Circulating cytokines and alarmins associated with placental inflammation in high-risk pregnancies

Understanding a Potential Role for the NLRP3 Inflammasome in Placenta-Mediated Pregnancy Complications

Stillbirth affects approximately 2 million pregnancies annually and is closely linked to placental dysfunction, which may also present clinically as foetal growth restriction (FGR) or pre-eclampsia (PE). Placental dysfunction can arise from a range of insults, including the inflammatory conditions villitis of unknown aetiology (VUE) and chronic histiocytic intervillositis (CHI). Despite ample research regarding the pathophysiology of placental dysfunction, the literature surrounding placental inflammation is more limited, with no currently established treatments. In the absence of infection, placental inflammation is hypothesised to be stimulated by damage-associated molecular patterns (DAMPs), known as sterile inflammation. The NLRP3 inflammasome, a protein scaffold that unites within the cytosol of cells, is a proposed contributor. The NLRP3 inflammasome is dysregulated in numerous diseases and has shown evidence of activation through the sterile inflammatory pathway via DAMPs. Studies have demonstrated the upregulation of the NLRP3 inflammasome and its components in placentally-mediated pregnancy pathologies. However, the link between placental dysfunction seen in these disorders and the NLRP3 inflammasome is not yet firmly established. This manuscript aims to review the evidence regarding placental inflammation seen with placental dysfunction, discuss its association with the NLRP3 inflammasome, and identify potential therapeutic interventions for this pathological inflammatory response.

Identification of divergent placental profiles in clinically distinct pregnancy complications revealed by the transcriptome

INTRODUCTION

Pregnancy complications, including preeclampsia (PE), preterm birth (PTB), and intra-uterine growth restriction (IUGR) have individually been associated with inflammation but the combined comparative analysis of their placental profiles at the transcriptomic and histological levels is lacking.

METHODS

Bulk RNA-sequencing of human placental biopsies from uncomplicated term pregnancies (CTL) and pregnancies complicated with early-onset (EO), and late-onset (LO) PE, as well as PTB and term IUGR were used to characterize individual molecular profiles. We also applied immune-cell-specific cellular deconvolution to address local immune cell compositions and analyzed placental lesions by histology to further characterize these complications.

RESULTS

Transcriptome analysis revealed that clinically distinct complications differentiated themselves in unique ways compared to CTLs. Only TMEM136 was commonly modulated. Compared to CTLs, we found that PTB and IUGR were the most distinct, with LOPE being the least distinct. PTB and IUGR revealed differently enhanced inflammatory pathways, where PTB had general inflammatory responses and IUGR had immune cell activation. This inflammation was reflected in the histological profile for PTB only, whereas structural lesions were elevated in all complications. Placental lesions additionally had corresponding enhancement in inflammatory and structural biological processes. We observed that having co-complications, particularly for PTB with or without IUGR, impacted placental transcriptomes. Lastly, cellular deconvolution uncovered shared immune features among the complications.

DISCUSSION

Overall, we provide evidence that these pregnancy complications are not only distinct in their clinical manifestations but also in their placental profiles, which could be leveraged to understand their underlying mechanisms and could offer therapeutic targets.

Thrombospondin-1 Regulates Trophoblast Necroptosis via NEDD4-Mediated Ubiquitination of TAK1 in Preeclampsia

Preeclampsia (PE) is considered as a disease of placental origin. However, the specific mechanism of placental abnormalities remains elusive. This study identified thrombospondin-1 (THBS1) is downregulated in preeclamptic placentae and negatively correlated with blood pressure. Functional studies show that THBS1 knockdown inhibits proliferation, migration, and invasion and increases the cycle arrest and apoptosis rate of HTR8/SVneo cells. Importantly, THBS1 silencing induces necroptosis in HTR8/SVneo cells, accompanied by the release of damage-associated molecular patterns (DAMPs). Necroptosis inhibitors necrostatin-1 and GSK'872 restore the trophoblast survival while pan-caspase inhibitor Z-VAD-FMK has no effect. Mechanistically, the results show that THBS1 interacts with transforming growth factor B-activated kinase 1 (TAK1), which is a central modulator of necroptosis quiescence and affects its stability. Moreover, THBS1 silencing up-regulates the expression of neuronal precursor cell-expressed developmentally down-regulated 4 (NEDD4), which acts as an E3 ligase of TAK1 and catalyzes K48-linked ubiquitination of TAK1 in HTR8/SVneo cells. Besides, THBS1 attenuates PE phenotypes and improves the placental necroptosis in vivo. Taken together, the down-regulation of THBS1 destabilizes TAK1 by activating NEDD4-mediated, K48-linked TAK1 ubiquitination and promotes necroptosis and DAMPs release in trophoblast cells, thus participating in the pathogenesis of PE.

Predictive biomarkers and initial analysis of maternal immune alterations in postpartum preeclampsia reveal an immune-driven pathology

Introduction

Postpartum preeclampsia (PPPE) is an under-diagnosed condition, developing within 48 hours to 6 weeks following an uncomplicated pregnancy. The etiology of PPPE is still unknown, leaving patients vulnerable and making the identification and treatment of patients requiring postpartum care an unmet need. We aimed to understand the immune contribution to PPPE at the time of diagnosis, as well as uncover the predictive potential of perinatal biomarkers for the early postnatal identification of high-risk patients.

Methods

Placentas were collected at delivery from uncomplicated pregnancies (CTL) and PPPE patients for immunohistochemistry analysis. In this initial study, blood samples in PPPE patients were collected at the time of PPPE diagnosis (48h-25 days postpartum; mean 7.4 days) and compared to CTL blood samples taken 24h after delivery. Single-cell transcriptomics, flow cytometry, intracellular cytokine staining, and the circulating levels of inflammatory mediators were evaluated in the blood.

Results

Placental CD163+ cells and 1st trimester blood pressures can be valuable non-invasive and predictive biomarkers of PPPE with strong clinical application prospects. Furthermore, changes in immune cell populations, as well as cytokine production by CD14+, CD4+, and CD8+ cells, suggested a dampened response with an exhausted phenotype including decreased IL1β, IL12, and IFNγ as well as elevated IL10.

Discussion

Understanding maternal immune changes at the time of diagnosis and prenatally within the placenta in our sizable cohort will serve as groundwork for pre-clinical and clinical research, as well as guiding clinical practice for example in the development of immune-targeted therapies, and early postnatal identification of patients who would benefit from more thorough follow-ups and risk education in the weeks following an uncomplicated pregnancy.

ATP functions as a primary alarmin in allergen-induced type 2 immunity

Environmental allergens that interact with the airway epithelium can activate cellular stress pathways that lead to the release of danger signals known as alarmins. The mechanisms of alarmin release are distinct from damage-associated molecular patterns (DAMPs), which typically escape from cells after loss of plasma membrane integrity. Oxidative stress represents a form of allergen-induced cellular stress that stimulates oxidant-sensing mechanisms coupled to pathways, which facilitate alarmin mobilization and efflux across the plasma membrane. In this review, we highlight examples of alarmin release and discuss their roles in the initiation of type 2 immunity and allergic airway inflammation. In addition, we discuss the concept of alarmin amplification, where "primary" alarmins, which are directly released in response to a specific cellular stress, stimulate additional signaling pathways that lead to secretion of "secondary" alarmins that include proinflammatory cytokines, such as IL-33, as well as genomic and mitochondrial DNA that coordinate or amplify type 2 immunity. Accordingly, allergen-evoked cellular stress can elicit a hierarchy of alarmin signaling responses from the airway epithelium that trigger local innate immune reactions, impact adaptive immunity, and exacerbate diseases including asthma and other chronic inflammatory conditions that affect airway function.

The association between dietary mineral intake and the risk of preeclampsia in Chinese pregnant women: a matched case-control study

Previous studies on the relationship between dietary minerals and preeclampsia (PE) have given inconsistent results. The aim of this study was to further clarify the relationship between dietary minerals intake and PE in Chinese pregnant women. In this study, 440 pairs of hospital-based preeclamptic and healthy women were matched 1:1. Dietary intake was obtained through a 78-item semi-quantitative food frequency questionnaire. Multivariate conditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). Restricted cubic splines were plotted to evaluate the dose-response relationship between dietary minerals intake and PE. This study found significant inverse associations for dietary intake of calcium, magnesium, phosphorus, iron, copper, manganese and zinc and the risk of PE in both univariate and multivariate models (all P- trend < 0.05). After adjusting for possible confounders, compared with the lowest quartile, the odds ratio of the highest quartile was 0.74 (95% CI 0.56-0.98) for calcium, 0.63 (95% CI 0.42-0.93) for magnesium, 0.45 (95% CI 0.31-0.65) for phosphorus, 0.44 (95% CI 0.30-0.65) for iron, 0.72 (95% CI 0.53-0.97) for copper, 0.66 (95% CI 0.48-0.91) for manganese and 0.38 (95% CI 0.25-0.57) for zinc. In addition, a reverse J-shaped relationship between dietary minerals intake and PE risk was observed (P-overall association < 0.05). In Chinese pregnant women, a higher intake of dietary minerals, including calcium, magnesium, phosphorus, copper, iron, manganese, and zinc was associated with a lower odds of PE.

HMGB1: a double-edged sword and therapeutic target in the female reproductive system

HMGB1 that belongs to the High Mobility Group-box superfamily, is a nonhistone chromatin associated transcription factor. It is present in the nucleus of eukaryotes and can be actively secreted or passively released by kinds of cells. HMGB1 is important for maintaining DNA structure by binding to DNA and histones, protecting it from damage. It also regulates the interaction between histones and DNA, affecting chromatin packaging, and can influence gene expression by promoting nucleosome sliding. And as a DAMP, HMGB1 binding to RAGE and TLRs activates NF-κB, which triggers the expression of downstream genes like IL-18, IL-1β, and TNF-α. HMGB1 is known to be involved in numerous physiological and pathological processes. Recent studies have demonstrated the significance of HMGB1 as DAMPs in the female reproductive system. These findings have shed light on the potential role of HMGB1 in the pathogenesis of diseases in female reproductive system and the possibilities of HMGB1-targeted therapies for treating them. Such therapies can help reduce inflammation and metabolic dysfunction and alleviate the symptoms of reproductive system diseases. Overall, the identification of HMGB1 as a key player in disease of the female reproductive system represents a significant breakthrough in our understanding of these conditions and presents exciting opportunities for the development of novel therapies.

Placenta analysis of Hofbauer cell profile according to the class of antiretroviral therapy used during pregnancy in people living with HIV

INTRODUCTION

The use of antiretroviral therapy drastically reduces vertical transmission of Human Immunodeficiency Virus. However, recent studies demonstrate associations between ART use during pregnancy and placental inflammation, particularly within protease inhibitor (PI)-based regimens. We sought to characterize placental macrophages, namely Hofbauer cells, according to the class of ART used during pregnancy.

METHODS

Using immunofluorescence and immunohistochemistry, placentas from 79 pregnant people living with HIV (PPLWH) and 29 HIV-uninfected people were analyzed to quantify the numbers and frequencies of leukocytes (CD45⁺) and Hofbauer cells (CD68⁺ and/or CD163⁺). PPLWH were stratified into three groups based on class of ART: non-nucleoside reverse transcriptase inhibitor (NNRTI)-based, integrase strand-transfer inhibitor (INSTI)-based, and PI-based regimens.

RESULTS

Placentas of PPLWH contained significantly more leukocytes and Hofbauer cells than controls. Multivariable analyses revealed that this increase in immune cells was associated with a predominantly CD163⁺ profile in all ART subgroups compared to the HIV-negative group. This was characterized by an increase in total CD163⁺ cells in the PI and INSTI subgroups, and a higher frequency of CD163⁺ cells and CD163⁺/CD68⁺ ratio in the NNRTI and PI subgroups.

DISCUSSION

Placentas of PPLWH treated with any ART regimen during their entire pregnancy displayed a selection for CD163⁺ cells compared to the HIV-negative group, regardless of class of ART, suggesting that class of ART does not intrinsically affect selection of CD163+ and CD68⁺ Hofbauer cells. Further investigations into the role of Hofbauer cells in ART-associated placental inflammation are warranted to identify the mechanisms behind their potential involvement in maternal-fetal tolerance maintenance.

Cell-free fetal DNA impairs trophoblast migration in a TLR9-dependent manner and can be reversed by hydroxychloroquine

Growing evidence suggests a relationship between elevated circulating placental-derived cell-free fetal DNA (cffDNA) and preeclampsia. Hypomethylation of CpG motifs, a hallmark of cffDNA, allows it to activate Toll-like receptor 9 (TLR9). Using an in vitro human first trimester extravillous trophoblast cell model, we sought to determine if trophoblast-derived cffDNA and ODN 2216, a synthetic unmethylated CpG oligodeoxynucleotide, directly impacted spontaneous trophoblast migration. The role of the DNA sensors TLR9, AIM2, and cGAS was assessed using the inhibitor A151. To test whether any effects could be reversed by therapeutic agents, trophoblasts were treated with or without cffDNA or ODN 2216 with or without aspirin (ASA; a known cGAS inhibitor), aspirin-triggered lipoxin (ATL), or hydroxychloroquine (HCQ; a known TLR9 inhibitor). Trophoblast-derived cffDNA and ODN 2216 reduced trophoblast migration without affecting cell viability. Reduced trophoblast migration in response to cffDNA or ODN 2216 was reversed by A151. cffDNA inhibition of trophoblast migration was reversed by HCQ, while ASA or ATL had no effect. In contrast ODN 2216 inhibition of trophoblast migration was reversed by ASA, ATL and HCQ. Our findings suggest that cffDNA can exert a local effect on placental function by impairing trophoblast migration through activation of innate immune DNA sensors. HCQ, a known TLR9 inhibitor, reversed the effects of cffDNA on trophoblast migration. Greater insights into the molecular underpinnings of how cffDNA impacts placentation can aid in our understanding of the pathogenesis of preeclampsia, and in the development of novel therapeutic approaches for preeclampsia therapy.

Proinflammatory changes in the maternal circulation, maternal-fetal interface, and placental transcriptome in preterm birth

BACKGROUND

Preterm birth remains a leading obstetrical complication because of the incomplete understanding of its multifaceted etiology. It is known that immune alterations toward a proinflammatory profile are observed in women with preterm birth, but therapeutic interventions are still lacking because of scarcity of evidence in the integration of maternal and placental interrelated compartments.

OBJECTIVE

This study aimed to obtain an integrated view of the maternal and placental contribution to preterm birth compared with normal term pregnancies for an in-depth understanding of the immune/inflammatory involvement, intending to identify novel strategies to mitigate the negative impact of inflammation.

STUDY DESIGN

We prospectively recruited 79 women with preterm or term deliveries and collected placentas for RNA sequencing, histologic analyses, and to assess levels of inflammatory mediators. Blood samples were also collected to determine the circulating immune profiles by flow cytometry and to evaluate the circulating levels of inflammatory mediators.

RESULTS

Placental transcriptomic analyses revealed 102 differentially expressed genes upregulated in preterm birth, including known and novel targets, which were highly enriched for inflammatory biological processes according to gene ontology analyses. Analysis of maternal immune cells revealed distinct profiles in preterm births vs term births, including an increased percentage of CD3^- cells and monocyte subsets and decreased CD3⁺ cells along with Th17 subsets of CD4⁺ lymphocytes. Supporting our bioinformatic findings, we found increases in proinflammatory mediators in the plasma, placenta, and fetal membranes (primarily the amnion) of women with preterm birth, such as interleukin-6 and tumor necrosis factor-α. These findings were not distinct between spontaneous and iatrogenic preterm births except at a molecular level where spontaneous preterm birth presented with an elevated inflammatory profile compared with iatrogenic preterm birth. Analysis of placental histology revealed increased structural and inflammatory lesions in preterm vs term births. We found that genes upregulated in placentas with inflammatory lesions have enrichment of proinflammatory pathways.

CONCLUSION

This work sheds light on changes within the immune system in preterm birth on multiple levels and compartments to help identify pregnancies at high risk of preterm birth and to discover novel therapeutic targets for preterm birth.

Is human labor at term an inflammatory condition?†

Parturition at term in normal pregnancy follows a predictable sequence of events. There is some evidence that a state of inflammation prevails in the reproductive tissues during labor at term, but it is uncertain whether this phenomenon is the initiating signal for parturition. The absence of a clear temporal sequence of inflammatory events prior to labor casts doubt on the concept that normal human labor at term is primarily the result of an inflammatory cascade. This review examines evidence linking parturition and inflammation in order to address whether inflammation is a cause of labor, a consequence of labor, or a separate but related phenomenon. Finally, we identify and suggest ways to reconcile inconsistencies regarding definitions of labor onset in published research, which may contribute to the variability in conclusions regarding the genesis and maintenance of parturition. A more thorough understanding of the processes underlying normal parturition at term may lead to novel insights regarding abnormal labor, including spontaneous preterm labor, preterm premature rupture of the fetal membranes, and dysfunctional labor, and the role of inflammation in each.

Fetal growth restriction and neonatal-pediatric lung diseases: Vascular mechanistic links and therapeutic directions

Bronchopulmonary dysplasia (BPD) is the most common respiratory sequela of prematurity, and infants born with fetal growth restriction (FGR) are disproportionately represented in BPD statistics, as factors which affect somatic growth may also affect pulmonary growth. Effects of in-utero hypoxia underlying FGR on lung parenchymal architecture predisposing to BPD are well documented, but the pulmonary vascular constructs are not well appreciated. Disruption of angiogenesis during critical periods of lung growth impairs alveolarization, contributing to BPD pathogenesis. Pulmonary artery thickness/stiffness has been noted in FGR in the initial postnatal weeks, and also in well-grown infants with established BPD. The lack of waveform cushioning by the major arteries exposes the pulmonary resistance vessels to higher pulsatile stress, thereby accelerating microvascular disease. Reactive oxygen species, increased sympathetic activity and endothelial dysfunction are common mediators in FGR and BPD; each putative targets for prevention and/or therapeutics using interleukin (IL)-1 receptor antagonist (IL-1Ra), melatonin or inhibition of renin-angiotensin-aldosterone system. While BPD is the archetypal respiratory disease of infancy, effects of FGR on pulmonary function are long-term, extending well into childhood. This narrative links FGR in very/extremely preterm infants with BPD through the vascular affliction as a mechanistic and potentially, therapeutic pathway. Our objectives were to depict the burden of disease for FGR and BPD amongst preterm infants, portray vascular involvement in the placenta in FGR and BPD cohorts, provide high resolution vascular ultrasound information in both cohorts with a view to address therapeutic relevance, and lastly, link this information with paediatric age-group lung diseases.

The immunobiology of preterm labor and birth: intra-amniotic inflammation or breakdown of maternal-fetal homeostasis

In brief

The syndrome of preterm labor comprises multiple established and novel etiologies. This review summarizes the distinct immune mechanisms implicated in preterm labor and birth and highlights potential strategies for its prevention.

Abstract

Preterm birth, the leading cause of neonatal morbidity and mortality worldwide, results from preterm labor, a syndrome that includes multiple etiologies. In this review, we have summarized the immune mechanisms implicated in intra-amniotic inflammation, the best-characterized cause of preterm labor and birth, as well as novel etiologies non-associated with intra-amniotic inflammation (i.e. formally known as idiopathic). While the intra-amniotic inflammatory responses driven by microbes (infection) or alarmins (sterile) have some overlap in the participating cellular and molecular processes, the distinct natures of these two conditions necessitate the implementation of specific approaches to prevent adverse pregnancy and neonatal outcomes. Intra-amniotic infection can be treated with the correct antibiotics, whereas sterile intra-amniotic inflammation could potentially be treated by administering a combination of anti-inflammatory drugs (e.g. betamethasone, inflammasome inhibitors, etc.). Recent evidence also supports the role of fetal T-cell activation as a newly described trigger for preterm labor and birth in a subset of cases diagnosed as idiopathic. Moreover, herein we also provide evidence of two maternally-driven immune mechanisms responsible for preterm births formerly considered to be idiopathic. First, the impairment of maternal Tregs can lead to preterm birth, likely due to the loss of immunosuppressive activity resulting in unleashed effector T-cell responses. Secondly, homeostatic macrophages were shown to be essential for maintaining pregnancy and promoting fetal development, and the adoptive transfer of homeostatic M2-polarized macrophages shows great promise for preventing inflammation-induced preterm birth. Collectively, in this review, we discuss the established and novel immune mechanisms responsible for preterm birth and highlight the potential targets for novel strategies aimed at preventing the multi-etiological syndrome of preterm labor leading to preterm birth.

A Systematic Review of the Safety of Blocking the IL-1 System in Human Pregnancy

Blockade of the interleukin-1 (IL-1) pathway has been used therapeutically in several inflammatory diseases including arthritis and cryopyrin-associated periodic syndrome (CAPS). These conditions frequently affect women of childbearing age and continued usage of IL-1 specific treatments throughout pregnancy has been reported. IL-1 is involved in pregnancy complications and its blockade could have therapeutic potential. We systematically reviewed all reported cases of IL-1 blockade in human pregnancy to assess safety and perinatal outcomes. We searched several databases to find reports of specific blockade of the IL-1 pathway at any stage of pregnancy, excluding broad spectrum or non-specific anti-inflammatory intervention. Our literature search generated 2439 references of which 22 studies included, following extensive review. From these, 88 different pregnancies were assessed. Most (64.8%) resulted in healthy term deliveries without any obstetrical/neonatal complications. Including pregnancy exposed to Anakinra or Canakinumab, 12 (15.0%) resulted in preterm birth and one stillbirth occurred. Regarding neonatal complications, 2 cases of renal agenesis (2.5%) were observed, and 6 infants were diagnosed with CAPS (7.5%). In conclusion, this systematic review describes that IL-1 blockade during pregnancy is not associated with increased adverse perinatal outcomes, considering that treated women all presented an inflammatory disease associated with elevated risk of pregnancy complications.

A prospective cohort study providing insights for markers of adverse pregnancy outcome in older mothers

Background

Advanced maternal age (≥35 years) is associated with increased rates of adverse pregnancy outcome. Better understanding of underlying pathophysiological processes may improve identification of older mothers who are at greatest risk. This study aimed to investigate changes in oxidative stress and inflammation in older women and identify clinical and biochemical predictors of adverse pregnancy outcome in older women.

Methods

The Manchester Advanced Maternal Age Study (MAMAS) was a multicentre, observational, prospective cohort study of 528 mothers. Participants were divided into three age groups for comparison 20–30 years (n = 154), 35–39 years (n = 222) and ≥ 40 years (n = 152). Demographic and medical data were collected along with maternal blood samples at 28 and 36 weeks’ gestation. Multivariable analysis was conducted to identify variables associated with adverse outcome, defined as one or more of: small for gestational age (< 10th centile), FGR (<5th centile), stillbirth, NICU admission, preterm birth < 37 weeks’ gestation or Apgar score < 7 at 5 min. Biomarkers of inflammation, oxidative stress and placental dysfunction were quantified in maternal serum. Univariate and multivariable logistic regression was used to identify associations with adverse fetal outcome.

Results

Maternal smoking was associated with adverse outcome irrespective of maternal age (Adjusted Odds Ratio (AOR) 4.22, 95% Confidence Interval (95%CI) 1.83, 9.75), whereas multiparity reduced the odds (AOR 0.54, 95% CI 0.33, 0.89). In uncomplicated pregnancies in older women, lower circulating anti-inflammatory IL-10, IL-RA and increased antioxidant capacity (TAC) were seen. In older mothers with adverse outcome, TAC and oxidative stress markers were increased and levels of maternal circulating placental hormones (hPL, PlGF and sFlt-1) were reduced (p < 0.05). However, these biomarkers only had modest predictive accuracy, with the largest area under the receiver operator characteristic (AUROC) of 0.74 for placental growth factor followed by TAC (AUROC = 0.69).

Conclusions

This study identified alterations in circulating inflammatory and oxidative stress markers in older women with adverse outcome providing preliminary evidence of mechanistic links. Further, larger studies are required to determine if these markers can be developed into a predictive model of an individual older woman’s risk of adverse pregnancy outcome, enabling a reduction in stillbirth rates whilst minimising unnecessary intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04178-6.

Etiological Value of Sterile Inflammation in Preeclampsia: Is It a Non-Infectious Pregnancy Complication?

Understanding of sterile inflammation and its associated biological triggers and diseases is still at the elementary stage. This becomes more warranted in cases where infections are not associated with the pathology. Detrimental effects of bacterial and viral infections on the immune responses at the maternal-fetal interface as well as pregnancy outcomes have been well documented. However, an infection-induced etiology is not thought to be a major contributing component to severe pregnancy complications such as preeclampsia (PE) and gestational diabetes. How is then an inflammatory signal thought to be associated with these pregnancy complications? It is not clear what type of inflammation is involved in the onset of PE-like features. We opine that sterile inflammation regulated by the inflammasome-gasdermins-caspase-1 axis is a contributory factor to the onset of PE. We hypothesize that increased production and release of damage-associated molecular patterns (DAMPs) or Alarmins such as high-mobility group box1 (HMGB1), cell-free fetal DNA, uric acid, the NOD-like receptor pyrin-containing receptor 3 (NLRP3) inflammasome, IL-1β and IL-18 occur in the PE placenta. Some of these molecules have already been observed in the placenta from women with PE. Mechanistically, emerging evidence has demonstrated that excessive placental endoplasmic reticulum (ER) stress, impaired autophagy and gasdermine D (GSDMD)-mediated intrinsic pyroptosis are key events that contribute to systemic sterile inflammation in patients with PE, especially early-onset PE (e-PE). In this review, we highlight the advances on the roles of sterile inflammation and inflammatory signaling cascades involving ER stress, autophagy deficiency and pyroptosis in PE pathophysiology. Deciphering the mechanisms underlying these inflammatory pathways may provide potential diagnostic biomarkers and facilitate the development of therapeutic strategies to treat this devastating disease.

Extracellular vesicle mediated feto-maternal HMGB1 signaling induces preterm birth

Preterm birth (PTB; <37 weeks of gestation) impacts ∼11% of all pregnancies and contributes to 1 million neonatal deaths worldwide annually. An understanding of the feto-maternal (F-M) signals that initiate birthing (parturition) at term is critical to design strategies to prevent their premature activation, resulting in PTB. Although endocrine and immune cell signaling are well-reported, fetal-derived paracrine signals capable of transitioning quiescent uterus to an active state of labor are poorly studied. Recent reports have suggested that senescence of the fetal amnion membrane coinciding with fetal growth and maturation generates inflammatory signals capable of triggering parturition. This is by increasing the inflammatory load at the feto-maternal interface (FMi) tissues (i.e., amniochorion-decidua). High mobility group box 1 protein (HMGB1), an alarmin, is one of the inflammatory signals released by senescent amnion cells via extracellular vesicles (exosomes; 40-160 nm). Increased levels of HMGB1 in the amniotic fluid, cord and maternal blood are associated with term and PTB. This study tested the hypothesis that senescent amnion cells release HMGB1, which is fetal signaling capable of increasing FMi inflammation, predisposing them to parturition. To test this hypothesis, exosomes from amnion epithelial cells (AECs) grown under normal conditions were engineered to contain HMGB1 by electroporation (eHMGB1). eHMGB1 was characterized (quantity, size, shape, markers and loading efficiency), and its propagation through FMi was tested using a four-chamber microfluidic organ-on-a-chip device (FMi-OOC) that contained four distinct cell types (amnion and chorion mesenchymal, chorion trophoblast and decidual cells) connected through microchannels. eHMGB1 propagated through the fetal cells and matrix to the maternal decidua and increased inflammation (receptor expression [RAGE and TLR4] and cytokines). Furthermore, intra-amniotic injection of eHMGB1 (containing 10 ng) into pregnant CD-1 mice on embryonic day 17 led to PTB. Injecting carboxyfluorescein succinimidyl ester (CFSE)-labeled eHMGB1, we determined in vivo kinetics and report that eHMGB1 trafficking resulting in PTB was associated with increased FMi inflammation. This study determined that fetal exosome mediated paracrine signaling can generate inflammation and induce parturition. Besides, in vivo functional validation of FMi-OOC experiments strengthens the reliability of such devices to test physiologic and pathologic systems.

Hypoxia and oxidative stress induce sterile placental inflammation in vitro

Fetal growth restriction (FGR) and stillbirth are associated with placental dysfunction and inflammation and hypoxia, oxidative and nitrative stress are implicated in placental damage. Damage-associated molecular patterns (DAMPs) are elevated in pregnancies at increased risk of FGR and stillbirth and are associated with increase in pro-inflammatory placental cytokines. We hypothesised that placental insults lead to release of DAMPs, promoting placental inflammation. Placental tissue from uncomplicated pregnancies was exposed in vitro to hypoxia, oxidative or nitrative stress. Tissue production and release of DAMPs and cytokines was determined. Oxidative stress and hypoxia caused differential release of DAMPs including uric acid, HMGB1, S100A8, cell-free fetal DNA, S100A12 and HSP70. After oxidative stress pro-inflammatory cytokines (IL-1α, IL-1β, IL-6, IL-8, TNFα, CCL2) were increased both within explants and in conditioned culture medium. Hypoxia increased tissue IL-1α/β, IL-6, IL-8 and TNFα levels, and release of IL-1α, IL-6 and IL-8, whereas CCL2 and IL-10 were reduced. IL1 receptor antagonist (IL1Ra) treatment prevented hypoxia- and oxidative stress-induced IL-6 and IL-8 release. These findings provide evidence that relevant stressors induce a sterile inflammatory profile in placental tissue which can be partially blocked by IL1Ra suggesting this agent has translational potential to prevent placental inflammation evident in FGR and stillbirth.

NLRP3 inflammasome: a new therapeutic target for high-risk reproductive disorders?

ABSTRACT

The NOD-like receptor protein 3 (NLRP3) inflammasome is a key regulator of the host's immune response, and many immune and metabolic disorders are linked to its activation. This review aimed to investigate and clarify the relationship between this inflammasome and high-risk reproductive disorders. Papers cited here were retrieved from PubMed up to August 2020 using the keywords "NLRP3" or "NALP3", "caspase-1", "endometriosis", "gestational diabetes", "interleukin (IL)-18", "IL-1β", "pre-eclampsia (PE)", "preterm birth", "polycystic ovarian syndrome (PCOS)", "recurrent spontaneous abortion (RSA)", and combinations of these terms. The results show that NLRP3 inflammasome is associated with various high-risk reproductive disorders and many inflammatory factors are secreted during its activation, such as IL-1β induced during the development of endometriosis. PCOS is also associated with activation of the NLRP3 inflammasome, especially in overweight patients. It also participates in the pathogenesis of RSA and is activated in fetal membranes before preterm birth. The placentas of pregnant women with PE show higher expression of the NLRP3 inflammasome, and gestational diabetes mellitus occurs simultaneously with its activation. Current evidence suggest that the NLRP3 inflammasome plays an important role in female reproductive disorders. New treatment and management methods targeting it might help reduce the incidence of such disorders and improve neonatal outcomes.

A structured review of placental morphology and histopathological lesions associated with SARS-CoV-2 infection

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus, was first identified after a cluster of cases in Wuhan, China in December 2019. Whether vertical transmission or placental pathology might occur following maternal infection during pregnancy remains unknown. This review aimed to summarise all studies that examined the placenta or neonates following infection with SARS-CoV-2, or closely related highly pathogenic coronavirus (SARS-CoV-1, or the Middle East respiratory syndrome coronavirus (MERS-CoV)). Structured literature searches found 50 studies that met the inclusion criteria. Twenty studies reported placental histopathology findings in third trimester placentas following maternal SARS-CoV-2 infection. Using the Amsterdam Consensus criteria to categorise the histopathology results, evidence of both fetal vascular malperfusion (35.3% of cases; 95% Confidence Interval (CI) 27.7-43.0%) and maternal vascular malperfusion (46% of cases; 95% CI 38.0-54.0%) were reported, along with evidence of inflammation in the placentas (villitis 8.7% cases, intervillositis 5.3% of cases, chorioamnionitis 6% of cases). The placental pathologies observed in SARS-CoV-2 were consistent with findings following maternal SARS-CoV-1 infection. Of those tested, a minority of neonates (2%) and placental samples tested positive for SARS-CoV-2 infection (21%). Limited conclusions can be drawn about the effect of maternal SARS-CoV-2 infection on placental pathology as most lack control groups and the majority of reports followed third trimester infection. Collaboration to maximise the number of samples examined will increase the reliability and generalisability of findings. A better understanding of the association between maternal SARS-CoV-2 infection and placental pathology will inform maternity care during the coronavirus pandemic.

High-mobility group box 1 is a driver of inflammation throughout pregnancy

A proinflammatory response driven by high-mobility group box 1 (HMGB1) is important for the success of both the early stages of pregnancy and parturition initiation. However, the tight regulation of HMGB1 within these two stages is critical, as increased HMGB1 can manifest into pregnancy-related pathologies. Although during the early stages of pregnancy HMGB1 is critical for the development and implantation of the embryo, and uterine decidualization, high levels within the uterine cavity have been linked to pregnancy failure. In addition, chronic inflammation, resultant from increased HMGB1 within the maternal circulation and gestational tissues, also increases the risk for preterm labor, preterm birth, or infant mortality. Due to the link between HMGB1 and several pregnancy pathologies, the possibility of leveraging HMGB1 as a biomarker has been assessed. However, data are limited that demonstrate how known HMGB1 inhibitors could reduce inflammation within pregnancy. Thus, further research is warranted to improve our understanding of the potential of HMGB1 as a therapeutic target to reduce inflammation within pregnancy. This review aims to describe what is understood about the role of HMGB1 that drives inflammation throughout pregnancy and highlight its potential as a biomarker and therapeutic target within this context.

Reprint of: Myometrial activation: Novel concepts underlying labor

Term labour is a state of physiological inflammation orchestrated by multiple uterine tissues (both fetal and maternal). This physiological inflammation preceding and accompanying labour onset is characterized by an increase in cytokine and chemokine secretion by the fetal membranes, as well as uterine tissues (i.e., decidua and myometrium). Pro-inflammatory cytokines and chemokines activate circulating maternal peripheral leukocytes as well as the uterine vascular endothelium to permit leukocyte infiltration into the uterus. This inflammatory milieu, in the absence of infection, is required for the initiation of labour as the uterine-infiltrated leukocytes secrete matrix metalloproteinases to induce fetal membrane rupture and cervical ripening as well as various labour mediators, which promote contractions of the myometrium. Myometrial activation at term and the onset of labour contractions are directly related to the changes in the ovarian/placental hormone progesterone and its downstream mediators (i.e., the progesterone receptors, PRA/B), which are also critical for maintenance of pregnancy. Our recent data provides direct evidence in support of local and functional P4 withdrawal in the uterine muscle (myometrium) via the activator protein-1 (AP-1) mediated pathway. This review outlines known mechanisms regulating activation of human labour, including progesterone and cytokine signaling. Understanding of the molecular mechanism of myometrial activation and labour onset could facilitate the development of new therapeutics for high-risk pregnant women to prevent premature uterine activation and preterm birth.

Specific inflammatory profile in each pregnancy complication: A comparative study

PROBLEM

Pre-eclampsia (PE), preterm birth (PTB) and intra-uterine growth restriction (IUGR) affect 5%-12% of pregnancies. They have been associated with placental inflammation, although the detection of inflammatory mediators in the maternal circulation is still controversial. Our goal was to determine the inflammatory changes occurring in the second part of pregnancy to identify profiles distinguishing pathological pregnancies from each other.

METHOD OF STUDY

We performed a nested case-control study of 200 women randomly selected from a cohort recruited at the CHU de Quebec-Universite Laval, Quebec, Canada. Women with uncomplicated term pregnancy (CTRL); PE (severe or not); PTB or IUGR (N = 50/each) were included. Plasma samples, obtained from the late second trimester and at delivery, were analysed for over 30 selected mediators (including cytokines/alarmins), by multiplex, ELISA or specific assays. Demographic and obstetrical information were obtained for classification.

RESULTS

In CTRL, we observed significant differences between 2nd trimester and delivery, with increased levels of inflammatory mediators (ex. MCP-1, IL-6), supporting an inflammatory profile towards term. Increased levels of IL-6, CXCL10 and CRP were observed in PE as compared to CTRL. In PTB, we observed increased CXCL9 in 2nd trimester and decreased progesterone at delivery. In IUGR, increased HMGB1 and IL-1α were observed only in the 2nd trimester.

CONCLUSIONS

Our work showed significant inflammatory changes in uncomplicated pregnancies towards delivery, supporting that normal delivery is pro-inflammatory, although not to the same extent as in pathological pregnancies. Inflammatory profiles are specific to each pregnancy complication which may help to understand the contribution of inflammation to the clinical presentation of these conditions.

The role of RORγt at maternal-fetal interface during murine pregnancy

PROBLEM

Innate lymphoid cells (ILCs, including NK cells) and their subsets are the most frequent lymphocytes at the maternal-fetal interface (decidua). Recent recognition of extensive ILC subset diversity at mucosal sites and the possible role they might play at different stages of pregnancy poses questions about their composition and lineage stability. Namely, RORγt-dependent ILC3s have been recognized as a key cellular mediator of tissue organization in the gut and secondary lymphoid organs, prompting examination of their distribution and role in decidua during pregnancy.

METHOD OF STUDY

We employed highly polychromatic flow cytometry with conventional and machine learning-aided analysis to map ILC subsets and dissected the role of canonical transcription factor RORγt using fate-mapping animals and RORγt-/- animals.

RESULTS

We demonstrate a comprehensive immunome map of ILCs/NKs, revealing a dynamic interface even in the absence of antigenic or allogeneic challenge. Strikingly, we demonstrate plasticity of RORγt expression in decidual ILCs with across gestation. However, gross reproductive efficiency is not affected in RORγt-/- animals.

CONCLUSION

These results indicated that RORγt+ ILCs are highly plastic at the maternal-fetal interface, but dispensable for normal pregnancy, revealing a novel mechanism of transcriptional immunoregulation in pregnancy.

Heme Oxygenase Protects against Placental Vascular Inflammation and Abortion by the Alarmin Heme in Mice

Both infectious as non-infectious inflammation can cause placental dysfunction and pregnancy complications. During the first trimester of human gestation, when palatogenesis takes place, intrauterine hematoma and hemorrhage are common phenomena, causing the release of large amounts of heme, a well-known alarmin. We postulated that exposure of pregnant mice to heme during palatogenesis would initiate oxidative and inflammatory stress, leading to pathological pregnancy, increasing the incidence of palatal clefting and abortion. Both heme oxygenase isoforms (HO-1 and HO-2) break down heme, thereby generating anti-oxidative and -inflammatory products. HO may thus counteract these heme-induced injurious stresses. To test this hypothesis, we administered heme to pregnant CD1 outbred mice at Day E12 by intraperitoneal injection in increasing doses: 30, 75 or 150 μmol/kg body weight (30H, 75H or 150H) in the presence or absence of HO-activity inhibitor SnMP from Day E11. Exposure to heme resulted in a dose-dependent increase in abortion. At 75H half of the fetuses where resorbed, while at 150H all fetuses were aborted. HO-activity protected against heme-induced abortion since inhibition of HO-activity aggravated heme-induced detrimental effects. The fetuses surviving heme administration demonstrated normal palatal fusion. Immunostainings at Day E16 demonstrated higher numbers of ICAM-1 positive blood vessels, macrophages and HO-1 positive cells in placenta after administration of 75H or SnMP + 30H. Summarizing, heme acts as an endogenous “alarmin” during pregnancy in a dose-dependent fashion, while HO-activity protects against heme-induced placental vascular inflammation and abortion.

Occurrence of a RAGE-Mediated Inflammatory Response in Human Fetal Membranes

Context:

Sterile inflammation has been shown to play a key role in the rupture of the fetal membranes (FMs). Moreover, an early and exacerbated runaway inflammation can evolve into a preterm premature rupture of membranes and lead to potential preterm birth. In this context, we investigated the receptor for advanced glycation end products (RAGE), an axis implied in physiological sterile inflammation, in conjunction with two major ligands: AGEs and High-Mobility Group Box 1 (HMGB1). Our first objective was to determine the spatiotemporal expression profiles of the different actors of the RAGE-signaling axis in human FMs, including its intracellular adaptors Diaphanous-1 and Myd88. Our second goal was to evaluate the functionality of RAGE signaling in terms of FMs inflammation.

Methods

The presence of the actors (RAGE, HMGB1, Myd88, and Diaphanous-1) at the mRNA level was investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in the human amnion and choriodecidua at the three trimesters and at term. Measurements were conducted at two distinct zones: the zone of intact morphology (ZIM) and the zone of altered morphology (ZAM). Then, proteins were quantified using Western blot analysis, and their localization was evaluated by immunofluorescence in term tissues. In addition, pro-inflammatory cytokine secretion was quantified using a Multiplex assay after the treatment of amnion and choriodecidua explants with two RAGE ligands (AGEs and HMGB1) in the absence or presence of a RAGE inhibitor (SAGEs).

Results

The FMs expressed the RAGE-signaling actors throughout pregnancy. At term, RNA and protein overexpression of the RAGE, HMGB1, and Diaphanous-1 were found in the amnion when compared to the choriodecidua, and the RAGE was overexpressed in the ZAM when compared to the ZIM. The two RAGE ligands (AGEs and HMGB1) induced differential cytokine production (IL1β and TNFα) in the amnion and choriodecidua.

Conclusion

Considered together, these results indicate that RAGE signaling is present and functional in human FMs. Our work opens the way to a better understanding of FMs weakening dependent on a RAGE-based sterile inflammation.

Increased placental macrophages and a pro-inflammatory profile in placentas and maternal serum in infants with a decreased growth rate in the third trimester of pregnancy

PROBLEM

There is growing evidence for the role of placental inflammation in the pathophysiology of pregnancy complications including fetal growth restriction (FGR). This study aimed to characterize the inflammatory profile in the maternal circulation and the placenta of infants who were growth restricted and those that were small for gestational age (SGA).

METHOD OF STUDY

Placental villous tissue and maternal serum were obtained from pregnancies where infants were SGA at birth or who had a decreasing growth rate (≥25 centiles) across the third trimester. Immunohistochemical and histological analyses of placental samples were conducted for macrophage number, alongside vascular and cell turnover analysis. Inflammatory profile was analyzed in maternal and placental compartments via ELISAs and multiplex assays.

RESULTS

There were significantly more CD163⁺ macrophages in placentas of infants with a decreased growth rate compared to controls, but not in SGA infants (median 8.6/ nuclei vs 3.8 and 2.9, P = .008 and P = .003, respectively). Uric acid (P = .0007) and IL-8 (P = .0008) were increased in placentas, and S100A8 (P < .0002) was increased in maternal serum of infants with decreased growth rate. No changes in the maternal serum or placental lysates of SGA infants were observed.

CONCLUSION

The evidence of an altered inflammatory profile in infants with a decreasing growth rate, but not in those that were born SGA, provides further evidence that inflammation plays a role in true FGR. It remains unclear whether the increased placental macrophages occur as a direct result, or as a consequence of the pro-inflammatory environment observed in fetal growth restriction.

Dose-dependent structural and immunological changes in the placenta and fetal brain in response to systemic inflammation during pregnancy

PROBLEM

Systemic maternal inflammation is associated with adverse neonatal sequelae. We tested the hypothesis that IL-1β is a key inflammatory regulator of adverse pregnancy outcomes.

METHOD OF STUDY

Pregnant mice were treated with intraperitoneal injections of IL-1β (0, 0.1, 0.5, or 1 μg) from embryonic day (E)14 to E17. Placenta and fetal brains were harvested and analyzed for morphologic changes and IL-1β signaling markers.

RESULTS

As compared with non-treated dams, maternal injections with IL-1β resulted in increased p-NF-κB and caspase-1 in placentas and fetal brains, but not consistently in spleens, suggesting induction of intrinsic IL-1β production. These findings were confirmed by increased levels of IL-1β in the placentas of the IL-1β-treated dams. Systemic treatment of dams with IL-1β suppressed Stat1 signaling. Maternal inflammation caused by IL-1β treatment reduced fetal viability to 80.6% and 58.9%, in dams treated with either 0.5 or 1 μg of IL-1β, respectively. In the placentas, there was an IL-1β dose-dependent distortion of the labyrinth structure, decreased numbers of mononuclear trophoblast giant cells, and reduced proportions of endothelial cells as compared to placentas from control dams. In fetal brains collected at E17, there was an IL-1β dose-dependent reduction in cortical neuronal morphology.

CONCLUSION

This work demonstrates that systemic IL-1β injection causes dose-dependent structural and functional changes in the placenta and fetal brain.

Exploring Inflammatory Mediators in Fetal and Maternal Compartments During Human Parturition

OBJECTIVE

To examine inflammatory mediators in three fetomaternal biological compartments to inform theory related to the fetal and maternal inflammatory contributions to parturition at term and preterm.

METHODS

We conducted a cross-sectional study of amniotic fluid, cord blood, and maternal plasma from women with singleton pregnancies. Women had one of four conditions: term labor (n=11), term not in labor (n=13), spontaneous preterm birth with intact membranes (preterm birth; n=13), or preterm prelabor rupture of membranes (PROM; n=8). We measured two damage-associated molecular pattern markers (high-mobility group box-1 [HMGB1] and uric acid) and two acute phase response markers (interleukin [IL]-6 and C-reactive protein [CRP]) using enzyme-linked immunosorbent assay. The distribution of each analyte within amniotic fluid, cord blood, and maternal plasma across the four conditions (term not in labor, term labor, preterm birth, and preterm PROM) were calculated. To explore whether there were distributional differences in each analyte across each of the four labor conditions, we used a nonparametric Kruskal-Wallis test. For analytes that differed across groups, we further compared distributions by labor group (term labor vs term not in labor, and preterm PROM vs preterm birth).

RESULTS

Fetal compartments (amniotic fluid and cord blood) showed higher HMGB1 in term labor vs term not in labor and preterm PROM vs preterm birth. Amniotic fluid IL-6, cord blood CRP and cord blood uric acid were higher in term vs term not in labor. Cord blood uric acid was higher in preterm PROM vs preterm birth. Only maternal plasma IL-6 was higher in term labor vs term not in labor.

CONCLUSION

Accumulation of HMGB1 and an overall increase in inflammation observed on the fetal side, but not the maternal side, may be signals of parturition. Understanding fetal-derived proparturition inflammatory signals at term and preterm, especially in preterm PROM, might provide fetal-specific biomarkers and identify underlying mechanisms and targets for interventions to reduce the risk of preterm birth and preterm PROM.

Myometrial activation: Novel concepts underlying labor

Term labour is a state of physiological inflammation orchestrated by multiple uterine tissues (both fetal and maternal). This physiological inflammation preceding and accompanying labour onset is characterized by an increase in cytokine and chemokine secretion by the fetal membranes, as well as uterine tissues (i.e., decidua and myometrium). Pro-inflammatory cytokines and chemokines activate circulating maternal peripheral leukocytes as well as the uterine vascular endothelium to permit leukocyte infiltration into the uterus. This inflammatory milieu, in the absence of infection, is required for the initiation of labour as the uterine-infiltrated leukocytes secrete matrix metalloproteinases to induce fetal membrane rupture and cervical ripening as well as various labour mediators, which promote contractions of the myometrium. Myometrial activation at term and the onset of labour contractions are directly related to the changes in the ovarian/placental hormone progesterone and its downstream mediators (i.e., the progesterone receptors, PRA/B), which are also critical for maintenance of pregnancy. Our recent data provides direct evidence in support of local and functional P4 withdrawal in the uterine muscle (myometrium) via the activator protein-1 (AP-1) mediated pathway. This review outlines known mechanisms regulating activation of human labour, including progesterone and cytokine signaling. Understanding of the molecular mechanism of myometrial activation and labour onset could facilitate the development of new therapeutics for high-risk pregnant women to prevent premature uterine activation and preterm birth.

Role of the NLRP3 Inflammasome in Preeclampsia

Reproduction involves tightly regulated series of events and the immune system is involved in an array of reproductive processes. Disruption of well-controlled immune functions leads to infertility, placental inflammation, and numerous pregnancy complications, including preeclampsia (PE). Inflammasomes are involved in the process of pathogen clearance and sterile inflammation. They are large multi-protein complexes that are located in the cytosol and play key roles in the production of the pivotal inflammatory cytokines, interleukin (IL)-1β and IL-18, and pyroptosis. The nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome is a key mediator of sterile inflammation induced by various types of damage-associated molecular patterns (DAMPs). Recent evidence indicates that the NLRP3 inflammasome is involved in pregnancy dysfunction, including PE. Many DAMPs (uric acid, palmitic acid, high-mobility group box 1, advanced glycation end products, extracellular vesicles, cell-free DNA, and free fatty acids) are increased and associated with pregnancy complications, especially PE. This review focuses on the role of the NLRP3 inflammasome in the pathophysiology of PE.

Initiation of human parturition: signaling from senescent fetal tissues via extracellular vesicle mediated paracrine mechanism

A better understanding of the underlying mechanisms by which signals from the fetus initiate human parturition is required. Our recent findings support the core hypothesis that oxidative stress (OS) and cellular senescence of the fetal membranes (amnion and chorion) trigger human parturition. Fetal membrane cell senescence at term is a natural physiological response to OS that occurs as a result of increased metabolic demands by the maturing fetus. Fetal membrane senescence is affected by the activation of the p38 mitogen activated kinase-mediated pathway. Similarly, various risk factors of preterm labor and premature rupture of the membranes also cause OS-induced senescence. Data suggest that fetal cell senescence causes inflammatory senescence-associated secretory phenotype (SASP) release. Besides SASP, high mobility group box 1 and cell-free fetal telomere fragments translocate from the nucleus to the cytosol in senescent cells, where they represent damage-associated molecular pattern markers (DAMPs). In fetal membranes, both SASPs and DAMPs augment fetal cell senescence and an associated ‘sterile’ inflammatory reaction. In senescent cells, DAMPs are encapsulated in extracellular vesicles, specifically exosomes, which are 30–150 nm particles, and propagated to distant sites. Exosomes traffic from the fetus to the maternal side and cause labor-associated inflammatory changes in maternal uterine tissues. Thus, fetal membrane senescence and the inflammation generated from this process functions as a paracrine signaling system during parturition. A better understanding of the premature activation of these signals can provide insights into the mechanisms by which fetal signals initiate preterm parturition.

Delineating differential regulatory signatures of the human transcriptome in the choriodecidua and myometrium at term labor

Preterm deliveries remain the leading cause of neonatal morbidity and mortality. Current therapies target only myometrial contractions and are largely ineffective. As labor involves multiple coordinated events across maternal and fetal tissues, identifying fundamental regulatory pathways of normal term labor is vital to understanding successful parturition and consequently labor pathologies. We aimed to identify transcriptomic signatures of human normal term labor of two tissues: in the fetal-facing choriodecidua and the maternal myometrium. Microarray transcriptomic data from choriodecidua and myometrium following term labor were analyzed for functional hierarchical networks, using Cytoscape 2.8.3. Hierarchically high candidates were analyzed for their regulatory casual relationships using Ingenuity Pathway Analysis. Selected master regulators were then chemically inhibited and effects on downstream targets were assessed using real-time quantitative PCR (RT-qPCR). Unbiased network analysis identified upstream molecular components in choriodecidua including vimentin, TLR4, and TNFSF13B. In the myometrium, candidates included metallothionein 2 (MT2A), TLR2, and RELB. These master regulators had significant differential gene expression during labor, hierarchically high centrality in community cluster networks, interactions amongst the labor gene set, and strong causal relationships with multiple downstream effects. In vitro experiments highlighted MT2A as an effective regulator of labor-associated genes. We have identified unique potential regulators of the term labor transcriptome in uterine tissues using a robust sequence of unbiased mathematical and literature-based in silico analyses. These findings encourage further investigation into the efficacy of predicted master regulators in blocking multiple pathways of labor processes across maternal and fetal tissues, and their potential as therapeutic approaches.

Effects of hydroxychloroquine on the human placenta-Findings from in vitro experimental data and a systematic review

Hydroxychloroquine (HCQ), a toll like receptor (TLR) 7 and 9 antagonist, is used during pregnancy for inflammatory conditions with limited understanding of its placental toxicology. We hypothesized that HCQ does not have toxic effects on the placenta and can modulate cytokine release in response to TLR7/9 activation. A systematic review was conducted and no studies of HCQ on multicellular human placental tissue were identified. Accordingly, placental villous explants were cultured for 7 days with HCQ +/- TLR7/9 agonists. HCQ did not affect cell turnover, nutrient transport or cytokine release but increased IL-10 (anti-inflammatory) secretion and promoted syncytiotrophoblast regeneration. Cytokine release stimulated by TLR7/9 agonists was unaffected by HCQ. In conclusion, HCQ did not adversely affect placental tissue and may have a protective anti-inflammatory function. Further research is needed to determine the mechanisms of HCQ actions on human placenta and whether they could be utilized to improve pregnancy outcomes.

Melatonin decreases and cytokines increase in women with placental insufficiency

Purpose: To investigate the levels of melatonin, proinflammatory and anti-inflammatory cytokines in pregnant women with placental insufficiency (PI).Materials and Methods: The PI was manifested as the intrauterine growth restriction syndrome of fetus (IUGR) in the third pregnancy trimester. The control group consisted of 20 women with uncomplicated pregnancy in the same term. The blood concentrations of melatonin, proinflammatory cytokines, such as tumor necrotizing factor-α (TNF-α), interleukin-1-β (IL-1-β), interleukin-6 (IL-6), and anti-inflammatory cytokines, such as interleukin-4 (IL-4), and interleukin-10 (IL-10), were studied.Results: The concentration of melatonin was found to decrease significantly if pregnancy was complicated by intrauterine fetal growth retardation (study group -126.87 ± 14.87 pg/ml, control group -231.25 ± 21.56 pg/ml, p < .001). The levels of proinflammatory cytokines in the study group were significantly higher as compared with the control group (TNF-α: study group -10.05 ± 1.35 pg/ml, control group -5.60 ± 1.50 pg/ml, p < .05; IL-1-β: study group -14.67 ± 2.13 pg/ml, control group -3.96 ± 0.92 pg/ml, p < .001; IL-6: study group -6.91 ± 0.99 pg/ml, control group -2.69 ± 0.99 pg/ml, p < .05). The same is true about anti-inflammatory cytokines (IL-4: study group -5.97 ± 0.50 pg/ml, control group -3.74 ± 0.62 pg/ml, p < .05; IL-10: study group -11.40 ± 1.50 pg/ml, control group -4.70 ± 3.20 pg/ml, p < .001). A moderate negative correlation between melatonin and IL-1-β in the group with PI (r = -0.3776, p = .0097), a closed negative correlation between the same indexes in the control group (r = -0.6785, p = .001), and a moderate negative correlation between melatonin and TNF-α (r = -0.4908, p = .02) were found.Conclusions: The blood level of melatonin significantly decreases in case of placental insufficiency, manifested as intrauterine fetal growth restriction. Strengthening of the proinflammatory immunity shown as the increasing of the levels of TNF-α, IL-1-β, and IL-6 levels is also present in case of IUGR. Increase of the serum concentration of the anti-inflammatory cytokines, such as IL-4 and IL-10, in our opinion, can be explained by activation of compensatory mechanisms, which decrease the risk of premature labor.

High mobility group box 1 and markers of oxidative stress in human cord blood

BACKGROUND

Parturition induces considerable oxidative stress and many inflammatory mediators, such as high mobility group box 1 (HMGB1), are involved from the beginning of the pregnancy to birth. The aim of the present study was to evaluate serum cord blood concentration of diacron-reactive oxygen metabolites (d-ROM), biological antioxidant potential (BAP), and HMGB1 to investigate the perinatal oxidative status of neonates and correlation with mode of delivery, as well as the influence of labor.

METHODS

The subjects consisted of 214 neonates delivered at University Hospital "G. Martino", Messina, in a 6 months period. Venous blood samples were collected from the umbilical cord after cord separation.

RESULTS

Umbilical cord venous blood HMGB1 was significantly higher in the spontaneous vaginal delivery (SVD) group than in the elective or emergency cesarean section (CS) group (P = 0.018). Regarding labor, there was no significant difference in HMGB1 concentration in umbilical vein blood between the spontaneous and induced labor groups (P = 0.250). Furthermore, d-ROM was significantly different between the SVD group and the elective or emergency CS group (P = 0.044). BAP concentration, however, was not significantly different, not even with regard to mode of labor.

CONCLUSION

Oxidation is higher in newborns delivered by SVD than in those delivered by CS, and HMGB1 may be involved in the mechanisms of birth, and responsible for decidual modifications that lead to birth.

Knowledge Gaps and Emerging Research Areas in Intrauterine Growth Restriction-Associated Brain Injury

Intrauterine growth restriction (IUGR) is a complex global healthcare issue. Concerted research and clinical efforts have improved our knowledge of the neurodevelopmental sequelae of IUGR which has raised the profile of this complex problem. Nevertheless, there is still a lack of therapies to prevent the substantial rates of fetal demise or the constellation of permanent neurological deficits that arise from IUGR. The purpose of this article is to highlight the clinical and translational gaps in our knowledge that hamper our collective efforts to improve the neurological sequelae of IUGR. Also, we draw attention to cutting-edge tools and techniques that can provide novel insights into this disorder, and technologies that offer the potential for better drug design and delivery. We cover topics including: how we can improve our use of crib-side monitoring options, what we still need to know about inflammation in IUGR, the necessity for more human post-mortem studies, lessons from improved integrated histology-imaging analyses regarding the cell-specific nature of magnetic resonance imaging (MRI) signals, options to improve risk stratification with genomic analysis, and treatments mediated by nanoparticle delivery which are designed to modify specific cell functions.

Alarmins at the maternal-fetal interface: involvement of inflammation in placental dysfunction and pregnancy complications 1

Inflammation is known to be associated with placental dysfunction and pregnancy complications. Infections are well known to be a cause of inflammation but they are frequently undetectable in pregnancy complications. More recently, the focus has been extended to inflammation of noninfectious origin, namely caused by endogenous mediators known as "damage-associated molecular patterns (DAMPs)" or alarmins. In this manuscript, we review the mechanism by which inflammation, sterile or infectious, can alter the placenta and its function. We discuss some classical DAMPs, such as uric acid, high mobility group box 1 (HMGB1), cell-free fetal deoxyribonucleic acid (DNA) (cffDNA), S100 proteins, heat shock protein 70 (HSP70), and adenosine triphosphate (ATP) and their impact on the placenta. We focus on the main placental cells (i.e., trophoblast and Hofbauer cells) and describe the placental response to, and release of, DAMPs. We also covered the current state of knowledge about the role of DAMPs in pregnancy complications including preeclampsia, fetal growth restriction, preterm birth, and stillbirth and possible therapeutic strategies to preserve placental function.

Differential effect of LPS and IL-1β in term placental explants

INTRODUCTION

Inflammation is an important cause of placental dysfunction often associated with pregnancy complications. One well-known cause of inflammation is infection, through conserved "pathogen-associated molecular patterns" (PAMPs). Endogenous inducers of inflammation, known as "damage-associated molecular patterns" (DAMPs), have also been associated with pathological pregnancies and could contribute to the observed placental inflammation. Although both stimuli (i.e. PAMPs/DAMPs) can induce inflammation, they have yet to be studied together to compare their inflammatory effects on the placenta.

METHODS

We used a model of term placental explants to compare the effects of a classical PAMP, bacterial lipopolysaccharide (LPS), and a DAMP, the pro-inflammatory cytokine interleukin (IL)-1. Gene and protein expression of several cytokines were analysed by qPCR and ELISAs and immunohistochemistry performed to study placental resident immune cells and apoptosis.

RESULTS

LPS induced pro-inflammatory mediators (IL-6, IL-1β/α, TNF-α) whereas IL-1β induced only IL-6. Furthermore, LPS but not IL-1 exposure, led to elevated IL-10 and IL-1Ra secretion. Blocking the IL-1 signalling pathway abrogated the pro-inflammatory actions of LPS, whilst anti-inflammatory effects were preserved. The number of CD45 ⁺ immune cells was elevated in explants treated with LPS only. A subpopulation of CD45 ⁺ cells were positive for PCNA indicating proliferation of tissue resident macrophages.

DISCUSSION

We conclude that LPS, a classical PAMP, and IL-1, a DAMP, have shared and distinct actions with pro-inflammatory effects mediated through IL-1 but anti-inflammatory actions having a distinct pathway. Identification of an inflammatory mediator (i.e. IL-1) common to multiple stimuli could be a therapeutic target to preserve the placenta.

Different concentration of human cord blood HMGB1 according to delivery and labour: A pilot study

OBJECTIVE

Oxidative stress is involved in several maternal conditions characterized both by an increase in free radicals synthesis and a parallel decrease in the antioxidant activity. Parturition induces considerable oxidative stress and many inflammatory mediators, among which HMGB1, are involved from the beginning of pregnancy to the birth of the infant. We evaluated serum cord blood HMGB1 levels in a population of neonates to investigate correlation with mode of delivery, as well as the influence of labour.

SETTING AND PATIENTS

The study subjects were 325 neonates delivered at University Hospital "G. Martino" of Messina over an 18-month period. Following cord separation, venous blood sampling was performed on umbelical cords.

RESULTS

In the cord venous blood, we found HMGB1 values significantly more elevated in spontaneous vaginal group when compared to elective or emergency caesarean section group. Regarding labour, umbilical cord venous blood HMGB1 levels were significantly higher in the spontaneous and induced labour group, compared to non-labouring women.

CONCLUSION

These results could highlight a possible role of HMGB1 during birth time related to mode of delivery and labour.

Zika-virus-infected human full-term placental explants display pro-inflammatory responses and undergo apoptosis

Zika virus (ZIKV) is a flavivirus that has been highly correlated with the development of neurological disorders and other malformations in newborns and stillborn fetuses after congenital infection. This association is supported by the presence of ZIKV in the fetal brain and amniotic fluid, and findings suggest that infection of the placental barrier is a critical step for fetal ZIKV infection in utero. Therefore, relevant models to investigate the interaction between ZIKV and placental tissues are essential for understanding the pathogenesis of Zika syndrome. In this report, we demonstrate that explant tissue from full-term human placentas sustains a productive ZIKV infection, though the results depend on the strain. Viral infection was found to be associated with pro-inflammatory cytokine expression and apoptosis of the infected tissue, and these findings confirm that placental explants are targets of ZIKV replication. We propose that human placental explants are useful as a model for studying ZIKV infection ex vivo.

Effects of micronutrients on placental function: evidence from clinical studies to animal models

Micronutrient deficiencies are common in pregnant women due to low dietary intake and increased requirements for fetal development. Low maternal micronutrient status is associated with a range of pregnancy pathologies involving placental dysfunction, including fetal growth restriction (FGR), small-for-gestational age (SGA), pre-eclampsia and preterm birth. However, clinical trials commonly fail to convincingly demonstrate beneficial effects of supplementation of individual micronutrients, attributed to heterogeneity and insufficient power, potential interactions and lack of mechanistic knowledge of effects on the placenta. We aimed to provide current evidence of relationships between selected micronutrients (vitamin D, vitamin A, iron, folate, vitamin B12) and adverse pregnancy outcomes, combined with understanding of actions on the placenta. Following a systematic literature search, we reviewed data from clinical, in vitro and in vivo studies of micronutrient deficiency and supplementation. Key findings are potential effects of micronutrient deficiencies on placental development and function, leading to impaired fetal growth. Studies in human trophoblast cells and rodent models provide insights into underpinning mechanisms. Interestingly, there is emerging evidence that deficiencies in all micronutrients examined induce a pro-inflammatory state in the placenta, drawing parallels with the inflammation detected in FGR, pre-eclampsia, stillbirth and preterm birth. Beneficial effects of supplementation are apparent in vitro and in animal models and for combined micronutrients in clinical studies. However, greater understanding of the roles of these micronutrients, and insight into their involvement in placental dysfunction, combined with more robust clinical studies, is needed to fully ascertain the potential benefits of supplementation in pregnancy.

Elevated Serum Level of HMGB1 in Patients with the Antiphospholipid Syndrome

Pregnancy problems are common in patients with rheumatic disease; indeed, autoimmune disorders and autoantibodies can affect pregnancy progress and lead to maternal complications. Recent studies have highlighted a close association between HMGB1, chronic inflammation, and autoimmune diseases. Thus, in this investigation, we analyzed serum levels of HMGB1, an alarmin which plays a pivotal role in inducing and enhancing immune cell function. Sera from 30 patients with antiphospholipid syndrome (11 primary and 19 secondary APS), 35 subjects with pregnancy morbidity, and 30 healthy women were analysed for HMGB1 and its putative receptor RAGE (sRAGE) by Western blot and for TNF-α by ELISA. Results revealed that APS patients showed significantly increased serum levels of HMGB1, sRAGE, and the proinflammatory cytokine TNF-α, as compared to healthy women. However, also, the pregnancy morbidity subjects showed significantly increased levels of HMGB1 and sRAGE as well as TNF-α compared to healthy women. Our findings suggest that in subjects with pregnancy morbidity, including obstetric APS, elevated levels of HMGB1/sRAGE may represent an alarm signal, indicating an increase of proinflammatory triggers. Further studies are needed to evaluate the role of HMGB1/sRAGE as a possible tool to evaluate the risk stratification of adverse pregnancy outcomes.

Placenta response of inflammation and oxidative stress in low-risk term childbirth: the implication of delivery mode

Background

Caesarean delivery rate is increasing gradually in China and there is no doubt that delivery mode is closely associated with the maternal health and infant development.This study examined the independent effect of delivery mode on placenta inflammation response and oxidative stress response.

Methods

A total of 3474 pregnant women recruited in Ma’anshan Birth Cohort Study were the initial study population. Data on maternal socio-demographic characteristics and pre-pregnancy BMI were collected at their 1st antenatal checkups. Pregnancy-specific anxiety was assessed during the three trimesters of pregnancy. Common pregnant complications were monitored in the whole pregnancy period. Delivery modes, as well as newborn characteristics were abstracted from medical records. Delivery modes included vaginal deliveries (VD), caesarean delivery with medical indications (CDMI), caesarean delivery on maternal request (CDMR) and urgent cesarean delivery (UCD). Placentas were collected during childbirth. The mRNA expression of IL-1β, TNF-a, IL-6, IFN-γ, IL-4, IL-10, IL-8, and HO-1 were assessed in the final sample of 1978 low-risk women with singleton term-births.

Results

The overall rate of caesarean delivery (CD) was 50.5% (1650/3265) in singleton term childbirths in this study. Among women who reported definite CD reasons, 56.8%of them chose the surgery without any medical indications.It shows a non-linear relationship between cytokines related with placenta inflammatory response, oxidative stress response and different delivery modes. At high percentiles of IL-1β, IFN-γ and IL-8, women with CDMR had higher expression levels compared to women with VD. Women with CDMI had higher levels at median percentiles of IL-1β, IFN-γ and IL-8. Women with CDMR had higher expression compared with VD at high percentiles of IL-6 and HO-1, and women with CDMI had higher levels of these two cytokines at their low percentiles. It is worth noting that at high percentiles, compared with normal delivery, the expression of IL-1β, IFN-γ, IL-8 and HO-1 have significantly altered in women with CDMR.

Conclusion

A high overall CD rate was found in this study, and caesarean delivery on maternal request was the major contributor to the high prevalence. Maternal placental oxidative stress and inflammatory response were closely associated with delivery mode. The effect is much amplified at high levels of expression in women who chose CD on maternal request.Such difference needs to be noticed and may have important implications for obstetricians, midwives and other perinatal health care workers.

Increased expression of high mobility group box protein 1 and vascular endothelial growth factor in placenta previa

Placenta previa is often associated with preterm delivery, reduced birth weight, a higher frequency of placental accreta and postpartum haemorrhage, and increased likelihood of blood transfusion. The present study aimed to examine the expression of high mobility group box protein 1 (HMGB1) in the placenta of women with or without placenta previa. The study group consisted of placental tissues obtained from women with or without placenta previa. The expression levels of HMGB1 and vascular endothelial growth factor (VEGF) were evaluated in the placental tissues using reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry. The mRNA expression levels of HMGB1 and VEGF were significantly increased in the placenta previa group compared with in the normal group. In addition, the placenta previa group exhibited increased HMGB1 and VEGF staining in vascular endothelial cells and trophoblasts. There were no significant differences in the expression of HMGB1 or VEGF between groups with or without placenta accreta or postpartum haemorrhage. The present study hypothesised that the increased expression of HMGB1 in the placenta may be associated with the pathogenesis of placenta previa by regulating the expression of the proangiogenic factor VEGF.

Damage-Associated molecular pattern markers HMGB1 and cell-Free fetal telomere fragments in oxidative-Stressed amnion epithelial cell-Derived exosomes

Term labor in humans is associated with increased oxidative stress (OS) -induced senescence and damages to amnion epithelial cells (AECs). Senescent fetal cells release alarmin high-mobility group box 1 (HMGB1) and cell-free fetal telomere fragments (cffTF) which can be carried by exosomes to other uterine tissues to produce parturition-associated inflammatory changes. This study characterized AEC-derived exosomes under normal and OS conditions and their packaging of HMGB1 and cffTF. Primary AECs were treated with either standard media or oxidative stress-induced media (exposure to cigarette smoke extract for 48h). Senescence was determined, and exosomes were isolated and characterized. To colocalize HMGB1 and cffTF in amnion exosomes, immunofluorescent staining and in situ hybridization were performed, followed by confocal microscopy. Next generation sequencing (NGS) determined exosomal cffTF and other cell-free amnion cell DNA specificity. Regardless of condition, primary AECs produce exosomes with a classic size, shape, and markers. OS and senescence caused the translocation of HMGB1 and cffTF from AECs' nuclei to cytoplasm compared to untreated cells, which was inhibited by antioxidant N-acetyl cysteine (NAC). Linescans confirmed colocalization of HMGB1 and cffTF in exosomes were higher in the cytoplasm after CSE treatment compared to untreated AECs. NGS determined that besides cffTF, AEC exosomes also carry genomic and mitochondrial DNA, regardless of growth conditions. Sterile inflammatory markers HMGB1 and cffTF from senescent fetal cells are packaged inside exosomes. We postulate that this exosomal cargo can act as a fetal signal at term and can cause labor-associated changes in neighboring tissues.

A novel in vitro model of villitis of unknown etiology demonstrates altered placental hormone and cytokine profile

PROBLEM

Placental dysfunction is present over 50% of cases of stillbirth and fetal growth restriction (FGR). Villitis of unknown etiology (VUE), an inflammatory condition of the placenta characterized by maternal T cell infiltrates in the villous stroma and dysregulation of inflammatory cytokines, is more frequent in FGR and stillbirth.

METHOD OF STUDY

A novel in vitro model of placental inflammation was developed to test the hypothesis that inflammatory cells seen in VUE and/or cytokines impair placental function.

RESULTS

Coculture of placental explants with maternal leukocytes resulted in increased leukocytes in villous tissue and elevated concentrations of IL-1β, IL-1Ra, IL-6, IL-10, and IFN-γ (P≤.05). Human chorionic gonadotrophin secretion was reduced following coculture with leukocytes (P≤.01) and cytokines (P≤.05).

CONCLUSION

These observations support the hypothesis that altered placental inflammation has deleterious effects on placental function. This model could be used to further understanding about the pathophysiology of VUE and to test potential therapies.

Programmed Fetal Membrane Senescence and Exosome-Mediated Signaling: A Mechanism Associated With Timing of Human Parturition

Human parturition is an inflammatory process that involves both fetal and maternal compartments. The precise immune cell interactions have not been well delineated in human uterine tissues during parturition, but insights into human labor initiation have been informed by studies in animal models. Unfortunately, the timing of parturition relative to fetal maturation varies among viviparous species-indicative of different phylogenetic clocks and alarms-but what is clear is that important common pathways must converge to control the birth process. Herein, we hypothesize a novel signaling mechanism initiated by human fetal membrane aging and senescence-associated inflammation. Programmed events of fetal membrane aging coincide with fetal growth and organ maturation. Mechanistically, senescence involves in telomere shortening and activation of p38 mitogen-activated signaling kinase resulting in aging-associated phenotypic transition. Senescent tissues release inflammatory signals that are propagated via exosomes to cause functional changes in maternal uterine tissues. In vitro, oxidative stress causes increased release of inflammatory mediators (senescence-associated secretory phenotype and damage-associated molecular pattern markers) that can be packaged inside the exosomes. These exosomes traverse through tissues layers, reach maternal tissues to increase overall inflammatory load transitioning them from a quiescent to active state. Animal model studies have shown that fetal exosomes can travel from fetal to the maternal side. Thus, aging fetal membranes and membrane-derived exosomes cargo fetal signals to the uterus and cervix and may trigger parturition. This review highlights a novel hypothesis in human parturition research based on data from ongoing research using human fetal membrane model system.