Activated macrophages inhibit human cytotrophoblast invasiveness in vitro

Interleukin-10: a novel metabolic inducer of macrophage differentiation and subsequently contributing to improved pregnancy outcomes of mice by orchestrating oxidative phosphorylation metabolism†

Metabolism regulates the phenotype and function of macrophages. After recruitment to local tissues, monocytes are influenced by the local microenvironment and differentiate into various macrophages depending on different metabolic pathways. However, the metabolic mechanisms underlying decidual macrophage differentiation remain unknown. Interleukin-10 (IL-10) is an important decidual macrophage inducer and promotes oxidative phosphorylation (OXPHOS) of bone marrow-derived macrophages. In this study, we mainly investigate the metabolic changes involved in IL-10-generated macrophages from monocytes using in vitro models. We demonstrate that exposure of monocytes (either peripheral or THP-1) to IL-10 altered the phenotype and function of resultant macrophages that are linked with OXPHOS changes. Interleukin-10 enhanced the mitochondrial complex I and III activity of THP-1 cell-differentiated macrophages and increased the mitochondrial membrane potential, intracellular adenosine triphosphate, and reactive oxygen species levels. Oxidative phosphorylation blockage with oligomycin changed the cell morphology of IL-10-generated macrophages and the expression levels of cytokines, such as transforming growth factor beta, tumor necrosis factor-alpha, interferon gamma, and IL-10, apart from changes in the expression level of the surface markers CD206, CD209, and CD163. Moreover, in vivo IL-10 administration reduced the lipopolysaccharide (LPS)-induced embryo resorption rate, and this effect was diminished when OXPHOS was inhibited, demonstrating that OXPHOS is important for the improved pregnancy outcomes of IL-10 in LPS-induced abortion-prone mice. Our findings provide deep insights into the roles of IL-10 in macrophage biology and pregnancy maintenance. Nevertheless, the direct evidence that OXPHOS is involved in decidual macrophage differentiation needs further investigations.

Decidual macrophages and Hofbauer cells in fetal growth restriction

Placental macrophages, which include maternal decidual macrophages and fetal Hofbauer cells, display a high degree of phenotypical and functional plasticity. This provides these macrophages with a key role in immunologically driven events in pregnancy like host defense, establishing and maintaining maternal-fetal tolerance. Moreover, placental macrophages have an important role in placental development, including implantation of the conceptus and remodeling of the intrauterine vasculature. To facilitate these processes, it is crucial that placental macrophages adapt accordingly to the needs of each phase of pregnancy. Dysregulated functionalities of placental macrophages are related to placental malfunctioning and have been associated with several adverse pregnancy outcomes. Although fetal growth restriction is specifically associated with placental insufficiency, knowledge on the role of macrophages in fetal growth restriction remains limited. This review provides an overview of the distinct functionalities of decidual macrophages and Hofbauer cells in each trimester of a healthy pregnancy and aims to elucidate the mechanisms by which placental macrophages could be involved in the pathogenesis of fetal growth restriction. Additionally, potential immune targeted therapies for fetal growth restriction are discussed.

Uterine macrophages and NK cells exhibit population and gene-level changes after implantation but maintain pro-invasive properties

Introduction

Prior to pregnancy, hormonal changes lead to cellular adaptations in the endometrium allowing for embryo implantation. Critical for successful pregnancy establishment, innate immune cells constitute a significant proportion of uterine cells prior to arrival of the embryo and throughout the first trimester in humans and animal models. Abnormal uterine immune cell function during implantation is believed to play a role in multiple adverse pregnancy outcomes. Current work in humans has focused on uterine immune cells present after pregnancy establishment, and limited in vitro models exist to explore unique functions of these cells.

Methods

With single-cell RNA-sequencing (scRNAseq), we comprehensively compared the human uterine immune landscape of the endometrium during the window of implantation and the decidua during the first trimester of pregnancy.

Results

We uncovered global and cell-type-specific gene signatures for each timepoint. Immune cells in the endometrium prior to implantation expressed genes associated with immune metabolism, division, and activation. In contrast, we observed widespread interferon signaling during the first trimester of pregnancy. We also provide evidence of specific inflammatory pathways enriched in pre- and post-implantation macrophages and natural killer (NK) cells in the uterine lining. Using our novel implantation-on-a-chip (IOC) to model human implantation ex vivo, we demonstrate for the first time that uterine macrophages strongly promote invasion of extravillous trophoblasts (EVTs), a process essential for pregnancy establishment. Pre- and post-implantation uterine macrophages promoted EVT invasion to a similar degree as pre- and post-implantation NK cells on the IOC.

Conclusions

This work provides a foundation for further investigation of the individual roles of uterine immune cell subtypes present prior to embryo implantation and during early pregnancy, which will be critical for our understanding of pregnancy complications associated with abnormal trophoblast invasion and placentation.

Deciphering the immunological interactions: targeting preeclampsia with Hydroxychloroquine's biological mechanisms

Preeclampsia (PE) is a complex pregnancy-related disorder characterized by hypertension, followed by organ dysfunction and uteroplacental abnormalities. It remains a major cause of maternal and neonatal morbidity and mortality worldwide. Although the pathophysiology of PE has not been fully elucidated, a two-stage model has been proposed. In this model, a poorly perfused placenta releases various factors into the maternal circulation during the first stage, including pro-inflammatory cytokines, anti-angiogenic factors, and damage-associated molecular patterns into the maternal circulation. In the second stage, these factors lead to a systemic vascular dysfunction with consecutive clinical maternal and/or fetal manifestations. Despite advances in feto-maternal management, effective prophylactic and therapeutic options for PE are still lacking. Since termination of pregnancy is the only curative therapy, regardless of gestational age, new treatment/prophylactic options are urgently needed. Hydroxychloroquine (HCQ) is mainly used to treat malaria as well as certain autoimmune conditions such as systemic lupus and rheumatoid arthritis. The exact mechanism of action of HCQ is not fully understood, but several mechanisms of action have been proposed based on its pharmacological properties. Interestingly, many of them might counteract the proposed processes involved in the development of PE. Therefore, based on a literature review, we aimed to investigate the interrelated biological processes of HCQ and PE and to identify potential molecular targets in these processes.

CTRP6 regulates M1 macrophage polarization via the PPAR-γ/NF-κB pathway and reprogramming glycolysis in recurrent spontaneous abortion

Aberrant polarization and functions of decidual macrophages are closely related to recurrent spontaneous abortion (RSA). C1q/tumor necrosis factor-related protein 6 (CTRP6) is a member of the adiponectin paralog family, and plays indispensable roles in inflammation, glucose uptake and tumor metastasis. However, the regulatory effect of CTRP6 on macrophage polarization and glycolysis in RSA and the underlying mechanisms have not been fully elucidated. In the present study, we first found that CTRP6 expression was positively correlated with the M1 macrophage marker (CD86) in decidual tissues by dual immunofluorescence analysis. In vitro experiments indicated that CTRP6 could facilitate M1 macrophage activation through the PPAR-γ/NF-κB pathway and manipulate the glycolysis of macrophages. Notably, in addition to silencing CTRP6, treatment with a PPAR-γ agonist (GW1929) inhibited M1 macrophage polarization and rescued embryo absorption in vivo. Taken together, these results identify previously unrevealed functions of CTRP6 in macrophage transformation during RSA.

A comparison of rat models that best mimic immune-driven preeclampsia in humans

Preeclampsia (PE), a hypertensive pregnancy disorder, can originate from varied etiology. Placenta malperfusion has long been considered the primary cause of PE. However, we and others have showed that this disorder can also result from heightened inflammation at the maternal-fetal interface. To advance our understanding of this understudied PE subtype, it is important to establish validated rodent models to study the pathophysiology and test therapies. We evaluated three previously described approaches to induce inflammation-mediated PE-like features in pregnant rats: 1) Tumor necrosis factor-α (TNF-α) infusion via osmotic pump from gestational day (GD) 14-19 at 50ng/day/animal; 2) Polyinosinic:polycytidylic acid (Poly I:C) intraperitoneal (IP) injections from GD 10-18 (alternate days) at 10mg/kg/day/animal; and, 3) Lipopolysaccharide (LPS) IP injections from GD 13-18 at 20ug-70ug/kg/day per animal. Maternal blood pressure was measured by tail-cuff. Upon sacrifice, fetal and placenta weights were recorded. Placenta histomorphology was assessed using H&E sections. Placenta inflammation was determined by quantifying TNF-α levels and inflammatory gene expression. Placenta metabolic and mitochondrial health were determined by measuring mitochondrial respiration rates and placenta NAD+/NADH content. Of the three rodent models tested, we found that Poly I:C and LPS decreased both fetal weight and survival; and correlated with a reduction in region specific placenta growth. As the least effective model characterized, TNF-α treatment resulted in a subtle decrease in fetal/placenta weight and placenta mitochondrial respiration. Only the LPS model was able to induce maternal hypertension and exhibited pronounced placenta metabolic and mitochondrial dysfunction, common features of PE. Thus, the rat LPS model was most effective for recapitulating features observed in cases of human inflammatory PE. Future mechanistic and/or therapeutic intervention studies focuses on this distinct PE patient population may benefit from the employment of this rodent model of PE.

Decidual lymphatic endothelial cell-derived granulocyte-macrophage colony-stimulating factor induces M1 macrophage polarization via the NF-κB pathway in severe pre-eclampsia

PROBLEM

Direct interactions between macrophages and lymphatic vessels have been shown previously. In pre-eclampsia (PE), macrophages are dominantly polarized into a proinflammatory M1 phenotype and lymphangiogenesis is defective in the decidua. Here, we investigated whether decidual lymphatic endothelial cells (dLECs) affect macrophage polarization in PE.

METHOD OF STUDY

THP-1 macrophages were cocultured with dLECs or cultured in the conditioned medium (CM) of dLECs. Macrophage polarization was measured using flow cytometry. Granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in dLECs was measured using qRT-PCR and ELISA. The activation of nuclear translocation of nuclear factor-κ (NF-κB), an upstream signaling molecule of GM-CSF, was assessed by immunocytochemical localization of p65. Through GM-CSF knockdown and NF-κB inhibition in dLEC, we evaluated whether the GM-CSF/NF-κB pathway of PE dLEC affects decidual macrophage polarization.

RESULTS

The ratio of inflammatory M1 macrophages with HLA-DR⁺ /CD80⁺ markers significantly increased following coculturing with PE dLECs or culturing in PE dLEC CM, indicating that the PE dLEC-derived soluble factor acts in a paracrine manner. GM-CSF expression was significantly upregulated in PE dLECs. Recombinant human GM-CSF induced macrophage polarization toward an M1-like phenotype, whereas its knockdown in PE dLECs suppressed it, suggesting PE dLECs induce M1 macrophage polarization by secreting GM-CSF. The NF-κB p65 significantly increased in PE dLECs compared to the control, and pretreatment with an NF-κB inhibitor significantly suppressed GM-CSF production from PE dLECs.

CONCLUSIONS

In PE, dLECs expressing high levels of GM-CSF via the NF-κB-dependent pathway play a role in inducing decidual M1 macrophage polarization.

The Distribution of Foxp3 and CD68 in Preeclamptic and Healthy Placentas: A Histomorphological Evaluation

Preeclampsia is a complication of pregnancy that affects 3-5% of pregnancies and is one of the major causes of maternal/neonatal mortality and morbidities worldwide. We aimed to investigate the distribution of Foxp3+ regulatory T-cells and CD68+ Hofbauer cells in the placenta of preeclamptic and healthy pregnant women with a special focus on correlating these findings with placental histology. Decidua and chorionic villi of the placenta obtained from healthy and preeclamptic pregnancies were evaluated in full-thickness sections. Sections were stained with hematoxylin and eosin and Masson's trichrome and immunostained for Foxp3 and CD68 for histological analyses. The total histomorphological score for placentas was found to be higher in preeclamptic placentas than that in the controls. The CD68 immunoreactivity was higher in the chorionic villi of preeclamptic placentas than that in the controls. The immunoreactivity of Foxp3 was found widely distributed within the decidua in both the groups and did not differ significantly. Interestingly, Foxp3 immunoreactivity in the chorionic villi was found mainly in the villous core and, to a lesser extent, in the syncytiotrophoblasts. We found no significant relation between Foxp3 expressions and morphological changes observed in preeclamptic placentas. Although extensive research is being carried out regarding the pathophysiology of preeclampsia, the findings are still controversial.

The Mac Is Back: The Role of Macrophages in Human Healthy and Complicated Pregnancies

Pregnancy is a fascinating immunological paradox: the semi-allogeneic fetus generally grows without any complications. In the placenta, fetal trophoblast cells come into contact with maternal immune cells. Inaccurate or inadequate adaptations of the maternal immune system could lead to problems with the functioning of the placenta. Macrophages are important for tissue homeostasis, cleanup, and the repair of damaged tissues. This is crucial for a rapidly developing organ such as the placenta. The consensus on macrophages at the maternal-fetal interface in pregnancy is that a major proportion have an anti-inflammatory, M2-like phenotype, that expresses scavenger receptors and is involved in tissue remodeling and the dampening of the immune reactions. Recent multidimensional analyses have contributed to a more detailed outlook on macrophages. The new view is that this lineage represents a highly diverse phenotype and is more prevalent than previously thought. Spatial-temporal in situ analyses during gestation have identified unique interactions of macrophages both with trophoblasts and with T cells at different trimesters of pregnancy. Here, we elaborate on the role of macrophages during early human pregnancy and at later gestation. Their possible effect is reviewed in the context of HLA incompatibility between mother and fetus, first in naturally conceived pregnancies, but foremost in pregnancies after oocyte donation. The potential functional consequences of macrophages for pregnancy-related immune reactions and the outcome in patients with recurrent pregnancy loss are also discussed.

Dysfunction of CCR1+ decidual macrophages is a potential risk factor in the occurrence of unexplained recurrent pregnancy loss

Recurrent pregnancy loss (RPL) puzzles 1-3% of women of childbearing age worldwide. Immunological factors account for more than 60% of cases of unexplained RPL (URPL); however, the underlying mechanism remains unclear. Here, using single-cell sequencing data and functional experiments with clinical samples, we identified a distinct population of CCR1⁺ decidual macrophages (dMφ) that were preferentially enriched in the decidua from normal early pregnancies but were substantially decreased in patients with URPL. Specific gene signatures endowed CCR1⁺ dMφ with immunosuppressive and migration-regulatory properties, which were attenuated in URPL. Additionally, CCR1⁺ dMφ promoted epithelial-to-mesenchymal transition (EMT) to promote trophoblast migration and invasion by activating the ERK1/2 signaling pathway. Decidual stromal cell (DSC)-derived CCL8 was the key regulator of CCR1⁺ dMφ as CCL8 recruited peripheral CCR1⁺ monocytes, induced a CCR1⁺ dMφ-like phenotype, and reinforced the CCR1⁺ dMφ-exerted modulation of trophoblasts. In patients with URPL, CCL8 expression in DSCs was decreased and trophoblast EMT was defective. Our findings revealed that CCR1⁺ dMφ play an important role in immune tolerance and trophoblast functions at the maternal-fetal interface. Additionally, decreased quantity and dysregulated function of CCR1⁺ dMφ result in URPL. In conclusion, we provide insights into the crosstalk between CCR1⁺ dMφ, trophoblasts, and DSCs at the maternal-fetal interface and macrophage-targeted interventions of URPL.

Animal Models of Preeclampsia: Mechanistic Insights and Promising Therapeutics

Preeclampsia (PE) is a common pregnancy-specific disorder that is a major cause of both maternal and fetal morbidity and mortality. Central to the pathogenesis of PE is the production of antiangiogenic and inflammatory factors by the hypoxic placenta, leading to the downstream manifestations of the disease, including hypertension and end-organ damage. Currently, effective treatments are limited for PE; however, the development of preclinical animal models has helped in the development and evaluation of new therapeutics. In this review, we will summarize some of the more commonly used models of PE and highlight their similarities to the human syndrome, as well as the therapeutics tested in each model.

Imaging Mass cytometry reveals the prominent role of myeloid cells at the maternal-fetal interface

Although the immunological complexity of the maternal-fetal interface is well appreciated, the actual interaction of maternal immune cells and fetal trophoblasts is insufficiently understood. To comprehend the composition and spatial orientation of maternal immune cells and fetal extravillous trophoblasts, we applied imaging mass cytometry on decidua basalis of the three trimesters of healthy pregnancy. Within all trimesters, we observed considerably higher frequencies of myeloid cells in the decidua than is seen with single-cell suspension techniques. Moreover, they were the most pronounced cell type in the microenvironment of other decidual cells. In first trimester, HLA-DR^- macrophages represented the most abundant myeloid subcluster and these cells were frequently observed in the vicinity of trophoblasts. At term, HLA-DR⁺ macrophage subclusters were abundantly present and frequently observed in the microenvironment of T cells. Taken together, our results highlight the dynamic role of myeloid cells at the human maternal-fetal interface throughout gestation.

•

Frequency of myeloid cells is underestimated after tissue digestion

•

Myeloid cells could support NK cells with proper trophoblast invasion

•

Myeloid cells are dynamic in their role throughout gestation

Interactions between Macrophages and Mast Cells in the Female Reproductive System

Mast cells (MCs) and macrophages (Mϕs) are innate immune cells that differentiate from early common myeloid precursors and reside in all body tissues. MCs have a unique capacity to neutralize/degrade toxic proteins, and they are hypothesized as being able to adopt two alternative polarization profiles, similar to Mϕs, with distinct or even opposite roles. Mϕs are very plastic phagocytic cells that are devoted to the elimination of senescent/anomalous endogenous entities (to maintain tissue homeostasis), and to the recognition and elimination of exogenous threats. They can adopt several functional phenotypes in response to microenvironmental cues, whose extreme profiles are the inflammatory/killing phenotype (M1) and the anti-inflammatory/healing phenotype (M2). The concomitant and abundant presence of these two cell types and the partial overlap of their defensive and homeostatic functions leads to the hypothesis that their crosstalk is necessary for the optimal coordination of their functions, both under physiological and pathological conditions. This review will examine the relationship between MCs and Mϕs in some situations of homeostatic regulation (menstrual cycle, embryo implantation), and in some inflammatory conditions in the same organs (endometriosis, preeclampsia), in order to appreciate the importance of their cross-regulation.

Deletion of ACLY Disrupts Histone Acetylation and IL-10 Secretion in Trophoblasts, Which Inhibits M2 Polarization of Macrophages: A Possible Role in Recurrent Spontaneous Abortion

Changes to macrophage polarization affect the local microenvironment of the placenta, resulting in pathological pregnancy diseases such as recurrent spontaneous abortion (RSA). Macrophages are in close contact with trophoblasts during placental development, and trophoblast-derived cytokines are important regulators of macrophage polarization and function. Histone acetylation can affect the expression and secretion of cytokines, and ATP citrate lyase (ACLY) is an important factor that regulates histone acetylation. The aim of this study was to investigate the effect of ACLY expression differences in trophoblast on macrophage polarization and its mechanism. Our data demonstrate that ACLY level in placental villi of patients with RSA is decreased, which may lead to the inhibition of histone acetylation in trophoblasts, thereby reducing the secretion of IL-10. Reduced IL-10 secretion activates endoplasmic reticulum stress in macrophages, thus inhibiting their M2 polarization.

Immunological Changes in Pregnancy and Prospects of Therapeutic Pla-Xosomes in Adverse Pregnancy Outcomes

Stringent balance of the immune system is a key regulatory factor in defining successful implantation, fetal development, and timely parturition. Interference in these primary regulatory mechanisms, either at adolescence or prenatal state led to adverse pregnancy outcomes. Fertility restoration with the help of injectable gonadotrophins/progesterone, ovulation-inducing drugs, immunomodulatory drugs (corticosteroids), and reproductive surgeries provides inadequate responses, which manifest its own side effects. The development of a potential diagnostic biomarker and an effectual treatment for adverse pregnancy outcomes is a prerequisite to maternal and child health. Parent cell originated bi-layered-intraluminal nano-vesicles (30-150 nm) also known as exosomes are detected in all types of bodily fluids like blood, saliva, breast milk, urine, etc. Exosomes being the most biological residual structures with the least cytotoxicity are loaded with cargo in the form of RNAs (miRNAs), proteins (cytokines), hormones (estrogen, progesterone, etc.), cDNAs, and metabolites making them chief molecules of cell-cell communication. Their keen involvement in the regulation of biological processes has portrayed them as the power shots of cues to understand the disease's pathophysiology and progression. Recent studies have demonstrated the role of immunexosomes (immunomodulating exosomes) in maintaining unwavering immune homeostasis between the mother and developing fetus for a healthy pregnancy. Moreover, the concentration and size of the exosomes are extensively studied in adverse pregnancies like preeclampsia, gestational diabetes mellitus (GDM), and preterm premature rupture of membrane (pPROMs) as an early diagnostic marker, thus giving in-depth information about their pathophysiology. Exosomes have also been engineered physically as well as genetically to enhance their encapsulation efficiency and specificity in therapy for cancer and adverse pregnancies. Successful bench to bedside discoveries and interventions in cancer has motivated developmental biologists to investigate the role of immunexosomes and their active components. Our review summarizes the pre-clinical studies for the use of these power-shots as therapeutic agents. We envisage that these studies will pave the path for the use of immunexosomes in clinical settings for reproductive problems that arise due to immune perturbance in homeostasis either at adolescence or prenatal state.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Crosstalk Between Trophoblast and Macrophage at the Maternal-Fetal Interface: Current Status and Future Perspectives

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.

MNSFβ Regulates TNFα Production by Interacting with RC3H1 in Human Macrophages, and Dysfunction of MNSFβ in Decidual Macrophages Is Associated With Recurrent Pregnancy Loss

Decidual macrophages (dMϕ) are the second largest population of leukocytes at the maternal–fetal interface and play critical roles in maintaining pregnancy. Our previous studies demonstrated the active involvement of monoclonal nonspecific suppressor factor-β (MNSFβ) in embryonic implantation and pregnancy success. MNSFβ is a ubiquitously expressed ubiquitin-like protein that also exhibits immune regulatory potential, but its function in human dMϕ remains unknown. Here, we observed that the proportion of CD11c^high (CD11cHI) dMϕ was significantly increased in dMϕ derived from patients with recurrent pregnancy loss (RPL dMϕ) compared to those derived from normal pregnant women (Control dMϕ). The production of MNSFβ and TNFα by RPL dMϕ was also significantly increased compared to that by Control dMϕ. Conditioned medium from RPL dMϕ exerted an inhibitory effect on the invasiveness of human trophoblastic HTR8/SVneo cells, and this effect could be partially reversed by a neutralizing antibody against TNFα. Bioinformatics analysis indicated a potential interaction between MNSFβ and RC3H1, a suppressor of TNFα transcription. Immunoprecipitation experiments with human Mϕ differentiated from the human monocyte cell line Thp1 (Thp1-derived Mϕ) proved the binding of MNSFβ to RC3H1. Specific knockdown of MNSFβ in Thp1-derived Mϕ led to a marked decrease in TNFα production, which could be reversed by inhibiting RC3H1 expression. Interestingly, a significant decrease in the protein level of RC3H1 was observed in RPL dMϕ. Together, our findings indicate that aberrantly increased MNSFβ expression in dMϕ may promote TNFα production via its interaction with RC3H1, and these phenomena could result in the disruption of the immune balance at the maternal–fetal interface and thus pregnancy loss.

Benefits of α-lipoic acid in high-risk pregnancies (Review)

α-Lipoic acid (ALA) is a natural molecule that is inconsistently synthesized by the human body and must be provided from exogenous sources, such as food and dietary supplements. Once absorbed, the oxidized form of ALA is transformed into its reduced form, dihydrolipoic acid (DHLA). ALA/DHLA exert direct and indirect antioxidant, anti-inflammatory and fine immunomodulatory effects. ALA/DHLA reduce the levels of pro-inflammatory cytokines (IL-1β, IL-6, IL-8 and IL-17), while increasing the secretion of anti-inflammatory cytokines (IL-10). They also inhibit cyclooxygenase 2, thereby decreasing the secretion of prostaglandin E2 and nitrogen oxide, and reducing the risk of miscarriage in the first trimester of pregnancy. In patients at risk of abortion, administration of ALA from the first trimester has shown efficacy by accelerating subchorionic hematoma resorption, with a significant decrease in the accompanying abdominal pain. ALA has been proven to be efficient in maintaining the length of the cervix and keeping it closed following one episode of premature labor. Preeclampsia is a dysfunction caused by abnormal placentation and an excessive maternal inflammatory response, leading to extreme hypoxia in the placental bed and exaggerated oxidative stress, with release of oxygen free radicals. Oxidative stress plays a key role in the development of preeclampsia and intrauterine growth restriction. The hypothesis of antioxidant supplementation may play an essential part in disease prevention and fetal neuroprotection.

Syncytiotrophoblast Extracellular Vesicles From Late-Onset Preeclampsia Placentae Suppress Pro-Inflammatory Immune Response in THP-1 Macrophages

Syncytiotrophoblast derived Extracellular Vesicles (STBEV) from normal pregnancy (NP) have previously been shown to interact with circulating monocytes and B cells and induce pro-inflammatory cytokine release. Early-onset preeclampsia (EOPE) is associated with an exacerbated inflammatory response, yet there is little data regarding late-onset PE (LOPE) and immune function. Here, using a macrophage/monocyte cell line THP-1, we investigated the inflammatory potential of STBEV, comprising medium/large-STBEV (>200nm) and small-STBEV (<200nm), isolated from LOPE (n=6) and normal (NP) (n=6) placentae via dual-lobe ex-vivo placental perfusion and differential centrifugation. THP-1 cells bound and internalised STBEV isolated from NP and LOPE placentae, as revealed by flow cytometry, confocal microscopy, and ELISA. STBEV-treated THP-1 cells were examined for cytokine gene expression by RT-qPCR and the cell culture media examined for secreted cytokines/chemokines. As expected, NP medium/large-STBEV significantly upregulated the transcriptional expression of TNF-α, IL-10, IL-6, IL-12, IL-8 and TGF-β compared to PE medium/large-STBEV. However, there was no significant difference in the small STBEV population between the two groups, although in general, NP small STBEVs slightly upregulated the same cytokines. In contrast, LOPE STBEV (medium and large) did not induce pro-inflammatory responses by differentiated THP-1 macrophages. This decreased effect of LOPE STBEV was echoed in cytokine/chemokine release. Our results appear to suggest that STBEV from LOPE placentae do not have a major immune-modulatory effect on macrophages. In contrast, NP STBEV caused THP-1 cells to release pro-inflammatory cytokines. Thus, syncytiotrophoblast extracellular vesicles from LOPE dampen immune functions of THP-1 macrophages, suggesting an alternative mechanism leading to the pro-inflammatory environment observed in LOPE.

Extracellular vesicles derived from M1 macrophages deliver miR-146a-5p and miR-146b-5p to suppress trophoblast migration and invasion by targeting TRAF6 in recurrent spontaneous abortion

Rationale: Emerging evidence demonstrates that insufficient migration and invasion of trophoblasts play critical roles in the pathogenesis of recurrent spontaneous abortion (RSA). Cell-to-cell communication at the maternal-fetal interface is essential to maintain the invasion and migration of trophoblasts. M1 macrophages, important immune cellular components at the maternal-fetal interface, have been reported to be elevated in decidua tissues from patients with RSA. Recent studies indicate that M1 macrophages modulate trophoblast biological behaviors; however, the underlying mechanisms remain poorly understood. Methods: Extracellular vesicles (EVs) were isolated from the supernatant of M1 macrophages inducted from THP-1 cells (M1-EVs) by ultracentrifugation, identified by transmission electron microscopy, nanoparticle tracking analysis, and western blotting, and their miRNA profile was characterized by miRNA sequencing. Scratch wound healing and transwell assays were used to investigate the effect of M1-EVs on trophoblast migration and invasion. RT-PCR, western blotting, and luciferase reporter assays were conducted to uncover the underlying mechanism. Finally, animal experiments were employed to explore the effect of M1-EVs on embryo absorption in mice. Results: M1 macrophages suppressed trophoblast EMT to reduce their migration and invasion abilities in vitro by secreting EVs. Through miRNA sequencing, miR-146a-5p and miR-146b-5p were identified as the most upregulated miRNAs in trophoblasts treated with M1-EVs. Further functional experiments showed that M1-EVs inhibited trophoblast migration and invasion by transferring miR-146a-5p and miR-146b-5p. Mechanistically, EV miR-146a-5p and miR-146b-5p inhibited EMT of trophoblasts by directly suppressing TNF receptor-associated factor 6 (TRAF6) expression at the post-transcriptional level. Furthermore, M1-EVs aggravated embryo absorption in mice. Clinically, expression of miR-146a-5p, miR-146b-5p, and TRAF6 were aberrant in placental villous tissues from patients with RSA, and negative correlations were found between miR-146a-5p/miR-146b-5p and TRAF6 expression levels. Conclusions: Our findings indicate that miR-146a-5p and miR-146b-5p derived from EVs play important roles in intercellular communication between M1 macrophages and trophoblasts, illuminating a novel mechanism in M1 macrophage regulation of trophoblasts and their role in RSA.

Changes in the Distribution of Intrauterine Microbiota May Attribute to Immune Imbalance in the CBA/J×DBA/2 Abortion-Prone Mice Model

Background: Female Genital Tract (FGT) is an important micro-ecological area of human body. Microbiota in the lower reproductive tract may subsequently invade the uterine cavity during embryo implantation and produce immune responses. CBA/J×DBA/2 mating combination has been widely used as an abortion-prone mice model but whether microbiota existed in their uterine cavity remains unclear. In this context, the role of the microbial communities in immune response deserves attention.

Objective: To investigate the relationship between the distribution of microbiota in the uterine cavity of CBA/J×DBA/2 abortion-prone mouse model and the immune imbalance of the maternal-fetal interface.

Methods: In this study, female CBA/J mice were paired with male DBA/2 mice to develop an abortion-prone model (BA group), and with male BALB/c mice to build a standard pregnancy model (BC group). The non-pregnant female mice were served as the control group (C group). Uterine flushing fluid and sera were collected on day 13.5 of pregnancy. 16S rRNA sequencing technology was used to analyze the distribution of intrauterine microbiota. Phylogenetic Investigation of Communities were conducted to predict the microbiota functions by Reconstruction of Unobserved States (PICRUST) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The serum IL 10, INF-γ, and TNF-α levels were examined using Enzyme-linked immunosorbent assay (ELISA) method.

Results: All samples were detected with microbial communities. The α diversity (p = 0.00077) had significant differences among three groups. Proteobacteria was the most dominant phylum in C group (mean = 83.21%) and BA group (mean = 43.23%). Firmicutes was dominant in BC group (mean = 46.4%), as well as the second dominant one in C group (mean = 12.63%) and BA group (mean = 40.55%). Microbiota functions were associated with metabolism and immune response through the NOD-like receptor signaling pathway. The serum IL 10 level in BA group were significantly lower than that in BC group (10.14 ± 1.90 pg/ml, n = 8; vs. 19.03 ± 1.82 pg/ml, n = 10; p = 0.004). The serum TNF-α and INF-γ level in BA group were also significantly higher than that in BC group (523.1 ± 58.14 pg/ml, n = 8 vs. 310.3 ± 28.51 pg/ml, n = 10, p = 0.0029; 69.22 ± 5.38 pg/ml, n = 8 vs. 50.85 ± 2.45 pg/ml, n = 10, p = 0.0042).

Conclusion: Microbial communities were colonized in uterine cavity of CBA/J mice both at non-pregnant stage and pregnant stage when mated with both BALB/c and DBA/2 male mice. The differentially abundant microbiome may be attributed to the immune tolerance through binding to the NOD-like receptor.

Role of Kisspeptin in Regulation of Reproductive and Immune Reactions

The work is focused on physiological role of the hormone kisspeptin produced by neurons of the hypothalamus anterior zone, which is a key regulator of reproduction processes. Role of the hormone in transmission of information on metabolic activity and induction of the secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus that determines gestation processes involving fertilization, placentation, fetal development, and child birth is considered. The literature data on molecular mechanisms and effects of kisspeptin on reproductive system including puberty initiation are summarized and analyzed. In addition, attention is paid to hormone-mediated changes in the cardiovascular system in pregnant women. For the first time, the review examines the effect of kisspeptin on functional activity of immune system cells presenting molecular mechanisms of the hormone signal transduction on the level of lymphoid cells that lead to the immune tolerance induction. In conclusion, a conceptual model is presented that determines the role of kisspeptin as an integrator of reproductive and immune functions during pregnancy.

Functional regulation of decidual macrophages during pregnancy

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.

Palmitic acid induces inflammation in placental trophoblasts and impairs their migration toward smooth muscle cells through plasminogen activator inhibitor-1

A critical component of early human placental development includes migration of extravillous trophoblasts (EVTs) into the decidua. EVTs migrate toward and displace vascular smooth muscle cells (SMCs) surrounding several uterine structures, including spiral arteries. Shallow trophoblast invasion features in several pregnancy complications including preeclampsia. Maternal obesity is a risk factor for placental dysfunction, suggesting that factors within an obese environment may impair early placental development. Herein, we tested the hypothesis that palmitic acid, a saturated fatty acid circulating at high levels in obese women, induces an inflammatory response in EVTs that hinders their capacity to migrate toward SMCs. We found that SMCs and SMC-conditioned media stimulated migration and invasion of an EVT-like cell line, HTR8/SVneo. Palmitic acid impaired EVT migration and invasion toward SMCs, and induced expression of several vasoactive and inflammatory mediators in EVTs, including endothelin, interleukin (IL)-6, IL-8 and PAI1. PAI1 was increased in plasma of women with early-onset preeclampsia, and PAI1-deficient EVTs were protected from the anti-migratory effects of palmitic acid. Using first trimester placental explants, palmitic acid exposure decreased EVT invasion through Matrigel. Our findings reveal that palmitic acid induces an inflammatory response in EVTs and attenuates their migration through a mechanism involving PAI1. High levels of palmitic acid in pathophysiological situations like obesity may impair early placental development and predispose to placental dysfunction.

Expression of trophoblast derived prostaglandin E2 receptor 2 (EP2) is reduced in patients with recurrent miscarriage and EP2 regulates cell proliferation and expression of inflammatory cytokines

BACKGROUD

Prostaglandin E2 (PGE2), an inflammatory mediator, modulates cytokines, regulates immune responses in reproductive processes and stimulates inflammatory reactions via the prostaglandin E2 receptor 2 (EP2). However, the regulatory effects of EP2 signaling on trophoblasts and its role in unexplained recurrent miscarriage (uRM) remains unclear.

PATIENTS AND METHODS

A total of 19 placentas from patients with a history of more than two consecutive pregnancy losses of unknown cause (uRM group) and placentas of 19 healthy patients following a legal termination of their pregnancy were used for PGE2 receptor (EP1, EP2 and EP4) expression analyses via immunohistochemistry. Double immunofluorescence was also used to identify EP2 expressing cells in the decidua. Finally, HTR-8/SVneo cells were used to clarify the role of EP2 in in vitro experiments.

RESULTS

The expression of EP2 and EP4 was found to be reduced in the syncytiotrophoblast and decidua of uRM patients. A selective EP2 receptor antagonist (PF-04,418,948) reduced the proliferation and secretion of ß-hCG, inhibited interleukin -6 (IL-6) and interleukin-8 (IL-8) and up-regulated the production of the tumor necrosis factor-α (TNF-α) and plasminogen activator inhibitor type 1 (PAI-1) in HTR-8/SVneo cells in vitro.

CONCLUSION

PGE2-EP2 signaling pathway may represent a novel therapy option for uRM. The involvement of EP2 in uRM acts perhaps via inflammatory cytokines and indicates that the PGE2-EP2 signaling pathway might represent an unexplored etiology for uRM.

T Helper (Th) Cell Profiles in Pregnancy and Recurrent Pregnancy Losses: Th1/Th2/Th9/Th17/Th22/Tfh Cells

During pregnancy, various immune effectors and molecules participating in the immune-microenvironment establish specific maternal tolerance toward the semi-allogeneic fetus. Activated maternal immune effectors by the trophoblast antigens, such as T helper (Th), T cytotoxic (Tc), T regulatory (Treg), and B cells, are involved in the regulation of adaptive immunity. Recognition of active signal through the T cell receptors stimulate the differentiation of naive CD3⁺CD4⁺ T cells into specific T cell subsets, such as Th1, Th2, Th9, Th17, Th22, and follicular Th cells (Tfh). Each of these subsets has a significant and distinct role in human pregnancy. Th1 immunity, characterized by immune-inflammatory responses, becomes dominant during the peri-implantation period, and the “controlled” Th1 immunity benefits the invading trophoblasts rather than harm. Quickly after the placental implantation, the early inflammatory Th1 immunity is shifted to the Th2 anti-inflammatory immune responses. The predominant Th2 immunity, which overrules the Th1 immunity at the placental implantation site, protects a fetus by balancing Th1 immunity and accommodate fetal and placental development. Moreover, Treg and Th9 cells regulate local inflammatory immune responses, potentially detrimental to the fetus. Th17 cells induce protective immunity against extracellular microbes during pregnancy. However, excessive Th17 immunity may induce uncontrolled neutrophil infiltration at the maternal-fetal interface. Other Th cell subsets such as Tfh cells, also contribute to pregnancy by setting up favorable humoral immunity during pregnancy. However, dysregulation of Th cell immunity during pregnancy may result in obstetrical complications, such as recurrent pregnancy losses (RPL) and preeclampsia (PE). With this review, we intend to deliver a comprehensive overview of CD4⁺ Th cell subsets, including Th1, Th2, Th9, Th17, Th22, and Tfh cells, in human pregnancy by reviewing their roles in normal and pathological pregnancies.

Decidual glycodelin-A polarizes human monocytes into a decidual macrophage-like phenotype through Siglec-7

Decidual macrophages constitute 20-30% of the total leukocytes in the uterus of pregnant women, regulating the maternal immune tolerance and placenta development. Abnormal number or activities of decidual macrophages (dMs) are associated with fetal loss and pregnancy complications, such as preeclampsia. Monocytes differentiate into dMs in a decidua-specific microenvironment. Despite their important roles in pregnancy, the exact factors that regulate the differentiation into dMs remain unclear. Glycodelin-A (PAEP, hereafter referred to as GdA) is a glycoprotein that is abundantly present in the decidua, and plays an important role in fetomaternal defense and placental development. It modulates the differentiation and activity of several immune cell types residing in the decidua. In this study, we demonstrated that GdA induces the differentiation of human monocytes into dM-like phenotypes in terms of transcriptome, cell surface marker expression, secretome, and regulation of trophoblast and endothelial cell functions. We found that Sialic acid-binding Ig-like lectin 7 (Siglec-7) mediates the binding and biological actions of GdA in a sialic acid-dependent manner. We, therefore, suggest that GdA, induces the polarization of monocytes into dMs to regulate fetomaternal tolerance and placental development.

Fas ligand neutralization attenuates hypertension, endothelin-1, and placental inflammation in an animal model of HELLP syndrome

Neutralization of FasL is linked to suppression of hypertension, placental inflammation, and endothelin system activation in an animal model of hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome. During HELLP syndrome the placenta has been reported to serve as the primary source of Fas ligand (FasL), which has an impact on inflammation and hypertension during pregnancy and is dysregulated in women with severe preeclampsia and HELLP syndrome. We hypothesize that neutralization of FasL during pregnancy in an animal model of HELLP syndrome decreases inflammation and placental apoptosis, improves endothelial damage, and improves hypertension. On gestational day (GD) 12, rats were chronically infused with placental antiangiogenic factors sFlt-1 and sEng to induce HELLP syndrome. To neutralize FasL, MFL4 or FasL antibody was infused into a subset of HELLP or normal pregnant rats on GD13. IgG infusion into another group of NP and HELLP rats on GD13 was used as a control for FasL antibody, and all rats were euthanized on GD19 after blood pressure measurement. Plasma and placentas were collected to assess inflammation, apoptosis, and the degree of placental debris activation of endothelial cells. Administration of MFL4 to HELLP rats significantly decreased blood pressure compared with untreated HELLP rats and HELLP rats infused with IgG and improved the biochemistry of HELLP syndrome. Both circulating and placental FasL were significantly attenuated in response to MFL4 infusion, as were levels of placental and circulating TNFα when compared with untreated HELLP rats and HELLP rats infused with IgG. Endothelial cells exposed to placental debris and media from HP + MFL4 rats secreted significantly less endothelin-1 compared with stimulated endothelial cells from HELLP placentas. Neutralization of FasL is associated with decreased MAP and improvement in placental inflammation and endothelial damage in an animal model of HELLP syndrome.

Maternal Obesity and the Uterine Immune Cell Landscape: The Shaping Role of Inflammation

Inflammation is often equated to the physiological response to injury or infection. Inflammatory responses defined by cytokine storms control cellular mechanisms that can either resolve quickly (i.e., acute inflammation) or remain prolonged and unabated (i.e., chronic inflammation). Perhaps less well-appreciated is the importance of inflammatory processes central to healthy pregnancy, including implantation, early stages of placentation, and parturition. Pregnancy juxtaposed with disease can lead to the perpetuation of aberrant inflammation that likely contributes to or potentiates maternal morbidity and poor fetal outcome. Maternal obesity, a prevalent condition within women of reproductive age, associates with increased risk of developing multiple pregnancy disorders. Importantly, chronic low-grade inflammation is thought to underlie the development of obesity-related obstetric and perinatal complications. While diverse subsets of uterine immune cells play central roles in initiating and maintaining healthy pregnancy, uterine leukocyte dysfunction as a result of maternal obesity may underpin the development of pregnancy disorders. In this review we discuss the current knowledge related to the impact of maternal obesity and obesity-associated inflammation on uterine immune cell function, utero-placental establishment, and pregnancy health.

Emerging Therapeutic Potential of Mesenchymal Stem/Stromal Cells in Preeclampsia

PURPOSE OF REVIEW

Preeclampsia is a dangerous pregnancy condition affecting both the mother and offspring. It is a multifactorial disease with poorly understood pathogenesis, lacking effective treatments. Maternal immune response, inflammation and oxidative stress leading to endothelial dysfunction are the most prominent pathogenic processes implicated in preeclampsia development. Here, we give a detailed overview of the therapeutic applications and mechanisms of mesenchymal stem/stromal cells (MSCs) as a potential new treatment for preeclampsia.

RECENT FINDINGS

MSCs have gained growing attention due to low immunogenicity, easy cultivation and expansion in vitro. Accumulating evidence now suggests that MSCs act primarily through their secretomes facilitating paracrine signalling that leads to potent immunomodulatory, pro-angiogenic and regenerative therapeutic effects. MSCs have been studied in different animal models of preeclampsia demonstrating promising result, which support further investigations into the therapeutic effects and mechanisms of MSC-based therapies in preeclampsia, steering these therapies into clinical trials.

Dynamic Function and Composition Changes of Immune Cells During Normal and Pathological Pregnancy at the Maternal-Fetal Interface

A successful pregnancy requires a fine-tuned and highly regulated balance between immune activation and embryonic antigen tolerance. Since the fetus is semi-allogeneic, the maternal immune system should exert tolerant to the fetus while maintaining the defense against infection. The maternal-fetal interface consists of different immune cells, such as decidual natural killer (dNK) cells, macrophages, T cells, dendritic cells, B cells, and NKT cells. The interaction between immune cells, decidual stromal cells, and trophoblasts constitute a vast network of cellular connections. A cellular immunological imbalance may lead to adverse pregnancy outcomes, such as recurrent spontaneous abortion, pre-eclampsia, pre-term birth, intrauterine growth restriction, and infection. Dynamic changes in immune cells at the maternal-fetal interface have not been clearly stated. While many studies have described changes in the proportions of immune cells in the normal maternal-fetus interface during early pregnancy, few studies have assessed the immune cell changes in mid and late pregnancy. Research on pathological pregnancy has provided clues about these dynamic changes, but a deeper understanding of these changes is necessary. This review summarizes information from previous studies, which may lay the foundation for the diagnosis of pathological pregnancy and put forward new ideas for future studies.

The role of the PD-1/PD-L1 axis in macrophage differentiation and function during pregnancy

STUDY QUESTION

What is the role of the programmed cell death-1 (PD-1)/PD-1 ligand-1 (PD-L1) axis in macrophage polarization during early pregnancy?

SUMMARY ANSWER

PD-1 signaling is a major regulator of macrophage differentiation and function, and it is critical for the success of a pregnancy.

WHAT IS KNOWN ALREADY

The predominance of decidual macrophages (DMs) with an M2 phenotype is an important contributor to maternal-fetal tolerance during early pregnancy.

STUDY DESIGN, SIZE, DURATION

Twenty-four women with recurrent miscarriage (RM) and 70 women undergoing elective termination of an early normal pregnancy (NP) were included. Twelve female CBA/J, four male DBA/2, and four male BALB/c mice were included and mating carried out. The 12 CBA/J pregnant mice were then categorized into three groups of four mice: healthy control group CBA/J×BALB/c, abortion-prone pregnant group CBA/J×DBA/2 and normal pregnancies CBA/J×BALB/c treated with anti-PD-1 monoclonal antibodies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The profile of DMs, and the expression of PD-1 and PD-L1 in DMs from women with NP and RM were measured by flow cytometry. PD-L1 expression in human villi was determined by quantitative RT-PCR (qRT-PCR) and western blot. An in vitro model consisting of peripheral CD14+ monocytes isolated from women with NP was used. The profile of differentiated macrophages and their phagocytotic activity were then measured by flow cytometry. The mRNA levels of genes potentially underlying macrophage polarization modulated by PD-1 signaling were determined by qRT-PCR. Twelve pregnant mice were included in our in vivo model and underwent different treatment. The embryo resorption rate, and macrophage profile as well as PD-1 expression in murine spleens and uterus were analyzed by flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared with NP, women with RM had elevated percentages of M1 DMs (P < 0.01), and reduced frequencies of M2 DMs (P < 0.05), as well as decreased PD-1 protein expression (P < 0.05) in the DMs. In addition, decreased mRNA and protein levels of PD-L1 expression in placental villi were observed in women with RM (P < 0.001). Using in vitro experiments, compared to the control group, we found that PD-1 activation by recombinant human (rh) PD-L1 Fc (human PD-L1 fused to the Fc region of human IgG1) drove the differentiation of macrophages with immuno-modulatory characteristics (P < 0.01). However, PD-1 blockade promoted dominance of the M1 phenotype (P < 0.01). PD-1 polarized macrophages showed enhanced phagocytic activity (P < 0.01), which was decreased with PD-1 blockade (P < 0.001). Furthermore, PD-1 blockade promoted the expression of pro-inflammatory cytokines and interferon regulatory factor (IRF) 5 (P < 0.05), while IRF4 expression was inhibited (P < 0.05). In addition, PD-1 blockade promoted macrophage glycolysis (P < 0.01) and inhibited fatty acid oxidation (P < 0.05). The mRNA expression levels of both phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin and mitogen-activated protein kinase/extracellular signal-regulated kinase/extracellular signal-regulated kinase were upregulated (P < 0.05) with PD-1 blockade during DM metabolic reprogramming. Moreover, in vivo mice data showed that PD-1 blockade or deficiency was associated with decreased M2 percentages at the maternal-fetal interface (P < 0.05) and embryo loss (P < 0.05).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Whether the changes in DM polarization seen in miscarriage tissues are a cause or consequence of the demise of the pregnancy still requires further investigation. In addition, conducting metabolite analysis is required to further measure bioenergetic profiles.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study on the role of the PD-1/PD-L1 axis in macrophage polarization during early pregnancy; such exploration enhances our understanding of the physiology of early pregnancy. Our study also indicates that targeting the PD-1 pathway may represent a novel therapeutic strategy to prevent pregnancy loss.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Nature Science Foundation of China (No. 81671490) and Integrated Innovative Team for Major Human Diseases Program of Tongji Medical College, HUST (No. 5001519002). None of the authors has any conflict of interest to declare.

Macrophage Polarization in Physiological and Pathological Pregnancy

The immunology of pregnancy is complex and poorly defined. During the complex process of pregnancy, macrophages secrete many cytokines/chemokines and play pivotal roles in the maintenance of maternal-fetal tolerance. Here, we summarized the current knowledge of macrophage polarization and the mechanisms involved in physiological or pathological pregnancy processes, including miscarriage, preeclampsia, and preterm birth. Although current evidence provides a compelling argument that macrophages are important in pregnancy, our understanding of the roles and mechanisms of macrophages in pregnancy is still rudimentary. Since macrophages exhibit functional plasticity, they may be ideal targets for therapeutic manipulation during pathological pregnancy. Additional studies are needed to better define the functions and mechanisms of various macrophage subsets in both normal and pathological pregnancy.

The role of maternal T cell and macrophage activation in preterm birth: Cause or consequence?

The role of the immune system in term (TL) and preterm labor (PTL) is unknown. Despite the fact that globally, PTL remains the most important cause of childhood mortality. Infection, typically of the fetal membranes, termed chorioamnionitis, is the best-understood driver of PTL, but the mechanisms underpinning other causes, including idiopathic and stretch-induced PTL, are unclear, but may well involve activation of the maternal immune system. The final common pathway of placental dysfunction, fetal membrane rupture, cervical dilation and uterine contractions are highly complex processes. At term, choriodecidual rather than myometrial inflammation is thought to drive the onset of labor and similar findings are present in different types of PTL including idiopathic PTL. Although accumulated data has confirmed an association between the immune response and preterm birth, there is yet a need to understand if this response is an initiator or a consequence of tissue-level dysregulation. This review focuses on the potential role of macrophages and T cells in innate and adaptive immunity relevant to preterm birth in humans and animal models.

Developmental onset of cardiovascular disease-Could the proof be in the placenta?

The Barker Hypothesis states change to the maternal environment may have significant impacts on fetal development, setting the stage for adult disease to occur. The development of the maternofetal vasculature during implantation and maintenance during pregnancy is extremely precise, yet dynamic. Delays or dysfunction in the orchestration of anatomical remodeling, maintenance of blood pressure, or responsiveness to metabolic demand may have severe consequences to the developing fetus. While these intermissions may not be fatal to the developing fetus, an interruption, reduction, or an inability to meet fetal demand of blood flow during crucial stages of development may predispose young to disease later in life. Maternal inability to meet fetal demand can be attributed to improper placental development and vascular support through morphological change or physiological function will significantly limit nutrient delivery and waste exchange to the developing fetus. Therefore, we present an overview of the uteroplacental vascular network, maternal cardiovascular adaptations that occur during pregnancy, placental blood flow, and common maternal comorbidities and/or exposures that may perturb maternal homeostasis and affect fetal development. Overall, we examine uterine microvasculature pathophysiology contributing to a hostile gestational environment and fetal predisposition to disease as it relates to the Barker Hypothesis.

Preeclampsia and Related Cardiovascular Risk: Common Genetic Background

PURPOSE OF REVIEW

Preeclampsia (PE) is a hypertensive disorder exclusive for pregnancy. It affects women all over the world and poses a great threat to life, both for mother and child. No definitive treatment exists and placenta delivery comprises the only known cure for PE. One of the most severe complications observed in preeclamptic women is the occurrence of cardiovascular diseases (CVDs) later in life.

RECENT FINDINGS

Both PE and CVDs share some of their pathogenic pathways and gene variations. Thus far, a number of publications have examined those relationships; however, almost all of them focus only on common risk factors. The precise pathomechanism and genetic basis of PE and its associated cardiovascular complications remain unknown. Therefore, the aim of this review is to unify and clarify the current state of knowledge and provide direction for future studies, especially those regarding the genetic aspect.

Weathering the storm; a review of pre-pregnancy stress and risk of spontaneous abortion

The Weathering Effect is a theory that links stress exposure, over the life-course, with racial disparities in reproductive outcomes, through the effects of social adversity on a woman's body. The concept of maternal "weathering" captures cumulative somatic and psychological adversities that can exacerbate the effects of aging. Much of the evidence for weathering comes from observational studies linking self-report measures with reproductive outcomes. The purpose of this review is to explore biological mechanisms that underlie these observations. We focus on spontaneous abortion because this event is understudied despite evidence of racial disparities in this outcome. Spontaneous abortion is the most common pregnancy failure, and it happens early in pregnancy. Early pregnancy is a time most susceptible to the harmful effects of immune dysregulation that may, in part, result from adversities experienced before pregnancy begins. In exploring these mechanisms, we draw on well-defined signaling processes observed in the stressor-depression relationship. Pro-inflammatory dysregulation, for example, has particular relevance to immunological control occurring early in pregnancy. Early pregnancy immunologic changes affect the trajectories of pregnancy via control of trophoblastic invasion. Within the first few weeks of pregnancy, uterine derived cytokines operate within cytokine networks and play a critical role in this invasion. Programming for pro-inflammatory dysregulation can occur before conception. This dysregulation, brought into early pregnancy, has implications for viability and success of the index pregnancy. These patterns suggest early pregnancy health is susceptible to stress processing pathways that influence this immunologic control in the first six to eight weeks of pregnancy. In this review, we discuss the known mediating role of immune factors in the stressor-depression relationship. We also discuss how adversity experienced before the index pregnancy, or "pre-pregnancy" may influence these pathways, and subsequently influence early pregnancy health. There is a need to understand adversity, experienced before pregnancy, and mechanisms driving the effects of these experiences on pregnancy outcomes. This approach is a useful entry point for understanding racial inequities in pregnancy health through an understanding of differences in exposures to adversity. We hypothesize that spontaneous abortion involves cyclical changes within a woman's reproductive tract in response to stressors that are established well before a woman enters into pregnancy. Furthermore, we propose mechanisms that potentially drive weathering processes relevant to reproductive disparities. We also examine what is known about pre-pregnancy stress exposures associated with race, inequity, and adversity, and their potential impact on neuroendocrine and immune changes affecting early pregnancy risk.

Innate immune cells in the placental bed in healthy pregnancy and preeclampsia

Immune cells in the placental bed are important for adequate development of the placental bed. The most prominent immune cells in the placental bed early in pregnancy are uterine natural killer cells (uNK) cells and macrophages. Also dendritic cells and mast cells can be found in the early placental bed. These cells not only have an immune regulatory function, but are also involved in the regulation of trophoblast invasion, angiogenesis and spiral artery remodeling. In preeclampsia, one of the major complications of pregnancy, decreased trophoblast invasion and spiral artery remodeling has been found. This is associated with decreased numbers of uNK cells, increased numbers of macrophages around the spiral arteries and similar or increased numbers of dendritic cells in the placental bed. In this review, we discuss the current insights in the functions of uNK cells, macrophages, dendritic cells and mast cells in the placental bed in humans during healthy pregnancy and during preeclampsia. As animal models are instrumental in understanding the role of immune cells in the placental bed, we also review studies on the function and phenotype of these innate immune cells in experimental preeclampsia. A better understanding of the dynamics and functional changes of these immune cells in the placental bed may eventually lead to new therapeutic targets for preeclampsia.

Pioneer Factors FOXA1 and FOXA2 Assist Selective Glucocorticoid Receptor Signaling in Human Endometrial Cells

Successful pregnancy relies on dynamic control of cell signaling to achieve uterine receptivity and the necessary biological changes required for endometrial decidualization, embryo implantation, and fetal development. Glucocorticoids are master regulators of intracellular signaling and can directly regulate embryo implantation and endometrial remodeling during murine pregnancy. In immortalized human uterine cells, we have shown that glucocorticoids and estradiol (E2) coregulate thousands of genes. Recently, glucocorticoids and E2 were shown to coregulate the expression of Left-right determination factor 1 (LEFTY1), previously implicated in the regulation of decidualization. To elucidate the molecular mechanism by which glucocorticoids and E2 regulate the expression of LEFTY1, immortalized and primary human endometrial cells were evaluated for gene expression and receptor recruitment to regulatory regions of the LEFTY1 gene. Glucocorticoid administration induced expression of LEFTY1 messenger RNA and protein and recruitment of the glucocorticoid receptor (GR) and activated polymerase 2 to the promoter of LEFTY1. Glucocorticoid-mediated recruitment of GR was dependent on pioneer factors FOXA1 and FOXA2. E2 was found to antagonize glucocorticoid-mediated induction of LEFTY1 by reducing recruitment of GR, FOXA1, FOXA2, and activated polymerase 2 to the LEFTY1 promoter. Gene expression analysis identified several genes whose glucocorticoid-dependent induction required FOXA1 and FOXA2 in endometrial cells. These results suggest a molecular mechanism by which E2 antagonizes GR-dependent induction of specific genes by preventing the recruitment of the pioneer factors FOXA1 and FOXA2 in a physiologically relevant model.

Medroxyprogesterone acetate drives M2 macrophage differentiation toward a phenotype of decidual macrophage

M1 macrophage differentiation plays a crucial role in enhanced inflammation during pregnancy, which may lead to pregnancy complications. Therefore, modulation of macrophage differentiation toward the M2 phenotype is desirable to ensure a successful pregnancy. Medroxyprogesterone acetate (MPA) is a potent progestin with an anti-inflammatory property, but its effect on macrophage differentiation is unknown. This study aimed to examine whether MPA can induce an M2 macrophage differentiation by using the human monocytes cell line THP-1 or primary monocytes. THP-1 cells were primed with phorbol-12-myristate-13 acetate (PMA) to initiate macrophage differentiation. By incubating with MPA, the cells (denoted as MPA-pTHP-1) underwent M2 macrophage differentiation with downregulations of CD11c, IL-1β and TNF-α, and upregulations of CD163 and IL-10; while cells incubated with progesterone (P4) did not show the M2 phenotype. Primary monocytes treated with MPA also had the same M2 phenotype. Moreover, M1 macrophages derived from IFN-γ/LPS-treated THP-1 cells, which had high levels of IL-1b and iNOS, and low levels of IL-10 and IDO, were reversed to the M2 phenotype by the MPA treatment. We also found that the MPA-pTHP-1 promoted the decidualization of endometrial stromal cells and the invasion of trophoblast cells. To mimic conditions of exposure to various pathogens, MPA-pTHP-1 cells were stimulated by different types of TLR ligands. We found they produced lower levels of IL-1β and TNF-α, as well as a higher level of IL-10, compared to untreated cells. Finally, we found the level of phosphorylated ERK in the MPA-pTHP-1 cells was increased, but its IL-10 production was suppressed by either the progesterone/glucocorticoid antagonist (Mifepristone) or MEK inhibitor (U0126). Taken together, MPA could drive monocyte differentiation toward an M2 phenotype that mimics decidual macrophages. This finding holds great potential to combat chronic endometrial inflammation.

Role of Plasminogen Activator Inhibitor Type 1 in Pathologies of Female Reproductive Diseases

Normal pregnancy is a state of hypercoagulability with diminishing fibrinolytic activity, which is mainly caused by an increase of plasminogen activator inhibitor type 1 (PAI-1). PAI-1 is the main inhibitor of plasminogen activators, including tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). In human placentas, PAI-1 is expressed in extravillous interstitial trophoblasts and vascular trophoblasts. During implantation and placentation, PAI-1 is responsible for inhibiting extra cellular matrix (ECM) degradation, thereby causing an inhibition of trophoblasts invasion. In the present study, we have reviewed the literature of various reproductive diseases where PAI-1 plays a role. PAI-1 levels are increased in patients with recurrent pregnancy losses (RPL), preeclampsia, intrauterine growth restriction (IUGR), gestational diabetes mellitus (GDM) in the previous pregnancy, endometriosis and polycystic ovary syndrome (PCOS). In general, an increased expression of PAI-1 in the blood is associated with an increased risk for infertility and a worse pregnancy outcome. GDM and PCOS are related to the genetic role of the 4G/5G polymorphism of PAI-1. This review provides an overview of the current knowledge of the role of PAI-1 in reproductive diseases. PAI-1 represents a promising monitoring biomarker for reproductive diseases and may be a treatment target in the near future.

Human extravillous trophoblast invasion: intrinsic and extrinsic regulation

During the establishment of pregnancy, a human blastocyst implants into the uterine endometrium to facilitate the formation of a functional placenta. Implantation involves the blastocyst adhering to the uterine luminal epithelium before the primitive syncytiotrophoblast and subsequently specialised cells, the extravillous trophoblast (EVT), invade into the decidua in order to engraft and remodel uterine spiral arteries, creating the placental blood supply at the end of the first trimester. Defects in EVT invasion lead to abnormal placentation and thus adverse pregnancy outcomes. The local decidual environment is thought to play a key role in regulating trophoblast invasion. Here we describe the major cell types present in the decidua during the first trimester of pregnancy and review what is known about their regulation of EVT invasion. Overall, the evidence suggests that in a healthy pregnancy almost all cell types in the decidua actively promote EVT invasion and, further, that reduced EVT invasion towards the end of the first trimester is regulated, in part, by the reduced invasive capacity of EVTs shown at this time.

Extranuclear Translocation of High-Mobility Group A1 Reduces the Invasion of Extravillous Trophoblasts Involved in the Pathogenesis of Preeclampsia: New Aspect of High-Mobility Group A1

OBJECTIVE

High-mobility group A1 (HMGA1) protein is known to express in trophoblast; however, the role of migration has not been reported to date. In this study, we investigated the role of HMGA1 on the pathogenesis of preeclampsia using immortalized human trophoblast cell (HTR-8/SVneo).

MATERIALS AND METHODS

We investigated HMGA1 expression in cytotrophoblasts derived from our preeclampsia model mouse, the CD40L mouse, using immunofluorescence. Wound healing and transwell migration assays were also performed using HTR-8/SVneo (extravillous trophoblast) cells transfected with DNA or siRNA of HMGA1. The effect of extranuclear translocation of HMGA1 on the migration of extravillous trophoblastic cells was evaluated using deoxycholic acid (DCA).

RESULTS

HMGA1 was expressed exclusively in the nuclei of trophoblasts derived from control mice; cytoplasmic expression was observed only in CD40L mice with preeclampsia. Furthermore, overexpression of HMGA1 in the nuclei of HTR-8/SVneo cells stimulated cell proliferation and migration. Translocation of nuclear HMGA1 to cytoplasm treated with DCA reduced cell migration.

CONCLUSIONS

Collectively, these findings demonstrate that proper subcellular localization of HMGA1 is important for its function in trophoblast cells, and suggest that aberrant cytoplasmic expression of HMGA1 contributes to the pathogenesis of preeclampsia through impairment of trophoblast migration.

Association between higher expression of interleukin-8 (IL-8) and haplotype -353A/-251A/+678T of IL-8 gene with preeclampsia: A case-control study

Preeclampsia (PE) is a common pregnancy-specific disorder associated with significant maternal and fetal morbidity and mortality worldwide.The present study was performed to investigate the role of a CXC chemokine interleukin-8 (IL-8), in the pathogenesis of PE. IL-8 expression levels were assessed in placental and serum samples from 160 pregnant women with PE (N = 68 severe, 92 mild) and 140 healthy donors.Results from enzyme-linked immunosorbent assay showed that the concentration of serum IL-8 in PE patients (180.27 ± 5.81 ng/L) was significantly higher than that in healthy controls (41.57 ± 5.67 ng/L). Patients with severe PE had even higher serum IL-8 levels. Similar messenger RNA and protein expression patterns of IL-8 in placental tissues were confirmed by quantitative real-time polymerase chain reaction and immunohistochemical assay (N = 30 each in the mild PE, severe PE, and control groups). In addition, single nucleotide polymorphisms of IL-8 gene were detected with polymerase chain reaction-restricted fragment length polymorphism/SSP. The frequency of IL-8-251A allele was significantly higher than that in controls (58.4% vs 48.9%, P < 0.05). The occurrence frequency of haplotype -353A/-251A/+678T (AAT) in PE subjects was 27.2% as compared to 21.9% in the control participants (P < 0.05).Our study reveals that IL-8 expression is positively associated with the severity of PE. Presence of haplotype AAT in pregnant women appears to be a risk factor for PE.

Decidual macrophages: key regulators of vascular remodeling in human pregnancy

Successful remodeling of the uterine spiral arteries is essential for a complication-free pregnancy and is best described in terms of its morphologic features. The molecular mediators and cellular sources of spiral artery remodeling are not known, although a role for uterine leukocytes has been proposed. Immunohistochemical assessment of placental bed biopsies demonstrated uterine NK cells, macrophages, and T lymphocytes in the wall and adventitia of spiral arteries at different stages of remodeling, regardless of the presence of extravillous trophoblast cells. Leukocytes were more prevalent in vessel adventitia than wall, and macrophages were the most abundant leukocyte population. Macrophages, separated from early pregnancy decidua, did not alter extravillous trophoblast cells invasion or vascular smooth muscle cell organization or differentiation status but did induce extracellular matrix breakdown (reduced immunostaining of laminin, P = 0.05; fibronectin, P = 0.02) and were able to phagocytose apoptotic vascular smooth muscle cells. Decidual macrophages were shown to secrete a wide range of cytokines (IL-1β, -2, -4, -5, -6, -8, -10, and -13 and TNF-α), proteases (matrix metalloproteinase-1, -2, -7, -9, and -10), and angiogenic growth factors (angiogenin, keratinocyte growth factor, fibroblast growth factor B, vascular endothelial growth factor A, and angiopoietin-1 and -2). We conclude that spiral artery remodeling involves the coordinated activity of a range of cell types, including extravillous trophoblast cells, decidual uterine NK cells, and macrophages in a carefully, spatiotemporally regulated manner.