Characterization of cytokine production by human term placenta macrophages in vitro

Fetal ezrin expression affects macrophages and regulatory T cells in mouse placental decidua

Ezrin is a cross-linker protein between membrane proteins and cytosolic actin, abundantly expressed in the placenta among the ERM protein family. Ezrin gene knockout mice exhibit fetal growth restriction after gestational day (GD) 15.5. This study aimed to clarify the effect of ezrin on immune cells that influence fetal growth and immune tolerance. Ezrin heterozygous knockout (Ez+/-) mice were interbred, and the gene expressions and immune cell distributions in the placentas of wild-type (Ez+/+) and ezrin knockout (Ez-/-) fetuses were analyzed. IL-6 expression in the placenta of Ez-/- fetuses was significantly higher than in Ez+/+ fetuses at GD 15.5. The mRNA expression of IL-6 in the uterine decidua attached to Ez-/- fetuses was higher compared to that attached to Ez+/+ fetuses but not in the junctional zone and labyrinth. Classical M1 and M2 macrophages in the decidua were analyzed by flow cytometry using CD86 and CD206 as markers. M1 macrophages increased in the decidua attached to Ez-/- mice compared to Ez+/+ mice, while M2 macrophages did not increase. CD4-positive T cells showed a reduction in the decidua attached to Ez-/- fetuses. Further analysis involved the subcutaneous administration of tacrolimus in pregnant Ez+/- mice from GD 8.5 to GD 15.5, which prevented the decrease in fetal body weight and decidual CD4-positive T cells in Ez-/- mice at GD 15.5. These results suggest that impaired expression of fetoplacental-derived ezrin induces inflammatory conditions in the uterine decidua through M1 polarization of macrophages, increased IL-6, and decreased CD4-positive T cells, including Treg cells.

Hsa-miR-3928-3p targets the CCL3/CCR5 axis to induce amniotic epithelial cell senescence involved in labor initiation

INTRODUCTION

Senescence in human amniotic epithelial cells (hAECs) and increased sterile inflammation in the amniotic cavity can lead to the initiation of term labor (TL). We investigated the possible roles of hsa-miR-3928-3p and chemokine ligand 3 (CCL3) in labor initiation and the underlying molecular mechanisms.

METHODS

Microarray chip screening was used to analyse the differential expression of miRNAs in amniotic fluid exosomes from women in TL and term not-in-labor. The GEO and miRWalk databases were used to identify differential genes, and a dual luciferase assay was used to verify the relationship. Reverse transcription quantitative PCR (RT-qPCR) and immunofluorescence were used to determine the expression and localization of CCL3/CCR5 in fetal membranes. RT-qPCR and western blotting were used to detect the expression of CCL3/CCR5 in hAECs with hsa-miR-3928-3p knockdown/overexpression. Cell counting kit 8, flow cytometry, EdU proliferation, senescence-associated β-galactosidase, and enzyme-linked immunosorbent assays were performed to detect the impact of hsa-miR-3928-3p on hAEC function.

RESULTS

hsa-miR-3928-3p expression was downregulated in TL. CCL3 (macrophage inflammatory protein-1α) was identified as a differentially expressed target gene. hsa-miR-3928-3p targeted the 3' UTR of CCL3. Downregulation of hsa-miR-3928-3p expression increased CCL3 expression. CCL3, via its CCR5 receptor, decreased the proliferation, but increased the senescence, apoptosis rate, secretion of inflammatory factors (IL-8, TNF-α, and IL-6), and expression of senescence-associated protein p21 in hAECs.

DISCUSSION

hsa-miR-3928-3p negatively regulates CCL3, promoting hAEC senescence through the CCL3-CCR5 axis and inducing signals for labor initiation. These findings provide novel insights for labor initiation in clinical settings.

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.

A pivotal role for the IL-1β and the inflammasome in preterm labor

During labor, monocytes infiltrate massively the myometrium and differentiate into macrophages secreting high levels of reactive oxygen species and of pro-inflammatory cytokines (i.e. IL-1β), leading to myometrial contraction. Although IL-1β is clearly implicated in labor, its function and that of the inflammasome complex that cleaves the cytokine in its active form, has never been studied on steps preceding contraction. In this work, we used our model of lipopolysaccharide-induced preterm labor to highlight their role. We demonstrated that IL-1β was secreted by the human myometrium during labor or in presence of infection and was essential for myometrial efficient contractions as its blockage with an IL-1 receptor antagonist (Anakinra) or a neutralizing antibody completely inhibited the induced contractions. We evaluated the implication of the inflammasome on myometrial contractions and differentiation stages of labor onset. We showed that the effects of macrophage-released IL-1β in myometrial cell transactivation were blocked by inhibition of the inflammasome, suggesting that the inflammasome by producing IL-1β was essential in macrophage/myocyte crosstalk during labor. These findings provide novel innovative approaches in the management of preterm labor, specifically the use of an inflammasome inhibitor to block the precursor stages of labor before the acquisition of the contractile phenotype.

First-trimester urinary extracellular vesicles as predictors of preterm birth: an insight into immune programming

Background: The programming of innate and adaptive immunity plays a pivotal role in determining the course of pregnancy, leading to either normal term birth (TB) or preterm birth (PB) through the modulation of macrophage (M1/M2) differentiation. Extracellular vesicles (EVs) in maternal blood, harboring a repertoire of physiological and pathological messengers, are integral players in pregnancy outcomes. It is unknown whether urinary EVs (UEVs) could serve as a non-invasive mechanistic biomarker for predicting PB. Methods: This study investigated first-trimester UEVs carrying M1 messengers with altered immune programming, aiming to discern their correlation to subsequent PB. A birth cohort comprising 501 pregnant women, with 40 women experiencing PB matched to 40 women experiencing TB on the same day, was examined. First-trimester UEVs were isolated for the quantification of immune mediators. Additionally, we evaluated the UEV modulation of "trained immunity" on macrophage and lymphocyte differentiations, including mRNA expression profiles, and chromatin activation modification at histone 3 lysine 4 trimethylation (H3K4me3). Results: We found a significant elevation (p < 0.05) in the particles of UEVs bearing characteristic exosome markers (CD9/CD63/CD81/syntenin) during the first trimester of pregnancy compared to non-pregnant samples. Furthermore, UEVs from PB demonstrated significantly heightened levels of MCP-1 (p = 0.003), IL-6 (p = 0.041), IL-17A (p = 0.007), IP-10 (p = 0.036), TNFα (p = 0.004), IL-12 (p = 0.045), and IFNγ (p = 0.030) relative to those from TB, indicative of altered M1 and Th17 differentiation. Notably, MCP-1 (>174 pg/mL) exhibited a sensitivity of 71.9% and specificity of 64.6%, and MCP-1 (>174 pg/mL) and IFNγ (>8.7 pg/mL) provided a higher sensitivity (84.6%) of predicting PB and moderate specificity of 66.7%. Subsequent investigations showed that UEVs from TB exerted a significant suppression of M1 differentiation (iNOS expression) and Th17 differentiation (RORrT expression) compared to those of PB. Conversely, UEVs derived from PB induced a significantly higher expression of chromatin modification at H3K4me3 with higher production of IL-8 and TNFα cytokines (p < 0.001). Implications: This pioneering study provides critical evidence for the early detection of altered M1 and Th17 responses within UEVs as a predictor of PB and early modulation of altered M1 and Th17 polarization associated with better T-cell regulatory differentiation as a potential prevention of subsequent PB.

Leptin-Mediated Induction of IL-6 Expression in Hofbauer Cells Contributes to Preeclampsia Pathogenesis

Leptin plays a crucial role in regulating energy homoeostasis, neuroendocrine function, metabolism, and immune and inflammatory responses. The adipose tissue is a main source of leptin, but during pregnancy, leptin is also secreted primarily by the placenta. Circulating leptin levels peak during the second trimester of human pregnancy and fall after labor. Several studies indicated a strong association between elevated placental leptin levels and preeclampsia (PE) pathogenesis and elevated serum interleukin-6 (IL-6) levels in PE patients. Therefore, we hypothesized that a local increase in placental leptin production induces IL-6 production in Hofbauer cells (HBCs) to contribute to PE-associated inflammation. We first investigated HBCs-specific IL-6 and leptin receptor (LEPR) expression and compared their immunoreactivity in PE vs. gestational age-matched control placentas. Subsequently, we examined the in vitro regulation of IL-6 as well as the phosphorylation levels of intracellular signaling proteins STAT3, STAT5, NF-κB, and ERK1/2 by increasing recombinant human leptin concentrations (10 to 1000 ng/mL) in primary cultured HBCs. Lastly, HBC cultures were incubated with leptin ± specific inhibitors of STAT3 or STAT5, or p65 NF-κB or ERK1/2 MAPK signaling cascades to determine relevant cascade(s) involved in leptin-mediated IL-6 regulation. Immunohistochemistry revealed ~three- and ~five-fold increases in IL-6 and LEPR expression, respectively, in HBCs from PE placentas. In vitro analysis indicated that leptin treatment in HBCs stimulate IL-6 in a concentration-dependent manner both at the transcriptional and secretory levels (p < 0.05). Moreover, leptin-treated HBC cultures displayed significantly increased phosphorylation levels of STAT5, p65 NF-κB, and ERK1/2 MAPK and pre-incubation of HBCs with a specific ERK1/2 MAPK inhibitor blocked leptin-induced IL-6 expression. Our in situ results show that HBCs contribute to the pathogenesis of PE by elevating IL-6 expression, and in vitro results indicate that induction of IL-6 expression in HBCs is primarily leptin-mediated. While HBCs display an anti-inflammatory phenotype in normal placentas, elevated levels of leptin may transform HBCs into a pro-inflammatory phenotype by activating ERK1/2 MAPK to augment IL-6 expression.

Placental macrophage responses to viral and bacterial ligands and the influence of fetal sex

Bacterial and viral infections of the placenta are associated with inflammation and adverse pregnancy outcomes. Hofbauer cells (HBCs) are fetal-origin macrophages in the placenta, proposed to protect the fetus from vertical pathogen transmission. We performed quantitative proteomics on term HBCs under resting conditions and following exposure to bacterial and viral pathogen-associated molecular patterns (PAMPs), and investigated the contribution of fetal sex. Resting HBCs expressed proteins pertinent to macrophage function, including chemokines, cytokines, Toll-like receptors, and major histocompatibility complex class I and II molecules. HBCs mounted divergent responses to bacterial versus viral PAMPs but exhibited protein expression changes suggestive of a more pro-inflammatory phenotype. A comparison between male and female HBCs showed that the latter mounted a stronger and wider response. Here, we provide a comprehensive understanding of the sex-dependent responses of placental macrophages to infectious triggers, which were primarily associated with lipid metabolism in males and cytoskeleton organization in females.

Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery

At the end of gestation, the cervical tissue changes profoundly. As a result of these changes, the uterine cervix becomes soft and vulnerable to dilation. The process occurring in the cervical tissue can be described as cervical ripening. The ripening is a process derivative of enzymatic breakdown and inflammatory response. Therefore, it is apparent that cervical remodeling is a derivative of the reactions mediated by multiple factors such as hormones, prostaglandins, nitric oxide, and inflammatory cytokines. However, despite the research carried out over the years, the cellular pathways responsible for regulating this process are still poorly understood. A comprehensive understanding of the entire process of cervical ripening seems crucial in the context of labor induction. Greater knowledge could provide us with the means to help women who suffer from dysfunctional labor. The overall objective of this review is to present the current understanding of cervical ripening in terms of molecular regulation and cell signaling.

The Expression of IL-1β Correlates with the Expression of Galectin-3 in the Tissue at the Maternal-Fetal Interface during the Term and Preterm Labor

The inflammatory processes that occur at the maternal−fetal interface are considered one of the factors that are responsible for preterm birth. The pro-inflammatory roles of the Gal-3-induced activation of NLRP3 inflammasome and the consecutive production of IL-1β have been described in several acute and chronic inflammatory diseases, but the role of this inflammatory axis in parturition has not been studied. The aim of this study was to analyze the protein expression of Gal-3, NLRP3, and IL-1β in the decidua, villi, and fetal membranes, and to analyze their mutual correlation and correlation with the clinical parameters of inflammation in preterm birth (PTB) and term birth (TB). The study included 40 women that underwent a preterm birth (gestational age of 25.0−36.6) and histological chorioamnionitis (PTB) and control subjects, 22 women that underwent a term birth (gestational age of 37.0−41.6) without histological chorioamnionitis (TB). An analysis of the tissue sections that were stained with anti- Gal-3, -NLRP3, and -IL-1β antibodies was assessed by three independent investigators. The expression levels of Gal-3 and IL-1β were significantly higher (p < 0.001) in the decidua, villi, and fetal membranes in the PTB group when they compared to those of the TB group, while there was no difference in the expression of NLRP3. A further analysis revealed that there was no correlation between the protein expression of NLRP3 and the expression of Gal-3 and IL-1β, but there was a correlation between the expression of Gal-3 and IL-1β in decidua (R = 0.401; p = 0.008), villi (R = 0.301; p = 0.042) and the fetal membranes (R = 0.428; p = 0.002) in both of the groups, PTB and TB. In addition, the expression of Gal-3 and IL-1β in decidua and the fetal membranes was in correlation with the parameters of inflammation in the maternal and fetal blood (C-reactive protein, leukocyte number, and fibrinogen). The strong correlation between the expression of Gal-3 and IL-1β in the placental and fetal tissues during labor indicates that Gal-3 may participate in the regulation of the inflammatory processes in the placenta, leading to increased production of IL-1β, a cytokine that plays the main role in both term and preterm birth.

Impact of Oxidative Stress on Molecular Mechanisms of Cervical Ripening in Pregnant Women

Uterine cervix is one of the essential factors in labor and maintaining the proper course of pregnancy. During the last days of gestation, the cervix undergoes extensive changes manifested by transformation from a tight and rigid to one that is soft and able to dilate. These changes can be summarized as “cervical ripening”. Changes in the cervical tissue can be referred to as remodeling of the extracellular matrix. The entire process is the result of a close relationship between biochemical and molecular pathways, which is strictly controlled by inflammatory and endocrine factors. When the production of reactive oxygen species exceeds the antioxidant capacity, oxidative stress occurs. A physiologic increase of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is observed through pregnancy. ROS play important roles as second messengers in many intracellular signaling cascades contributing to the course of gestation. This review considers their involvement in the cervical ripening process, emphasizing the molecular and biochemical pathways and the clinical implications.

Spontaneous preterm birth: Involvement of multiple feto-maternal tissues and organ systems, differing mechanisms, and pathways

Survivors of preterm birth struggle with multitudes of disabilities due to improper in utero programming of various tissues and organ systems contributing to adult-onset diseases at a very early stage of their lives. Therefore, the persistent rates of low birth weight (birth weight < 2,500 grams), as well as rates of neonatal and maternal morbidities and mortalities, need to be addressed. Active research throughout the years has provided us with multiple theories regarding the risk factors, initiators, biomarkers, and clinical manifestations of spontaneous preterm birth. Fetal organs, like the placenta and fetal membranes, and maternal tissues and organs, like the decidua, myometrium, and cervix, have all been shown to uniquely respond to specific exogenous or endogenous risk factors. These uniquely contribute to dynamic changes at the molecular and cellular levels to effect preterm labor pathways leading to delivery. Multiple intervention targets in these different tissues and organs have been successfully tested in preclinical trials to reduce the individual impacts on promoting preterm birth. However, these preclinical trial data have not been effectively translated into developing biomarkers of high-risk individuals for an early diagnosis of the disease. This becomes more evident when examining the current global rate of preterm birth, which remains staggeringly high despite years of research. We postulate that studying each tissue and organ in silos, as how the majority of research has been conducted in the past years, is unlikely to address the network interaction between various systems leading to a synchronized activity during either term or preterm labor and delivery. To address current limitations, this review proposes an integrated approach to studying various tissues and organs involved in the maintenance of normal pregnancy, promotion of normal parturition, and more importantly, contributions towards preterm birth. We also stress the need for biological models that allows for concomitant observation and analysis of interactions, rather than focusing on these tissues and organ in silos.

Preterm Birth in Women With HIV: The Role of the Placenta

Maternal HIV infection is associated with an increased risk of preterm birth (PTB). However, the mechanisms underlying this increased risk in women with HIV remain poorly understood. In this regard, it is well-established that labor is an inflammatory process and premature activation of the pro-inflammatory signals (associated with labor) can result in preterm labor which can subsequently lead to PTB. HIV infection is known to cause severe immune dysregulation within its host characterized by altered immune profiles, chronic inflammation and eventually, the progressive failure of the immune system. The human placenta comprises different immune cell subsets, some of which play an important role during pregnancy including participating in the inflammatory processes that accompany labor. It is therefore plausible that HIV/antiretroviral therapy (ART)-associated immune dysregulation within the placental microenvironment may underlie the increased risk of PTB reported in women with HIV. Here, we review evidence from studies that point toward the placental origin of spontaneous PTB and discuss possible ways maternal HIV infection and/or ART could increase this risk. We focus on key cellular players in the maternal decidua including natural killer cells, CD4+ T cells including CD4+ regulatory T cells, CD8+ T cells as well as macrophages.

Placental Macrophage (Hofbauer Cell) Responses to Infection During Pregnancy: A Systematic Scoping Review

BACKGROUND

Congenital infection of the fetus via trans-placental passage of pathogens can result in severe morbidity and mortality. Even without transmission to the fetus, infection of the placenta itself is associated with pregnancy complications including pregnancy loss and preterm birth. Placental macrophages, also termed Hofbauer cells (HBCs), are fetal-origin macrophages residing in the placenta that are likely involved in responding to placental infection and protection of the developing fetus. As HBCs are the only immune cell present in the villous placenta, they represent one of the final opportunities for control of infection and prevention of passage to the developing fetus.

OBJECTIVE AND RATIONALE

The objective of this review was to provide a systematic overview of the literature regarding HBC responses during infection in pregnancy, including responses to viral, bacterial, and parasitic pathogens.

METHODS

PubMed and Scopus were searched on May 20th, 2021, with no limit on publication date, to identify all papers that have studied placental macrophages/Hofbauer cells in the context of infection. The following search strategy was utilized: (hofbauer* OR "hofbauer cells" OR "hofbauer cell" OR "placental macrophage" OR "placental macrophages") AND [infect* OR virus OR viral OR bacteri* OR parasite* OR pathogen* OR LPS OR "poly(i:c)" OR toxoplasm* OR microb* OR HIV)].

OUTCOMES

86 studies were identified for review. This included those that investigated HBCs in placentas from pregnancies complicated by maternal infection and in vitro studies investigating HBC responses to pathogens or Pathogen-Associated Molecular Patterns (PAMPs). HBCs can be infected by a variety of pathogens, and HBC hyperplasia was a common observation. HBCs respond to pathogen infection and PAMPs by altering their transcriptional, translational and secretion profiles. Co-culture investigations demonstrate that they can replicate and transmit pathogens to other cells. In other cases, they may eliminate the pathogen through a variety of mechanisms including phagocytosis, cytokine-mediated pathogen elimination, release of macrophage extracellular traps and HBC-antibody-mediated neutralization. HBC responses differ across gestation and may be influenced by pre-existing immunity. Clinical information, including gestational age at infection, gestational age of the samples, mode of sample collection and pregnancy outcome were missing for the majority of studies.

The Fetal-Maternal Immune Interface in Uterus Transplantation

Uterus transplants (UTxs) have been performed worldwide. Overall frequencies have been low, but globally initiated UTx programs are expected to increase clinical implementation. The uterus constitutes a unique immunological environment with specific features of tissue renewal and a receptive endometrium. Decidual immune cells facilitate embryo implantation and placenta development. Although UTx adds to the complexity of immunity during pregnancy and transplantation, the procedure provides a unique clinical and experimental model. We posit that understanding the distinct immunological properties at the interface of the transplanted uterus, the fetus and maternal circulation might provide valuable novel insights while improving outcomes for UTx. Here, we discuss immunological challenges and opportunities of UTx affecting mother, pregnancy and healthy livebirths.

The determinant role of IL-6 in the establishment of inflammation leading to spontaneous preterm birth

Preterm birth (PTB) and its consequences are a major public health concern as preterm delivery is the main cause of mortality and morbidity at birth. There are many causes of PTB, but inflammation is undeniably associated with the process of premature childbirth and fetal injury. At present, treatments clinically available mostly involve attempt to arrest contractions (tocolytics) but do not directly address upstream maternal inflammation on development of the fetus. One of the possible solutions may lie in the modulation of inflammatory mediators. Of the many pro-inflammatory cytokines involved in the induction of PTB, IL-6 stands out for its pleiotropic effects and its involvement in both acute and chronic inflammation. Here, we provide a detailed review of the effects of IL-6 on the timing of childbirth, its occurrence during PTB and its indissociable roles with associated fetal tissue damage.

Maternal stress in relation to sex-specific expression of placental genes involved in nutrient transport, oxygen tension, immune response, and the glucocorticoid barrier

INTRODUCTION

Murine models provide evidence that maternal stress during pregnancy can influence placenta morphology and function, including altered expression of genes involved in the maintenance and progression of pregnancy and fetal development. Corresponding research evaluating the impact of maternal stress on placental gene expression in humans is limited. We examined maternal stress in relation to placental expression of 17 candidate genes in a community-based sample.

METHODS

Participants included 60 mother-newborn pairs enrolled in the PRogramming of Intergenerational Stress Mechanisms pregnancy cohort based at the Mount Sinai Hospital in New York City. Placentas were collected immediately following delivery and gene expression was measured using a qPCR-based platform. Maternal experiences of traumatic and non-traumatic stress were measured using the Life Stressor Checklist-Revised (LSC-R) administered during a mid-pregnancy interview. We used multivariable linear regression to examine associations between LSC-R scores and expression of each gene in separate models in the sample overall and stratified by fetal sex.

RESULTS

Higher maternal stress was associated with significantly increased placental expression of the nutrient sensor gene OGT, the glucose transporter gene GLUT1, and the hypoxia sensor gene HIF3A. In models stratified by fetal sex, significant associations remained only among males.

DISCUSSION

This study represents one of the most comprehensive examinations of maternal lifetime traumatic and non-traumatic stress in relation to placental gene expression in human tissue. Our findings support that maternal stress may alter sex-specific placental expression of genes involved in critical developmental processes.

Two patterns of cytokine production by placental macrophages

INTRODUCTION

Macrophages participate in the regulation immune and morphogenetic events in the placenta. However, these roles remain unclear for placental macrophages (Hofbauer cells). The aims of this study were to characterize the consecutive steps of cytokine production (intracellular synthesis and secretion) in placental macrophages in early and late gestation and to compare the secretory profiles of placental macrophages and villous tissue.

METHODS

Macrophages and villous tissue were isolated from placentas obtained from normal pregnancies at either 9-12 or 38-40 weeks of gestation. Intracellular cytokines were determined by flow cytometry after staining with monoclonal antibodies. Secreted cytokines were quantified by cytometric bead array and ELISA.

RESULTS

Two patterns of cytokine production were revealed in placental macrophages. Cytokines in the first group (IL-1, IL-6, IL-8, IL-10, TNFα) demonstrated low basal production and were stimulated by bacterial endotoxin. Cytokines in the second group (IL-11, IL-17A, IL-17F, TGF-β, VEGF) were characterized by constitutive production and did not respond to stimulation. Gestational age-dependent changes were observed: basal secretion of TNFα and IL-8 increased whereas IL-11 and IL-17 secretion decreased in third-trimester macrophages compared with the first-trimester cells. Comparison of cytokine production at the cellular and tissue levels suggested the contribution of the placental macrophages both in intraplacental and extraplacental cytokine production.

DISCUSSION

It would be safe to assume that the two patterns of cytokine production, revealed in our study, correspond to two regulatory roles of placental macrophages: "immune" and "morphogenetic". The inflammatory phenotype of macrophages is attenuated in early gestation and increases with the progression of pregnancy. The cytokines of the first group supposedly contribute to both local and extraplacental levels, whereas the cytokine effects of the second group are more likely confined to the placental tissue.

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.

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.

Expression of Matrix Metalloproteinases in the Mouse Uterus and Human Myometrium During Pregnancy, Labor, and Preterm Labor

BACKGROUND

Uterine extracellular matrix (ECM) remodeling occurs throughout pregnancy and at parturition. Imbalanced availability of key mediators in ECM degradation, namely, matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), is implicated in the pathogenesis of preterm labor (PTL).

OBJECTIVES

Examine the expression of MMPs and their inhibitors TIMPs in (a) the mouse uterus throughout normal gestation, at labor, and during inflammation-induced PTL and (b) the human term and preterm myometrium.

METHODS

The expression of Mmp-2/9/3/10 and Timp-1/2 was determined in the uterus of C57BL/6 mice (n = 6/group) during pregnancy (on days (d) 5, 8, 12, 15, 17, and 18), at normal labor, and during lipopolysaccharide-induced PTL (n = 6/group). The expression of MMP-10 and TIMP-1 was determined in human term and preterm myometrium before the onset of labor (TNL, n = 7; PTNL, n = 7) and during active labor (TL, n = 8; PTL, n = 8). Gene expression and tissue localization were assessed by quantitative polymerase chain reaction and immunohistochemistry, respectively.

RESULTS

Mmp-10 was higher during murine labor (53-fold vs early pregnancy) in contrast to Mmp-2/3/9 and Timp-1, the expression of which reached a nadir at labor ( P < .001 vs d5 [ Mmp-2/ 9] or P < .05 vs d8 [ Mmp-3 and Timp-1]). The Mmp-3/10 and Timp-1 were localized to the uterine epithelium and stroma/myometrium. In the human myometrium, TIMP-1 messenger RNA was higher and MMP-10 was lower in TL versus TNL ( P < .05), PTL ( P < .001), and PTNL ( P < .001). MMP-10 and TIMP-1 were localized to the myometrial smooth muscle cells, interstitial fibroblasts, and inflammatory cells.

CONCLUSIONS

These data implicate MMP-3, TIMP-1, and MMP-10 in the uterine ECM remodeling during physiological and pathological parturition.

Diversity of progesterone action on lipopolysaccharide-induced expression changes in cultured human cervical fibroblasts according to inflammation and treatment timing

PROBLEM

The effectiveness of progesterone (P4) treatment for preventing preterm births is unclear. Its effects on the uterine cervix were tested using cultured human uterine cervical fibroblasts (UCFs).

METHOD OF STUDY

UCFs were incubated with lipopolysaccharide (LPS) in the presence or absence of P4 under various conditions. mRNA was subjected to PCR arrays and real-time RT-PCR to assess IL-6, IL-8, IL-1beta, PTGS2, MMP-1, and CXCL10 expression.

RESULTS

When exposed to a high-LPS concentration (2.0 μg/mL), expression of these genes was not suppressed by simultaneous P4 (1.0 μmol/L) treatment, but it was significantly inhibited when P4 was administered 1 hour prior to LPS, with the exception of the chemokines IL-8 and CXCL10. Expression of all genes was restricted by P4 under low-level LPS (0.2 μg/mL) stimulation, especially when administered prior to LPS treatment.

CONCLUSION

These data suggest that early or prophylactic P4 administration is an effective and important measure for reducing preterm birth risk.

Coordinated expression of TNFα- and VEGF-mediated signaling components by placental macrophages in early and late pregnancy

INTRODUCTION

Mononuclear phagocytes are thought to significantly contribute to cytokine regulation at the maternal-foetal interface, but the role of placental macrophages has been poorly investigated. TNFα and VEGF were demonstrated to have regulatory effects on basic structures of the placenta, particularly the trophoblast and blood vessels. The aims of this study were to determine the expression of TNFα, VEGF and related receptors in placental macrophages, and how does the participation of placental macrophages alter with gestational age in TNFα- and VEGF-mediated signaling.

METHODS

Macrophages were isolated from placental villous tissue from normal pregnancies at either 9-12 or 38-40 weeks gestation. Cell surface receptors (TNFR1, TNFR2, VEGFR1, and VEGFR2) and intracellular TNFα and VEGF were quantified by flow cytometry after antibody staining. Basal and stimulated secretion of both cytokines and soluble TNF receptors was quantified by cytometric bead arrays. Secreted VEGFR1 was measured by ELISA.

RESULTS

The expression of TNFR1 and VEGFR1 was remarkably variable and did not change from first to third trimester. There was minimal basal TNFα production in the placental macrophages, but nearly all cells in the population produced VEGF. TNFα and VEGF secretion increased with gestational age accompanied by decreased secretion of the antagonists sTNFR1 and sVEGFR. Macrophages isolated from early term placentas were less effective in responding to bacterial endotoxin. Lipopolysaccharide induced increases in the secretion of TNFα, TNFR1, TNFR2, and VEGFR1 but did not affect the production of VEGF. In late pregnancy, a significant correlation was observed between TNFR1 and VEGFR1.

DISCUSSION

The progression of pregnancy is accompanied by the concerted increase in TNFα and VEGF secretion and decrease in the production of their soluble receptors, but the expression of cell surface receptors does not depend on gestational age. The observed patterns of basal and stimulated expression of TNFα and VEGF may reflect the dual immune and morphogenetic roles of placental macrophages in gestation. Compatible patterns of TNFR1 and VEGFR1 expression suggest common regulatory pathways for these receptors.

Role of decidual CD14(+) macrophages in the homeostasis of maternal-fetal interface and the differentiation capacity of the cells during pregnancy and parturition

OBJECTIVE

Decidual macrophages (dMΦs) have been implicated in fetal tolerance, but little information is known regarding their differentiation capacity and interactions with T cells. The present study aimed to investigate the immunological characteristics of dMΦs at mid and term pregnancy.

METHODS

The dMΦs were analyzed for their phenotypes and cytokine production by flow cytometry and ELISA, respectively. The transendothelial trafficking model was implemented to allow the dMΦs to differentiate. The differentiated cells from dMΦs were also measured for their phenotypes and cytokine production with same methods. The capacity of dMΦs or the differentiated cells from dMΦs to stimulate allogeneic T lymphocyte proliferation was evaluated by T lymphocyte stimulation assays. T cell differentiation was determined by flow cytometry.

RESULTS

The dMΦs in the mid-pregnancy (Mid-dMΦs) resembled the M2 phenotype. The differentiated cells from Mid-dMΦs had little stimulatory capacity on T cell proliferation and favored regulatory T cell differentiation. The dMΦs at term differentiated into dendritic (DC)-like cells, stimulating T cell activation, proliferation, and differentiation into IFN-γ-producing T cellsdecidual

CONCLUSIONS

The present study suggests that the differences in phenotypes and cytokine production between Mid- and Term-dMΦs relate to their different roles in the homeostasis of the maternal-fetal interface. Mid-dMΦs differentiate into DC-like cells with immunosuppressive properties, playing an important role in maintaining homeostasis required for a successful pregnancy. Term-dMΦs differentiate into DC-like cells with immunostimulatory properties, likely involved in the activation of labor. The different differentiation capacities of dMΦs in the varied pregnancy stages may be due to the placental microenvironment.

A critical role of interleukin-1 in preterm labor

Preterm birth (PTB) is a leading cause of neonatal mortality and morbidity worldwide, and represents a heavy economic and social burden. Despite its broad etiology, PTB has been firmly linked to inflammatory processes. Pro-inflammatory cytokines are produced in gestational tissues in response to stressors and can prematurely induce uterine activation, which precedes the onset of preterm labor. Of all cytokines implicated, interleukin (IL)-1 has been largely studied, revealing a central role in preterm labor. However, currently approved IL-1-targeting therapies have failed to show expected efficacy in pre-clinical studies of preterm labor. Herein, we (a) summarize animal and human studies in which IL-1 or IL-1-targeting therapeutics are implicated with preterm labor, (b) focus on novel IL-1-targeting therapies and diagnostic tests, and (c) develop the case for commercialization and translation means to hasten their development.

Immune cells in term and preterm labor

Labor resembles an inflammatory response that includes secretion of cytokines/chemokines by resident and infiltrating immune cells into reproductive tissues and the maternal/fetal interface. Untimely activation of these inflammatory pathways leads to preterm labor, which can result in preterm birth. Preterm birth is a major determinant of neonatal mortality and morbidity; therefore, the elucidation of the process of labor at a cellular and molecular level is essential for understanding the pathophysiology of preterm labor. Here, we summarize the role of innate and adaptive immune cells in the physiological or pathological activation of labor. We review published literature regarding the role of innate and adaptive immune cells in the cervix, myometrium, fetal membranes, decidua and the fetus in late pregnancy and labor at term and preterm. Accumulating evidence suggests that innate immune cells (neutrophils, macrophages and mast cells) mediate the process of labor by releasing pro-inflammatory factors such as cytokines, chemokines and matrix metalloproteinases. Adaptive immune cells (T-cell subsets and B cells) participate in the maintenance of fetomaternal tolerance during pregnancy, and an alteration in their function or abundance may lead to labor at term or preterm. Also, immune cells that bridge the innate and adaptive immune systems (natural killer T (NKT) cells and dendritic cells (DCs)) seem to participate in the pathophysiology of preterm labor. In conclusion, a balance between innate and adaptive immune cells is required in order to sustain pregnancy; an alteration of this balance will lead to labor at term or preterm.

Effect of factors produced by the placenta on cytokine secretion by THP-1 cells cultured on a 3D scaffold

We compared the effects of soluble products from the placenta obtained from women with normal pregnancy and pregnancy complicated by preeclampsia on cytokine secretion by THP-1 cells cultured on a 3D Matrigel scaffold. In the presence of soluble products from all placentas, the cells actively secreted IL-8, MCP-1, and soluble forms of CD14, TNFRI, and TNFRII receptors. Secretion of VEGF was below the spontaneous level. Secretion of IL-6 by THP-1 cells after incubation with soluble products of the placentas obtained during weeks 9-11 of physiological pregnancy and 38-39 of pregnancy complicated by preeclampsia surpassed the spontaneous level. In the presence of soluble factors of trimester I placentas, secretion of IL-6 and soluble form of TNFRI receptor was higher than in the presence of trimester III placental factors. Secretion of IL-6 by THP-1 cells was higher, while secretion of soluble TNFRII receptor was lower in the presence of placentas from women with preeclampsia in comparison with physiological pregnancy.

Aberrant placental immune parameters in the feline immunodeficiency virus (FIV)-infected cat suggest virus-induced changes in T cell function

Background

Immune activity during pregnancy must be tightly regulated to ensure successful pregnancy. This regulation includes the suppression of inflammatory activity that could target the semi-allogeneic fetus. Tregs are immunosuppressive; Th17 cells are pro-inflammatory. A precise balance in the two cell populations is critical to pregnancy maintenance, while dysregulation in this balance accompanies compromised pregnancy in humans and mice. FIV is known to target Tregs preferentially in the infected cat. Therefore, it may be hypothesized that FIV infection alters the placental Treg/Th17 cell balance resulting in aberrant immunomodulator expression by these cells and consequent pregnancy perturbation.

Methods

RNA was purified from random sections of whole placental tissues collected from both uninfected and FIV-infected queens at early pregnancy, including tissues from viable and nonviable fetuses. Real time qPCR was performed to quantify expression of intranuclear markers of Tregs (FoxP3) and Th17 cells (RORγ); cytokine products of Tregs (IL-10 and TGF-β), Th17 cells (IL-2, IL-6, and IL-17a), and macrophages (IL-1β); and the FIV gag gene. Pairwise comparisons were made to evaluate coexpression patterns between the cytokines and between the cytokines and the virus.

Results

Both FoxP3 and RORγ were reduced in placentas of infected animals. Neither infection status nor fetal viability affected placental expression of IL-1β. However, fetal nonviability was associated with reduced levels of all other cytokines. Infection and fetal nonviability impacted coexpression of various cytokine pairs. No obvious bias toward Treg or Th17 cells was observed.

Conclusions

FIV infection coupled with fetal nonviability alters expression patterns of T cell cytokines. These data suggest that functionally altered placental T cell leukocyte populations may occur in the infected queen and possibly contribute to fetal nonviability.

Comparative phenotypic characterization of human cord blood monocytes and placental macrophages at term

The expression of surface molecules in cord blood monocytes and placental macrophages was studied using flow cytometry. When compared with monocytes, macrophages presented a decrease in HLA-DR and LAP/TGF-β1 levels and increased expression of alternative activation markers, especially CD206. No difference in the production of the apoptotic factors TRAIL and TWEAK was observed, whereas the levels of cytokine receptors in monocytes were significantly higher than in macrophages. Most remarkable was the difference in the expression of IL-17 and TNFα receptors. A strong correlation between VEGF and TNFα receptors was revealed in both cell populations. The results obtained in this study provide antigenic phenotypes for two related cell populations and outline the feasible functional alterations during tissue macrophage differentiation.

Evidence for a role for the adaptive immune response in human term parturition

PROBLEM

Spontaneous labor at term involves leukocyte recruitment and infiltration into the choriodecidua; yet, characterization of these leukocytes and their immunological mediators is incomplete. The purpose of this study was to characterize the immunophenotype of choriodecidual leukocytes as well as the expression of inflammatory mediators in human spontaneous parturition at term.

METHOD OF STUDY

Choriodecidual leukocytes were analyzed by FACS, immunohistochemistry, and RT-PCR in three different groups: (i) preterm gestation delivered for medical indications without labor; (ii) term pregnancy without labor; and (iii) term pregnancy after spontaneous labor.

RESULTS

Two T-cell subsets of memory-like T cells (CD3(+) CD4(+) CD45RO(+) and CD3(+) CD4(-) CD8(-) CD45RO(+) cells) were identified in the choriodecidua of women who had spontaneous labor. Evidence for an extensive immune signaling network composed of chemokines (CXCL8 and CXCL10), chemokine receptors (CXCR1-3), cytokines (IL-1β and TNF-α), cell adhesion molecules, and MMP-9 was identified in these cells during spontaneous labor at term.

CONCLUSIONS

The influx of memory-like T cells in the choriodecidua and the evidence that they are active by producing chemokines and cytokines, and expressing chemokine receptors, cell adhesion molecules, and a matrix-degrading enzyme provides support for the participation of the adaptive immune system in the mechanisms of spontaneous parturition at term.

The presence of maternal asthma during pregnancy suppresses the placental pro-inflammatory response to an immune challenge in vitro

The mechanisms that contribute to adverse outcomes for the neonate in pregnancies complicated by asthma may be mediated via changes in placental immune function. This study was designed to determine whether the presence of maternal asthma during pregnancy alters the placental pro-inflammatory immune response in vitro. A prospective cohort study of women with asthma (n = 22) and control (n = 11) subjects had placentae collected immediately after delivery. Placental explants were exposed to an immune challenge, lipopolysaccharide, in the presence and absence of cortisol in vitro. Cytokines, glucocorticoid receptor α (GR α) and p38 MAPK protein were measured. Placentae of control pregnancies had an increase in pro-inflammatory cytokine production over a 24 h period. Placentae from pregnancies complicated by maternal asthma had a reduced pro-inflammatory cytokine response to an immune challenge relative to the controls especially in relation to the production of interleukin (IL)-1β and TNFα regardless of fetal sex. Cortisol inhibition of placental cytokine production was dependent on timing of exposure, fetal sex and presence and absence of asthma. GRα and p38 MAPK protein expression did not appear to contribute to differences in response to endotoxin or cortisol. Maternal asthma during pregnancy induces a hyposensitive inflammatory state in the placenta which is regulated by cortisol in a sexually dimorphic manner.