Antigen-presenting cells and materno-fetal tolerance: an emerging role for dendritic cells

Dendritic Cells and the Establishment of Fetomaternal Tolerance for Successful Human Pregnancy

Pregnancy is a remarkable event where the semi-allogeneic fetus develops in the mother's uterus, despite genetic and immunological differences. The antigen handling and processing at the maternal-fetal interface during pregnancy appear to be crucial for the adaptation of the maternal immune system and for tolerance to the developing fetus and placenta. Maternal antigen-presenting cells (APCs), such as macrophages (Mφs) and dendritic cells (DCs), are present at the maternal-fetal interface throughout pregnancy and are believed to play a crucial role in this process. Despite numerous studies focusing on the significance of Mφs, there is limited knowledge regarding the contribution of DCs in fetomaternal tolerance during pregnancy, making it a relatively new and growing field of research. This review focuses on how the behavior of DCs at the maternal-fetal interface adapts to pregnancy's unique demands. Moreover, it discusses how DCs interact with other cells in the decidual leukocyte network to regulate uterine and placental homeostasis and the local maternal immune responses to the fetus. The review particularly examines the different cell lineages of DCs with specific surface markers, which have not been critically reviewed in previous publications. Additionally, it emphasizes the impact that even minor disruptions in DC functions can have on pregnancy-related complications and proposes further research into the potential therapeutic benefits of targeting DCs to manage these complications.

The Endometrial Microbiota: Challenges and Prospects

Contrary to popular belief, we have known for many years that the endometrium is not a sterile environment and is considered to be a low-biomass milieu compared to the vagina. Numerous trials and studies have attempted to establish a valid sampling method and assess its physiological composition, but no consensus has been reached. Many factors, such as ethnicity, age and inflammation, can influence the microbiome. Moreover, it possesses a higher alpha-diversity and, therefore, contains more diverse bacteria than the vagina. For instance, Lactobacillus has been shown to be a predominant genus in the vaginal microbiome of healthy women. Consequently, even if a majority of scientists postulate that a predominance of Lactobacillus inside the uterus improves reproductive outcomes, vaginal contamination by these bacteria during sampling cannot be ruled out. Certain pathologies, such as chronic endometritis, have been identified as inflammation perpetrators that hinder the embryo implantation process. This pro-inflammatory climate created by dysbiosis of the endometrial microbiota could induce secondary inflammatory mediators via Toll-like receptors, creating an environment conducive to the development of endometriosis and even promoting carcinogenesis. However, studies to this day have focused on small populations. In addition, there is no clearly defined healthy uterine composition yet. At most, only a few taxa have been identified as pathogenic. As sampling and analysis methods become increasingly precise, we can expect the endometrial microbiota to be incorporated into future diagnostic tools and treatments for women's health.

Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

Insights into the immunomodulatory regulation of matrix metalloproteinase at the maternal-fetal interface during early pregnancy and pregnancy-related diseases

Trophoblast immune cell interactions are central events in the immune microenvironment at the maternal-fetal interface. Their abnormalities are potential causes of various pregnancy complications, including pre-eclampsia and recurrent spontaneous abortion. Matrix metalloproteinase (MMP) is highly homologous, zinc(II)-containing metalloproteinase involved in altered uterine hemodynamics, closely associated with uterine vascular remodeling. However, the interactions between MMP and the immune microenvironment remain unclear. Here we discuss the key roles and potential interplay of MMP with the immune microenvironment in the embryo implantation process and pregnancy-related diseases, which may contribute to understanding the establishment and maintenance of normal pregnancy and providing new therapeutic strategies. Recent studies have shown that several tissue inhibitors of metalloproteinases (TIMPs) effectively prevent invasive vascular disease by modulating the activity of MMP. We summarize the main findings of these studies and suggest the possibility of TIMPs as emerging biomarkers and potential therapeutic targets for a range of complications induced by abnormalities in the immune microenvironment at the maternal-fetal interface. MMP and TIMPs are promising targets for developing new immunotherapies to treat pregnancy-related diseases caused by immune imbalance.

Inflammation in preterm birth: Novel mechanism of preterm birth associated with innate and acquired immunity

Preterm birth (PB) is the most-frequent complication occurring during pregnancy, with a significant impact on neonatal morbidity and mortality. Chorioamnionitis (CAM), the neutrophil infiltration into chorioamniotic membranes, is a major cause of PB. However, several cases of PB have also been reported without apparent pathogenic infection or CAM. Such cases are now attributed to "sterile inflammation." The concept of sterile inflammation has already attracted attention in various diseases, like cardiovascular diseases, diabetes, and autoimmune diseases; recently been discussed for obstetric complications such as miscarriage, PB, gestational hypertension, and gestational diabetes. Sterile inflammation is induced by alarmins, such as high-mobility group box 1 (HMGB1), interleukins (IL-33 and IL-1α), and S100 proteins, that are released by cellular damage without apparent pathogenic infection. These antigens are recognized by pattern-recognition receptors, expressed mainly on antigen-presenting cells of decidua, placenta, amnion, and myometrium, which consequently trigger inflammation. In reproduction, these alarmins are associated with the development of various pregnancy complications, including PB. In this review, we have summarized the development of PB related to acute CAM, chronic CAM, and sterile inflammation as well as proposed a new mechanism for PB that involves innate immunity, acquired immunity, and sterile inflammation.

Immune–Metabolic Interactions and T Cell Tolerance in Pregnancy

Pregnancy depends on a state of maternal immune tolerance mediated by CD4+ regulatory T (Treg) cells. Uterine Treg cells release anti-inflammatory factors, inhibit effector immunity, and support adaptation of the uterine vasculature to facilitate placental development. Insufficient Treg cells or inadequate functional competence is implicated in infertility and recurrent miscarriage, as well as pregnancy complications preeclampsia, fetal growth restriction, and preterm birth, which stem from placental insufficiency. In this review we address an emerging area of interest in pregnancy immunology–the significance of metabolic status in regulating the Treg cell expansion required for maternal–fetal tolerance. We describe how hyperglycemia and insulin resistance affect T cell responses to suppress generation of Treg cells, summarize data that implicate a role for altered glucose metabolism in impaired maternal–fetal tolerance, and explore the prospect of targeting dysregulated metabolism to rebalance the adaptive immune response in women experiencing reproductive disorders.

Context is key: Maternal immune responses to pig allogeneic embryos

Successful establishment of pregnancy includes the achievement of a state of immune tolerance toward the embryos (and placenta), where the well‐coordinated maternal immune system is capable of recognizing conceptus antigens while maintaining maternal defense against pathogens. In physiological pregnancies, following natural mating or artificial insemination (AI), the maternal immune system is exposed to the presence of hemi‐allogeneic embryos, that is, embryos containing maternal self‐antigens and foreign antigens from the paternal side. In this scenario, the hemi‐allogeneic embryo is recognized by the mother, but the immune system is locally modified to facilitate embryo implantation and pregnancy progression. Pig allogeneic pregnancies (with embryos containing both paternal and maternal material foreign to the recipient female), occur during embryo transfer (ET), with conspicuously high rates of embryonic death. Mortality mainly occurs during the peri‐attachment phase, suggesting that immune responses to allogeneic embryos are more complex and less efficient, hindering the conceptuses to survive to term. Reaching a similar maternal tolerance as in conventional breeding would render ET successful. The present review critically summarizes mechanisms of maternal immune recognition of pregnancy and factors associated with impaired maternal immune response to the presence of allogeneic embryos in the porcine species.

Insight on Polyunsaturated Fatty Acids in Endometrial Receptivity

Endometrial receptivity plays a crucial role in fertilization as well as pregnancy outcome in patients faced with fertility challenges. The optimization of endometrial receptivity may help with normal implantation of the embryo, and endometrial receptivity may be affected by numerous factors. Recently, the role of lipids in pregnancy has been increasingly recognized. Fatty acids and their metabolites may be involved in all stages of pregnancy and play a role in supporting cell proliferation and development, participating in cell signaling and regulating cell function. Polyunsaturated fatty acids, in particular, are essential fatty acids for the human body that can affect the receptivity of the endometrium through in a variety of methods, such as producing prostaglandins, estrogen and progesterone, among others. Additionally, polyunsaturated fatty acids are also involved in immunity and the regulation of endometrial decidualization. Fatty acids are essential for fetal placental growth and development. The interrelationship of polyunsaturated fatty acids with these substances and how they may affect endometrial receptivity will be reviewed in this article.

Physiological and metabolic adaptations in pregnancy: importance of trimester-specific reference intervals to investigate maternal health and complications

Diagnosis, prognostication, and monitoring of maternal health throughout pregnancy relies on laboratory testing, including but not limited to key markers of thyroid, hepatic, cardiac, hematology, and renal function. Dynamic physiological processes during gestation significantly influence the maternal biochemistry that supports both the mother and fetus. Resultant changes in blood biochemistry alter the expected values of common laboratory tests. However, the importance of pregnancy-specific reference intervals for laboratory test result interpretation and appropriate monitoring of maternal health and complications is underappreciated. Most clinical laboratories continue to use non-pregnant adult reference intervals for laboratory test interpretation in pregnancy. The current review summarizes and critically evaluates the available literature regarding physiological and metabolic adaptations in pregnancy and their influence on common biomarkers of health and disease. The main laboratory parameters discussed include thyroid, hepatic, metabolic, renal, hematology, inflammatory, and cardiac markers. Considering the available data, further studies are urgently needed to establish trimester-specific reference intervals in healthy pregnant women on updated analytical platforms. Without such data, the standard of clinical laboratory service in pregnancy remains compromised and affects the quality of maternal-fetal healthcare.

Immune Profile of the Normal Maternal-Fetal Interface in Rhesus Macaques and Its Alteration Following Zika Virus Infection

The maternal decidua is an immunologically complex environment that balances maintenance of immune tolerance to fetal paternal antigens with protection of the fetus against vertical transmission of maternal pathogens. To better understand host immune determinants of congenital infection at the maternal-fetal tissue interface, we performed a comparative analysis of innate and adaptive immune cell subsets in the peripheral blood and decidua of healthy rhesus macaque pregnancies across all trimesters of gestation and determined changes after Zika virus (ZIKV) infection. Using one 28-color and one 18-color polychromatic flow cytometry panel we simultaneously analyzed the frequency, phenotype, activation status and trafficking properties of αβ T, γδ T, iNKT, regulatory T (Treg), NK cells, B lymphocytes, monocytes, macrophages, and dendritic cells (DC). Decidual leukocytes showed a striking enrichment of activated effector memory and tissue-resident memory CD4+ and CD8+ T lymphocytes, CD4+ Tregs, CD56+ NK cells, CD14+CD16+ monocytes, CD206+ tissue-resident macrophages, and a paucity of B lymphocytes when compared to peripheral blood. t-distributed stochastic neighbor embedding (tSNE) revealed unique populations of decidual NK, T, DC and monocyte/macrophage subsets. Principal component analysis showed distinct spatial localization of decidual and circulating leukocytes contributed by NK and CD8+ T lymphocytes, and separation of decidua based on gestational age contributed by memory CD4+ and CD8+ T lymphocytes. Decidua from 10 ZIKV-infected dams obtained 16-56 days post infection at third (n=9) or second (n=1) trimester showed a significant reduction in frequency of activated, CXCR3+, and/or Granzyme B+ memory CD4+ and CD8+ T lymphocytes and γδ T compared to normal decidua. These data suggest that ZIKV induces local immunosuppression with reduced immune recruitment and impaired cytotoxicity. Our study adds to the immune characterization of the maternal-fetal interface in a translational nonhuman primate model of congenital infection and provides novel insight in to putative mechanisms of vertical transmission.

Maternal Neutrophil Depletion Fails to Avert Systemic Lipopolysaccharide-Induced Early Pregnancy Defects in Mice

Maternal infection-induced early pregnancy complications arise from perturbation of the immune environment at the uterine early blastocyst implantation site (EBIS), yet the underlying mechanisms remain unclear. Here, we demonstrated in a mouse model that the progression of normal pregnancy from days 4 to 6 induced steady migration of leukocytes away from the uterine decidual stromal zone (DSZ) that surrounds the implanted blastocyst. Uterine macrophages were found to be CD206⁺ M2-polarized. While monocytes were nearly absent in the DSZ, DSZ cells were found to express monocyte marker protein Ly6C. Systemic endotoxic lipopolysaccharide (LPS) exposure on day 5 of pregnancy led to: (1) rapid (at 2 h) induction of neutrophil chemoattractants that promoted huge neutrophil infiltrations at the EBISs by 24 h; (2) rapid (at 2 h) elevation of mRNA levels of MyD88, but not Trif, modulated cytokines at the EBISs; and (3) dose-dependent EBIS defects by day 7 of pregnancy. Yet, elimination of maternal neutrophils using anti-Ly6G antibody prior to LPS exposure failed to avert LPS-induced EBIS defects allowing us to suggest that activation of Tlr4-MyD88 dependent inflammatory pathway is involved in LPS-induced defects at EBISs. Thus, blocking the activation of the Tlr4-MyD88 signaling pathway may be an interesting approach to prevent infection-induced pathology at EBISs.

Down-regulation of HLA-DRs and HLA-DPs reflects the deficiency of antigen-presenting cells in endometrium from infertile women with and without ovarian endometriosis

This study aimed to explore common molecular changes in the infertile endometrium from women with and without endometriosis (EM). By analyzing the dataset GSE120103 from Gene Expression Omnibus, a total of 3252 shared differentially expressed genes were identified between ovarian EM in infertile vs. fertile endometrium and EM-free infertile vs. fertile endometrium. In addition, the gene annotation and pathway analysis of the shared differentially expressed genes with the same expression trend indicated that the pathway 'MHC class II antigen presentation' and five candidate genes: HLA-DRA, HLA-DRB1, HLA-DRB3, HLA-DPA1, HLA-DPB1 were both down-regulated in infertile endometrium with or without EM. Logistic regression showed that HLA-DRA might be an independent predictor of the infertile status of the endometrium. Single sample gene set enrichment analysis (ssGSEA) showed that some classic antigen-presenting cells: macrophages type 1, macrophages type 2, and mature dendritic cells were significantly down-regulated in infertile endometrium with or without EM, whose enrichment correlated positively with the expression of candidate HLA molecules. Hence, the down-regulation of HLA-DRs and HLA-DPs reflecting the deficiency of antigen-presenting cells in endometrium might serve as a common biomarker for diagnosing endometrium-associated infertility in women with and without endometriosis.

Mifepristone regulates Tregs function mediated by dendritic cells through suppressing the expression of TGF-β

BACKGROUND

Previous studies have demonstrated that mifepristone in the daily low-dose affects the function of endometrium. These researches also implied an alteration of endometrium immune balance, which might be involved in regulating endometrial function. However, the detailed mechanisms remain to be further explored.

METHODS

In this study, the expressions of CD80, CD86, and ICAM-1 in dendritic cells (DCs), which were stimulated with different concentrations of mifepristone (20, 65, and 200 nM), were detected by FACS. After that, we further evaluated the expression of Forkhead box P3 (FOXP3) and IL-10 in Tregs, which co-cultured with mifepristone treated DCs. In mechanism, we compared the indoleamine 2,3-dioxygenase (IDO) and TGF-β expression with enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results indicated that mifepristone promoted the expressions of CD80, CD86, and ICAM-1 in a dosage dependent manner. Reversely, FOXP3 and IL-10 expression levels in Tregs co-cultured with mifepristone-treated DCs were significantly decreased compared with those co-cultured with nontreated DC. Furthermore, a significant reduce in IDO and TGF-β expression was observed in DCs treated with mifepristone. By using the IDO inhibitor (1-methyl tryptophan, 1-MT) or TGF-b supplement, we confirmed that TGF-β, but not IDO could rescue the downregulation of FOXP3 and IL-10 in Tregs co-cultured with mifepristone treated DCs. All of these results suggest that mifepristone may regulate DC function by decreasing TGF-β expression, which further results in the downregulations of FOXP3 and IL-10 in Tregs.

CONCLUSION

Therefore, our research provides a theoretical basis for a potentially clinical application of mifepristone as a novel contraceptive.

Reproductive immunology in viviparous mammals: evolutionary paradox of interactions among immune mechanisms and autologous or allogeneic gametes and semiallogeneic foetuses

Literally, reproductive immunology was born in bovine on-farm reproduction where seminal experiments intended for developing methods for embryo transfer in cattle were performed. Actually, these experiments led to two of major concepts and fundamental principles of reproductive immunology using the bovine species as a model for biomedical research, namely the concept of acquired immunological tolerance and the paradox of the semiallogeneic bovine foetus whereby such organism can develop within an immunologically competent host. Peter Medawar, a scientist who together with Frank Macfarlande Burnet shared the 1960 Nobel Prize in physiology or medicine for discovery of acquired immunological tolerance, while studying dizygotic cattle twins, thereby giving birth to reproductive immunology. Also, these findings significantly influenced development of organ transplants and showed that using farm animals as models for studying transplantation immunology had general relevance for mammalian biology and health including those of humans. However, the interest for further research of the fascinating maternal immune influences on pregnancy and perinatal outcomes and of the prevention and treatment of immunologically mediated reproductive disorders in viviparous mammals of veterinary relevance by veterinary immunologists and reproductive clinicians have been very scarce regarding the application of nonspecific immunomodulatory agents for prevention and treatment of subfertility and infertility in pigs and cattle, but still broadening knowledge in this area and hold great potential for improving such therapy in the future. The aim of the current overview is to provide up-to-date information and explaining/translating relevant immunology phenomena into veterinary practice for specialists and scientists/clinicians in reproduction of animals.

Dendritic cells in pregnancy and pregnancy-associated diseases

Dendritic cells (DCs) play a critical immuno-modulating role in pregnancy, which requires the maternal immune system to tolerate semiallogeneic fetus and at the same time to maintain adequate defense against pathogens. DCs interact closely with other immune components such as T cells, natural killer cells and macrophages, as well as the endocrine system to keep a pregnancy-friendly environment. Aberrant DC activities have been related to various pregnancy-associated diseases such as recurrent spontaneous abortion, preterm birth, pre-eclampsia, peripartum cardiomyopathy and infectious pregnancy complications. These findings make DCs an attractive candidate for prevention or therapy on the pregnancy-associated diseases. Here, we review recent findings that provide new insights into the roles of DCs in pregnancy and the related diseases. We also discuss the medical potentials to manipulate DCs in clinics. Whereas this is an emerging area with much work remaining, we anticipate that a better understanding of the role of DCs in maternal-fetal immunotolerance and a therapeutic manipulation of DCs will help women suffering from the pregnancy-associated diseases.

Inappropriate activation of invariant natural killer T cells and antigen-presenting cells with the elevation of HMGB1 in preterm births without acute chorioamnionitis

PROBLEM

Acute chorioamnionitis (aCAM) associated with microbial infection is a primary cause of preterm birth (PB). However, recent studies have demonstrated that innate immunity and sterile inflammation are causes of PB in the absence of aCAM. Therefore, we analyzed immune cells in the decidua of early to moderate PB without aCAM.

METHOD OF STUDY

Deciduas were obtained from patients with PB at a gestational age of 24⁺⁰ to 33⁺⁶  weeks without aCAM in pathological diagnosis. The patients were divided into two groups as follows: patients with labor and/or rupture of membrane (ROM) (no aCAM with labor and/or ROM: nCAM-w-LR), and patients without labor and/or ROM (no aCAM without labor and/or ROM: nCAM-w/o-LR). The immune cells and high mobility group box 1 (HMGB1) levels in the decidua were analyzed using flow cytometry. Co-culture of CD56⁺ cells with dendritic cells (DCs) and macrophages obtained from the decidua was also performed in the presence of HMGB1.

RESULTS

The nCAM-w-LR group demonstrated an accumulation of iNKT cells, and increased expression of HMGB1, TLR4, receptors for advanced glycation end products, and CD1d on DCs and macrophages. HMGB1 facilitated the proliferation of iNKT cells co-cultured with DCs and macrophages, which was found to be inhibited by heparin.

CONCLUSIONS

Inappropriate activation of innate immune cells and increased HMGB1 expression may represent parturition signs in human pregnancy. Therefore, control of these cells and HMGB1 antigenicity may be represent a potential therapeutic target for the prevention of PB.

Harmful and beneficial effects of inflammatory response on reproduction: sterile and pathogen-associated inflammation

In reproduction, inflammatory processes play important roles in the development of many pregnancy complications such as preterm labor/birth, recurrent pregnancy loss, recurrent implantation failure, and preeclampsia. Inflammation can be initiated by both microbial and non-microbial causes. Bacterial infection in the feto-maternal interface and uterus can provoke preterm labor/birth, miscarriage, and chronic endometritis. By contrast, inflammation without infection, or 'sterile inflammation,' can also lead to many kinds of complications, such as preterm labor/birth, miscarriage, or preeclampsia. Aberrant inflammation is facilitated by immune cells such as macrophages, dendritic cells, natural killer cells, and invariant natural killer T cells. In addition, cytokines, chemokines, and several kinds of inflammatory mediators are involved. On the other hand, appropriate inflammation is required for a successful offspring during the progression of the entire pregnancy. Herein, we discuss the relation between pregnancy and inflammation with immunological alterations. Understanding the role of inflammation in complications during pregnancy may establish new perspectives of the progress of normal pregnancy as well as treatments during pregnancy complications.

Immunological aspects of nanocellulose

Cellulose is the most abundant natural polymer in the world. Nanoscale forms of cellulose, including cellulose nanofibers (CNF), cellulose nanocrystals (CNC) and bacterial nanocellulose (BC), are very attractive in industry, medicine and pharmacy. Biomedical applications of nanocellulose in tissue engineering, regenerative medicine, and controlled drug delivery are the most promising. Nanocellulose is considered a biocompatible nanomaterial and relatively safe for biomedical applications. However, more studies are needed to prove this hypothesis, especially those related to chronic exposure to nanocellulose. Besides toxicity, the response of the immune system is of particular importance in this sense. This paper provides a comprehensive and critical review of the current-state knowledge of the impact of nanocellulose on the immune system, especially on macrophages and dendritic cells (DC), as the central immunoregulatory cells, which has not been addressed in the literature sufficiently. Nanocellulose, especially CNC, can induce the inflammatory response upon the internalization by macrophages, but this reaction may be significantly modulated by introducing different functional groups on their surface. Our original results showed that nanocellulose has a potent immunotolerogenic potential. Native CNF potentiated the capacity of DC to induce conventional Tregs. When carboxyl groups were introduced on the CNF surface, the tolerogenic potential of DC was shifted towards the induction of regulatory CD8⁺ T cells, whereas the introduction of phosphonates on CNF surface potentiated DCs' capacity to induce both regulatory CD8⁺ T cells and Type 1 regulatory (Tr-1) cells. These results are extremely important when considering the application of nanocellulose in vivo, especially for tissue regeneration and wound healing.

Cytochrome c injection induced embryo loss

Cytochrome c has been used as first-aid in the clinic for organs which are lacking oxygen. But recent report show cytochrome c injection destroys dendritic cells (DCs) which play a pivotal role in feto-maternal tolerance. However, it is not clear whether cytochrome c injection causes abortion. The cytochrome c was injected by tail vein of mice at the Day 5.5 of pregnancy (E5.5) after mating with male BALB/c mice. The total number of implantations and resorption sites was recorded at the E12.5 in pregnant mice. Expression of interferon-γ, tumor necrosis-α interleukin (IL)-4, IL-10, IL-12 and transforming growth factor-β in the mouse endometrium was measured by ELISA. Injection of cytochrome c via tail vein at the E5.5 induced fetal resorption at E12.5, and evoked an immune imbalance at the maternal-fetal interface. Notably, injection of mouse bone marrow-derived DCs (BM-DCs) rescued the cytochrome c-evoked embryo resorption. The present study suggests cytochrome c injection causes embryo resorption in mice, hinting caution regarding the use of cytochrome c in pregnant women. In addition, it may provide an easy and novel way to establish a mouse model of abortion.HighlightsCytochrome c injection induced fetal rejection.Cytochrome c injection leads to a T helper 1/T helper 2 imbalance at the maternal-fetal interface.A mouse model of abortion was established by injecting tail vein with cytochrome c.

Uterine Dendritic Cells Modulation by Mesenchymal Stem Cells Provides A Protective Microenvironment at The Feto-Maternal Interface: Improved Pregnancy Outcome in Abortion-Prone Mice

Objective

Dendritic cells (DCs) as major regulators of the immune response in the decidua play a pivotal role in establishment and maintenance of pregnancy. Immunological disorders are considered to be the main causes of unexplained recurrent spontaneous abortions (RSAs). Recently, we reported that mesenchymal stem cells (MSCs) therapy could improve fetal survival and reduce the abortion rate in abortion-prone mice, although the precise mechanisms of this action are poorly understood. Since MSCs have been shown to exert immunomodulatory effects on the immune cells, especially DCs, this study was performed to investigate the capability of MSCs to modulate the frequency, maturation state, and phenotype of uterine DCs (uDCs) as a potential mechanism for the improvement of pregnancy outcome.

Materials and Methods

In this experimental study, adipose-derived MSCs were intraperitoneally administered to abortion-prone pregnant mice on the fourth day of gestation. On the day 13.5 of pregnancy, after the determination of abortion rates, the frequency, phenotype, and maturation state of uDCs were analyzed using flow cytometry.

Results

Our results indicated that the administration of MSCs, at the implantation window, could significantly decrease the abortion rate and besides, increase the frequency of uDCs. MSCs administration also remarkably decreased the expression of DCs maturation markers (MHC-II, CD86, and CD40) on uDCs. However, we did not find any difference in the expression of CD11b on uDCs in MSCs-treated compared to control mice.

Conclusion

Regarding the mutual role of uDCs in establishment of a particular immunological state required for appropriate implantation, proper maternal immune responses and development of successful pregnancy, it seems that the modulation of uDCs by MSCs could be considered as one of the main mechanisms responsible for the positive effect of MSCs on treatment of RSA.

Cytochrome P450 26A1 modulates uterine dendritic cells in mice early pregnancy

Cytochrome P450 26A1 (CYP26A1) plays important roles in the mice peri‐implantation period. Inhibiting its expression or function leads to pregnancy failure. However, little is known about the underlying mechanisms involved, especially the relationship between CYP26A1 and immune cells. In this study, using Cyp26a1‐specific antisense morpholigos (Cyp26a1‐MO) knockdown mice model and pCR3.1‐Cyp26a1 vaccine mice model, we found that the number of uterine CD45⁺CD11c⁺MHCII^lo‐hiF4/80⁻ dendritic cells (DCs) was significantly decreased in the treated mice. The percentage of mature DCs (CD86^hi) was obviously lower and the percentage of immature DCs (CD86^lo) was remarkably higher in uterine DCs in the treatment group than that of the control group. Further experiments found that ID2, a transcription factor associated with DCs development, and CD86, a DC mature marker molecule, were both significantly reduced in mice uteri in the treated group. In vitro, ID2 and CD86 also decreased in bone marrow‐derived DCs under Cyp26a1‐MO treatment. These findings provide novel information that CYP26A1 might affect the embryo implantation via modulating the differentiation and maturation of uterine DCs.

IL-36 Cytokines: Regulators of Inflammatory Responses and Their Emerging Role in Immunology of Reproduction

The IL-36 subfamily of cytokines has been recently described as part of the IL-1 superfamily. It comprises three pro-inflammatory agonists (IL-36α, IL-36β, and IL-36γ), their receptor (IL-36R), and one antagonist (IL-36Ra). Although expressed in a variety of cells, the biological relevance of IL-36 cytokines is most evident in the communication between epithelial cells, dendritic cells, and neutrophils, which constitute the common triad responsible for the initiation, maintenance, and expansion of inflammation. The immunological role of IL-36 cytokines was initially described in studies of psoriasis, but novel evidence demonstrates their involvement in further immune and inflammatory processes in physiological and pathological situations. Preliminary studies have reported a dynamic expression of IL-36 cytokines in the female reproductive tract throughout the menstrual cycle, as well as their association with the production of immune mediators and cellular recruitment in the vaginal microenvironment contributing to host defense. In pregnancy, alteration of the placental IL-36 axis has been reported upon infection and pre-eclampsia suggesting its pivotal role in the regulation of maternal immune responses. In this review, we summarize current knowledge regarding the regulatory mechanisms and biological actions of IL-36 cytokines, their participation in different inflammatory conditions, and the emerging data on their potential role in normal and complicated pregnancies.

Failure of Decidualization and Maternal Immune Tolerance Underlies Uterovascular Resistance in Intra Uterine Growth Restriction

Failure of uterine vascular transformation is associated with pregnancy complications including Intra Uterine Growth Restriction (IUGR). The decidua and its immune cell populations play a key role in the earliest stages of this process. Here we investigate the hypothesis that abnormal decidualization and failure of maternal immune tolerance in the second trimester may underlie the uteroplacental pathology of IUGR. Placental bed biopsies were obtained from women undergoing elective caesarian delivery of a healthy term pregnancy, an IUGR pregnancy or a pregnancy complicated by both IUGR and preeclampsia. Decidual tissues were also collected from second trimester terminations from women with either normal or high uterine artery Doppler pulsatile index (PI). Immunohistochemical image analysis and flow cytometry were used to quantify vascular remodeling, decidual leukocytes and decidual status in cases vs. controls. Biopsies from pregnancies complicated by severe IUGR with a high uterine artery pulsatile index (PI) displayed a lack of: myometrial vascular transformation, interstitial, and endovascular extravillous trophoblast (EVT) invasion, and a lower number of maternal leukocytes. Apoptotic mural EVT were observed in association with mature dendritic cells and T cells in the IUGR samples. Second trimester pregnancies with high uterine artery PI displayed a higher incidence of small for gestational age fetuses; a skewed decidual immunology with higher numbers of; CD8 T cells, mature CD83 dendritic cells and lymphatic vessels that were packed with decidual leukocytes. The decidual stromal cells (DSCs) failed to differentiate into the large secretory DSC in these cases, remaining small and cuboidal and expressing lower levels of the nuclear progesterone receptor isoform B, and DSC markers Insulin Growth Factor Binding protein-1 (IGFBP-1) and CD10 as compared to controls. This study shows that defective progesterone mediated decidualization and a hostile maternal immune response against the invading endovascular EVT contribute to the failure of uterovascular remodeling in IUGR pregnancies.

LILRB4 Decrease on uDCs Exacerbate Abnormal Pregnancy Outcomes Following Toxoplasma gondii Infection

Toxoplasma gondii (T. gondii) infection in early pregnancy can result in miscarriage, dead fetus, and other abnormalities. The LILRB4 is a central inhibitory receptor in uterine dendritic cells (uDCs) that plays essential immune-regulatory roles at the maternal–fetal interface. In this study, T. gondii-infected human primary uDCs and T. gondii-infected LILRB4^-/- pregnant mice were utilized. The immune mechanisms underlying the role of LILRB4 on uDCs were explored in the development of abnormal pregnancy outcomes following T. gondii infection in vitro and in vivo. Our results showed that the expression levels of LILRB4 on uDCs from normal pregnant mice were obviously higher than non-pregnant mice, and peaked in mid-gestation. The LILRB4 expression on uDC subsets, especially tolerogenic subsets, from mid-gestation was obviously down-regulated after T. gondii infection and LILRB4 decrease could further regulate the expression of functional molecules (CD80, CD86, and HLA-DR or MHC II) on uDCs, contributing to abnormal pregnancy outcomes. Our results will shed light on the molecular immune mechanisms of uDCs in abnormal pregnancy outcomes by T. gondii infection.

Vitamin D-deficiency and sex-specific dysregulation of placental inflammation

To investigate an immunomodulatory role for vitamin D in pregnancy we used mice raised on vitamin D-sufficient (SUFF), or -deficient (DEF) diets. At embryonic day 14, pregnant mice received intraperitoneal injection of lipopolysaccharide (LPS) or vehicle for 24h, with age-matched non-pregnant mice as controls. In non-pregnant mice, 6 serum analytes (IL-1β, IL-18, MDC/CCL22, MIP-1α/CCL3, EGF, IgA) were lower in DEF mice. In pregnant DEF mice only GH was higher. In non-pregnant mice LPS induced 28 analytes, with 5 (IL-18, IP-10/CXCL10, MCP-1/CCL2, MIP-1β/CCL4, MIP-3β/CCL19) being highest in DEF mice. In pregnant SUFF mice 16 serum analytes increased with LPS, and 6 of these (IP-10/CXCL10, MCP-1/CCL2, SAP, TIMP-1, VCAM-1, vWF) were higher and 1 (GCP-2/CXCL6) lower in DEF mice. Parallel analysis of placental mRNAs showed elevated mRNA for Il-6, Ccl2 and Cxcl10 in placentae from male and female fetuses in LPS-DEF mice. However, LPS-induced expression of Ifnγ, Tnfα, and Cxcl6 was only observed in female placentae from DEF mice. LPS-DEF mice also showed smaller litter sizes relative to control SUFF mice. Numbers of female fetuses per dam were significantly lower for DEF mice with or without LPS challenge. LPS had no effect on numbers of male fetuses from DEF mothers, but significantly decreased male fetuses from SUFF mothers. These data indicate that vitamin D is an important component of anti-inflammatory immune responses during pregnancy, with the placenta and fetal sex playing pivotal roles in this process.

Developmental vitamin D deficiency and autism: Putative pathogenic mechanisms

Autism is a neurodevelopmental disease that presents in early life. Despite a considerable amount of studies, the neurobiological mechanisms underlying autism remain obscure. Both genetic and environmental factors are involved in the development of autism. Vitamin D deficiency is emerging as a consistently reported risk factor in children. One reason for the prominence now being given to this risk factor is that it would appear to interact with several other epidemiological risk factors for autism. Vitamin D is an active neurosteroid and plays crucial neuroprotective roles in the developing brain. It has important roles in cell proliferation and differentiation, immunomodulation, regulation of neurotransmission and steroidogenesis. Animal studies have suggested that transient prenatal vitamin D deficiency is associated with altered brain development. Here we review the potential neurobiological mechanisms linking prenatal vitamin D deficiency and autism and also discuss what future research targets must now be addressed.

Update on Dendritic Cell-Induced Immunological and Clinical Tolerance

Dendritic cells (DCs) as highly efficient antigen-presenting cells are at the interface of innate and adaptive immunity. As such, they are key mediators of immunity and antigen-specific immune tolerance. Due to their functional specialization, research efforts have focused on the characterization of DCs subsets involved in the initiation of immunogenic responses and in the maintenance of tissue homeostasis. Tolerogenic DCs (tolDCs)-based therapies have been designed as promising strategies to prevent and control autoimmune diseases as well as allograft rejection after solid organ transplantation (SOT). Despite successful experimental studies and ongoing phase I/II clinical trials using autologous tolDCs in patients with type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and in SOT recipients, additional basic research will be required to determine the optimal DC subset(s) and conditioning regimens for tolDCs-based treatments in vivo. In this review, we discuss the characteristics of human DCs and recent advances in their classification, as well as the role of DCs in immune regulation and their susceptibility to in vitro or in vivo manipulation for the development of tolerogenic therapies, with a focus on the potential of tolDCs for the treatment of autoimmune diseases and the prevention of allograft rejection after SOT.

The unique immunological and microbial aspects of pregnancy

The comparison of the immunological state of pregnancy to an immunosuppressed host-graft model continues to lead research and clinical practice to ill-defined approaches. This Review discusses recent evidence that supports the idea that immunological responses at the receptive maternal-fetal interface are not simply suppressed but are instead highly dynamic. We discuss the crucial role of trophoblast cells in shaping not only the way in which immune cells respond to the invading blastocyst but also how they collectively react to external stimuli. We also discuss the role of the microbiota in promoting a tolerogenic maternal immune system and highlight how subclinical viral infections can disrupt this status quo, leading to pregnancy complications.

Association of peripheral blood dendritic cells with recurrent pregnancy loss: a case-controlled study

PROBLEM

Dendritic cells (DCs) have been reported to play an important role in pregnancy. However, the role of DCs in recurrent pregnancy loss (RPL) has not been investigated well.

METHOD OF STUDY

Forty-three women affected by RPL and 16 fertile controls were recruited from June 2013 to December 2014. The peripheral blood DCs subsets, including myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), the levels (%) of CD80(+) , CD86(+) , and CD200(+) DCs were analyzed using flow cytometry.

RESULTS

The levels of total DCs, mDCs, and CD86(+) DCs were significantly higher (all P<.05); however, the level of CD200(+) DCs in the RPL group was significantly lower than that of the control group (P<.05). The logistical regression analyses showed that the elevated level of mDCs was significantly associated with RPL after adjustment for age (OR: 1.14, 95% CI, 1.01-1.29, P<.05).

CONCLUSION

The elevated level of mDCs was significantly associated with RPL, which might lead to the intervention of targeted immunosuppression in women with RPL.

The Balance between Conventional DCs and Plasmacytoid DCs Is Pivotal for Immunological Tolerance during Pregnancy in the Mouse

Dendritic cells (DCs), which can shape their functions depending on the microenvironment, are crucial for the delicate balance of immunity and tolerance during pregnancy. However, the mechanism underlying the microenvironment-educated plasticity of DC differentiation during pregnancy remains largely unclear. Here, we found that the differentiation of conventional DCs (cDCs) and plasmacytoid DCs (pDCs) is regulated in a tissue-specific manner during pregnancy. The ratio of cDCs and pDCs remained constant in the spleen. However, the ratio changed in the para-aortic lymph nodes (LNs), where cDC percentages were significantly reduced concurrent with an increase in pDCs from E8.5 to E16.5. Moreover, the expansion of pDCs and T regulatory (Treg) cells was correlated in the para-aortic LNs, and pDCs had more potential to induce regulatory T cells (Tregs) compared with cDCs (independent of IDO expression). Notably, the balance between cDCs and pDCs is disrupted in IFN-γ-induced abnormal pregnancy, accompanied by lower Treg percentages in the para-aortic LNs and decidua. To further identify the underlying mechanism, we found that elevated IFN-γ can increase the levels of GM-CSF to alter the differentiation of pDCs into cDCs in vivo. Therefore, we provide a novel regulatory mechanism underlying pregnancy-related immune tolerance that involves the balance of DC subsets, which may offer a new target for the prevention of human spontaneous abortion.

Decoding the chemokine network that links leukocytes with decidual cells and the trophoblast during early implantation

Chemokine network is central to the innate and adaptive immunity and entails a variety of proteins and membrane receptors that control physiological processes such as wound healing, angiogenesis, embryo growth and development. During early pregnancy, the chemokine network coordinates not only the recruitment of different leukocyte populations to generate the maternal-placental interface, but also constitutes an additional checkpoint for tissue homeostasis maintenance. The normal switch from a pro-inflammatory to an anti-inflammatory predominant microenvironment characteristic of the post-implantation stage requires redundant immune tolerance circuits triggered by key master regulators. In this review we will focus on the recruitment and conditioning of maternal immune cells to the uterus at the early implantation period with special interest on high plasticity macrophages and dendritic cells and their ability to induce regulatory T cells. We will also point to putative immunomodulatory polypeptides involved in immune homeostasis maintenance at the maternal-placental interface.

Human monocytes undergo functional re-programming during differentiation to dendritic cell mediated by human extravillous trophoblasts

Maternal immune adaptation is required for a successful pregnancy to avoid rejection of the fetal–placental unit. Dendritic cells within the decidual microenvironment lock in a tolerogenic profile. However, how these tolerogenic DCs are induced and the underlying mechanisms are largely unknown. In this study, we show that human extravillous trophoblasts redirect the monocyte-to-DC transition and induce regulatory dendritic cells. DCs differentiated from blood monocytes in the presence of human extravillous trophoblast cell line HTR-8/SVneo displayed a DC-SIGN⁺CD14⁺CD1a⁻ phenotype, similar with decidual DCs. HTR8-conditioned DCs were unable to develop a fully mature phenotype in response to LPS, and altered the cytokine secretory profile significantly. Functionally, conditioned DCs poorly induced the proliferation and activation of allogeneic T cells, whereas promoted CD4⁺CD25⁺Foxp3⁺ Treg cells generation. Furthermore, the supernatant from DC and HTR-8/SVneo coculture system contained significant high amount of M-CSF and MCP-1. Using neutralizing antibodies, we discussed the role of M-CSF and MCP-1 during monocyte-to-DCs differentiation mediated by extravillous trophoblasts. Our data indicate that human extravillous trophoblasts play an important role in modulating the monocyte-to-DC differentiation through M-CSF and MCP-1, which facilitate the establishment of a tolerogenic microenvironment at the maternal–fetal interface.

Placental Microparticles and MicroRNAs in Pregnant Women with Plasmodium falciparum or HIV Infection

Background

During pregnancy, syncytiotrophoblast vesicles contribute to maternal tolerance towards the fetus, but also to pathologies such as pre-eclampsia. The aim of the study was to address whether Plasmodium falciparum and HIV infections in pregnancy affect the secretion, microRNA content and function of trophoblast microparticles.

Methods

Microparticles were isolated and characterized from 122 peripheral plasmas of Mozambican pregnant women, malaria- and/or HIV-infected and non-infected. Expression of placenta-related microRNAs in microparticles was analysed by qPCR and the effect of circulating microparticles on dendritic cells assessed by phenotype analysis and cytokine/chemokine measurement.

Results

Concentrations of total and trophoblast microparticles detected by flow cytometry were higher in HIV-positive (P = 0.005 and P = 0.030, respectively) compared to non-infected mothers, as well as in women delivering low birthweight newborns (P = 0.032 and P = 0.021, respectively). miR-517c was overexpressed in mothers with placental malaria (P = 0.034), compared to non-infected. Microparticles from HIV-positive induced a higher expression of MHCII (P = 0.021) and lower production of MCP1 (P = 0.008) than microparticles from non-infected women.

Conclusions

In summary, alterations in total and trophoblast microparticles associated with malaria and HIV in pregnant women may have an immunopathogenic role. The potential for placental-derived vesicles and microRNAs as biomarkers of adverse outcomes during pregnancy and malaria infection should be confirmed in future studies.

Acetylcholine contributes to control the physiological inflammatory response during the peri-implantation period

BACKGROUND

Maternal antigen-presenting cells attracted to the pregnant uterus interact with trophoblast cells and modulate their functional profile to favour immunosuppressant responses. Non-neuronal cholinergic system is expressed in human cytotrophoblast cells and in immune cells with homeostatic regulatory functions.

AIM

The aim of this work was to evaluate whether non-neuronal acetylcholine conditions maternal monocyte and DC migration and activation profiles.

METHODS

We used an in vitro model resembling maternal-placental interface represented by the co-culture of human trophoblast cells (Swan-71 cell line) and monocytes or DC.

RESULTS

When cytotrophoblast cells were treated with neostigmine (Neo) to concentrate endogenous acetylcholine levels, monocyte migration was increased. In parallel, high levels of IL-10 and decreased levels of TNF-α were observed upon interaction of maternal monocytes with trophoblast cells. This effect was synergized by Neo and was prevented by atropine, a muscarinic acetylcholine receptor antagonist. Similarly, trophoblast cells increased the migration of DC independently of Neo treatment; however, enhanced IL-10 and MCP-1 synthesis in trophoblast-DC co-cultures with no changes in TNF-α and IL-6 was observed. In fact, there were no changes in HLA-DR, CD86 or CD83 expression. Finally, trophoblast cells treated with Neo increased the expression of two antigen-presenting cells attracting chemokines, MCP-1, MIP-1α and RANTES through muscarinic receptors, and it was prevented by atropine.

CONCLUSIONS

Our present results support a novel role of acetylcholine synthesized by trophoblast cells to modulate antigen-presenting cell migration and activation favouring an immunosuppressant profile that contributes to immune homeostasis maintenance at the maternal-foetal interface.

Human endogenous retrovirus envelope proteins target dendritic cells to suppress T-cell activation

Though mostly defective, human endogenous retroviruses (HERV) can retain open reading frames, which are especially expressed in the placenta. There, the envelope (env) proteins of HERV-W (Syncytin-1), HERV-FRD (Syncytin-2), and HERV-K (HML-2) were implicated in tolerance against the semi-allogenic fetus. Here, we show that the known HERV env-binding receptors ASCT-1 and -2 and MFSD2 are expressed by DCs and T-cells. When used as effectors in coculture systems, CHO cells transfected to express Syncytin-1, -2, or HML-2 did not affect T-cell expansion or overall LPS-driven phenotypic DC maturation, however, promoted release of IL-12 and TNF-α rather than IL-10. In contrast, HERV env expressing choriocarcinoma cell lines suppressed T-cell proliferation and LPS-induced TNF-α and IL-12 release, however, promoted IL-10 accumulation, indicating that these effects might not rely on HERV env interactions. However, DCs conditioned by choriocarcinoma, but also transgenic CHO cells failed to promote allogenic T-cell expansion. This was associated with a loss of DC/T-cell conjugate frequencies, impaired Ca(2+) mobilization, and aberrant patterning of f-actin and tyrosine phosphorylated proteins in T-cells. Altogether, these findings suggest that HERV env proteins target T-cell activation indirectly by modulating the stimulatory activity of DCs.

HLA-G Orchestrates the Early Interaction of Human Trophoblasts with the Maternal Niche

Extravillous trophoblasts (EVTs) play a central role in educating maternal leukocytes, endometrial stromal and endothelial cells to generate a receptive decidual microenvironment tailored to accept the semi-allogeneic fetus. HLA-G, a non-classical HLA class I molecule endowed with immune-regulatory functions, is primarily expressed on EVTs lining the placenta and on the naturally occurring tolerogenic dendritic cells, named DC-10, which are enriched in the human first trimester decidua. Decidual DC-10 are involved in HLA-G-mediated tolerance at the maternal–fetal interface. EVTs not only establish a tolerogenic microenvironment through the interaction with maternal innate and adaptive cells but also orchestrate placenta vascular and tissue remodeling, leading to a successful pregnancy. Here, we discuss the potential implications of the HLA-G-mediated cross-talk among the cells present at the maternal–fetal interface, and its role in maintaining a positive relationship between the mother and the fetus.

Role of tumor-associated glycoprotein-72 in the progression of endometrial adenocarcinoma: a proposed study

Endometrial adenocarcinoma is on the basis of the molecular, immunohistological and clinicopathologic features broadly divided into two groups, referred as type I and type II. Type I appears more frequently and in principle patients have a good prognosis; however a significant number of patients develop local recurrences. We hypothesize that TAG-72, expressed on endometrial carcinoma binds and internalizes endocytic pattern recognition receptors on surrounding tissue antigen presenting cells (dendritic cells and macrophages), powers their anti-inflammatory maturation program and make them capable to elicit or modulated tolerogenic immune response mediated by local T and NK effectors. This could support uncontrolled local tumor growth, deeper tumor invasion into surrounding tissues, frequent local recurrences and/or lymph node metastasis. To test this hypothesis, we propose a semi-quantitative immunohistochemical analysis of TAG-72 expression in endometrial adenocarcinoma samples and to correlate the results with clinical and pathological parameters (age, type and histological grade of the tumor, estrogen and progesterone receptor expression, invasion into the myometrium and capillaries, presence of lymph node metastases, FIGO stage, and TNM classification). It would be worthwhile to investigate the local tissue immune response in the tumor environment using tissue samples removed during surgery. These studies could elucidate the underlying immunopathological mechanisms that govern the early recurrence and possibly distant metastases of TAG-72-expressing adenocarcinomas and might help in deciding the type of treatment to be applied in a selected group of cancer patients including application of biological therapy with anti-TAG-72 antibodies, according the principle of personalized oncology treatments.

Immunological role of vitamin D at the maternal-fetal interface

During pregnancy, immune activity is tightly regulated so that antimicrobial protection of the mother and fetus is balanced with the need for immune tolerance to prevent fetal rejection. In this setting, the maternal-fetal interface, in the form of the uterine decidua, provides a heterogeneous immune cell population with the potential to mediate diverse activities throughout pregnancy. Recent studies have suggested that vitamin D may be a key regulator of immune function during pregnancy, with the fetal-maternal interface representing a prominent target. Among its non-classical actions are potent immunomodulatory effects, including induction of antibacterial responses and modulation of T-lymphocytes to suppress inflammation and promote tolerogenesis. Thus, vitamin D may play a pivotal role in normal decidual immune function by promoting innate responses to infection, while simultaneously preventing an over-elaboration of inflammatory adaptive immunity. Research to date has focused upon the potential role of vitamin D in preventing infectious diseases such as tuberculosis, as well as possibly suppressing of autoimmune disease. Nevertheless, vitamin D may also influence facets of immune function not immediately associated with primary innate responses. This review summarises our current understanding of decidual immune function with respect to the vitamin D metabolism and signalling, and as to how this may be affected by variations in maternal vitamin D status. There has recently been much interest in vitamin D supplementation of pregnant women, but our knowledge of how this may influence the function of decidua remains limited. Further insight into the immunomodulatory actions of vitamin D during pregnancy will help shed light upon this.

Progestin-Containing Contraceptives Alter Expression of Host Defense-Related Genes of the Endometrium and Cervix

Epidemiological studies indicate that progestin-containing contraceptives increase susceptibility to HIV, although the underlying mechanisms involving the upper female reproductive tract are undefined. To determine the effects of depot medroxyprogesterone acetate (DMPA) and the levonorgestrel intrauterine system (LNG-IUS) on gene expression and physiology of human endometrial and cervical transformation zone (TZ), microarray analyses were performed on whole tissue biopsies. In endometrium, activated pathways included leukocyte chemotaxis, attachment, and inflammation in DMPA and LNG-IUS users, and individual genes included pattern recognition receptors, complement components, and other immune mediators. In cervical TZ, progestin treatment altered expression of tissue remodeling and viability but not immune function genes. Together, these results indicate that progestins influence expression of immune-related genes in endometrium relevant to local recruitment of HIV target cells with potential to increase susceptibility and underscore the importance of the upper reproductive tract when assessing the safety of contraceptive products.

Involvement of TLR7 and TLR8 in conceptus development and establishment of pregnancy in sheep

Toll-like receptors (TLRs) belong to the innate immune system and regulate inflammatory events that affect mammalian reproduction. In Study 1, we demonstrated that abundance of ovine TLR1-TLR9 mRNAs in the uterus differs due to reproductive status (TLR2, TLR3, TLR7, and TLR8) and the day of the estrous cycle and pregnancy (TLR1-TLR3, TLR5-TLR7, and TLR9). Expression of TLR7 and TLR8 proteins was localized primarily to uterine epithelia and stroma and regulated in a temporal manner. In Study 2, we determined that ovine conceptuses express TLR7 and TLR8 on all days studied and that expression of the envelope protein of ovine endogenous retrovirus (enJSRV-Env) declined in conceptus trophectoderm from Day 13 to Day 16 of pregnancy. In Study 3, loss-of-function experiments were conducted in vivo using morpholino antisense oligonucleotides (MAOs) injected into the uterine lumen to block synthesis of TLR7 and TLR8 proteins, individually and jointly. Conceptuses were recovered on Day 16 to assess their morphology. MAO-treated conceptuses were developmentally retarded, produced less interferon tau (IFNT), and had fewer binucleate cells (BNCs) compared with MAO-Controls. Moreover, expression of enJSRV-Env mRNA in MAO-TLR7 conceptuses was greater than that for MAO-Control and MAO-TLR8 conceptuses, but similar to MAO-TLR7/TLR8 conceptuses. Results of this study indicated differences in TLR1-TLR9 expression due to reproductive status and the day of the estrous cycle and pregnancy. TLR7 and TLR8 also influence development, enJSRV-Env abundance, secretion of IFNT, and formation of BNCs by conceptuses. These findings corroborate our hypothesis that TLR7 and TLR8 mediate pathways whereby enJSRV-Env regulates key peri-implantation events in conceptus development and differentiated functions of trophectoderm cells.

Biopsy-induced inflammatory conditions improve endometrial receptivity: the mechanism of action

A decade ago, we first reported that endometrial biopsy significantly improves the success of pregnancy in IVF patients with recurrent implantation failure, an observation that was later confirmed by others. Recently, we have demonstrated that this treatment elevated the levels of endometrial pro-inflammatory cytokines and increased the abundance of macrophages (Mac) and dendritic cells (DCs). We therefore hypothesised that the biopsy-related successful pregnancy is secondary to an inflammatory response, and aimed at deciphering its mechanism of action. Supporting our hypothesis, we found that the pro-inflammatory TNFα stimulated primary endometrial stromal cells to express cytokines that attracted monocytes and induced their differentiation into DCs. These monocyte-derived DCs stimulated endometrial epithelial cells to express the adhesive molecule SPP1 (osteopontin (OPN)) and its receptors ITGB3 and CD44, whereas MUC16, which interferes with adhesion, was downregulated. Other implantation-associated genes, such as CHST2, CCL4 (MIP1B) and GROA, were upregulated by monocyte-derived Mac. These findings suggest that uterine receptivity is mediated by the expression of molecules associated with inflammation. Such an inflammatory milieu is not generated in some IVF patients with recurrent implantation failure in the absence of local injury provoked by the biopsy treatment.

A holobiont birth narrative: the epigenetic transmission of the human microbiome

This essay plans to explore, expand, and re-tell the human birth narrative. Usually, human birth narratives focus on the origins of a new individual, focusing on the mother and fetus. This essay discusses birth as the origin of a new community. For not only is the eukaryotic body being reproduced, but so also are the bodies of its symbiotic microbes and so is the set of relationships between these organic components. Several parts of the new narrative are surprising: (1) bacterial symbionts might cause some of the characteristics of pregnancy and prepare a symbiotic community for transfer; (2) the first bacterial colonizers of the mammalian organism my enter the fetus prior to the lysing of the amniotic membrane and birth; (3) the same signals that often cause immunological attack against a microbe may serve under these conditions to signal homeostatic stability between symbiont and host; and (4) the mother may actively provide substances that promote the growth and settlement of helpful bacteria. The birth of the holobiont exemplifies principles of co-evolution, co-development, niche construction, and scaffolding. Birth is nothing less than the passage from one set of symbiotic relationships to another.