A Role for the Inflammasome in Spontaneous Labor at Term with Acute Histologic Chorioamnionitis

Risk of adverse perinatal outcomes among women with clinical and subclinical histopathological chorioamnionitis

Introduction

Histologic chorioamnionitis (HCA) is a placental inflammatory condition associated with adverse perinatal outcomes (APOs). This historical cohort study explores the risk of APOs in pregnant women with HCA and compares the impact of clinical chorioamnionitis (CCA) with subclinical chorioamnionitis (SCCA).

Methodology

Placentas were evaluated by a perinatal pathologist tand all women with HCA were included. Two groups were integrated: (1) women with clinical chorioamnionitis (CCA) and (2) women with subclinical chorioamnionitis (SCCA). Additionally, we conducted a secondary analysis to compare the prevalence of APOs among stage 1, 2 and 3 of HCA and the risk of APOs between grades 1 and 2 of HCA. The APOs analyzed were preterm birth, stillbirth, neonatal weight < 1,500 g, neonatal sepsis. Relative risk with 95% confidence interval was calculated.

Results

The study included 41 cases of CCA and 270 cases of SCCA. The mean gestational age at diagnosis and birth was 30.2 ± 5.4 weeks and 32.5 ± 5.1 weeks, for group 1 and 2, respectively. The study also found that women with HCA stage 3 and grade 2 had a higher prevalence and risk of adverse perinatal outcomes.

Discussion

The findings of this study suggest the importance of placental histological study to excluded SCCA, which represents a significant risk to both maternal and neonatal health, contributing to high morbidity and mortality.

In premature rupture of membranes, maternal serum delta neutrophil index may be a predictive factor for histological chorioamnionitis and affect fetal inflammatory markers: A retrospective cross-sectional study

PROBLEM

We aimed to investigate the predictive value of delta neutrophil index (DNI) for histological choriomanionitis (HCAM) and the effect of maternal inflammatory markers on neonatal outcomes and fetal inflammatory parameters.

METHOD OF STUDY

In this retrospective cross-sectional study, 68 pregnant women without HCAM (group 1) and 46 pregnant women diagnosed with HCAM (group 2) were divided into two groups. Demographic stories of the groups; maternal hematological parameters; maternal DNI and systemic inflammatory index (SII) values; outcomes of newborns; fetal inflammatory markers were recorded and compared between groups.

RESULTS

Maternal DNI, and SII levels were significantly higher in group 2 (p value < .05 for all). Admission to the neonatal unit (NICU) was higher in group 2 than in group 1 (p = .0001). We found that fetal inflammatory markers were significantly higher in group 2 (p values .001 for CRP, .0001 for DNI, and .002 for leukocyte). Maternal DNI was determined to be significantly diagnostic at a value of ≥1.3 in HCAM (p = .001). We observed that SII had a significant predictive value of 953036.6 (p = .019) for NICU admission. There is also a positive correlation between fetal inflammatory markers and maternal inflammatory markers.

CONCLUSIONS

We found that maternal inflammatory markers are high in HCAM, maternal DNI can predict patients who will develop HCAM, maternal SII value can predict NICU admission, fetal inflammatory markers are high in HCAM, and these markers are affected by maternal inflammatory markers.

[Effects of VX765 on osteoarthritis and chondrocyte inflammation in rats]

Objective

To investigate the effects and underlying mechanisms of VX765 on osteoarthritis (OA) and chondrocytes inflammation in rats.

Methods

Chondrocytes were isolated from the knee joints of 4-week-old Sprague Dawley (SD) rats. The third-generation cells were subjected to cell counting kit 8 (CCK-8) analysis to assess the impact of various concentrations (0, 1, 5, 10, 20, 50, 100 μmol/L) of VX765 on rat chondrocyte activity. An in vitro lipopolysaccharide (LPS) induced cell inflammation model was employed, dividing cells into control group, LPS group, VX765 concentration 1 group and VX765 concentration 2 group without obvious cytotoxicity. Western blot, real-time fluorescence quantitative PCR, and ELISA were conducted to measure the expression levels of inflammatory factors-transforming growth factor β 1 (TGF-β 1), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α). Additionally, Western blot and immunofluorescence staining were employed to assess the expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1). Thirty-two SD rats were randomly assigned to sham surgery group (group A), OA group (group B), OA+VX765 (50 mg/kg) group (group C), and OA+VX765 (100 mg/kg) group (group D), with 8 rats in each group. Group A underwent a sham operation with a medial incision, while groups B to D underwent additional transverse incisions to the medial collateral ligament and anterior cruciate ligament, with removal of the medial meniscus. One week post-surgery, groups C and D were orally administered 50 mg/kg and 100 mg/kg VX765, respectively, while groups A and B received an equivalent volume of saline. Histopathological examination using HE and safranin-fast green staining was performed, and Mankin scoring was utilized for evaluation. Immunohistochemical staining technique was employed to analyze the expressions of matrix metalloproteinase 13 (MMP-13) and collagen type Ⅱ.

Results

The CCK-8 assay indicated a significant decrease in cell viability at VX765 concentrations exceeding 10 μmol/L ( P<0.05), so 4 μmol/L and 8 μmol/L VX765 without obvious cytotoxicity were selected for subsequent experiments. Following LPS induction, the expressions of TGF-β 1, IL-6, and TNF-α in cells significantly increased when compared with the control group ( P<0.05). However, intervention with 4 μmol/L and 8 μmol/L VX765 led to a significant decrease in expression compared to the LPS group ( P<0.05). Western blot and immunofluorescence staining demonstrated a significant upregulation of Nrf2 pathway-related molecules Nrf2 and HO-1 protein expressions by VX765 ( P<0.05), indicating Nrf2 pathway activation. Histopathological examination of rat knee joint tissues and immunohistochemical staining revealed that, compared to group B, treatment with VX765 in groups C and D improved joint structural damage in rat OA, alleviated inflammatory reactions, downregulated MMP-13 expression, and increased collagen type Ⅱ expression.

Conclusion

VX765 can improve rat OA and reduce chondrocyte inflammation, possibly through the activation of the Nrf2 pathway.

Impact of pre-pregnancy weight on the risk of premature rupture of membranes in Chinese women

Objective

The objective of this study was to investigate the influence of pre-pregnancy body mass index (BMI) on the incidence of premature rupture of membranes (PROM) among Chinese women.

Methods

This was a hospital-based retrospective cohort study of 75,760 Chinese women who had live singleton births between 2016 and 2020. In this study, we utilized logistic regression analysis to estimate the association between pre-pregnancy BMI and PROM based on gestational age.

Results

Prior to pregnancy, being overweight or obese was found to be significantly associated with an increased risk of preterm premature rupture of membranes (PPROM), as evidenced by adjusted odds ratios and 95 % confidence intervals of 1.336 (1.173-1.522) and 1.411 (1.064-1.872), respectively. Those with PPROM were divided into three groups according to gestational age: 22-27, 28-31, and 32-36 weeks. Women who were overweight or obese prior to pregnancy had a higher likelihood of experiencing PROM between 22 and 27 weeks of gestation. This finding remained consistent even after controlling for potential confounding factors, such as gestational diabetes mellitus (GDM), gestational hypertension, preeclampsia, hydramnios, cervical abnormalities, and a history of preterm birth.

Conclusion

Our research findings indicate that being overweight or obese before pregnancy is linked to a higher likelihood of experiencing PPROM. Therefore, achieving optimal weight before pregnancy is important to prevent PPROM and its associated complications.

Rescuing fertility during COVID-19 infection: exploring potential pharmacological and natural therapeutic approaches for comorbidity, by focusing on NLRP3 inflammasome mechanism

The respiratory system was primarily considered the only organ affected by Coronavirus disease 2019 (COVID-19). As the pandemic continues, there is an increasing concern from the scientific community about the future effects of the virus on male and female reproductive organs, infertility, and, most significantly, its impact on the future generation. The general presumption is that if the primary clinical symptoms of COVID-19 are not controlled, we will face several challenges, including compromised infertility, infection-exposed cryopreserved germ cells or embryos, and health complications in future generations, likely connected to the COVID-19 infections of parents and ancestors. In this review article, we dedicatedly studied severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) virology, its receptors, and the effect of the virus to induce the activation of inflammasome as the main arm of the innate immune response. Among inflammasomes, nucleotide oligomerization domain-like receptor protein, pyrin domain containing 3 (NLRP3) inflammasome pathway activation is partly responsible for the inflicted damages in both COVID-19 infection and some reproductive disorders, so the main focus of the discussion is on NLRP3 inflammasome in the pathogenesis of COVID-19 infection alongside in the reproductive biology. In addition, the potential effects of the virus on male and female gonad functions were discussed, and we further explored the potential natural and pharmacological therapeutic approaches for comorbidity via NLRP3 inflammasome neutralization to develop a hypothesis for averting the long-term repercussions of COVID-19. Since activation of the NLRP3 inflammasome pathway contributes to the damage caused by COVID-19 infection and some reproductive disorders, NLRP3 inflammasome inhibitors have a great potential to be considered candidates for alleviating the pathological effects of the COVID-19 infection on the germ cells and reproductive tissues. This would impede the subsequent massive wave of infertility that may threaten the patients.

Maternal fever in labor: etiologies, consequences, and clinical management

Intrapartum fever is common and presents diagnostic and treatment dilemmas for the clinician. True maternal sepsis is rare; only an estimated 1.4% of women with clinical chorioamnionitis at term develop severe sepsis. However, the combination of inflammation and hyperthermia adversely impacts uterine contractility and, in turn, increases the risk for cesarean delivery and postpartum hemorrhage by 2- to 3-fold. For the neonate, the rates of encephalopathy or the need for therapeutic hypothermia have been reported to be higher with a maternal fever >39°C when compared with a temperature of 38°C to 39°C (1.1 vs 4.4%; P<.01). In a large cohort study, the combination of intrapartum fever and fetal acidosis was particularly detrimental. This suggests that intrapartum fever may lower the threshold for fetal hypoxic brain injury. Because fetal hypoxia is often difficult to predict or prevent, every effort should be made to reduce the risk for intrapartum fever. The duration of exposure to epidural analgesia and the length of labor in unmedicated women remain significant risk factors for intrapartum fever. Therefore, paying careful attention to maintaining labor progress can potentially reduce the rates of intrapartum fever and the risk for cesarean delivery if fever does occur. A recent, double-blind randomized trial of nulliparas at >36 weeks' gestation demonstrated that a high-dose oxytocin regimen (6×6 mU/min) when compared with a low-dose oxytocin regimen (2×2 mU/min) led to clinically meaningful reductions in the rate of intrapartum fever (10.4% vs 15.6%; risk rate, 0.67; 95% confidence interval, 0.48-0.92). When fever does occur, antibiotic treatment should be initiated promptly; acetaminophen may not be effective in reducing the maternal temperature. There is no evidence that reducing the duration of fetal exposure to intrapartum fever prevents known adverse neonatal outcomes. Therefore, intrapartum fever is not an indication for cesarean delivery to interrupt labor with the purpose of improving neonatal outcome. Finally, clinicians should be ready for the increased risk for postpartum hemorrhage and have uterotonic agents on hand at delivery to prevent delays in treatment.

The Role of the Interleukin-1 Family in Complications of Prematurity

Preterm birth is a major contributor to neonatal morbidity and mortality. Complications of prematurity such as bronchopulmonary dysplasia (BPD, affecting the lung), pulmonary hypertension associated with BPD (BPD-PH, heart), white matter injury (WMI, brain), retinopathy of prematurity (ROP, eyes), necrotizing enterocolitis (NEC, gut) and sepsis are among the major causes of long-term morbidity in infants born prematurely. Though the origins are multifactorial, inflammation and in particular the imbalance of pro- and anti-inflammatory mediators is now recognized as a key driver of the pathophysiology underlying these illnesses. Here, we review the involvement of the interleukin (IL)-1 family in perinatal inflammation and its clinical implications, with a focus on the potential of these cytokines as therapeutic targets for the development of safe and effective treatments for early life inflammatory diseases.

The role of interleukin-1 in perinatal inflammation and its impact on transitional circulation

Preterm birth is defined as delivery at <37 weeks of gestational age (GA) and exposes 15 million infants worldwide to serious early life diseases. Lowering the age of viability to 22 weeks GA entailed provision of intensive care to a greater number of extremely premature infants. Moreover, improved survival, especially at extremes of prematurity, comes with a rising incidence of early life diseases with short- and long-term sequelae. The transition from fetal to neonatal circulation is a substantial and complex physiologic adaptation, which normally happens rapidly and in an orderly sequence. Maternal chorioamnionitis or fetal growth restriction (FGR) are two common causes of preterm birth that are associated with impaired circulatory transition. Among many cytokines contributing to the pathogenesis of chorioamnionitis-related perinatal inflammatory diseases, the potent pro-inflammatory interleukin (IL)-1 has been shown to play a central role. The effects of utero-placental insufficiency-related FGR and in-utero hypoxia may also be mediated, in part, via the inflammatory cascade. In preclinical studies, blocking such inflammation, early and effectively, holds great promise for improving the transition of circulation. In this mini-review, we outline the mechanistic pathways leading to abnormalities in transitional circulation in chorioamnionitis and FGR. In addition, we explore the therapeutic potential of targeting IL-1 and its influence on perinatal transition in the context of chorioamnionitis and FGR.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

Human fetal membrane IL-1β production in response to bacterial components is mediated by uric-acid induced NLRP3 inflammasome activation

Inflammatory interleukin-1β (IL-1β) is an important mediator of preterm birth. IL-1β secretion is mediated by the inflammasome that processes pro-IL-1β into its active form. However the mechanisms involved at the level of the fetal membrane (FM) are not fully understood. This study sought to determine the FM compartment involved in IL-1β production in response to bacterial components and to evaluate the mechanism of inflammasome activation. Since IL-18 is also mediated by the inflammasome and IL-8 is a chemoattractant that contributes to neutrophil recruitment in chorioamnionitis, we also evaluated the production of these factors. A human explant system was used to evaluate the response of the chorion, amnion, and intact FMs to the bacterial components lipopolysaccharide (LPS), peptidoglycan (PGN), or muramyl dipeptide (MDP). The chorion was the major source of IL-1β and IL-8 production in response to LPS, PGN, and MDP. LPS, PGN, and MDP induced FM IL-1β and IL-18 secretion in a non-pyroptotic manner through activation of the NLRP3 inflammasome with contributions from ATP release through Pannexin-1, and ROS signaling. Since LPS, PGN, and MDP are not known to activate NLRP3 directly, the role of uric acid as a potential mediator was assessed. FMs produced elevated uric acid in response to LPS, PGN and MDP. FM IL-1β secretion was inhibited by allopurinol, which blocks uric acid production, for LPS and PGN, and to a lesser degree, MDP. These findings shed light on the mechanisms by which fetal membrane inflammation and subsequent preterm birth may arise.

Inflammasome signaling in human placental trophoblasts regulates immune defense against Listeria monocytogenes infection

The human placenta is a dynamic organ that modulates physiological adaptations to pregnancy. To define the immunological signature of the human placenta, we performed unbiased profiling of secreted immune factors from human chorionic villi isolated from placentas at mid and late stages of pregnancy. We show that placental trophoblasts constitutively secrete the inflammasome-associated cytokines IL-1β and IL-18, which is blocked by NLRP3 inflammasome inhibitors and occurs without detectable gasdermin D cleavage. We further show that placenta-derived IL-1β primes monocytes for inflammasome induction to protect against Listeria monocytogenes infection. Last, we show that the human placenta responds to L. monocytogenes infection through additional inflammasome activation and that inhibition of this pathway sensitizes villi to infection. Our results thus identify the inflammasome as an important mechanism by which the human placenta regulates systemic and local immunity during pregnancy to defend against L. monocytogenes infection.

Hydrogen Sulfide Contributes to Uterine Quiescence Through Inhibition of NLRP3 Inflammasome Activation by Suppressing the TLR4/NF-κB Signalling Pathway

Background

The NLRP3 inflammasome plays a critical role in inflammatory responses in various diseases. Our previous study showed that NLRP3 expression was significantly increased in human pregnancy tissue during term labour. Therefore, we explored whether NLRP3 participated in inflammatory responses of preterm and term labour and whether this process could be relieved by H₂S, one anti-inflammatory gasotransmitter.

Methods

Human myometrium was obtained from non-labouring and labouring women. Mouse myometrium was obtained from LPS-induced infectious preterm labour. Uterine smooth muscle cells were isolated from non-labouring women’s myometrial tissues, transfected with siRNA, and treated cells with IL-1β, H₂S donor NaHS, NF-κB inhibitor BAY 11–7082 and TLR4 inhibitorTAK-242. The NLRP3 inflammasome, CSE, CBS, TLR4, uterine contraction-associated proteins (CAPs), NF-κB activation and inflammatory cytokine expression were assessed by Western blotting and RT-PCR.

Results

The NLRP3 inflammasome, TLR4 and activated NF-κB expression were upregulated in human term labour, mouse preterm labour and human uterine smooth muscle cells treated with IL-1β. NLRP3 levels were negatively correlated with CSE and CBS expression. Treatment with the H₂S donor NaHS delayed LPS-induced preterm birth in mice and inhibited NLRP3 inflammasome activation. In siNLRP3-transfected cells, there was a significant decrease in the expression of CAPs and inflammatory cytokines compared with IL-1β stimulation. In addition, treatment with the H₂S donor NaHS inhibited NLRP3 inflammasome activation, reduced the expression of uterine contraction-associated proteins and inflammatory cytokines and reduced the activation of TLR4 and NF-κB compared with stimulation with IL-1β in human uterine smooth muscle cells. Furthermore, treatment of uterine smooth muscle cells with BAY 11–7082 and TAK-242 found that NLRP3 activation was regulated by the TLR4 and NF-κB pathways.

Conclusion

H₂S suppresses CAP expression and the inflammatory response and contributes to uterine quiescence by inhibiting the TLR4/NF-κB signalling pathway and downstream NLRP3 inflammasome activation. Thus, H₂S contributes to uterine quiescence through inhibition of NLRP3 inflammasome activation by suppressing the TLR4/NF-κB signalling pathway.

Presence of Chlamydia trachomatis DNA in the amniotic fluid in women with preterm prelabor rupture of membranes

OBJECTIVE

The primary aim of this study was to assess the rate and load of amniotic fluid Chlamydia trachomatis DNA and their associations with intra-amniotic infection and intra-uterine inflammatory complications in women with preterm prelabor rupture of membranes (PPROM). The secondary aim was to assess the short-term morbidity of newborns from PPROM pregnancies complicated by amniotic fluid C. trachomatis DNA.

METHODS

A retrospective study of 788 women with singleton pregnancies complicated by PPROM between 24 + 0 and 36 + 6 weeks of gestation was performed. Transabdominal amniocenteses were performed at the time of admission. C. trachomatis DNA in the amniotic fluid was assessed by real-time polymerase chain reaction using a commercial AmpliSens® C. trachomatis/Ureaplasma/Mycoplasma hominis-FRT kit, and the level of Ct DNA was quantified.

RESULTS

Amniotic fluid C. trachomatis DNA complicated 2% (16/788) of the PPROM pregnancies and was present in very low loads (median 57 copies DNA/mL). In addition to amniotic fluid C. trachomatis DNA, other bacteria were detected in 62% (10/16) of the C. trachomatis DNA-complicated PPROM pregnancies. Amniotic fluid C. trachomatis DNA was associated with intra-amniotic infection, histologic chorioamnionitis (HCA), and funisitis in 31%, 47%, and 33%, respectively. The presence of C. trachomatis DNA accompanied by Ureaplasma species in the amniotic fluid was associated with a higher rate of HCA than the presence of amniotic fluid C. trachomatis DNA alone. The composite neonatal morbidity in newborns from PPROM pregnancies with amniotic fluid C. trachomatis DNA was 31%.

CONCLUSION

The presence of C. trachomatis DNA in the amniotic fluid is a relatively rare condition in PPROM. Amniotic fluid C. trachomatis DNA in PPROM is not related to intensive intra-amniotic and intr-auterine inflammatory responses or adverse short-term neonatal outcomes.

Neural progenitor cell pyroptosis contributes to Zika virus-induced brain atrophy and represents a therapeutic target

Mounting evidence has associated Zika virus (ZIKV) infection with congenital malformations, including microcephaly, which raises global alarm. Nonetheless, mechanisms by which ZIKV disrupts neurogenesis and causes microcephaly are far from being understood. In this study, we discovered direct effects of ZIKV on neural progenitor cell development by inducing caspase-1- and gasdermin D (GSDMD)-mediated pyroptotic cell death, linking ZIKV infection with the development of microcephaly. Importantly, caspase-1 depletion or its inhibitor VX-765 treatment reduced ZIKV-induced inflammatory responses and pyroptosis, and substantially attenuated neuropathology and brain atrophy in vivo. Collectively, our data identify caspase-1- and GSDMD-mediated pyroptosis in neural progenitor cells as a previously unrecognized mechanism for ZIKV-related pathological effects during neural development, and also provide treatment options for ZIKV-associated diseases.

A role for the NLRC4 inflammasome in premature rupture of membrane

PROM is one of the common complications of perinatal period, which seriously threatens the mother and newborn. The purpose of this study was to identify the role of NLRC4 inflammasomes in this process and their underlying mechanisms. We performed high-throughput RNA sequencing of fetal membrane tissue from 3 normal pregnant women and 3 term-premature rupture of fetal membrane (TPROM) patients who met the inclusion criteria, and found that NLRC4 was significantly up-regulated in TPROM patients. An observational study of TPROM patients (PROM group, n = 30) and normal pregnant women (control group, n = 30) was performed at the Xuzhou Maternal and Child Health Hospital affiliated to Xuzhou Medical University from May 2018 to May 2019. The expression of genes involved in inflammasome complex including NLRC1, NLRC3, AIM2, NLRC4, ASC, caspase-1, IL-6, IL-18 and IL-1βwas determined via real-time PCR, immunohistochemistry and immunofluorescence. Measurement of NLRC4 level in serum was conducted by ELISA assay. The results showed that the NLRC4, ASC, caspase-1, IL-1β and IL-18 levels in fetal membrane, placental tissues and maternal serum were markedly higher in the PROM group than that in the control group. In conclusion, NLRC4 is a markedly up-regulated gene in TPROM fetal membrane tissue, suggesting that NLRC4 is involved in the occurrence and development of TPROM; NLRC4 levels in maternal blood serum are closely related to TPROM and have the potential to assist doctors in predicting and diagnosing PROM.

Novel pathways of inflammation in human fetal membranes associated with preterm birth and preterm pre-labor rupture of the membranes

Spontaneous preterm birth (PTB) and preterm pre-labor rupture of the membranes (pPROM) are major pregnancy complications. Although PTB and pPROM have common etiologies, they arise from distinct pathophysiologic pathways. Inflammation is a common underlying mechanism in both conditions. Balanced inflammation is required for fetoplacental growth; however, overwhelming inflammation (physiologic at term and pathologic at preterm) can lead to term and preterm parturition. A lack of effective strategies to control inflammation and reduce the risk of PTB and pPROM suggests that there are several modes of the generation of inflammation which may be dependent on the type of uterine tissue. The avascular fetal membrane (amniochorion), which provides structure, support, and protection to the intrauterine cavity, is one of the key contributors of inflammation. Localized membrane inflammation helps tissue remodeling during pregnancy. Two unique mechanisms that generate balanced inflammation are the progressive development of senescence (aging) and cyclic cellular transitions: epithelial to mesenchymal (EMT) and mesenchymal to epithelial (MET). The intrauterine build-up of oxidative stress at term or in response to risk factors (preterm) can accelerate senescence and promote a terminal state of EMT, resulting in the accumulation of inflammation. Inflammation degrades the matrix and destabilizes membrane function. Inflammatory mediators from damaged membranes are propagated via extracellular vesicles (EV) to maternal uterine tissues and transition quiescent maternal uterine tissues into an active state of labor. Membrane inflammation and its propagation are fetal signals that may promote parturition. This review summarizes the mechanisms of fetal membrane cellular senescence, transitions, and the generation of inflammation that contributes to term and preterm parturitions.

Human Amnion Epithelial Cells (AECs) Respond to the FSL-1 Lipopeptide by Engaging the NLRP7 Inflammasome

Context and Objectives: Inflammation is the leading mechanism involved in both physiological and pathological rupture of fetal membranes. Our aim was to obtain a better characterization of the inflammasome-dependent inflammation processes in these tissues, with a particular focus on the nucleotide-binding oligomerization domain (NOD)–like receptor, pyrin domain containing protein 7 (NLRP7) inflammasome.

Methods: The presence of NLRP7 inflammasome actors [NLRP7, apoptosis-associated speck–like protein containing a CARD domain (ASC), and caspase-1] was confirmed by reverse transcriptase–polymerase chain reaction (RT-PCR) in human amnion and choriodecidua at the three trimesters and at term. The protein concentrations were then determined by enzyme-linked immunosorbent assay in term tissues, with or without labor. The presence of Mycoplasma salivarium and Mycoplasma fermentans in human fetal membranes was investigated using a PCR approach. Human amnion epithelial cells (AECs) were treated for 4 or 20 h with fibroblast-stimulating lipopeptide-1 (FSL-1), a M. salivarium–derived ligand. Transcripts and proteins quantity was then measured by RT–quantitative PCR and Western blotting, respectively. NLRP7 and ASC colocalization was confirmed by immunofluorescence. Western blots allowed analysis of pro–caspase-1 and gasdermin D cleavage.

Results: NLRP7, ASC, and caspase-1 transcripts were expressed in both sheets of human fetal membranes during all pregnancy stages, but only ASC protein expression was increased with labor. In addition, M. salivarium and M. fermentans were detected for the first time in human fetal membranes. NLRP7 and caspase-1 transcripts, as well as NLRP7, ASC, and pro–caspase-1 protein levels, were increased in FSL-1–treated AECs. The NLRP7 inflammasome assembled around the nucleus, and pro–caspase-1 and gasdermin D were cleaved into their mature forms after FSL-1 stimulation.

Conclusion: Two new mycoplasmas, M. salivarium and M. fermentans, were identified in human fetal membranes, and a lipopeptide derived from M. salivarium was found to induce NLRP7 inflammasome formation in AECs.

Inhibition of the NLRP3 inflammasome can prevent sterile intra-amniotic inflammation, preterm labor/birth, and adverse neonatal outcomes†

Sterile intra-amniotic inflammation is commonly observed in patients with spontaneous preterm labor, a syndrome that commonly precedes preterm birth, the leading cause of perinatal morbidity and mortality worldwide. However, the mechanisms leading to sterile intra-amniotic inflammation are poorly understood and no treatment exists for this clinical condition. Herein, we investigated whether the alarmin S100B could induce sterile intra-amniotic inflammation by activating the NLRP3 inflammasome, and whether the inhibition of this pathway could prevent preterm labor/birth and adverse neonatal outcomes. We found that the ultrasound-guided intra-amniotic administration of S100B induced a 50% rate of preterm labor/birth and a high rate of neonatal mortality (59.7%) without altering the fetal and placental weights. Using a multiplex cytokine array and immunoblotting, we reported that S100B caused a proinflammatory response in the amniotic cavity and induced the activation of the NLRP3 inflammasome in the fetal membranes, indicated by the upregulation of the NLRP3 protein and increased release of active caspase-1 and mature IL-1β. Inhibition of the NLRP3 inflammasome via the specific inhibitor MCC950 prevented preterm labor/birth by 35.7% and reduced neonatal mortality by 26.7%. Yet, inhibition of the NLRP3 inflammasome at term did not drastically obstruct the physiological process of parturition. In conclusion, the data presented herein indicate that the alarmin S100B can induce sterile intra-amniotic inflammation, preterm labor/birth, and adverse neonatal outcomes by activating the NLRP3 inflammasome, which can be prevented by inhibiting such a pathway. These findings provide evidence that sterile intra-amniotic inflammation could be treated by targeting the NLRP3 inflammasome.

Intra-amniotic inflammation induces preterm birth by activating the NLRP3 inflammasome†

Intra-amniotic inflammation is strongly associated with spontaneous preterm labor and birth, the leading cause of perinatal mortality and morbidity worldwide. Previous studies have suggested a role for the NLRP3 (NLR family pyrin domain-containing protein 3) inflammasome in the mechanisms that lead to preterm labor and birth. However, a causal link between the NLRP3 inflammasome and preterm labor/birth induced by intra-amniotic inflammation has not been established. Herein, using an animal model of lipopolysaccharide-induced intra-amniotic inflammation (IAI), we demonstrated that there was priming of the NLRP3 inflammasome (1) at the transcriptional level, indicated by enhanced mRNA expression of inflammasome-related genes (Nlrp3, Casp1, Il1b); and (2) at the protein level, indicated by greater protein concentrations of NLRP3, in both the fetal membranes and decidua basalis prior to preterm birth. Additionally, we showed that there was canonical activation of the NLRP3 inflammasome in the fetal membranes, but not in the decidua basalis, prior to IAI-induced preterm birth as evidenced by increased protein levels of active caspase-1. Protein concentrations of released IL1β were also increased in both the fetal membranes and decidua basalis, as well as in the amniotic fluid, prior to IAI-induced preterm birth. Finally, using the specific NLRP3 inhibitor, MCC950, we showed that in vivo inhibition of the NLRP3 inflammasome reduced IAI-induced preterm birth and neonatal mortality. Collectively, these results provide a causal link between NLRP3 inflammasome activation and spontaneous preterm labor and birth in the context of intra-amniotic inflammation. We also showed that, by targeting the NLRP3 inflammasome, adverse pregnancy and neonatal outcomes can be significantly reduced.

Inflammasomes: Their Role in Normal and Complicated Pregnancies

Inflammasomes are cytoplasmic multiprotein complexes that coordinate inflammatory responses, including those that take place during pregnancy. Inflammasomes and their downstream mediators caspase-1 and IL-1β are expressed by gestational tissues (e.g., the placenta and chorioamniotic membranes) during normal pregnancy. Yet, only the activation of the NLRP3 inflammasome in the chorioamniotic membranes has been partially implicated in the sterile inflammatory process of term parturition. In vivo and ex vivo studies have consistently shown that the activation of the NLRP3 inflammasome is a mechanism whereby preterm labor and birth occur in the context of microbial- or alarmin-induced inflammation. In the placenta, the activation of the NLRP3 inflammasome is involved in the pathogenesis of preeclampsia and other pregnancy syndromes associated with placental inflammation. This evidence suggests that inhibition of the NLRP3 inflammasome or its downstream mediators may foster the development of novel anti-inflammatory therapies for the prevention or treatment of pregnancy complications.

Cell-Free Fetal DNA Increases Prior to Labor at Term and in a Subset of Preterm Births

Cell-free fetal DNA in the maternal circulation has been associated with the onset of labor at term. Moreover, clinical studies have suggested that cell-free fetal DNA has value to predict pregnancy complications such as spontaneous preterm labor leading to preterm birth. However, a mechanistic link between cell-free fetal DNA and preterm labor and birth has not been established. Herein, using an allogeneic mouse model in which a paternal green fluorescent protein (GFP) can be tracked in the fetuses, we established that cell-free fetal DNA (Egfp) concentrations were higher in late gestation compared to mid-pregnancy and were maintained at increased levels during the onset of labor at term, followed by a rapid decrease after birth. A positive correlation between cell-free fetal DNA concentrations and the number of GFP-positive pups was also observed. The increase in cell-free fetal DNA concentrations prior to labor at term was not linked to a surge in any specific cytokine/chemokine; yet, specific chemokines (i.e., CCL2, CCL7, and CXCL2) increased as gestation progressed and maintained elevated levels in the postpartum period. In addition, cell-free fetal DNA concentrations increased prior to systemic inflammation-induced preterm birth, which was associated with a strong cytokine response in the maternal circulation. However, cell-free fetal DNA concentrations were not increased prior to intra-amniotic inflammation-induced preterm birth, but in this model, a mild inflammatory response was observed in the maternal circulation. Collectively, these findings suggest that an elevation in cell-free fetal DNA concentrations in the maternal circulation precedes the physiological process of labor at term and the pathological process of preterm labor linked with systemic inflammation, but not that associated with intra-amniotic inflammation.

Antibiotic administration can eradicate intra-amniotic infection or intra-amniotic inflammation in a subset of patients with preterm labor and intact membranes

BACKGROUND

Intra-amniotic infection is present in 10% of patients with an episode of preterm labor, and is a risk factor for impending preterm delivery and neonatal morbidity/mortality. Intra-amniotic inflammation is often associated with intra-amniotic infection, but is sometimes present in the absence of detectable microorganisms. Antibiotic treatment of intra-amniotic infection has traditionally been considered to be ineffective. Intra-amniotic inflammation without microorganisms has a prognosis similar to that of intra-amniotic infection.

OBJECTIVE

To determine whether antibiotics can eradicate intra-amniotic infection or intra-amniotic inflammation in a subset of patients with preterm labor and intact membranes.

MATERIALS AND METHODS

The study population consisted of women who met the following criteria: 1) singleton gestation between 20 and 34 weeks; 2) preterm labor and intact membranes; 3) transabdominal amniocentesis performed for the evaluation of the microbiologic/inflammatory status of the amniotic cavity; 4) intra-amniotic infection and/or intra-amniotic inflammation; and 5) received antibiotic treatment that consisted of ceftriaxone, clarithromycin, and metronidazole. Follow-up amniocentesis was performed in a subset of patients. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas, and polymerase chain reaction was performed for Ureaplasma spp. Intra-amniotic infection was defined as a positive amniotic fluid culture or positive polymerase chain reaction, and intra-amniotic inflammation was suspected when there was an elevated amniotic fluid white blood cell count or a positive result of a rapid test for matrix metalloproteinase-8. For this study, the final diagnosis of intra-amniotic inflammation was made by measuring the interleukin-6 concentration in stored amniotic fluid (>2.6 ng/mL). These results were not available to managing clinicians. Treatment success was defined as eradication of intra-amniotic infection and/or intra-amniotic inflammation or delivery ≥37 weeks.

RESULTS

Of 62 patients with intra-amniotic infection and/or intra-amniotic inflammation, 50 received the antibiotic regimen. Of those patients, 29 were undelivered for ≥7 days and 19 underwent a follow-up amniocentesis. Microorganisms were identified by culture or polymerase chain reaction of amniotic fluid obtained at admission in 21% of patients (4/19) who had a follow-up amniocentesis, and were eradicated in 3 of the 4 patients. Resolution of intra-amniotic infection/inflammation was confirmed in 79% of patients (15/19), and 1 other patient delivered at term, although resolution of intra-amniotic inflammation could not be confirmed after a follow-up amniocentesis. Thus, resolution of intra-amniotic inflammation/infection or term delivery (treatment success) occurred in 84% of patients (16/19) who had a follow-up amniocentesis. Treatment success occurred in 32% of patients (16/50) with intra-amniotic infection/inflammation who received antibiotics. The median amniocentesis-to-delivery interval was significantly longer among women who received the combination of antibiotics than among those who did not (11.4 days vs 3.1 days: P = .04).

CONCLUSION

Eradication of intra-amniotic infection/inflammation after treatment with antibiotics was confirmed in 79% of patients with preterm labor, intact membranes, and intra-amniotic infection/inflammation who had a follow-up amniocentesis. Treatment success occurred in 84% of patients who underwent a follow-up amniocentesis and in 32% of women who received the antibiotic regimen.

Evidence that antibiotic administration is effective in the treatment of a subset of patients with intra-amniotic infection/inflammation presenting with cervical insufficiency

BACKGROUND

Cervical insufficiency is a risk factor for spontaneous midtrimester abortion or early preterm birth. Intra-amniotic infection has been reported in 8-52% of such patients and intra-amniotic inflammation in 81%. Some professional organizations have recommended perioperative antibiotic treatment when emergency cervical cerclage is performed. The use of prophylactic antibiotics is predicated largely on the basis that they reduce the rate of complications during the course of vaginal surgery. However, it is possible that antibiotic administration can also eradicate intra-amniotic infection/inflammation and improve pregnancy outcome.

OBJECTIVE

To describe the outcome of antibiotic treatment in patients with cervical insufficiency and intra-amniotic infection/inflammation.

STUDY DESIGN

The study population consisted of 22 women who met the following criteria: (1) singleton pregnancy; (2) painless cervical dilatation of >1 cm between 16.0 and 27.9 weeks of gestation; (3) intact membranes and absence of uterine contractions; (4) transabdominal amniocentesis performed for the evaluation of the microbiologic and inflammatory status of the amniotic cavity; (5) presence of intra-amniotic infection/inflammation; and (6) antibiotic treatment (regimen consisted of ceftriaxone, clarithromycin, and metronidazole). Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas, and polymerase chain reaction for Ureaplasma spp. was performed. Intra-amniotic infection was defined as a positive amniotic fluid culture for microorganisms or a positive polymerase chain reaction for Ureaplasma spp., and intra-amniotic inflammation was suspected when there was an elevated amniotic fluid white blood cell count (≥19 cells/mm³) or a positive rapid test for metalloproteinase-8 (sensitivity 10 ng/mL). For the purpose of this study, the "gold standard" for diagnosis of intra-amniotic inflammation was an elevated interleukin-6 concentration (>2.6 ng/mL) using an enzyme-linked immunosorbent assay. The results of amniotic fluid interleukin-6 were not available to managing clinicians. Follow-up amniocentesis was routinely offered to monitor the microbiologic and inflammatory status of the amniotic cavity and fetal lung maturity. Treatment success was defined as resolution of intra-amniotic infection/inflammation or delivery ≥34 weeks of gestation.

RESULTS

Of 22 patients with cervical insufficiency and intra-amniotic infection/inflammation, 3 (14%) had microorganisms in the amniotic fluid. Of the 22 patients, 6 (27%) delivered within 1 week of amniocentesis and the remaining 16 (73%) delivered more than 1 week after the diagnostic procedure. Among these, 12 had a repeat amniocentesis to assess the microbial and inflammatory status of the amniotic cavity; in 75% (9/12), there was objective evidence of resolution of intra-amniotic inflammation or intra-amniotic infection demonstrated by analysis of amniotic fluid at the time of the repeat amniocentesis. Of the 4 patients who did not have a follow-up amniocentesis, all delivered ≥34 weeks, 2 of them at term; thus, treatment success occurred in 59% (13/22) of cases.

CONCLUSION

In patients with cervical insufficiency and intra-amniotic infection/inflammation, administration of antibiotics (ceftriaxone, clarithromycin, and metronidazole) was followed by resolution of the intra-amniotic inflammatory process or intra-amniotic infection in 75% of patients and was associated with treatment success in about 60% of cases.

Clinical chorioamnionitis at term IX: in vivo evidence of intra-amniotic inflammasome activation

Background The inflammasome has been implicated in the mechanisms that lead to spontaneous labor at term. However, whether the inflammasome is activated in the amniotic cavity of women with clinical chorioamnionitis at term is unknown. Herein, by measuring extracellular ASC [apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (CARD)], we investigated whether there is in vivo inflammasome activation in amniotic fluid of patients with clinical chorioamnionitis at term with sterile intra-amniotic inflammation and in those with intra-amniotic infection. Methods This was a retrospective cross-sectional study that included amniotic fluid samples collected from 76 women who delivered after spontaneous term labor with diagnosed clinical chorioamnionitis. Intra-amniotic inflammation was defined as an elevated amniotic fluid interleukin (IL)-6 concentration ≥2.6 ng/mL, and intra-amniotic infection was diagnosed by the presence of microbial invasion of the amniotic cavity (MIAC) accompanied by intra-amniotic inflammation. Patients were classified into the following groups: (1) women without intra-amniotic inflammation or infection (n=16); (2) women with MIAC but without intra-amniotic inflammation (n=5); (3) women with sterile intra-amniotic inflammation (n=15); and (4) women with intra-amniotic infection (n=40). As a readout of in vivo inflammasome activation, extracellular ASC was measured in amniotic fluid by enzyme-linked immunosorbent assay. Acute inflammatory responses in the amniotic fluid and placenta were also evaluated. Results In clinical chorioamnionitis at term: (1) amniotic fluid concentrations of ASC (extracellular ASC is indicative of in vivo inflammasome activation) and IL-6 were greater in women with intra-amniotic infection than in those without intra-amniotic inflammation, regardless of the presence of MIAC; (2) amniotic fluid concentrations of ASC and IL-6 were also higher in women with sterile intra-amniotic inflammation than in those without intra-amniotic inflammation, regardless of the presence of MIAC; (3) amniotic fluid concentrations of IL-6, but not ASC, were more elevated in women with intra-amniotic infection than in those with sterile intra-amniotic inflammation; (4) a positive and significant correlation was observed between amniotic fluid concentrations of ASC and IL-6; (5) no differences were observed in amniotic fluid ASC and IL-6 concentrations between women with and without MIAC in the absence of intra-amniotic inflammation; (6) women with intra-amniotic infection had elevated white blood cell counts and reduced glucose levels in amniotic fluid compared to the other three study groups; and (7) women with intra-amniotic infection presented higher frequencies of acute maternal and fetal inflammatory responses in the placenta than those with sterile intra-amniotic inflammation. Conclusion The intra-amniotic inflammatory response, either induced by alarmins or microbes, is characterized by the activation of the inflammasome - as evidenced by elevated amniotic fluid concentrations of extracellular ASC - in women with clinical chorioamnionitis at term. These findings provide insight into the intra-amniotic inflammatory response in women with clinical chorioamnionitis at term.

The frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes

OBJECTIVE

The objective of this study is to evaluate the frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes.

STUDY DESIGN

Amniotic fluid (AF) was retrieved from both sacs in 90 twin gestations with preterm labor and intact membranes (gestational age between 20 and 34 6/7 weeks). Preterm labor was defined as the presence of painful regular uterine contractions, with a frequency of at least 2 every 10 min, requiring hospitalization. Fluid was cultured and assayed for matrix metalloproteinase-8. Intra-amniotic inflammation was defined as an AF matrix metalloproteinase-8 concentration >23 ng/mL.

RESULTS

The prevalence of intra-amniotic inflammation for at least 1 amniotic sac was 39% (35/90), while that of proven intra-amniotic infection for at least one amniotic sac was 10% (9/90). Intra-amniotic inflammation without proven microbial invasion of the amniotic cavity was found in 29% (26/90) of the cases. Intra-amniotic inflammation was present in both amniotic sacs for 22 cases, in the presenting amniotic sac for 12 cases, and in the non-presenting amniotic sac for one case. Women with intra-amniotic inflammation observed in at least one amniotic sac and a negative AF culture for microorganisms had a significantly higher rate of adverse pregnancy outcome than those with a negative AF culture and without intra-amniotic inflammation (lower gestational age at birth, shorter amniocentesis-to-delivery interval, and significant neonatal morbidity). Importantly, there was no significant difference in pregnancy outcome between women with intra-amniotic inflammation and a negative AF culture and those with a positive AF culture.

CONCLUSION

Intra-amniotic inflammation is present in 39% of twin pregnancies with preterm labor and intact membranes and is a risk factor for impending preterm delivery and adverse outcome, regardless of the presence or absence of bacteria detected using cultivation techniques.

NLRP7 is increased in human idiopathic fetal growth restriction and plays a critical role in trophoblast differentiation

Fetal growth restriction (FGR) the leading cause of perinatal mortality and morbidity is highly related to abnormal placental development, and placentas from FGR pregnancies are often characterized by increased inflammation. However, the mechanisms of FGR-associated inflammation are far from being understood. NLRP7, a member of a family of receptors involved in the innate immune responses, has been shown to be associated with gestational trophoblastic diseases. Here, we characterized the expression and the functional role of NLRP7 in the placenta and investigated its involvement in the pathogenesis of FGR. We used primary trophoblasts and placental explants that were collected during early pregnancy, and established trophoblast-derived cell lines, human placental villi, and serum samples from early pregnancy (n = 38) and from FGR (n = 40) and age-matched controls (n = 32). Our results show that NLRP7 (i) is predominantly expressed in the trophoblasts during the hypoxic period of placental development and its expression is upregulated by hypoxia and (ii) increases trophoblast proliferation ([³H]-thymidine) and controls the precocious differentiation of trophoblasts towards syncytium (syncytin 1 and 2 and β-hCG production and xCELLigence analysis) and towards invasive extravillous trophoblast (2D and 3D cultures). We have also demonstrated that NLRP7 inflammasome activation in trophoblast cells increases IL-1β, but not IL-18 secretion. In relation to the FGR, we demonstrated that major components of NLRP7 inflammasome machinery are increased and that IL-1β but not IL-18 circulating levels are increased in FGR. Altogether, our results identified NLRP7 as a critical placental factor and provided evidence for its deregulation in FGR. NLRP7 inflammasome is abundantly expressed by trophoblast cells. It is regulated by a key parameter of placental development, hypoxia. It controls trophoblast proliferation, migration, and invasion and exhibits anti-apoptotic role. NLRP7 machinery is deregulated in FGR pregnancies. KEY MESSAGES: NLRP7 inflammasome is abundantly expressed by trophoblast cells. It is regulated by a key parameter of placental development, hypoxia. It controls trophoblast proliferation, migration, and invasion and exhibits anti-apoptotic role. NLRP7 machinery is deregulated in FGR pregnancies.

Genetic Variants in Preeclampsia: Lessons From Studies in Latin-American Populations

Placental vascularization is a tightly regulated physiological process in which the maternal immune system plays a fundamental role. Vascularization of the maternal-placental interface involves a wide range of mechanisms primarily orchestrated by the fetal extravillous trophoblast and maternal immune cells. In a healthy pregnancy, an immune cross-talk between the mother and fetal cells results in the secretion of immunomodulatory mediators, apoptosis of specific cells, cellular differentiation/proliferation, angiogenesis, and vasculogenesis, altogether favoring a suitable microenvironment for the developing embryo. In the context of vasculopathy underlying common pregnancy disorders, it is believed that inefficient invasion of extravillous trophoblast cells in the endometrium leads to a poor placental blood supply, which, in turn, leads to decreased secretion of angiogenic factors, hypoxia, and inflammation commonly associated with preterm delivery, intrauterine growth restriction, and preeclampsia. In this review, we will focus on studies published by Latin American research groups, providing an extensive review of the role of genetic variants from candidate genes involved in a broad spectrum of biological processes underlying the pathophysiology of preeclampsia. In addition, we will discuss how these studies contribute to fill gaps in the current understanding of preeclampsia. Finally, we discuss some trending topics from important fields associated with pregnancy vascular disorders (e.g., epigenetics, transplantation biology, and non-coding RNAs) and underscore their possible implications in the pathophysiology of preeclampsia. As a result, these efforts are expected to give an overview of the extent of scientific research produced in Latin America and encourage multicentric collaborations by highlighted regional research groups involved in preeclampsia investigation.

Inflammasome activation during spontaneous preterm labor with intra-amniotic infection or sterile intra-amniotic inflammation

PROBLEM

The inflammasome is implicated in the mechanisms that lead to spontaneous preterm labor (PTL). However, whether there is inflammasome activation in the amniotic cavity of women with PTL and intra-amniotic infection (IAI) or sterile intra-amniotic inflammation (SIAI) is unknown.

METHOD OF STUDY

Amniotic fluid samples were collected from women with PTL who delivered at term (n = 31) or preterm without IAI or SIAI (n = 35), with SIAI (n = 27), or with IAI (n = 17). As a readout of inflammasome activation, extracellular ASC (apoptosis-associated speck-like protein containing a CARD) was measured in amniotic fluid by ELISA and the expression of ASC, caspase-1, and interleukin (IL)-1β was detected in the chorioamniotic membranes by multiplex immunofluorescence. Acute inflammatory responses in amniotic fluid and the placenta were also evaluated.

RESULTS

(a) Amniotic fluid concentrations of ASC and IL-6 were higher in women with PTL and IAI or SIAI than in those who delivered preterm or at term without intra-amniotic inflammation; (b) amniotic fluid concentrations of ASC and IL-6 were lower in women with PTL and SIAI than in those with IAI; (c) there was a significant nonlinear correlation between ASC and IL-6 amniotic fluid concentrations; (d) the expression of inflammasome-related proteins (ASC, caspase-1, and IL-1β) in the chorioamniotic membranes was increased in women with PTL and IAI or SIAI than in those who delivered preterm or at term without intra-amniotic inflammation; (e) inflammasome activation in the chorioamniotic membranes was weaker in women with PTL and SIAI than in those with IAI; (f) women with PTL and IAI had elevated amniotic fluid white blood cell counts compared to those without this clinical condition; and (g) severe acute placental inflammatory lesions were observed in women with PTL and IAI and in a subset of women with PTL and SIAI.

CONCLUSION

Inflammasome activation occurs in the settings of intra-amniotic infection and sterile intra-amniotic inflammation during spontaneous preterm labor.

The frequency and type of placental histologic lesions in term pregnancies with normal outcome

Objective To determine the frequency and type of histopathologic lesions in placentas delivered by women with a normal pregnancy outcome. Methods This retrospective cohort study included placental samples from 944 women with a singleton gestation who delivered at term without obstetrical complications. Placental lesions were classified into the following four categories as defined by the Society for Pediatric Pathology and by our unit: (1) acute placental inflammation, (2) chronic placental inflammation, (3) maternal vascular malperfusion and (4) fetal vascular malperfusion. Results (1) Seventy-eight percent of the placentas had lesions consistent with inflammatory or vascular lesions; (2) acute inflammatory lesions were the most prevalent, observed in 42.3% of the placentas, but only 1.0% of the lesions were severe; (3) acute inflammatory lesions were more common in the placentas of women with labor than in those without labor; (4) chronic inflammatory lesions of the placenta were present in 29.9%; and (5) maternal and fetal vascular lesions of malperfusion were detected in 35.7% and 19.7%, respectively. Two or more lesions with maternal or fetal vascular features consistent with malperfusion (high-burden lesions) were present in 7.4% and 0.7%, respectively. Conclusion Most placentas had lesions consistent with inflammatory or vascular lesions, but severe and/or high-burden lesions were infrequent. Mild placental lesions may be interpreted either as acute changes associated with parturition or as representative of a subclinical pathological process (intra-amniotic infection or sterile intra-amniotic inflammation) that did not affect the clinical course of pregnancy.

Spontaneous preterm birth: advances toward the discovery of genetic predisposition

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.

NOD-like receptor pyrin domain-containing-3 (NLRP3) regulates inflammation-induced pro-labor mediators in human myometrial cells

PROBLEM

Inflammation plays a major role in preterm birth. Nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) plays a role in inflammatory diseases. The aims of this study were to determine the effect of term labor on the expression of NLRP3 in human myometrium and the effect of NLRP3 silencing on pro-labor mediators in myometrial cells.

METHOD OF STUDY

NLRP3 expression was assessed in myometrium from non-laboring and laboring women by qRT-PCR and Western blotting. Human primary myometrial cells were transfected with NLRP3 siRNA (siNLRP3), treated with pro-inflammatory cytokines and toll-like receptor (TLR) ligands, and assayed for pro-inflammatory mediators' expression.

RESULTS

NLRP3 expression was higher in myometrium after term spontaneous labor and by TNF, IL1B, fsl-1, and flagellin. In siNLRP3-transfected cells, there was a significant decrease in the expression of pro-inflammatory cytokines (IL1A, IL6), chemokines (CXCL8, CCL2), and adhesion molecules (ICAM1 and VCAM1) stimulated with IL1B, TNF, or TLR ligands; decrease in IL1B-stimulated PTGS2 and PTGFR mRNA expression and PGF_2α release; and increase in TNF-stimulated myometrial gel shrinkage as assessed by an in vitro cell contraction assay.

CONCLUSION

NLRP3 is increased with labor in myometrial, and knockdown of NLRP3 is associated with an attenuation of inflammation-induced expression of pro-inflammatory and pro-labor mediators in human myometrium.

Choriodecidual leukocytes display a unique gene expression signature in spontaneous labor at term

Prior to and during the process of human labor, maternal circulating leukocytes infiltrate the maternal-fetal interface (choriodecidua) and become activated resembling choriodecidual leukocytes. Since, there is no evidence comparing maternal circulating and choriodecidual leukocytes, herein, we characterized their transcriptome and explored the biological processes enriched in choriodecidual leukocytes. From women undergoing spontaneous term labor we isolated circulating and choriodecidual leukocytes, performed microarray analysis (n = 5) and qRT-PCR validation (n = 9) and interaction network analysis with up-regulated genes. We found 270 genes up-regulated and only 17 genes down-regulated in choriodecidual leukocytes compared to maternal circulating leukocytes. The most up-regulated genes were CCL18, GPNMB, SEPP1, FN1, RNASE1, SPP1, C1QC, and PLTP. The biological processes enriched in choriodecidual leukocytes were cell migration and regulation of immune response, chemotaxis, and humoral immune responses. Our results show striking differences between the transcriptome of choriodecidual and maternal circulating leukocytes. Choriodecidual leukocytes are enriched in immune mediators implicated in the spontaneous process of labor at term.

In vivo evidence of inflammasome activation during spontaneous labor at term

OBJECTIVE

Upon inflammasome activation, the adaptor protein of the inflammasome ASC (apoptosis-associated speck-like protein containing a CARD) forms intracellular specks, which can be released into the extracellular space. The objectives of this study were to investigate whether (1) extracellular ASC is present in the amniotic fluid of women who delivered at term; (2) amniotic fluid ASC concentrations are greater in women who underwent spontaneous labor at term than in those who delivered at term in the absence of labor; and (3) amniotic epithelial and mesenchymal cells can form intracellular ASC specks in vitro.

METHODS

This retrospective cross-sectional study included amniotic fluid samples from 41 women who delivered at term in the absence of labor (n = 24) or underwent spontaneous labor at term (n = 17). Amniotic epithelial and mesenchymal cells were also isolated from the chorioamniotic membranes obtained from a separate group of women who delivered at term (n = 3), in which ASC speck formation was assessed by confocal microscopy. Monocytes from healthy individuals were used as positive controls for ASC speck formation (n = 3).

RESULTS

(1) The adaptor protein of the inflammasome ASC is detectable in the amniotic fluid of women who delivered at term; (2) amniotic fluid ASC concentration was higher in women who underwent spontaneous labor at term than in those who delivered at term without labor; and (3) amniotic epithelial and mesenchymal cells are capable of forming ASC specks and/or filaments in vitro.

CONCLUSION

Amniotic fluid ASC concentrations are increased in women who undergo spontaneous labor at term. Amniotic epithelial and mesenchymal cells are capable of forming ASC specks, suggesting that these cells are a source of extracellular ASC in the amniotic fluid. These findings provide in vivo evidence that there is inflammasome activation in the amniotic cavity during the physiological process of labor at term.

A Role for the Inflammasome in Spontaneous Preterm Labor With Acute Histologic Chorioamnionitis

Inflammasomes are cytosolic multiprotein complexes that orchestrate inflammation in response to pathogens and endogenous danger signals. Herein, we determined whether the chorioamniotic membranes from women in spontaneous preterm labor with acute histologic chorioamnionitis (1) express major inflammasome components; (2) express caspase (CASP)-1 and CASP-4 as well as their active forms; (3) exhibit apoptosis-associated speck-like protein containing a CARD (ASC)/CASP-1 complex formation; and (4) release the mature forms of interleukin (IL)-1β and IL-18. We utilized quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, immunoblotting, and immunohistochemistry to determine the messenger RNA (mRNA) and protein expression of major inflammasome components, nucleotide-binding oligomerization domain (NOD) proteins, and the pro- and mature/active forms of CASP-1, CASP-4, IL-1β, and IL-18. The ASC/CASP-1 complex formation was determined using an in situ proximity ligation assay. When comparing the chorioamniotic membranes from women in spontaneous preterm labor with acute histologic chorioamnionitis to those without this placental lesion, we found that (1) the mRNA of NLR family pyrin domain-containing protein ( NLRP) 1, NLRP3, NLR family CARD domain-containing protein 4 ( NLRC4), and NOD2 were higher; (2) the NLRP3 protein was increased; (3) the mRNA and active form (p10) of CASP-1 were greater; (4) the mRNA and active form of CASP-4 were increased; (5) the mRNA and mature form of IL-1β were higher; (6) the mature form of IL-18 was elevated; and (7) ASC/CASP-1 complex formation was increased. In conclusion, spontaneous preterm labor with acute histologic chorioamnionitis is characterized by an upregulation of NLRP3 and the active form of CASP-4, as well as increased ASC/CASP-1 complex formation, which may participate in the activation of CASP-1 and the maturation of IL-1β and IL-18 in the chorioamniotic membranes. These findings provide the first evidence that supports a role for the inflammasome in the pathological inflammation implicated in spontaneous preterm labor with acute histologic chorioamnionitis.

Viral Infection Sensitizes Human Fetal Membranes to Bacterial Lipopolysaccharide by MERTK Inhibition and Inflammasome Activation

Chorioamnionitis, premature rupture of fetal membranes (FMs), and subsequent preterm birth are associated with local infection and inflammation, particularly IL-1β production. Although bacterial infections are commonly identified, other microorganisms may play a role in the pathogenesis. Because viral pandemics, such as influenza, Ebola, and Zika, are becoming more common, and pregnant women are at increased risk for associated complications, this study evaluated the impact that viral infection had on human FM innate immune responses. This study shows that a herpes viral infection of FMs sensitizes the tissue to low levels of bacterial LPS, giving rise to an exaggerated IL-1β response. Using an ex vivo human FM explant system and an in vivo mouse model of pregnancy, we report that the mechanism by which this aggravated inflammation arises is through the inhibition of the TAM receptor, MERTK, and activation of the inflammasome. The TAM receptor ligand, growth arrest specific 6, re-establishes the normal FM response to LPS by restoring and augmenting TAM receptor and ligand expression, as well as by preventing the exacerbated IL-1β processing and secretion. These findings indicate a novel mechanism by which viruses alter normal FM immune responses to bacteria, potentially giving rise to adverse pregnancy outcomes.

Twenty-four percent of patients with clinical chorioamnionitis in preterm gestations have no evidence of either culture-proven intraamniotic infection or intraamniotic inflammation

BACKGROUND

Recent studies on clinical chorioamnionitis at term suggest that some patients with this diagnosis have neither intraamniotic infection nor intraamniotic inflammation. A false-positive diagnosis of clinical chorioamnionitis in preterm gestation may lead to unwarranted preterm delivery.

OBJECTIVE

We sought to determine the frequency of intraamniotic inflammation and microbiologically proven amniotic fluid infection in patients with preterm clinical chorioamnionitis.

STUDY DESIGN

Amniocentesis was performed in singleton pregnant women with preterm clinical chorioamnionitis (<36 weeks of gestation). Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas and assayed for matrix metalloproteinase-8 concentration. Microbial invasion of the amniotic cavity was defined as a positive amniotic fluid culture; intraamniotic inflammation was defined as an elevated amniotic fluid matrix metalloproteinase-8 concentration of >23 ng/mL. Nonparametric and survival techniques were used for analysis.

RESULTS

Among patients with preterm clinical chorioamnionitis, 24% (12/50) had neither microbiologic evidence of intraamniotic infection nor intraamniotic inflammation. Microbial invasion of the amniotic cavity was present in 34% (18/53) and intraamniotic inflammation in 76% (38/50) of patients. The most common microorganisms isolated from the amniotic cavity were the Ureaplasma species. Finally, patients without microbial invasion of the amniotic cavity or intraamniotic inflammation had significantly lower rates of adverse outcomes (including lower gestational age at delivery, a shorter amniocentesis-to-delivery interval, acute histologic chorioamnionitis, acute funisitis, and significant neonatal morbidity) than those with microbial invasion of the amniotic cavity and/or intraamniotic inflammation.

CONCLUSION

Among patients with preterm clinical chorioamnionitis, 24% had no evidence of either intraamniotic infection or intraamniotic inflammation, and 66% had negative amniotic fluid cultures, using standard microbiologic techniques. These observations call for a reexamination of the criteria used to diagnose preterm clinical chorioamnionitis.

Inflammasome assembly in the chorioamniotic membranes during spontaneous labor at term

PROBLEM

Inflammasome activation requires two steps: priming and assembly of the multimeric complex. The second step includes assembly of the sensor molecule and adaptor protein ASC (an apoptosis-associated speck-like protein containing a CARD), which results in ASC speck formation and the recruitment of caspase (CASP)-1. Herein, we investigated whether there is inflammasome assembly in the chorioamniotic membranes and choriodecidual leukocytes from women who underwent spontaneous labor at term.

METHOD OF STUDY

Using in situ proximity ligation assays, ASC/CASP-1 complexes were determined in the chorioamniotic membranes from women who delivered at term without labor or underwent spontaneous labor at term with or without acute histologic chorioamnionitis (n=10-11 each). Also, ASC speck formation was determined by flow cytometry in the choriodecidual leukocytes isolated from women who delivered at term with or without spontaneous labor (n=9-12 each).

RESULTS

(i) ASC/CASP-1 complexes were detected in the chorioamniotic membranes; (ii) ASC/CASP-1 complexes were greater in the chorioamniotic membranes from women who underwent spontaneous labor at term than in those without labor; (iii) ASC/CASP-1 complexes were even more abundant in the chorioamniotic membranes from women who underwent spontaneous labor at term with acute histologic chorioamnionitis than in those without this placental lesion; (iv) ASC speck formation was detected in the choriodecidual leukocytes; and (v) ASC speck formation was greater in the choriodecidual leukocytes isolated from women who underwent spontaneous labor at term than in those without labor.

CONCLUSION

There is inflammasome assembly in the chorioamniotic membranes and choriodecidual leukocytes during spontaneous labor at term.

HMGB1 Induces an Inflammatory Response in the Chorioamniotic Membranes That Is Partially Mediated by the Inflammasome

Spontaneous preterm labor occurs in two subsets of patients with sterile intra-amniotic inflammation, a process induced by alarmins such as high-mobility group box-1 (HMGB1). Inflammasomes are implicated in the process of spontaneous preterm labor. Therefore, we investigated whether HMGB1 initiates an inflammasome-associated inflammatory response in the chorioamniotic membranes. Incubation of the chorioamniotic membranes with HMGB1 1) induced the release of mature IL-1beta and IL-6; 2) upregulated the mRNA expression of the pro-inflammatory mediators NFKB1, IL6, TNF, IL1A, IFNG, and HMGB1 receptors RAGE and TLR2; 3) upregulated the mRNA expression of the inflammasome components NLRP3 and AIM2 as well as NOD proteins (NOD1 and NOD2); 4) increased the protein concentrations of NLRP3 and NOD2; 5) increased the concentration of caspase-1 and the quantity of its active form (p20); and 6) upregulated the mRNA expression and active form of MMP-9. In addition, HMGB1 concentrations in chorioamniotic membrane extracts from women who underwent spontaneous preterm labor were greater than in those from women who had undergone spontaneous labor at term. Collectively, these results show that HMGB1 can induce an inflammatory response in the chorioamniotic membranes, which is partially mediated by the inflammasome. These results provide insight into the mechanisms whereby HMGB1 induces preterm labor and birth in mice and explain why the concentration of this alarmin is increased in women who undergo spontaneous preterm labor.