investigating CD8 T cells in peripheral blood and endometriosis-associated tissues of patients with surgically confirmed endometriosis between menarche and menopause, and animal models with oestrous cycles. Studies enrolling participants with other gynaecological pathologies (except uterine fibroids and tubal factor infertility used as controls), cancer, immune diseases, or taking immune or hormonal therapy were excluded.

Results

28 published case-control studies and gene set analyses investigating CD8 T cells in endometriosis were included. Data consistently indicate that CD8 T cells are enriched in endometriotic lesions in comparison to eutopic endometrium, with no differences in peripheral blood CD8 T populations between patients and healthy controls. Evidence on CD8 T cells in peritoneal fluid and eutopic endometrium is conflicting. CD8 T cell cytotoxicity was increased in the menstrual effluent of patients, and genomic analyses have shown a clear trend of enriched CD8 T effector memory cells in the eutopic endometrium of patients.

Conclusion

Literature on CD8 T cells in endometriosis-associated tissues is inconsistent. Increased CD8 T levels are found in endometriotic lesions, however, their activation potential is understudied in all relevant tissues. Future research should focus on identifying clinically relevant phenotypes to support the development of non-invasive diagnostic and treatment strategies.

Systematic Review Registration

PROSPERO identifier CRD42021233304.

Unveiling uterine aging: Much more to learn

Uterine aging is an important factor that impacts fertility, reproductive health, and uterus-related diseases; however, it remains poorly explored. Functionally, these disturbances have been associated with an abnormal hormonal response in the endometrium and decreased endometrial receptivity. Based on emerging evidence, these alterations are mediated via the senescence of endometrial stem cells and impaired decidualization of endometrial stromal cells. Multiple molecular activities may participate in uterine aging, including oxidative stress, inflammation, fibrosis, DNA damage response, and cellular senescence. Over the past decade, several protective strategies targeting these biological processes have afforded promising results, including stem cell therapy, anti-aging drugs, and herbal medicines. However, the currently available evidence is fragmented and scattered. Here, we summarize the most recent findings regarding uterine aging, including functional and structural alterations and potential cellular and molecular mechanisms, and discuss potential protective interventions against uterine aging. Thereby, we hope to provide a comprehensive understanding of the pathophysiological processes and underlying mechanisms associated with uterine aging, as well as improve fecundity and reproductive outcomes in females of advanced reproductive age.

Aging beyond menopause selectively decreases CD8+ T cell numbers but enhances cytotoxic activity in the human endometrium

BACKGROUND

Regulation of endometrial (EM) CD8+ T cells, which provide protection through cell-mediated cytotoxicity, is essential for successful reproduction, and protection against sexually transmitted infections and potential tumors. We have previously demonstrated that EM CD8+ T cell cytotoxicity is suppressed directly and indirectly by sex hormones and enhanced after menopause. What remains unclear is whether CD8+ T cell protection and the contribution of tissue-resident (CD103+) and non-resident (CD103-) T cell populations in the EM change as women age following menopause.

RESULTS

Using hysterectomy EM tissues, we found that EM CD8+ T cell numbers declined significantly in the years following menopause. Despite an overall decline in CD8+ T cells, cytotoxic activity per cell for both CD103- and CD103 + CD8+ T cells increased with age. Investigation of the underlying mechanisms responsible for cytotoxicity indicated that the percentage of total granzyme A and granzyme B positive CD8+ T cells, but not perforin, increased significantly after menopause and remained high and constant as women aged. Additionally, baseline TNFα production by EM CD8+ T cells increased significantly in the years following menopause, and estradiol suppressed TNFα secretion. Moreover, in response to PMA activation, TNFα and IFNγ were significantly up-regulated, and CD103-CD8+ T cells up-regulation of TNFα, IFNγ and IL-6 increased as women aged.

CONCLUSIONS

Understanding the underlying factors involved in regulating cell-mediated protection of the EM by CD8+ T cells will contribute to the foundation of information essential for developing therapeutic tools to protect women against gynecological cancers and infections as they age.

Double Negative T Regulatory Cells: An Emerging Paradigm Shift in Reproductive Immune Tolerance?

Immune regulation of female reproductive function plays a crucial role in fertility, as alterations in the relationship between immune and reproductive processes result in autoimmune subfertility or infertility. The breakdown of immune tolerance leads to ovulation dysfunction, implantation failure, and pregnancy loss. In this regard, immune cells with regulatory activities are essential to restore self-tolerance. Apart from regulatory T cells, double negative T regulatory cells (DNTregs) characterized by TCRαβ+/γδ+CD3+CD4–CD8– (and negative for natural killer cell markers) are emerging as effector cells capable of mediating immune tolerance in the female reproductive system. DNTregs are present in the female reproductive tract of humans and murine models. However, their full potential as immune regulators is evolving, and studies so far indicate that DNTregs exhibit features that can also maintain tolerance in the female reproductive microenvironment. This review describes recent progress on the presence, role and mechanisms of DNTregs in the female reproductive system immune regulation and tolerance. In addition, we address how DNTregs can potentially provide a paradigm shift from the known roles of conventional regulatory T cells and immune tolerance by maintaining and restoring balance in the reproductive microenvironment of female fertility.

Medroxyprogesterone acetate inhibits wound closure of human endometrial epithelial cells and stromal fibroblasts in vitro

Mucosal integrity in the endometrium is essential for immune protection. Since breaches or injury to the epithelial barrier exposes underlying tissue and is hypothesized to increase infection risk, we determined whether endogenous progesterone or three exogenous progestins (medroxyprogesterone acetate (MPA), norethindrone (NET), and levonorgestrel (LNG)) used by women as contraceptives interfere with wound closure of endometrial epithelial cells and fibroblasts in vitro. Progesterone and LNG had no inhibitory effect on wound closure by either epithelial cells or fibroblasts. MPA significantly impaired wound closure in both cell types and delayed the reestablishment of transepithelial resistance by epithelial cells. In contrast to MPA, NET selectively decreased wound closure by stromal fibroblasts but not epithelial cells. Following epithelial injury, MPA but not LNG or NET, blocked the injury-induced upregulation of HBD2, a broad-spectrum antimicrobial implicated in wound healing, but had no effect on the secretion of RANTES, CCL20 and SDF-1α. This study demonstrates that, unlike progesterone and LNG, MPA and NET may interfere with wound closure following injury in the endometrium, potentially conferring a higher risk of pathogen transmission. Our findings highlight the importance of evaluating progestins for their impact on wound repair at mucosal surfaces.

The impact of aging on innate and adaptive immunity in the human female genital tract

Mucosal tissues in the human female reproductive tract (FRT) are primary sites for both gynecological cancers and infections by a spectrum of sexually transmitted pathogens, including human immunodeficiency virus (HIV), that compromise women's health. While the regulation of innate and adaptive immune protection in the FRT by hormonal cyclic changes across the menstrual cycle and pregnancy are being intensely studied, little to nothing is known about the alterations in mucosal immune protection that occur throughout the FRT as women age following menopause. The immune system in the FRT has two key functions: defense against pathogens and reproduction. After menopause, natural reproductive function ends, and therefore, two overlapping processes contribute to alterations in immune protection in aging women: menopause and immunosenescence. The goal of this review is to summarize the multiple immune changes that occur in the FRT with aging, including the impact on the function of epithelial cells, immune cells, and stromal fibroblasts. These studies indicate that major aspects of innate and adaptive immunity in the FRT are compromised in a site‐specific manner in the FRT as women age. Further, at some FRT sites, immunological compensation occurs. Overall, alterations in mucosal immune protection contribute to the increased risk of sexually transmitted infections (STI), urogenital infections, and gynecological cancers. Further studies are essential to provide a foundation for the development of novel therapeutic interventions to restore immune protection and reverse conditions that threaten women's lives as they age.

Endometrial Cancer Suppresses CD8+ T Cell-Mediated Cytotoxicity in Postmenopausal Women

Endometrial cancer is the most common gynecological cancer. To investigate how it suppresses host immune function, we isolated CD8+ T cells from endometrial endometroid carcinomas and adjacent non-cancerous endometrium and determined if the tumor environment regulates cytotoxic capacity. Endometrial carcinomas had increased numbers of CD8+ T cells compared to adjacent non-cancerous endometrium. Tumor CD8+ T cells expressed significantly less granzyme A (GZA), B (GZB), and PD-1 than those in adjacent non-cancerous tissues and also had significantly lower cytotoxic killing of allogeneic target cells. CD103-CD8+ T cells, but not CD103+CD8+ T cells, from both adjacent and tumor tissue were primarily responsible for killing of allogeneic target cells. Secretions recovered from endometrial carcinoma tissues suppressed CD8+ cytotoxic killing and lowered perforin, GZB and PD-1 expression relative to non-tumor CD8+ T cells. Furthermore, tumor secretions contained significantly higher levels of immunosuppressive cytokines including TGFβ than non-tumor tissues. Thus, the tumor microenvironment suppresses cytotoxic killing by CD8+ T cells via the secretion of immunosuppressive cytokines leading to decreased expression of intracellular cytolytic molecules. These studies demonstrate the complexity of CD8+ T cell regulation within the endometrial tumor microenvironment and provide a foundation of information essential for the development of therapeutic strategies for gynecological cancers.