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The establishment and maintenance of a successful pregnancy rely heavily on maternal-fetal immune tolerance. Inflammatory and immune mechanisms during pregnancy bear a resemblance to those observed in tumor progression, with Treg cells exhibiting similar immunoregulatory functions in both contexts. Interferon regulatory factor 1 (IRF1) is implicated in modulating the immune milieu within tumors and influencing regulatory T (Treg) cell differentiation. However, the precise association between IRF1 and the onset of preeclampsia (PE) remains unclear. In our investigation, we identified trophoblasts as a significant source of IRF1 expression at the maternal-fetal interface through immunofluorescence analysis. Moreover, heightened levels of IRF1 expression were detected in both placental tissues and peripheral blood samples obtained from PE patients, concomitant with an imbalance in the Th17/Treg ratio. In the peripheral circulation, a notable inverse correlation was observed between IRF1 mRNA levels and Foxp3 mRNA, a transcription factor specific to Treg cells. IRF1 mRNA expression showed a positive association with systolic blood pressure and a negative association with serum albumin levels. Furthermore, co-culturing naïve T cells with supernatants from HTR-8/SV neo cells overexpressing IRF1 resulted in diminished differentiation of T cells into Treg cells. In summary, our study indicates elevated IRF1 expression in the peripheral blood and trophoblast cells of PE patients. Elevated IRF1 in trophoblast cells hinders the differentiation of maternal Treg cells, disrupting maternal-fetal immune tolerance and contributing to PE pathogenesis. Additionally, IRF1 expression correlates with disease severity, suggesting its potential as a novel sensitive target in PE., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Problem: Pregnancy complications such as spontaneous abortion, preeclampsia, and preterm birth persist, despite current interventions aimed at their prevention and treatment largely proving unsuccessful. Interleukin-27 (IL-27), composed of p28 and EBI3 subunits, binds to IL-27R, which consists of gp130 and IL-27Rα (also known as WSX-1 or TCCR), and plays a pivotal role in tumor development and inflammation regulation. At the maternal-fetal interface, IL-27 expression has been detected in trophoblasts, endometrial stromal cells, and decidual cells. Abnormal levels of IL-27/IL-27R have been linked to adverse pregnancy outcomes, including spontaneous miscarriage, preeclampsia, and preterm birth. This review aims to explore the expression of IL-27 at the maternal-fetal interface and its signaling pathway, uncovering the complex role of IL-27 in pregnancy complications., Method of Study: A comprehensive literature review was conducted using PubMed/Medline, Scopus, and Embase databases, analyzing studies on IL-27 expression and its signaling pathways at the maternal-fetal interface. The review focused on identifying the presence of IL-27 in various cell types and linking abnormal IL-27/IL-27R expression to pregnancy complications such as spontaneous miscarriage, preeclampsia, and preterm birth., Discussion and Conclusion: IL-27 plays a complex role at the maternal-fetal interface, with abnormal expression linked to several pregnancy complications. These findings highlight the need for further research to elucidate IL-27's mechanisms and develop targeted interventions. Future studies should aim to develop targeted interventions and improve therapeutic strategies for managing pregnancy complications., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Decidual macrophages residing at the maternal-fetal interface have been recognized as pivotal factors for maintaining normal pregnancy; however, they are also key target cells of Toxoplasma gondii (T. gondii) in the pathology of T. gondii-induced adverse pregnancy. Trem2, as a functional receptor on macrophage surface, recognizes and binds various kinds of pathogens. The role and underlying mechanism of Trem2 in T. gondii infection remain elusive. In the present study, we found that T. gondii infection downregulated Trem2 expression and that Trem2-/- mice exhibited more severe adverse pregnancy outcomes than wildtype mice. We also demonstrated that T. gondii infection resulted in increased decidual macrophages, which were significantly reduced in the Trem2-/- pregnant mouse model as compared to wildtype control animals. We further described the inhibited proliferation, migration, and invasion functions of trophoblast cell by T. gondii antigens through macrophages as an "intermediate bridge", while this inhibition can be rescued by Trem2 agonist HSP60. Concurrently, Trem2 deficiency in bone marrow-derived macrophages (BMDMs) heightened the inhibitory effect of TgAg on the migration and invasion of trophoblast cells, accompanied by higher pro-inflammatory factors (IL-1β, IL-6 and TNF-α) but a lower chemokine (CXCL1) in T. gondii antigens-treated BMDMs. Furthermore, compelling evidence from animal models and in vitro cell experiments suggests that T. gondii inhibits the Trem2-Syk-PI3K signaling pathway, leading to impaired function of decidual macrophages. Therefore, our findings highlight Trem2 signaling as an essential pathway by which decidual macrophages respond to T. gondii infection, suggesting Trem2 as a crucial sensor of decidual macrophages and potential therapeutic target in the pathology of T. gondii-induced adverse pregnancy., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The contribution of placental immune responses to congenital Zika virus (ZIKV) syndrome remains poorly understood. Here, we leveraged a mouse model of ZIKV infection to identify mechanisms of innate immune restriction exclusively in the fetal compartment of the placenta. ZIKV principally infected mononuclear trophoblasts in the junctional zone, which was limited by mitochondrial antiviral-signaling protein (MAVS) and type I interferon (IFN) signaling mechanisms. Single nuclear RNA sequencing revealed MAVS-dependent expression of IFN-stimulated genes (ISGs) in spongiotrophoblasts but not in other placental cells that use alternate pathways to induce ISGs. ZIKV infection of Ifnar1-/- or Mavs-/- placentas was associated with greater infection of the adjacent immunocompetent decidua, and heterozygous Mavs+/- or Ifnar1+/- dams carrying immunodeficient fetuses sustained greater maternal viremia and tissue infection than dams carrying wild-type fetuses. Thus, MAVS-IFN signaling in the fetus restricts ZIKV infection in junctional zone trophoblasts, which modulates dissemination and outcome for both the fetus and the pregnant mother., (© 2024 Alippe et al.)

Chorion trophoblasts (CTCs) and immune cell-enriched decidua (DECs) comprise the maternal-fetal membrane interface called the chorio-decidual interface (CDi) which constantly gets exposed to maternal stressors without leading to labor activation. This study explored how CTCs act as a barrier at CDi. The roles of human leukocyte antigen (HLA)-G and progesterone receptor membrane component 2 (PGRMC2) in mediating immune homeostasis were also investigated. The CDi was recreated in a two-chamber microfluidic device (CDi-on-chip) with an outer chamber of primary DECs and immune cell line-derived innate immune cells and an inner chamber of wild-type or PGRMC2 or HLA-G knockout immortalized CTCs. To mimic maternal insults, DECs were treated with lipopolysaccharide, poly(I:C), or oxidative stress inducer cigarette smoke extract. Expression levels of inflammation and immunity genes via targeted RNA sequencing, production of soluble mediators, and immune cell migration into CTCs were determined. In CDi-on-chip, decidua and immune cells became inflammatory in response to insults while CTCs were refractory, highlighting their barrier function. HLA-G and PGRMC2 are found to be vital to immune homeostasis at the CDi, with PGRMC2 serving as an upstream regulator of inflammation, HLA-G expression, and mesenchymal-epithelial transition, and HLA-G serving as a frontline immunomodulatory molecule, thus preventing fetal membrane compromise., (© 2024. The Author(s).)

Chronic histiocytic intervillositis (CHI) is a recurrent placental lesion where maternal macrophages infiltrate the intervillous space. Its cause is unknown, though due to similarities to rejected allografts one hypothesis is that CHI represents maternal-fetal rejection. Here, virtual crossmatching was applied to healthy pregnancies and those with a history of CHI. Anti-HLA antibodies, measured by Luminex, were present in slightly more controls than CHI (8/17 (47.1%) vs 5/14 (35.7%)), but there was no significant difference in levels of sensitisation or fetal specific antibodies. Quantification of immunohistochemical staining for HLA-Class II was increased in syncytiotrophoblast of placentas with CHI (Grade 0.44 [IQR 0.1-0.7]) compared to healthy controls (0.06 [IQR 0-0.2]) and subsequent pregnancies (0.13 [IQR 0-0.3]) (P = 0.0004). HLA-Class II expression was positively related both to the severity of CHI (r = 0.67) and C4d deposition (r = 0.48). There was no difference in overall C4d and HLA-Class I immunostaining. Though increased anti-HLA antibodies were not evident in CHI, increased expression of HLA-Class II at the maternal-fetal interface suggests that they may be relevant in its pathogenesis. Further investigation of antibodies immediately after diagnosis is warranted in a larger cohort of CHI cases to better understand the role of HLA in its pathophysiology., (© 2024. The Author(s).)

F. nucleatum , involved in carcinogenesis of colon carcinomas, has been described as part of the commensal flora of the female upper reproductive tract. Although its contribution to destructive inflammatory processes is well described, its role as commensal uterine bacteria has not been thoroughly investigated. Since carcinogenesis shares similar mechanisms with early pregnancy development (including proliferation, invasion, blood supply and the induction of tolerance), these mechanisms induced by F. nucleatum could play a role in early pregnancy. Additionally, implantation and placentation require a well-balanced immune activation, which might be suitably managed by the presence of a limited amount of bacteria or bacterial residues. We assessed the effect of inactivated F. nucleatum on macrophage-trophoblast interactions. Monocytic cells (THP-1) were polarized into M1, M2a or M2c macrophages by IFN-γ, IL-4 or TGF-β, respectively, and subsequently treated with inactivated fusobacteria (bacteria:macrophage ratio of 0.1 and 1). Direct effects on macrophages were assessed by viability assay, flow cytometry (antigen presentation molecules and cytokines), qPCR (cytokine expression), in-cell Western (HIF and P-NF-κB) and ELISA (VEGF secretion). The function of first trimester extravillous trophoblast cells (HTR-8/SVneo) in response to macrophage-conditioned medium was microscopically assessed by migration (scratch assay), invasion (sprouting assay) and tube formation. Underlying molecular changes were investigated by ELISA (VEGF secretion) and qPCR (matrix-degrading factors and regulators). Inflammation-primed macrophages (M1) as well as high bacterial amounts increased pro-inflammatory NF-κB expression and inflammatory responses. Subsequently, trophoblast functions were impaired. In contrast, low bacterial stimulation caused an increased HIF activation and subsequent VEGF-A secretion in M2c macrophages. Accordingly, there was an increase of trophoblast tube formation. Our results suggest that a low-mass endometrial/decidual microbiome can be tolerated and while it supports implantation and further pregnancy processes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Einenkel, Ehrhardt, Zygmunt and Muzzio.)

Women with antiphospholipid syndrome (APS) are at high risk for miscarriage and preeclampsia. Unlike pro-thrombotic systemic APS, obstetric APS is associated with insufficient placentation, as well as inflammation and vascular dysfunction at the maternal-fetal interface. Antiphospholipid antibodies (aPL) can target the placental trophoblast and induce inflammation. We reported that aPL trigger trophoblast cells to produce elevated levels of IL-8 through activation of Toll-like receptor 4 (TLR4). Downstream of TLR4, we found this IL-8 response is mediated by a TLR8-activating microRNA (miR), miR-146a-3p, which is also released by the trophoblast via extracellular vesicles (EVs). Since endothelial dysfunction is a feature of obstetric APS, we sought to determine if other miRs that can activate the RNA sensors, TLR7 and/or TLR8, are released by the trophoblast via EVs after exposure to aPL, and if these EVs can activate human endometrial endothelial cells (HEECs). Using a human first trimester extravillous trophoblast cell line we found that aPL elevated their release of small EVs (<150 nm). These extracellular vesicles released from trophoblast cells exposed to aPL expressed elevated levels of TLR7/8-activating miR-21a and miR-29a, in addition to the previously reported miR-146a-3p. Extracellular vesicles from aPL-exposed human trophoblast cells triggered human endometrial endothelial cells to generate an inflammatory IL-8 response, in part through TLR7. This study highlights EVs as a mode of communication between the placenta and the maternal vasculature, as well as a potential role for TLR7/8-activating miRs in contributing to inflammation at the maternal-fetal interface in obstetric APS., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bovine viral diarrhoea virus (BVDV) can infect cows on days 30-110 of gestation and crossing the placental barrier, resulting in persistently infected (PI) and causing significant economic losses to dairy farming. Bovine placental trophoblast cells (BTCs) are the major cells in the early chorionic tissue of the placenta and play important roles in placental resistance to viral transmission. In this study, we have confirmed that BTCs is among a groups of cell types those could be infected by BVDV in vivo, and BVDV infection stimulates the autophagic responses in BTCs and promotes the release of exosomes. Meanwhile, the exosomes derived from BTCs can be used by BVDV to spread between placental trophoblast cells, and this mode of transmission cannot be blocked by antibodies against the BVDV E2 protein, whereas the replication and spread of BVDV in BTCs can be blocked by inhibiting autophagy and exosomogenesis. Our study provides a theoretical and practical basis for scientific prediction and intervention of reproductive disorders caused by BVDV infection in cows of different gestation periods from a novel perspective., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

One of the main causes of human brucellosis is Brucella melitensis infecting small ruminants. To date, Rev1 is the only vaccine successfully used to control ovine and caprine brucellosis. However, it is pathogenic for pregnant animals, resulting in abortions and vaginal and milk shedding, as well as being infectious for humans. Therefore, there is an urgent need to develop an effective vaccine that is safer than Rev1. In efforts to further attenuate Rev1, we recently used wzm inactivation to generate a rough mutant (Rev1Δwzm) that retains a complete antigenic O-polysaccharide in the bacterial cytoplasm. The aim of the present study was to evaluate the placental pathogenicity of Rev1Δwzm in trophoblastic cells, throughout pregnancy in mice, and in ewes inoculated in different trimesters of pregnancy. This mutant was evaluated in comparison with the homologous 16MΔwzm derived from a virulent strain of B. melitensis and the naturally rough sheep pathogen B. ovis. Our results show that both wzm mutants triggered reduced cytotoxic, pro-apoptotic, and pro-inflammatory signaling in Bewo trophoblasts, as well as reduced relative expression of apoptosis genes. In mice, both wzm mutants produced infection but were rapidly cleared from the placenta, in which only Rev1Δwzm induced a low relative expression of pro-apoptotic and pro-inflammatory genes. In the 66 inoculated ewes, Rev1Δwzm was safe and immunogenic, displaying a transient serological interference in standard RBT but not CFT S-LPS tests; this serological response was minimized by conjunctival administration. In conclusion, these results support that B. melitensis Rev1Δwzm is a promising vaccine candidate for use in pregnant ewes and its efficacy against B. melitensis and B. ovis infections in sheep warrants further study., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Rev1Δwzm is protected under a CSIC-UPNA patent WO/2019/101993 (PCT/EP2018/082539) and both are public institutions without any conflict of interests with this publication. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Abstract: Normal pregnancy is a contradictory and complicated physiological process. Although the fetus carries the human leukocyte antigen (HLA) inherited from the paternal line, it does not cause maternal immune rejection. As the only exception to immunological principles, maternal-fetal immune tolerance has been a reproductive immunology focus. In early pregnancy, fetal extravillous trophoblast cells (EVTs) invade decidual tissues and come into direct contact with maternal decidual immune cells (DICs) and decidual stromal cells (DSCs) to establish a sophisticated maternal-fetal crosstalk. This study reviews previous research results and focuses on the establishment and maintenance mechanism of maternal-fetal tolerance based on maternal-fetal crosstalk. Insights into maternal-fetal tolerance will not only improve understanding of normal pregnancy but will also contribute to novel therapeutic strategies for recurrent spontaneous abortion, pre-eclampsia, and premature birth., (Copyright © 2024 The Chinese Medical Association, produced by Wolters Kluwer, Inc. under the CC-BY-NC-ND license.)

Recurrent spontaneous abortion (RSA) affects approximately 1 % of women striving for conception, posing a significant clinical challenge. This study aimed to identify a prognostic signature in RSA and elucidate its molecular mechanisms. Prognostic gene impacts were further assessed in HTR-8/SVneo and human primary extravillous trophoblast (EVT) cells in vitro experiments. A total of 6168 differentially expressed genes (DEGs) were identified, including 3035 upregulated and 3133 downregulated genes. WGCNA pinpointed 8 significant modules and 31 ferroptosis-related DEGs in RSA. Optimal clustering classified RSA patients into three distinct subgroups, showing notable differences in immune cell composition. Six feature genes (AEBP2, CISD2, PML, RGS4, SRSF9, STK11) were identified. The diagnostic model showed high predictive capabilities (AUC: 0.966). Mendelian randomization indicated a significant association between CISD2 levels and RSA (OR: 1.069, P-value: 0.049). Furthermore, the downregulation of CISD2 promotes ferroptosis in HTR-8/SVneo and human primary EVT cells. CISD2 emerged as a pivotal gene in RSA, serving as a ferroptosis-related therapeutic target. The diagnostic model based on gene expression and Mendelian randomization provides novel insights into the pathogenesis of RSA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article, (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objectives: Gestational diabetes mellitus (GDM) is a growing health concern. Since members of the galectin-family are identified to play a role in the pathogenesis of GDM, we determined galectin-12 as an essential protein due to its influence in lipolysis and inflammation processes. This study investigates the expression of galectin-12 in the placentas of women with GDM., Study Design: The study population includes 40 expectant women suffering from GDM and 40 healthy controls. The expression of galectin-12 in the syncytiotrophoblast (SCT) and the extra villous trophoblast (EVT) of the placenta was analyzed by immunohistological staining and double immunofluorescence. Immunoreactivity Score (IRS) was used for evaluation., Results: The results demonstrate a significant overexpression of galectin-12 in the nucleus of the SCT and the EVT of placentas with GDM compared to the healthy control group. Additionally, double immunofluorescence visualizes corresponding results with an overexpression of galectin-12 in the extra villous trophoblast of GDM placentas representing maternal cells., Conclusion: This study identifies galectin-12 to be associated with the process of gestational diabetes mellitus. These findings are in correspondence with the involvement of galectin-12 in inflammatory processes. Maternal BMI and male sex seem to be confounder for the expression of galectin-12 in the nuclear syncytiotrophoblast, but not in other parts of the investigated placental areas. Further investigations are necessary to verify the correlation between gestational diabetes mellitus and the expression of galectin-12 in the placenta and to further elucidate its distinct role., Competing Interests: Declaration of Competing Interest Thomas Kolben: holds stock of Bayer AG. Sven Mahner: Research support, advisory board, honoraria and travel expenses from AbbVie, AstraZeneca, Clovis, Eisai, GlaxoSmithKline, Medac, MSD, Novartis, Olympus, PharmaMar, Pfizer, Roche, Sensor Kinesis, Teva, Tesaro. The other authors declare no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

Implantation and maintenance of pregnancy involve intricate immunological processes that enable the developing fetus to coexist with the maternal immune system. Progesterone, a critical hormone during pregnancy, is known to promote immune tolerance and prevent preterm labor. However, the mechanism by which progesterone mediates these effects remains unclear. In this study, we investigated the role of the non-classical progesterone receptor membrane component 1 (PGRMC1) in progesterone signaling at the maternal-fetal interface. Using JEG3 cells, a trophoblast model cell line, we observed that progesterone stimulation increased the expression of human leukocyte antigen-C (HLA-C) and HLA-G, key molecules involved in immune tolerance. We also found that progesterone upregulated the expression of the transcription factor ELF3, which is known to regulate trophoblast-specific HLA-C expression. Interestingly, JEG3 cells lacked expression of classical progesterone receptors (PRs) but exhibited high expression of PGRMC1, a finding we confirmed in primary trophoblasts by mining sc-RNA seq data from human placenta. To investigate the role of PGRMC1 in progesterone signaling, we used CRISPR/Cas9 technology to knockout PGRMC1 in JEG3 cells. PGRMC1-deficient cells showed a diminished response to progesterone stimulation. Furthermore, we found that the progesterone antagonist RU486 inhibited ELF3 expression in a PGRMC1-dependent manner, suggesting that RU486 acts as a progesterone antagonist by competing for receptor binding. Additionally, we found that RU486 inhibited cell invasion, an important process for successful pregnancy, and this inhibitory effect was dependent on PGRMC1. Our findings highlight the crucial role of PGRMC1 in mediating the immunoregulatory effects of progesterone at the maternal-fetal interface., Competing Interests: Declaration of Competing Interest The authors report no conflicts of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Pre-eclampsia (PE) is a hypertension condition that occurs exclusively during pregnancy and has the potential to impact nearly all organ systems. It is estimated to complicate approximately 2-8% of pregnancies worldwide. PE is a prominent medical disorder that poses a significant risk to pregnant mothers and their infants. This review commences by giving the most up-to- date concepts about the pathophysiology of PE. The condition involves atypical infiltration of trophoblast cells into the spiral arteries of the decidua and myometrium, resulting in an insufficient establishment of proper blood flow between the uterus and placenta. The aberrant activation of natural killer (NK) cells in both the peripheral blood and the decidua has been identified as one of the contributing factors to the development of PE. The strong evidence for the genetic etiology of PE is provided by the association between maternal killer cell immunoglobulin-like receptor (KIR) and Human Leukocyte Antigen (HLA-C) in trophoblast cells. Recent observations provide evidence that changes in the expression of anti-angiogenic factors in the placenta are the underlying cause of the clinical symptoms associated with the condition. This review also provides a comprehensive overview of the latest advancements in understanding the underlying causes of PE. It specifically highlights the emergence of new diagnostic biomarkers and their potential implications for therapeutic interventions in managing this medical condition., Competing Interests: Declaration of Competing Interest I therefore declare that the review work "Pre-eclampsia: Re-visiting Pathophysiology, Role of Immunocells in Pre-Eclampsia, Biomarker Identification, and Recent Advances in its Management" is unique. I have acknowledged and properly cited all sources of information. This manuscript has not previously been published and is not currently being considered for publication elsewhere., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The current coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) remains a threat to pregnant women. However, the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood. Here, we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy. Compared to control placentas, SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection. However, subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface. Notably, the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester. Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection., (© The Author(s) 2024. Published by Oxford University Press on behalf of Higher Education Press.)

Background: Maternal-fetal immunology is intricate, and the effects of mRNA-S maternal vaccination on immune regulation at the maternal-fetal interface require further investigation. Our study endeavors to elucidate these immunological changes, enhancing our comprehension of maternal and fetal health outcomes. By analyzing immune profiles and cytokine responses, we aim to provide valuable insights into the impact of mRNA-S vaccination on the delicate balance of immune regulation during pregnancy, addressing critical questions in the field of reproductive pharmacology., Objectives: This investigation sought to examine the prospective influence of mRNA-S-based vaccines and extracellular vesicles (EVs) containing the Spike (S) protein at the maternal-fetal interface. Our primary emphasis was on evaluating their effects on maternal decidua cells and fetal chorion trophoblast cells (hFM-CTCs)., Methods: We validated the generation of EVs containing the S protein from small human airway epithelial cell lines (HSAECs) following mRNA-S vaccine exposure. We assessed the expression of angiotensin-converting enzyme 2 (ACE2) gene and protein in fetal membranes and the placenta, with specific attention to decidual cells and fetal membrane chorion cells. To assess cellular functionality, these cells were exposed to both recombinant S protein and EVs loaded with S proteins (eSPs)., Results: Our findings revealed that cells and EVs subjected to mRNA-S-based vaccination exhibited altered protein expression levels of S proteins. At the feto-maternal interface, both placental and fetal membrane tissues demonstrated similar ACE-2 expression levels. Among individual cellular layers, syncytiotrophoblast cells in the placenta and chorion cells in the fetal membrane exhibited elevated ACE-2 expression. Notably, EVs derived from HSAECs activated the MAPK pathway in decidual cells. Additionally, decidual cells displayed a substantial increase in gene expression of chemokines like CXCL-10 and CXCL-11, as well as proinflammatory cytokines such as IL-6 in response to eSPs. However, the levels of Ccl-2 and IL-1β remained unchanged in decidual cells under the same conditions. Conversely, hFM-CTCs demonstrated significant alterations in the proinflammatory cytokines and chemokines with respect to eSPs., Conclusion: In conclusion, our study indicates that mRNA-S-based maternal vaccination during pregnancy may influence the maternal-fetal interface's COVID-19 interaction and immune regulation. Further investigation is warranted to assess safety and implications., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Problem: In the cell column of anchoring villi, the cytotrophoblast differentiates into extravillous trophoblast (EVT) and invades the endometrium in contact with maternal immune cells. Recently, chemokines were proposed to regulate the decidual immune response. To investigate the roles of chemokines around the anchoring villi, we examined the expression profiles of chemokines in the first-trimester trophoblast-derived Swan71 cells using a three-dimensional culture model., Method of Study: The gene expressions in the spheroid-formed Swan71 cells were examined by microarray and qPCR analyses. The protein expressions were examined by immunochemical staining. The chemoattractant effects of spheroid-formed Swan71 cells were examined by migration assay using monocyte-derived THP-1 cells., Results: The expressions of an EVT marker, laeverin, and matrix metalloproteases, MMP2 and MMP9, were increased in the spheroid-cultured Swan71 cells. Microarray and qPCR analysis revealed that mRNA expressions of various chemokines, CCL2, CCL7, CCL20, CXCL1, CXCL2, CXCL5, CXCL6, CXCL8, and CXCL10, in the spheroid-cultured Swan71 cells were up-regulated as compared with those in the monolayer-cultured Swan71 cells. These expressions were significantly suppressed by hypoxia. Migration assay showed that culture media derived from the spheroid-formed Swan71 cells promoted THP-1 cell migration., Conclusion: This study indicated that chemokine expressions in Swan71 cells increase under a spheroid-forming culture and the culture media have chemoattractant effects. Since three-dimensional cell assembling in the spheroid resembles the structure of the cell column, this study also suggests that chemokines play important roles in the interaction between EVT and immune cells in their early differentiation stage., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Beginning in the first trimester, fetally derived extravillous trophoblasts (EVTs) invade the uterus and remodel its spiral arteries, transforming them into large, dilated blood vessels. Several mechanisms have been proposed to explain how EVTs coordinate with the maternal decidua to promote a tissue microenvironment conducive to spiral artery remodelling (SAR) 1-3 . However, it remains a matter of debate regarding which immune and stromal cells participate in these interactions and how this evolves with respect to gestational age. Here we used a multiomics approach, combining the strengths of spatial proteomics and transcriptomics, to construct a spatiotemporal atlas of the human maternal-fetal interface in the first half of pregnancy. We used multiplexed ion beam imaging by time-of-flight and a 37-plex antibody panel to analyse around 500,000 cells and 588 arteries within intact decidua from 66 individuals between 6 and 20 weeks of gestation, integrating this dataset with co-registered transcriptomics profiles. Gestational age substantially influenced the frequency of maternal immune and stromal cells, with tolerogenic subsets expressing CD206, CD163, TIM-3, galectin-9 and IDO-1 becoming increasingly enriched and colocalized at later time points. By contrast, SAR progression preferentially correlated with EVT invasion and was transcriptionally defined by 78 gene ontology pathways exhibiting distinct monotonic and biphasic trends. Last, we developed an integrated model of SAR whereby invasion is accompanied by the upregulation of pro-angiogenic, immunoregulatory EVT programmes that promote interactions with the vascular endothelium while avoiding the activation of maternal immune cells., (© 2023. The Author(s).)

During pregnancy, maternal immune system has to balance tightly between protection against pathogens and tolerance towards a semi-allogeneic organism. Dysfunction of this immune adaptation can lead to severe complications such as pregnancy loss, preeclampsia or fetal growth restriction. In the present study we analyzed the impact of the murine MHC class Ib molecule Qa-2 on pregnancy outcome in vivo . We demonstrate that lack of Qa-2 led to intrauterine growth restriction and increased abortion rates especially in late pregnancy accompanied by a disturbed trophoblast invasion and altered spiral artery remodeling as well as protein aggregation in trophoblast cells indicating a preeclampsia-like phenotype. Furthermore, lack of Qa-2 caused imbalanced immunological adaptation to pregnancy with altered immune cell and especially T-cell homeostasis, reduced T reg numbers and decreased accumulation and functional activation of myeloid-derived suppressor cells. Lastly, we show that application of sHLA-G reduced abortion rates in Qa-2 deficient mice by inducing MDSC. Our results highlight the importance of an interaction between HLA-G and MDSC for pregnancy success and the therapeutic potential of HLA-G for treatment of immunological pregnancy complications., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Dietz, Schwarz, Velic, González-Menéndez, Quintanilla-Martinez, Casadei, Marmé, Poets, Gille and Köstlin-Gille.)

A high number of leucocytes reside in the human endometrium and are distributed differentially during the menstrual cycle and pregnancy. During early pregnancy, decidual natural killer (dNK) cells are the most common type of natural killer (NK) cells in the uterus. The increase in the number of uterine NK (uNK) cells during the mid-secretory phase of the menstrual cycle, followed by further increase of dNK cells in early pregnancy, has heightened interest in their involvement during pregnancy. Extensive research has revealed various roles of dNK cells during pregnancy including the formation of new blood vessels, migration of trophoblasts, and immunological tolerance. The present review article is focused on the significance of NK cells during pregnancy and their role in pregnancy-related diseases. The article will provide an in-depth review of cellular and molecular interactions during pregnancy and related disorders, with NK cells playing a pivotal role. Moreover, this study will help researchers to understand the physiology of normal pregnancy and related complications with respect to NK cells, so that future research work can be designed to alleviate the complications.

Zika virus (ZIKV) during pregnancy infects fetal trophoblasts and causes placental damage and birth defects including microcephaly. Little is known about the anti-ZIKV cellular immune response at the maternal-fetal interface. Decidual natural killer cells (dNK), which directly contact fetal trophoblasts, are the dominant maternal immune cells in the first-trimester placenta, when ZIKV infection is most hazardous. Although dNK express all the cytolytic molecules needed to kill, they usually do not kill infected fetal cells but promote placentation. Here, we show that dNK degranulate and kill ZIKV-infected placental trophoblasts. ZIKV infection of trophoblasts causes endoplasmic reticulum (ER) stress, which makes them dNK targets by down-regulating HLA-C/G, natural killer (NK) inhibitory receptor ligands that help maintain tolerance of the semiallogeneic fetus. ER stress also activates the NK activating receptor NKp46. ZIKV infection of Ifnar1 -/- pregnant mice results in high viral titers and severe intrauterine growth restriction, which are exacerbated by depletion of NK or CD8 T cells, indicating that killer lymphocytes, on balance, protect the fetus from ZIKV by eliminating infected cells and reducing the spread of infection., Competing Interests: The authors declare no competing interest.

Throughout gestation, the maternal immune system is tightly modulated to allow growth of a semiallogeneic fetus. During the third trimester, the maternal immune system shifts to a proinflammatory phenotype in preparation for labor. What induces this shift remains unclear. Cell-free fetal DNA (cffDNA) is shed by the placenta and enters maternal circulation throughout pregnancy. Levels of cffDNA are increased as gestation progresses and peak before labor, coinciding with a shift to proinflammatory maternal immunity. Furthermore, cffDNA is abnormally elevated in plasma from women with complications of pregnancy, including preterm labor. Given the changes in maternal immunity at the end of pregnancy and the role of sterile inflammation in the pathophysiology of spontaneous preterm birth, we hypothesized that cffDNA can act as a damage-associated molecular pattern inducing an inflammatory cytokine response that promotes hallmarks of parturition. To test this hypothesis, we stimulated human maternal leukocytes with cffDNA from primary term cytotrophoblasts or maternal plasma and observed significant IL-1β and CXCL10 secretion, which coincides with phosphorylation of IFN regulatory factor 3 and caspase-1 cleavage. We then show that human maternal monocytes are crucial for the immune response to cffDNA and can activate bystander T cells to secrete proinflammatory IFN-γ and granzyme B. Lastly, we find that the monocyte response to cffDNA leads to vascular endothelium activation, induction of myometrial contractility, and PGE 2 release in vitro. Our results suggest that the immune response to cffDNA can promote key features of the parturition cascade, which has physiologic consequences relevant to the timing of labor., (Copyright © 2021 by The American Association of Immunologists, Inc.)

The mosquito-borne Rift Valley fever (RVF) is a prioritised disease that has been listed by the World Health Organization for urgent research and development of counteraction. Rift Valley fever virus (RVFV) can cause a cytopathogenic effect in the infected cell and induce hyperimmune responses that contribute to pathogenesis. In livestock, the consequences of RVFV infection vary from mild symptoms to abortion. In humans, 1-3% of patients with RVFV infection develop severe disease, manifested as, for example, haemorrhagic fever, encephalitis or blindness. RVFV infection has also been associated with miscarriage in humans. During pregnancy, there should be a balance between pro-inflammatory and anti-inflammatory mediators to create a protective environment for the placenta and foetus. Many viruses are capable of penetrating that protective environment and infecting the foetal-maternal unit, possibly via the trophoblasts in the placenta, with potentially severe consequences. Whether it is the viral infection per se, the immune response, or both that contribute to the pathogenesis of miscarriage remains unknown. To investigate how RVFV could contribute to pathogenesis during pregnancy, we infected two human trophoblast cell lines, A3 and Jar, representing normal and transformed human villous trophoblasts, respectively. They were infected with two RVFV variants (wild-type RVFV and RVFV with a deleted NSs protein), and the infection kinetics and 15 different cytokines were analysed. The trophoblast cell lines were infected by both RVFV variants and infection caused upregulation of messenger RNA (mRNA) expression for interferon (IFN) types I-III and inflammatory cytokines, combined with cell line-specific mRNA expression of transforming growth factor (TGF)-β1 and interleukin (IL)-10. When comparing the two RVFV variants, we found that infection with RVFV lacking NSs function caused a hyper-IFN response and inflammatory response, while the wild-type RVFV suppressed the IFN I and inflammatory response. The induction of certain cytokines by RVFV infection could potentially lead to teratogenic effects that disrupt foetal and placental developmental pathways, leading to birth defects and other pregnancy complications, such as miscarriage.

Pathological maternal inflammation and abnormal placentation contribute to several pregnancy-related disorders, including preterm birth, intrauterine growth restriction, and preeclampsia. TANK-binding kinase 1 (TBK1), a serine/threonine kinase, has been implicated in the regulation of various physiological processes, including innate immune response, autophagy, and cell growth. However, the relevance of TBK1 in the placental pro-inflammatory environment has not been investigated. In this study, we assessed the effect of TBK1 inhibition on lipopolysaccharide (LPS)-induced NLRP3 inflammasome activation and its underlying mechanisms in human trophoblast cell lines and mouse placenta. TBK1 phosphorylation was upregulated in the trophoblasts and placenta in response to LPS. Pharmacological and genetic inhibition of TBK1 in trophoblasts ameliorated LPS-induced NLRP3 inflammasome activation, placental inflammation, and subsequent interleukin (IL)-1 production. Moreover, maternal administration of amlexanox, a TBK1 inhibitor, reversed LPS-induced adverse pregnancy outcomes. Notably, TBK1 inhibition prevented LPS-induced NLRP3 inflammasome activation by targeting the mammalian target of rapamycin complex 1 (mTORC1). Thus, this study provides evidence for the biological significance of TBK1 in placental inflammation, suggesting that amlexanox may be a potential therapeutic candidate for treating inflammation-associated pregnancy-related complications., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lee, Shin, Kim, Shin, Lee and Park.)

Successful implantation requires the coordinated migration and invasion of trophoblast cells from out of the blastocyst and into the endometrium. This process relies on signals produced by cells in the maternal endometrium. However, the relative contribution of stroma cells remains unclear. The study of human implantation has major technical limitations, therefore the need of in vitro models to elucidate the molecular mechanisms. Using a recently described 3D in vitro models we evaluated the interaction between trophoblasts and human endometrial stroma cells (hESC), we assessed the process of trophoblast migration and invasion in the presence of stroma derived factors. We demonstrate that hESC promotes trophoblast invasion through the generation of an inflammatory environment modulated by TNF-α. We also show the role of stromal derived IL-17 as a promoter of trophoblast migration through the induction of essential genes that confer invasive capacity to cells of the trophectoderm. In conclusion, we describe the characterization of a cellular inflammatory network that may be important for blastocyst implantation. Our findings provide a new insight into the complexity of the implantation process and reveal the importance of inflammation for embryo implantation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 You, Stelzl, Joseph, Aldo, Maxwell, Dekel, Liao, Whirledge and Mor.)

The immune tolerance microenvironment is crucial for the establishment and maintenance of pregnancy at the maternal-fetal interface. The maternal-fetal interface is a complex system containing various cells, including lymphocytes, decidual stromal cells, and trophoblasts. Macrophages are the second-largest leukocytes at the maternal-fetal interface, which has been demonstrated to play essential roles in remodeling spiral arteries, maintaining maternal-fetal immune tolerance, and regulating trophoblast's biological behaviors. Many researchers, including us, have conducted a series of studies on the crosstalk between macrophages and trophoblasts at the maternal-fetal interface: on the one hand, macrophages can affect the invasion and migration of trophoblasts; on the other hand, trophoblasts can regulate macrophage polarization and influence the state of the maternal-fetal immune microenvironment. In this review, we systemically introduce the functions of macrophages and trophoblasts and the cell-cell interaction between them for the establishment and maintenance of pregnancy. Advances in this area will further accelerate the basic research and clinical translation of reproductive medicine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Ding, Zhang, Cai, Diao, Yang and Yang.)

Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The critical immune effectors, including T, B, and natural killer (NK) cells, dendritic cells, and macrophages participate in regulating immune responses during pregnancy. Among these immune cells, decidual NK (dNK) cells are involved in key placental development processes at the maternal-fetal interface, such as uterine spiral artery remodeling, trophoblast invasion, and decidualization. Mechanistically, dNK cells significantly influence pregnancy outcome by secreting cytokines, chemokines, and angiogenic mediators and by their interactions with trophoblasts and other decidual cells. MicroRNAs (miRNAs) are small non-coding RNA molecules that participate in the initiation and progression of human diseases. Although the functions of circulating miRNAs in pathological mechanism has been extensively studied, the regulatory roles of miRNAs in NK cells, especially in dNK cells, have been rarely reported. In this review, we analyze the effects of miRNA regulations of dNK cell functions on the immune system during gestation. We discuss aberrant expressions of certain miRNAs in dNK cells that may lead to pathological consequences, such as recurrent pregnancy loss (RPL). Interestingly, miRNA expression patterns are also different between dNK cells and peripheral NK (pNK) cells, and pNK cells in the first- and third-trimester of gestation. The dysregulation of miRNA plays a pivotal regulatory role in driving immune functions of dNK and pNK cells. Further understanding of the molecular mechanisms of miRNAs in dNK cells may provide new insights into the development of therapeutics to prevent pregnancy failure., (© 2021. The Author(s).)

NK cell development is affected by their cellular microenvironment and cytokines, including IL-15 and IL-18. NK cells can differentiate in secondary lymphoid organs, liver and within the uterus in close contact with trophoblast cells. The aim was to evaluate changes in the NK cell phenotype and function in the presence of IL-15, IL-18 and JEG-3, a trophoblast cell line. When cocultured with JEG-3 cells, IL-15 caused an increase in the number of NKG2D+ NK-92 cells and the intensity of CD127 expression. IL-18 stimulates an increase in the amount of NKp44+ NK-92 cells and in the intensity of NKp44 expression by pNK in the presence of trophoblast cells. NK-92 cell cytotoxic activity against JEG-3 cells increased only in presence of IL-18. Data on changes in the cytotoxic activity of NK-92 cells against JEG-3 cells in the presence of IL-15 and IL-18 indicate the modulation of NK cell function both by the cytokine microenvironment and directly by target cells. IL-15 and IL-18 were present in conditioned media (CM) from 1st and 3rd trimester placentas. In the presence of 1st trimester CM and JEG-3 cells, NK-92 cells showed an increase in the intensity of NKG2D expression. In the presence of 3rd trimester CM and JEG-3 cells, a decrease in the expression of NKG2D by NK-92 cells was observed. Thus, culturing of NK-92 cells with JEG-3 trophoblast cells stimulated a pronounced change in the NK cell phenotype, bringing it closer to the decidual NK cell-like phenotype., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

Human Leukocyte Antigen-G (HLA-G) prevents the activity of immune cells and is decreased in women with preeclampsia. We aimed to investigate the associations between circulating soluble HLA-G (sHLA-G) and 92 cardiovascular disease-related biomarkers from a previously published multiplex study in women with preeclampsia and controls. We found 15 markers significantly associated with circulating sHLA-G in univariate analyses. After multivariable adjusted regression, only proto-oncogene tyrosine-protein kinase Src (SRC) and vascular endothelial growth factor D were significantly associated with sHLA-G. Low SRC, previously observed in the circulation of preeclamptic women, may be regulated by low sHLA-G, and reflect decreased trophoblast differentiation and syncytical formation., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Objectives: Trophoblastic invasion at the maternal-fetal interface can affect pregnancy outcomes. To describe an intuitive theme trends and knowledge structure of trophoblastic invasion-related literature from a bibliometric perspective, and provide researchers with new research hotspots., Study Design: The literature form PubMed database related to trophoblastic invasion from January 1, 2012 to April 30, 2021 were extracted, and then biclustering analysis, co-word analysis, strategy diagram and social network analysis were performed to provide immature, or newly emerging research hotspots for researchers., Results: A total of 96 high-frequency medical subjects heading terms were extracted and classified into 6 clusters. Themes in the first and second quadrant of strategy diagram, including trophoblasts metabolism, placenta metabolism, pre-eclampsia, etc., as the mature parts of the research on trophoblastic invasion have been well developed. On the other hand, themes in the third and fourth quadrants of strategy diagram, such as embryo implantation and trophoblasts immunology, pregnancy complication, matrix metalloproteinase and trophoblasts metabolism, habitual abortion and trophoblasts metabolism, etc., are immature themes. Social network analysis suggests that themes at the edge, such as habitual abortion / metabolism, placenta / immunology, natural killer cells / physiology, natural killer cells / immunology, embryo implantation / immunology, are considered new research hotspots and have considerable research space., Conclusion: By analyzing the research hotspots related to trophoblastic invasion, immature themes and emerging hotspots deserve more attention and can be considered as hints when launching new research projects., (Copyright © 2021 Elsevier B.V. All rights reserved.)

To obtain a successful pregnancy, the establishment of maternal-fetal tolerance and successful placentation are required to be established. Disruption of this immune balance and/or inadequate placental perfusion is believed to be associated with a lot of pregnancy-related complications, such as recurrent spontaneous abortion, pre-eclampsia, and fetal intrauterine growth restriction. Extravillous trophoblasts (EVTs) have the unique ability to instruct decidual immune cells (DICs) to develop a regulatory phenotype for fetal tolerance. Utilizing immortalized human first trimester extravillous trophoblast cells and primary EVTs, we found that DICs promote EVT function and placental development. We have previously shown that checkpoints T-cell immunoglobulin mucin-3 (Tim-3) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are important for DIC function. In the present study, we showed that blockade of Tim-3 and CTLA-4 pathways leaded to the abnormal DICs-EVTs interaction, poor placental development, and increased fetal loss. Treatment with IL-4 and IL-10 could rescue the adverse effects of targeting Tim-3 and CTLA-4 on the pregnancy outcome. Hence, the reproductive safety must be a criterion considered in the assessment of immuno-therapeutic agents. In addition, IL-4 and IL-10 may represent novel therapeutic strategies to prevent pregnancy loss induced by checkpoint inhibition., (© 2021 Federation of American Societies for Experimental Biology.)

The syncytiotrophoblast (STB) of human placenta constitutively and throughout pregnancy produces and secretes exosomes - nanometer-sized membrane-bound extracellular vesicles from the endosomal compartment that convey cell-cell contact 'by proxy' transporting information between donor and recipient cells locally and at a distance. Released in the maternal blood, STB-derived exosomes build an exosomal gradient around the feto-placental unit acting as a shield that protects the fetus from maternal immune attack. They carry signal molecules and ligands that comprise distinct immunosuppressive protein signatures which interfere with maternal immune mechanisms, potentially dangerous for the ongoing pregnancy. We discuss three immunosuppressive signatures carried by STB exosomes and their role in three important immune mechanisms 1) NKG2D receptor-mediated cytotoxicity, 2) apoptosis of activated immune cells and 3) PD-1-mediated immunosuppression and priming of T regulatory cells. A schematic presentation is given on how these immunosuppressive protein signatures, delivered by STB exosomes, modulate the maternal immune system and contribute to the development of maternal-fetal tolerance., Competing Interests: The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Mincheva-Nilsson.)

The placenta controls the growth of the fetus and ensures its immune protection. Key to these functions, the syncytiotrophoblast (SYN) is a syncytium formed by fusion of underlying mononuclear trophoblasts. The SYN covers the placental surface and is bathed in maternal blood to mediate nutritional and waste exchanges between the mother and fetus. The bacterial pathogen Listeria monocytogenes breaches the trophoblast barrier and infects the placental/fetal unit resulting in poor pregnancy outcomes. In this work, we analyzed the L. monocytogenes intracellular lifecycle in primary human trophoblasts. In accordance with previous studies, we found that the SYN is 20-fold more resistant to infection compared to mononuclear trophoblasts, forming a protective barrier to infection at the maternal interface. We show for the first time that this is due to a significant reduction in L. monocytogenes uptake by the SYN rather than inhibition of the bacterial intracellular division or motility. We here report the first transcriptomic analysis of L. monocytogenes -infected trophoblasts (RNA sequencing). Pathway analysis showed that infection upregulated TLR2, NOD-like, and cytosolic DNA sensing pathways, as well as downstream pro-inflammatory circuitry (NF-κB, AP-1, IRF4, IRF7) leading to the production of mediators known to elicit the recruitment and activation of maternal leukocytes (IL8, IL6, TNFα, MIP-1). Signature genes associated with poor pregnancy outcomes were also upregulated upon infection. Measuring the release of 54 inflammatory mediators confirmed the transcriptomic data and revealed sustained production of tolerogenic factors (IL-27, IL-10, IL-1RA, TSLP) despite infection. Both the SYN and mononuclear trophoblasts produced cytokines, but surprisingly, some cytokines were predominantly produced by the SYN (IL-8, IL-6) or by non-fused trophoblasts (TNFα). Collectively, our data support that trophoblasts act as placental gatekeepers that limit and detect L. monocytogenes infection resulting in a pro-inflammatory response, which may contribute to the poor pregnancy outcomes if the pathogen persists., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Johnson, Azari, Webb, Zhang, Gavrilin, Marshall, Rood and Seveau.)

Epitope H contains an O-linked N-acetylglucosamine (O-GlcNAcH) residue in a specific conformation and/or environment recognized by the mouse monoclonal antibody H. O-GlcNAcH is present in several types of cells and in several polypeptides, including cytokeratin 8 and vimentin, on the latter in cells under stress. In the present work, we examined the expression of the O-GlcNAcH in 60 cases of endometrial curettings from missed miscarriage cases containing normal and simple hydropic degenerated chorionic villi in each case, using monoclonal antibody H and indirect immunoperoxidase and Western blot immunoblot. In all cases examined the expression of the O-GlcNAcH was cytoplasmic as follows: (1) syncytiotrophoblastic cells showed very low expression in chorionic villi (CV) with nonhydropic degeneration (NHD) and high expression in hydropic degenerated (HD) CV; (2) cytotrophoblastic cells showed low expression in CV with NHD and high expression in HD CV; (3) fibroblastic cells showed high expression in CV with NHD and very low expression in HD CV; (4) histiocytes showed very low expression in both types of CV; (5) endothelial cells showed high expression in both types of CV. An immunoblot of CV from one case of a legal abortion from a normal first-trimester pregnancy showed 5 polypeptides with 118.5, 106.3, 85, 53, and 36.7 kD bearing the epitope H and the 53 kD corresponded to cytokeratin 8. The expression of the O-GlcNAcH is upregulated in the trophoblastic cells and downregulated in the fibroblastic cells in the HD CV in comparison to the NHD CV., Competing Interests: The authors declare no conflict of interest., (Copyright © 2020 by the International Society of Gynecological Pathologists.)

Zika virus (ZIKV) re-emerged after circulating almost undetected for many years and the last spread in 2015 was the major outbreak reported. ZIKV infection was associated with congenital fetal growth anomalies such as microcephaly, brain calcifications, and low birth weight related to fetal growth restriction. In this study, we investigated the effect of ZIKV infection on first trimester trophoblast cell function and metabolism. We also studied the interaction of trophoblast cells with decidual immune populations. Results presented here demonstrate that ZIKV infection triggered a strong antiviral response in first trimester cytotrophoblast-derived cells, impaired cell migration, increased glucose uptake and GLUT3 expression, and reduced brain derived neurotrophic factor (BDNF) expression. ZIKV infection also conditioned trophoblast cells to favor a tolerogenic response since an increased recruitment of CD14+ monocytes bearing an anti-inflammatory profile, increased CD4+ T cells and NK CD56 Dim and NK CD56 Bright populations and an increment in the population CD4+ FOXP3+ IL-10+ cells was observed. Interestingly, when ZIKV infection of trophoblast cells occurred in the presence of the vasoactive intestinal peptide (VIP) there was lower detection of viral RNA and reduced toll-like receptor-3 and viperin messenger RNA expression, along with reduced CD56 Dim cells trafficking to trophoblast conditioned media. The effects of ZIKV infection on trophoblast cell function and immune-trophoblast interaction shown here could contribute to defective placentation and ZIKV persistence at the fetal-maternal interface. The inhibitory effect of VIP on ZIKV infection of trophoblast cells highlights its potential as a candidate molecule to interfere ZIKV infection during early pregnancy., (© 2020 Wiley Periodicals LLC.)

Congenital toxoplasmosis is represented by the transplacental passage of Toxoplasma gondii from the mother to the fetus. Our studies demonstrated that T. gondii developed mechanisms to evade of the host immune response, such as cyclooxygenase (COX)-2 and prostaglandin E 2 (PGE 2 ) induction, and these mediators can be produced/stored in lipid droplets (LDs). The aim of this study was to evaluate the role of COX-2 and LDs during T. gondii infection in human trophoblast cells and villous explants. Our data demonstrated that COX-2 inhibitors decreased T. gondii replication in trophoblast cells and villous. In BeWo cells, the COX-2 inhibitors induced an increase of pro-inflammatory cytokines (IL-6 and MIF), and a decrease in anti-inflammatory cytokines (IL-4 and IL-10). In HTR-8/SVneo cells, the COX-2 inhibitors induced an increase of IL-6 and nitrite and decreased IL-4 and TGF-β1. In villous explants, the COX-2 inhibitors increased MIF and decreased TNF-α and IL-10. Furthermore, T. gondii induced an increase in LDs in BeWo and HTR-8/SVneo, but COX-2 inhibitors reduced LDs in both cells type. We highlighted that COX-2 is a key factor to T. gondii proliferation in human trophoblast cells, since its inhibition induced a pro-inflammatory response capable of controlling parasitism and leading to a decrease in the availability of LDs, which are essentials for parasite growth.

The non-classical HLA class I molecule HLA-G is expressed in trophoblasts where it contributes to maternal-fetal tolerance. HLA-G has been implicated in the control of trophoblast invasion, uterine vascular remodeling, and maintenance of a local immunosuppressive state. Understanding HLA-G biology at the maternal-fetal interface is therefore a critical issue in reproduction. In this regard, we review here: (i) the effects of HLA-G on decidual leucocytes and stromal cells, (ii) the contribution of trogocytosis in HLA-G expression on decidual cells, (iii) its interaction with the ILT2, ILT4 and KIR2DL4 receptors, (iv) the link between HLA-G polymorphism and pregnancy disorders, and (v) the expression of newly-described HLA-G isoforms at the maternal-fetal interface., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Inc.)

MiR-126-3p is a prototype of an endothelial miRNA and has protective effects on endothelial cells. However, little is known about the effects of miR-126-3p on placental trophoblasts. In the present study, we tested the hypothesis that aberrant miR-126-3p expression is present in preeclamptic placenta which contributes to increased inflammatory response in trophoblasts. Placentas were obtained immediately after delivery from normotensive and preeclamptic pregnancies. Villous tissue was either fixed with formalin or used for trophoblast isolation. Trophoblast miR-126-3p expression was assessed by in situ hybridization of formalin-fixed tissue sections and by RT-PCR in cultured syncytiotrophoblasts. Culture medium was collected for measurement of IL-6, TNFα, and 8-Isoprostane production by ELISA and total cellular protein was collected for evaluation of HIF1α expression by Western blot. Effects of overexpression of miR-126-3p in trophoblasts on cytokine production were tested by transfection of pre-mir-126, a precursor of miR-126, into primary isolated trophoblasts. We found that downregulation of miR-126-3p expression was associated with increased IL-6 and TNFα production in trophoblasts from preeclamptic placentas vs. normal placentas. Moreover, transient overexpression of miR-126-3p significantly reduced IL-6 and TNFα production in trophoblasts from both normal and preeclamptic placentas. We further found that increase in miR-126-3p expression not only suppressed hypoxia-induced increases in IL-6 and TNFα production, but also attenuated hypoxia-induced increases in HIF1α expression and 8-Isoprostane production in trophoblasts cultured under hypoxic condition. These results provide plausible evidence that downregulation of miR-126-3p expression reduces anti-inflammatory and anti-oxidative stress activities in placental trophoblasts in preeclampsia., (Copyright © 2021 Elsevier B.V. All rights reserved.)

As most recently demonstrated by the SARS-CoV-2 pandemic, congenital and perinatal infections are of significant concern to the pregnant population as compared to the general population. These outcomes can range from no apparent impact all the way to spontaneous abortion or fetal infection with long term developmental consequences. While some pathogens have developed mechanisms to cross the placenta and directly infect the fetus, other pathogens lead to an upregulation in maternal or placental inflammation that can indirectly cause harm. The placenta is a temporary, yet critical organ that serves multiple important functions during gestation including facilitation of fetal nutrition, oxygenation, and prevention of fetal infection in utero. Here, we review trophoblast cell immunology and the molecular mechanisms utilized to protect the fetus from infection. Lastly, we discuss consequences in the placenta when these protections fail and the histopathologic result following infection.

Pregnancy is a unique situation of physiological immunomodulation, as well as a strong Multiple Sclerosis (MS) disease modulator whose mechanisms are still unclear. Both maternal (decidua) and fetal (trophoblast) placental cells secrete extracellular vesicles (EVs), which are known to mediate cellular communication and modulate the maternal immune response. Their contribution to the MS disease course during pregnancy, however, is unexplored. Here, we provide a first phenotypic and functional characterization of EVs isolated from cultures of term placenta samples of women with MS, differentiating between decidua and trophoblast. In particular, we analyzed the expression profile of 37 surface proteins and tested the functional role of placental EVs on mono-cultures of CD14 + monocytes and co-cultures of CD4 + T and regulatory T (Treg) cells. Results indicated that placental EVs are enriched for surface markers typical of stem/progenitor cells, and that conditioning with EVs from samples of women with MS is associated to a moderate decrease in the expression of proinflammatory cytokines by activated monocytes and in the proliferation rate of activated T cells co-cultured with Tregs. Overall, our findings suggest an immunomodulatory potential of placental EVs from women with MS and set the stage for a promising research field aiming at elucidating their role in MS remission.

HLA-C arose during evolution of pregnancy in the great apes 10 to 15 million years ago. It has a dual function on placental extravillous trophoblasts (EVTs) as it contributes to both tolerance and immunity at the maternal-fetal interface. The mode of its regulation is of considerable interest in connection with the biology of pregnancy and pregnancy abnormalities. First-trimester primary EVTs in which HLA-C is highly expressed, as well as JEG3, an EVT model cell line, were employed. Single-cell RNA-seq data and quantitative PCR identified high expression of the transcription factor ELF3 in those cells. Chromatin immunoprecipitation (ChIP)-PCR confirmed that both ELF3 and MED1 bound to the proximal HLA-C promoter region. However, binding of RFX5 to this region was absent or severely reduced, and the adjacent HLA-B locus remained closed. Expression of HLA-C was inhibited by ELF3 small interfering RNAs (siRNAs) and by wrenchnolol treatment. Wrenchnolol is a cell-permeable synthetic organic molecule that mimics ELF3 and is relatively specific for binding to ELF3's coactivator, MED23, as our data also showed in JEG3. Moreover, the ELF3 gene is regulated by a superenhancer that spans more than 5 Mb, identified by assay for transposase-accessible chromatin using sequencing (ATAC-seq), as well as by its sensitivity to (+)-JQ1 (inhibitor of BRD4). ELF3 bound to its own promoter, thus creating an autoregulatory feedback loop that establishes expression of ELF3 and HLA-C in trophoblasts. Wrenchnolol blocked binding of MED23 to ELF3, thus disrupting the positive-feedback loop that drives ELF3 expression, with down-regulation of HLA-C expression as a consequence., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Multinucleate syncytialized trophoblast is found in three forms in the human placenta. In the earliest stages of pregnancy, it is seen at the invasive leading edge of the implanting embryo and has been called primitive trophoblast. In later pregnancy, it is represented by the immense, multinucleated layer covering the surface of placental villi and by the trophoblast giant cells found deep within the uterine decidua and myometrium. These syncytia interact with local and/or systemic maternal immune effector cells in a fine balance that allows for invasion and persistence of allogeneic cells in a mother who must retain immunocompetence for 40 weeks of pregnancy. Maternal immune interactions with syncytialized trophoblast require tightly regulated mechanisms that may differ depending on the location of fetal cells and their invasiveness, the nature of the surrounding immune effector cells and the gestational age of the pregnancy. Some specifically reflect the unique mechanisms involved in trophoblast cell-cell fusion (aka syncytialization). Here we will review and summarize several of the mechanisms that support healthy maternal-fetal immune interactions specifically at syncytiotrophoblast interfaces., Competing Interests: The authors declare no conflict of interest.

Antiphospholipid antibodies (aPL) are autoantibodies that target phospholipid-binding proteins, such as β2 glycoprotein I (β2GPI), and can induce thrombosis systemically, as well as increase the risk of obstetric complications such as recurrent miscarriage and preeclampsia. Due to the expression of β2GPI by placental trophoblasts, aPL readily target the maternal-fetal interface during pregnancy and many studies have investigated the deleterious effects of aPL on placental trophoblast function. This review will focus on studies that have examined the effects of aPL on the production and modification of extracellular vesicles (EVs) from trophoblasts, as EVs are a key mode of feto-maternal communication in both normal and pathological pregnancy. A more comprehensive understanding of the effects of aPL on the quantity and cargo of EVs extruded by the human placenta may contribute to our current knowledge of how aPL induce both systemic and obstetric disease., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Extracellular vesicle (EV)-mediated communication has been implicated in the cooperative alliance between trophoblast and immune cells toward maternal tolerance and placentation. Syncytiotrophoblast cells secrete EVs directly into the maternal circulation, which are taken up by immune cells, endothelial cells, and other cell types. Initial evidence also shows that EVs produced by immune cells are, in turn, incorporated by trophoblast cells and modulate placental responses. Non-coding RNAs (ncRNAs), proteins, and lipid mediators transported in EVs are able to influence proliferation, differentiation, cytokine production, and immunological responses of recipient cells. The molecular alphabet and cellular targets involved in this dialogue are being revealed. Nevertheless, several questions regarding the whole content, surface markers, and biological functions of EVs still remain to be investigated in both physiological and pathological conditions. Analysis of circulating EVs in maternal blood has the potential to serve as a minimally invasive approach to monitoring placental functions and immunological features of pregnancy, aiding in the diagnostics of complications. This review addresses the immunomodulatory properties of EVs and their tasks in the communication between placental and immune cells., (© 2020 The Authors. American Journal of Reproductive Immunology published by John Wiley & Sons Ltd.)

A successful pregnancy requires that the maternal immune system recognizes and tolerates the semi-allogeneic fetus without compromising the capability of protecting both mother and fetus from various pathogens. Decidual macrophages present unique phenotypes to play a key role in the establishment of the immunological aspects of maternal-fetal interaction. Dysfunction of decidual macrophages gives rise to pregnancy complications such as preeclampsia, recurrent spontaneous miscarriage, preterm labor and fetal growth restriction. Here, we reviewed the latest knowledge on the origin, differentiation, unique phenotype and function of macrophages in normal pregnancy and in pregnancy complications. We mainly focused on the significant roles of decidual macrophages in the process of extravillous trophoblast invasion, spiral arterial remodeling, decidual stromal cells cultivation and immune tolerance maintenance in normal pregnancy, and their pathological roles in pregnancy-related complications, offering more integrated information in maternal-fetal immunity., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Implantation of the embryo is a rate-limiting step for a successful pregnancy, and it requires an intricate crosstalk between the embryo and the endometrium. Extracellular vesicles (EVs) are membrane-enclosed, nano-sized structures produced by cells to mediate cell to cell communication and modulate a diverse set of biological processes. Herein, we review the involvement of EVs in the process of embryo implantation and endometrial diseases. EVs have been isolated from uterine fluid, cultured endometrial epithelial/stromal cells and trophectodermal cells. The endometrial epithelial and stromal/decidual cell-derived EVs and its cargo are internalized bythe trophoblast cells, and they regulate a diverse set of genes involved in adhesion, invasion and migration. Conversely, the embryo-derived EVs and its cargo are internalized by epithelial and immune cells of the endometrium for biosensing and immunomodulation required for successful implantation. EVs have also been shown to play a role in infertility, recurrent implantation failure, endometriosis, endometritis and endometrial cancer. Further research should set a stage for EVs as non-invasive "liquid biopsy" tools for assessment of endometrial health., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Cells produce cytoplasmic vesicles to facilitate the processing and transport of RNAs, proteins, and other signaling molecules among intracellular organelles. Moreover, most cells release a range of extracellular vesicles (EVs) that mediate intercellular communication in both physiological and pathological settings. In addition to a better understanding of their biological functions, the diagnostic and therapeutic prospects of EVs, particularly the nano-sized small EVs (sEVs, exosomes), are currently being rigorously pursued. While EVs and viruses such as retroviruses might have evolved independently, they share a number of similar characteristics, including biogenesis pathways, size distribution, cargo, and cell-targeting mechanisms. The interplay of EVs with viruses has profound effects on viral replication and infectivity. Our research indicates that sEVs, produced by primary human trophoblasts, can endow other non-placental cell types with antiviral response. Better insights into the interaction of EVs with viruses may illuminate new ways to attenuate viral infections during pregnancy, and perhaps develop new antiviral therapeutics to protect the feto-placental unit during critical times of human development., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)