Neutrophil Extracellular Traps in the Amniotic Cavity of Women with Intra-Amniotic Infection: A New Mechanism of Host Defense

Maternal serum interleukin-1β, FoxO1 and Sestrin2 levels in predicting preterm delivery

The study aimed to investigate whether serum IL-1β, FoxO1and Sesn2 concentrations differed between threatened preterm labor (TPL) and uncomplicated pregnancies. This study was conducted on 54 women with TPL pregnancies and 26 healthy pregnant women. The TPL group was further divided into two subgroups according to the gestational age at delivery. Patients who gave birth within 48-72 hours after the hospitalization were referred to as preterm delivery (PD) and those who gave birth at ≥37 weeks were referred to as term delivery (TD). Maternal levels of serum IL-1β, FoxO1 and Sesn2 were measured with the use of enzyme-linked immunosorbent assay kits. The mean maternal serum IL-1β and FoxO1 of PD were significantly higher than TD (p<.000*) and the control group (p < .000*). The mean maternal serum IL-1β, FoxO1 level of TD was significantly higher than the control group (p<.000*). The mean maternal serum Sesn2 levels of TD and the control group were significantly higher than the preterm group (p<.000*). The mean maternal serum Sesn2 level of the control group was significantly higher than the TD group (p <.000*). A negative correlation was found between serum concentration of serum IL-1β, and FoxO1 with the gestational week of delivery (r= -0.722, p< .000*for, IL-1β; r = -0.625, p < .000* for FoxO1). A positive correlation was found between the serum concentration of serum Sesn2 with the gestational week of delivery (r = 0.507, p<.000* for sesn2). High serum IL-1β, FoxO1 levels, and low Sesn2 levels may have the potential to be used as biomarkers for the differentiation of PD and TD.

Antibiotic therapy in patients with amniotic fluid sludge and risk of preterm birth: a meta-analysis

PURPOSE

Amniotic Fluid Sludge (AFS) has been theorized to be sonographic evidence of an underlying infection/inflammation and studies have concluded that approximately 10% of the patients who show signs of preterm labor with intact membranes have an underlying intraamniotic infection, mostly subclinical, carrying an increased risk for preterm birth with its subsequent neonatal and maternal complications. The purpose of the present systematic review is to evaluate the impact of antibiotic therapy on preterm birth rates of women diagnosed with AFS.

METHODS

We searched Medline, Scopus, the Cochrane Central Register of Controlled Trials CENTRAL, Google Scholar, and Clinicaltrials.gov databases for relevant articles published until the 30th of September 2022. Observational studies (prospective and retrospective) that evaluated the impact of antibiotics on preterm delivery rates of patients with AFS were considered eligible for inclusion. Statistical meta-analysis was performed with RStudio and we calculated pooled risk ratios (OR) and 95% confidence intervals (CI). To evaluate the information size, we performed trial sequential analysis (TSA) and the methodological quality of the included studies was assessed using RoBINS tools.

RESULTS

Overall, four retrospective cohort studies were included in the present systematic review and 369 women were enrolled. We demonstrated that preterm delivery prior to 34, 32 and 28 weeks of gestational age was comparable among the groups of women that had antibiotics and those that did not (OR: 0.34, 95% CI 0.05, 2.14, 0.40 [0.09, 1.66], 0.35 [0.08, 1.58], respectively) but the statistical heterogenicity of the studies included was high for every gestational period that was examined.

CONCLUSIONS

According to our study, we cannot conclude that the use of antibiotics in women with amniotic fluid sludge benefit the prognostic risk to deliver prematurely. It is quite clear that data from larger sample sizes and more well adjusted and designed studies are needed.

Stages of NETosis Development upon Stimulation of Neutrophils with Activators of Different Types

Before NETs are released, the neutrophil undergoes structural changes. First, it flattens, accompanied by a change in cell shape and rearrangement of the cytoskeleton. Then, nuclear swelling begins, which ends with the ejection of NETs into the extracellular space. We used widefield and confocal fluorescence microscopy to register morphological and structural changes in neutrophils during activation and NETosis. Different types of activators were used, such as NOX-dependent PMA and calcium ionophore A23187. The measurements were performed in a series of sequential stages. In the first stage (30 s after addition of activators and immediately after stimulation of neutrophils), the response of neutrophils to A23187 and PMA exposure was studied. Subsequently, the characteristics of neutrophils in different phases of activation were examined over a longer period of time (30, 60, 120, 180, and 240 min). The specific features of NETosis development were analyzed separately. During the first 30 s, neutrophils appeared to be heterogeneous in shape and structure of the actin cytoskeleton. Characteristic cell shapes included 30″ type 1 cells, similar in shape to the control, with F-actin concentrated in the center of the cytoplasm, and 30″ type 2 cells, which had flattened (spread) shapes with increased frontal dimensions and F-actin distributed throughout the cell. Later, the development of nuclear swelling, the corresponding changes in neutrophil membranes, and NET release into the extracellular space were evaluated. The conditions determining the initiation of chromatin ejection and two characteristic types of decondensed chromatin ejection were revealed. The results obtained contribute to a better understanding of the biophysical mechanisms of neutrophil activation and NETosis development.

Intra-amniotic inflammation in the mid-trimester of pregnancy is a risk factor for neuropsychological disorders in childhood

OBJECTIVES

Intra-amniotic inflammation is a subclinical condition frequently caused by either microbial invasion of the amniotic cavity or sterile inflammatory stimuli, e.g., alarmins. An accumulating body of evidence supports a role for maternal immune activation in the genesis of fetal neuroinflammation and the occurrence of neurodevelopmental disorders such as cerebral palsy, schizophrenia, and autism. The objective of this study was to determine whether fetal exposure to mid-trimester intra-amniotic inflammation is associated with neurodevelopmental disorders in children eight to 12 years of age.

METHODS

This is a retrospective case-control study comprising 20 children with evidence of prenatal exposure to intra-amniotic inflammation in the mid-trimester and 20 controls matched for gestational age at amniocentesis and at delivery. Amniotic fluid samples were tested for concentrations of interleukin-6 and C-X-C motif chemokine ligand 10, for bacteria by culture and molecular microbiologic methods as well as by polymerase chain reaction for eight viruses. Neuropsychological testing of children, performed by two experienced psychologists, assessed cognitive and behavioral domains. Neuropsychological dysfunction was defined as the presence of an abnormal score (<2 standard deviations) on at least two cognitive tasks.

RESULTS

Neuropsychological dysfunction was present in 45% (9/20) of children exposed to intra-amniotic inflammation but in only 10% (2/20) of those in the control group (p=0.03). The relative risk (RR) of neuropsychological dysfunction conferred by amniotic fluid inflammation remained significant after adjusting for gestational age at delivery [aRR=4.5 (1.07-16.7)]. Of the 11 children diagnosed with neuropsychological dysfunction, nine were delivered at term and eight of them had mothers with intra-amniotic inflammation. Children exposed to intra-amniotic inflammation were found to have abnormalities in neuropsychological tasks evaluating complex skills, e.g., auditory attention, executive functions, and social skills, whereas the domains of reasoning, language, and memory were not affected in the cases and controls.

CONCLUSIONS

Asymptomatic sterile intra-amniotic inflammation in the mid-trimester of pregnancy, followed by a term birth, can still confer to the offspring a substantial risk for neurodevelopmental disorders in childhood. Early recognition and treatment of maternal immune activation in pregnancy may be a strategy for the prevention of subsequent neurodevelopmental disorders in offspring.

NETs promote ROS production to induce human amniotic epithelial cell apoptosis via ERK1/2 signaling in spontaneous preterm birth

PROBLEM

Premature birth is a common obstetric complication but its pathogenesis is unclear. Inflammation at the maternal-fetal interface in preterm labor leads to the infiltration of neutrophils, which promotes inflammatory responses and induces the degradation of extracellular matrix and cell apoptosis, thus contributing to preterm labor. It is unclear whether neutrophil extracellular traps (NETs), a functional form of neutrophils, are involved in preterm labor.

METHODS OF STUDY

After collecting amniotic membranes from research objects, we localized NETs by immunofluorescence and evaluated the expression of matrix metalloproteinase (MMP)-9 and MMP-2 by western blotting. Primary human amniotic epithelial cells (hAECs) subjected to treatment with NETs, 5-ethynyl-20-deoxyuridine cell proliferation assay, lactate dehydrogenase (LDH) assay, western blotting, and flow cytometry apoptosis assay were used to determine the effects of NETs on hAECs. We also elucidated possible mechanisms underlying the effects.

RESULTS

Compared with normal term women, NETs infiltration and MMP-9 expression in the amniotic membrane from preterm women had increased. Thereafter, NETs might suppress the proliferation and promote the apoptosis of hAECs. Furthermore, after NETs treatment, the mitochondrial membrane potential was significantly decreased, ERK1/2 phosphorylation expression was upregulated and reactive oxygen species (ROS) production was increased in hAECs. Changes in cell proliferation, LDH release, and cell apoptosis level due to NETs could be reversed by ROS inhibitor or ERK phosphorylation inhibitors.

CONCLUSIONS

NETs can promote the apoptosis of hAECs via ERK1/2 pathways dependent on ROS release.

Eating the Enemy: Mycoplasma Strategies to Evade Neutrophil Extracellular Traps (NETs) Promoting Bacterial Nucleotides Uptake and Inflammatory Damage

Neutrophils are effector cells involved in the innate immune response against infection; they kill infectious agents in the intracellular compartment (phagocytosis) or in the extracellular milieu (degranulation). Moreover, neutrophils release neutrophil extracellular traps (NETs), complex structures composed of a scaffold of decondensed DNA associated with histones and antimicrobial compounds; NETs entrap infectious agents, preventing their spread and promoting their clearance. NET formation is triggered by microbial compounds, but many microorganisms have evolved several strategies for NET evasion. In addition, the dysregulated production of NETs is associated with chronic inflammatory diseases. Mycoplasmas are reduced genome bacteria, able to induce chronic infections with recurrent inflammatory symptoms. Mycoplasmas' parasitic lifestyle relies on metabolite uptake from the host. Mycoplasmas induce NET release, but their surface or secreted nucleases digest the NETs' DNA scaffold, allowing them to escape from entrapment and providing essential nucleotide precursors, thus promoting the infection. The presence of Mycoplasma species has been associated with chronic inflammatory disorders, such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, Crohn's disease, and cancer. The persistence of mycoplasma infection and prolonged NET release may contribute to the onset of chronic inflammatory diseases and needs further investigation and insights.

The Role of Neutrophils in Pregnancy, Term and Preterm Labour

Neutrophils are surveillance cells, and the first to react and migrate to sites of inflammation and infection following a chemotactic gradient. Neutrophils play a key role in both sterile inflammation and infection, performing a wide variety of effector functions such as degranulation, phagocytosis, ROS production and release of neutrophil extracellular traps (NETs). Healthy term labour requires a sterile pro-inflammatory process, whereas one of the most common causes of spontaneous preterm birth is microbial driven. Peripheral neutrophilia has long been described during pregnancy, and evidence exists demonstrating neutrophils infiltrating the cervix, uterus and foetal membranes during both term and preterm deliveries. Their presence supports a role in tissue remodelling via their effector functions. In this review, we describe the effector functions of neutrophils. We summarise the evidence to support their role in healthy pregnancy and labour and describe their potential contribution to microbial driven preterm birth.

The amniotic fluid proteome predicts imminent preterm delivery in asymptomatic women with a short cervix

Preterm birth, the leading cause of perinatal morbidity and mortality, is associated with increased risk of short- and long-term adverse outcomes. For women identified as at risk for preterm birth attributable to a sonographic short cervix, the determination of imminent delivery is crucial for patient management. The current study aimed to identify amniotic fluid (AF) proteins that could predict imminent delivery in asymptomatic patients with a short cervix. This retrospective cohort study included women enrolled between May 2002 and September 2015 who were diagnosed with a sonographic short cervix (< 25 mm) at 16–32 weeks of gestation. Amniocenteses were performed to exclude intra-amniotic infection; none of the women included had clinical signs of infection or labor at the time of amniocentesis. An aptamer-based multiplex platform was used to profile 1310 AF proteins, and the differential protein abundance between women who delivered within two weeks from amniocentesis, and those who did not, was determined. The analysis included adjustment for quantitative cervical length and control of the false-positive rate at 10%. The area under the receiver operating characteristic curve was calculated to determine whether protein abundance in combination with cervical length improved the prediction of imminent preterm delivery as compared to cervical length alone. Of the 1,310 proteins profiled in AF, 17 were differentially abundant in women destined to deliver within two weeks of amniocentesis independently of the cervical length (adjusted p-value < 0.10). The decreased abundance of SNAP25 and the increased abundance of GPI, PTPN11, OLR1, ENO1, GAPDH, CHI3L1, RETN, CSF3, LCN2, CXCL1, CXCL8, PGLYRP1, LDHB, IL6, MMP8, and PRTN3 were associated with an increased risk of imminent delivery (odds ratio > 1.5 for each). The sensitivity at a 10% false-positive rate for the prediction of imminent delivery by a quantitative cervical length alone was 38%, yet it increased to 79% when combined with the abundance of four AF proteins (CXCL8, SNAP25, PTPN11, and MMP8). Neutrophil-mediated immunity, neutrophil activation, granulocyte activation, myeloid leukocyte activation, and myeloid leukocyte-mediated immunity were biological processes impacted by protein dysregulation in women destined to deliver within two weeks of diagnosis. The combination of AF protein abundance and quantitative cervical length improves prediction of the timing of delivery compared to cervical length alone, among women with a sonographic short cervix.

Pregnancy tailors endotoxin-induced monocyte and neutrophil responses in the maternal circulation

Objective

To comprehensively characterize monocyte and neutrophil responses to E. coli and its product [lipopolysaccharide (LPS) or endotoxin] in vitro during pregnancy.

Material or subjects

Peripheral blood was collected from pregnant women during the third trimester (n = 20) and from non-pregnant women (n = 20).

Methods

The number, phagocytic activity, and reactive oxygen species (ROS) production of peripheral monocytes and neutrophils were investigated using flow cytometry. The phenotypes of peripheral monocytes and neutrophils after acute or chronic LPS stimulation were also determined using flow cytometry. Cytokine profiles were quantified for LPS-stimulated peripheral blood mononuclear cells (PBMCs) and a whole blood TruCulture^® system using a multiplex immunoassay.

Results

Increased number, phagocytic activity, and ROS production capacity of monocytes and neutrophils were found in pregnant compared to non-pregnant women. Additionally, specific subsets of pro-inflammatory monocytes (IL-6⁺CD14⁺ or MIP-1α⁺CD14⁺ cells) and neutrophils (IL-1β⁺CD15⁺ or MIP-1β⁺CD15⁺ cells) were increased in pregnant women in response to acute LPS stimulation. Moreover, distinct subsets of intermediate-activated monocytes expressing CD142, IL-6, and IL-1RA were increased in pregnant women upon chronic LPS stimulation. Last, pregnant women displayed a different cytokine profile than non-pregnant women in LPS-stimulated PBMCs and in whole blood.

Conclusions

Pregnancy tailors the immune responses of circulating monocytes and neutrophils to endotoxin, a Gram-negative bacterial product.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00011-022-01569-z.

IL-22 Plays a Dual Role in the Amniotic Cavity: Tissue Injury and Host Defense against Microbes in Preterm Labor

IL-22 is a multifaceted cytokine with both pro- and anti-inflammatory functions that is implicated in multiple pathologies. However, the role of IL-22 in maternal-fetal immunity in late gestation is poorly understood. In this study, we first showed that IL-22+ T cells coexpressing retinoic acid-related orphan receptor γt (ROR-γt) are enriched at the human maternal-fetal interface of women with preterm labor and birth, which was confirmed by in silico analysis of single-cell RNA sequencing data. T cell activation leading to preterm birth in mice was preceded by a surge in IL-22 in the maternal circulation and amniotic cavity; however, systemic administration of IL-22 in mice did not induce adverse perinatal outcomes. Next, using an ex vivo human system, we showed that IL-22 can cross from the choriodecidua to the intra-amniotic space, where its receptors (Il22ra1, Il10rb, and Il22ra2) are highly expressed by murine gestational and fetal tissues in late pregnancy. Importantly, amniotic fluid concentrations of IL-22 were elevated in women with sterile or microbial intra-amniotic inflammation, suggesting a dual role for this cytokine. The intra-amniotic administration of IL-22 alone shortened gestation and caused neonatal death in mice, with the latter outcome involving lung maturation and inflammation. IL-22 plays a role in host response by participating in the intra-amniotic inflammatory milieu preceding Ureaplasma parvum-induced preterm birth in mice, which was rescued by the deficiency of IL-22. Collectively, these data show that IL-22 alone is capable of causing fetal injury leading to neonatal death and can participate in host defense against microbial invasion of the amniotic cavity leading to preterm labor and birth.

Does the Amniotic Fluid of Mice Contain a Viable Microbiota?

The existence of an amniotic fluid microbiota (i.e., a viable microbial community) in mammals is controversial. Its existence would require a fundamental reconsideration of fetal in utero exposure to and colonization by microorganisms and the role of intra-amniotic microorganisms in fetal immune development as well as in pregnancy outcomes. In this study, we determined whether the amniotic fluid of mice harbors a microbiota in late gestation. The profiles of the amniotic fluids of pups located proximally or distally to the cervix were characterized through quantitative real-time PCR, 16S rRNA gene sequencing, and culture (N = 21 dams). These profiles were compared to those of technical controls for bacterial and DNA contamination. The load of 16S rRNA genes in the amniotic fluid exceeded that in controls. Additionally, the 16S rRNA gene profiles of the amniotic fluid differed from those of controls, with Corynebacterium tuberculostearicum being differentially more abundant in amniotic fluid profiles; however, this bacterium was not cultured from amniotic fluid. Of the 42 attempted bacterial cultures of amniotic fluids, only one yielded bacterial growth – Lactobacillus murinus. The 16S rRNA gene of this common murine-associated bacterium was not detected in any amniotic fluid sample, suggesting it did not originate from the amniotic fluid. No differences in the 16S rRNA gene load, 16S rRNA gene profile, or bacterial culture were observed between the amniotic fluids located Proximally and distally to the cervix. Collectively, these data indicate that, although there is a modest DNA signal of bacteria in murine amniotic fluid, there is no evidence that this signal represents a viable microbiota. While this means that amniotic fluid is not a source of microorganisms for in utero colonization in mice, it may nevertheless contribute to fetal exposure to microbial components. The developmental consequences of this observation warrant further investigation.

The amniotic fluid proteome changes with gestational age in normal pregnancy: a cross-sectional study

The cell-free transcriptome in amniotic fluid (AF) has been shown to be informative of physiologic and pathologic processes in pregnancy; however, the change in AF proteome with gestational age has mostly been studied by targeted approaches. The objective of this study was to describe the gestational age-dependent changes in the AF proteome during normal pregnancy by using an omics platform. The abundance of 1310 proteins was measured on a high-throughput aptamer-based proteomics platform in AF samples collected from women during midtrimester (16-24 weeks of gestation, n = 15) and at term without labor (37-42 weeks of gestation, n = 13). Only pregnancies without obstetrical complications were included in the study. Almost 25% (320) of AF proteins significantly changed in abundance between the midtrimester and term gestation. Of these, 154 (48.1%) proteins increased, and 166 (51.9%) decreased in abundance at term compared to midtrimester. Tissue-specific signatures of the trachea, salivary glands, brain regions, and immune system were increased while those of the gestational tissues (uterus, placenta, and ovary), cardiac myocytes, and fetal liver were decreased at term compared to midtrimester. The changes in AF protein abundance were correlated with those previously reported in the cell-free AF transcriptome. Intersecting gestational age-modulated AF proteins and their corresponding mRNAs previously reported in the maternal blood identified neutrophil-related protein/mRNA pairs that were modulated in the same direction. The first study to utilize an aptamer-based assay to profile the AF proteome modulation with gestational age, it reveals that almost one-quarter of the proteins are modulated as gestation advances, which is more than twice the fraction of altered plasma proteins (~ 10%). The results reported herein have implications for future studies focused on discovering biomarkers to predict, monitor, and diagnose obstetrical diseases.

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.

JAK3 and PI3K mediates the suppressive effects of interferon tau on neutrophil extracellular traps formation during peri-implantation period

Interferon tau (IFNτ) is the main maternal signal for pregnancy in ruminants and modulates the functions of various immune cells, including neutrophils. Neutrophil extracellular traps (NETs) are one of the main defence mechanisms of neutrophils. In this study, we observed higher (p < 0.01) ex-vivo NETs extrusion by blood neutrophils from day 16-18 post artificial insemination (AI) in non-inseminated and inseminated non-pregnant cows compared to pregnant cows. In vitro study also showed that IFNτ hampers NETs formation in dose and time dependent manner. The lowest (p < 0.01) NETs formation and the highest (p < 0.01) mRNA expression (RT-PCR) of IFNτ stimulated genes (ISG15, OAS1, MX1) were observed when neutrophil incubated with 9 ng/mL IFNτ for 3.5 h. Signalling cascades mediating IFNτ impairment of NETs formation were identified using inhibitors of JAK2, JAK3, p38, PI3K/Akt and MAPK/Erk. IFNτ reduced (p < 0.01) the mRNA expression (RT-PCR) and concentration (ELISA) of genes and proteins that mediate NETs formation in blood neutrophils including histones (H1, H2), neutrophil elastase (NE) and myeloperoxidase (MPO). However, the effects of IFNτ on these genes and proteins were eliminated in the presence of JAK3 or PI3K inhibitors. Immunocytochemistry study also showed strong MPO signal in the presence of JAK3 or PI3K inhibitors as compared to positive control (PC, IFNτ alone). The results indicate that IFNτ impairs NETs formation using JAK3 and PI3K and thus essential for successful implantation and establishment of pregnancy in cows.

Interleukin-6 pathobiology in equine placental infection

PROBLEM

Ascending placentitis is the leading cause of abortion in the horse. Interleukin (IL)-6 is considered predictive of placental infection in other species, but little is understood regarding its role in the pathophysiology of ascending placentitis.

METHOD OF STUDY

Sub-acute ascending placentitis was induced via trans-cervical inoculation of S zooepidemicus, and various fluids/serum/tissues collected 8 days later. Concentrations of IL-6 were detected within fetal fluids and serum in inoculated (n = 6) and control (n = 6) mares. RNASeq was performed on the placenta (endometrium and chorioallantois) to assess transcripts relating to IL-6 pathways. IHC was performed for immunolocalization of IL-6 receptor (IL-6R) in the placenta.

RESULTS

IL-6 concentrations increased in allantoic fluid following inoculation, with a trend toward an increase in amniotic fluid. Maternal serum IL-6 was increased in inoculated animals, while no changes were noted in fetal serum. mRNA expression of IL-6-related transcripts within the chorioallantois indicates that IL-6 is activating the classical JAK/STAT pathway, thereby acting as anti-inflammatory, anti-apoptotic, and pro-survival. The IL-6R was expressed within the chorioallantois, indicating a paracrine signaling pathway of maternal IL-6 to fetal IL-6R.

CONCLUSION

IL-6 plays a crucial role in the placental response to induction of sub-acute equine ascending placentitis, and this could be noted in amniotic fluid, allantoic fluid, and maternal serum. Additionally, IL-6 is acting as anti-inflammatory in this disease, potentially altering disease progression, impeding abortion signals, and assisting with the production of a viable neonate.

Human β-defensin-3 participates in intra-amniotic host defense in women with labor at term, spontaneous preterm labor and intact membranes, and preterm prelabor rupture of membranes

Objective: Human β-defensin-3 (HBD-3) has a broad spectrum of antimicrobial activity, and activity and, therefore, plays a central role in host defense mechanisms against infection. Herein, we determined whether HBD-3 was a physiological constituent of amniotic fluid during midtrimester and at term and whether the concentration of this defensin was increased in amniotic fluid of women with spontaneous preterm labor and intact membranes and those with preterm prelabor rupture of membranes (pPROM) with intra-amniotic inflammation or intra-amniotic infection.Methods: Amniotic fluid was collected from 219 women in the following groups: (1) midtrimester who delivered at term (n = 35); (2) with or without spontaneous labor at term (n = 50); (3) spontaneous preterm labor with intact membranes who delivered at term (n = 29); (4) spontaneous preterm labor with intact membranes who delivered preterm with or without intra-amniotic inflammation or intra-amniotic infection (n = 69); and (5) pPROM with or without intra-amniotic infection (n = 36). Amniotic fluid HBD-3 concentrations were determined using a sensitive and specific ELISA kit.Results: (1) HBD-3 is a physiological constituent of amniotic fluid; (2) the amniotic fluid concentration of HBD-3 did not change with gestational age (midtrimester versus term not in labor); (3) amniotic fluid concentrations of HBD-3 were higher in women with spontaneous labor at term than in those without labor; (4) in the absence of intra-amniotic inflammation, amniotic fluid concentrations of HBD-3 were similar between women with spontaneous preterm labor who delivered preterm and those who delivered at term; (5) among patients with spontaneous preterm labor who delivered preterm, amniotic fluid concentrations of HBD-3 were greater in women with intra-amniotic infection than in those without this clinical condition; (6) among patients with spontaneous preterm labor, amniotic fluid concentrations of HBD-3 were higher in women with intra-amniotic inflammation or intra-amniotic infection who delivered preterm than in those without these clinical conditions who delivered at term; and (7) women with pPROM and intra-amniotic infection had higher median amniotic fluid concentrations of HBD-3 than those without this clinical condition.Conclusion: Human β-defensin-3 is a physiological constituent of amniotic fluid and increases during the process of labor at term. Amniotic fluid concentrations of HBD-3 were increased in women with spontaneous preterm labor with intact membranes or pPROM with intra-amniotic inflammation or intra-amniotic infection, indicating that this defensin participates in the host defense mechanisms in the amniotic cavity against microorganisms or danger signals. These findings provide insight into the soluble host defense mechanisms against intra-amniotic inflammation and intra-amniotic infection.

Management of clinical chorioamnionitis: an evidence-based approach

This review aimed to examine the existing evidence about interventions proposed for the treatment of clinical chorioamnionitis, with the goal of developing an evidence-based contemporary approach for the management of this condition. Most trials that assessed the use of antibiotics in clinical chorioamnionitis included patients with a gestational age of ≥34 weeks and in labor. The first-line antimicrobial regimen for the treatment of clinical chorioamnionitis is ampicillin combined with gentamicin, which should be initiated during the intrapartum period. In the event of a cesarean delivery, patients should receive clindamycin at the time of umbilical cord clamping. The administration of additional antibiotic therapy does not appear to be necessary after vaginal or cesarean delivery. However, if postdelivery antibiotics are prescribed, there is support for the administration of an additional dose. Patients can receive antipyretic agents, mainly acetaminophen, even though there is no clear evidence of their benefits. Current evidence suggests that the administration of antenatal corticosteroids for fetal lung maturation and of magnesium sulfate for fetal neuroprotection to patients with clinical chorioamnionitis between 24 0/7 and 33 6/7 weeks of gestation, and possibly between 23 0/7 and 23 6/7 weeks of gestation, has an overall beneficial effect on the infant. However, delivery should not be delayed to complete the full course of corticosteroids and magnesium sulfate. Once the diagnosis of clinical chorioamnionitis has been established, delivery should be considered, regardless of the gestational age. Vaginal delivery is the safer option and cesarean delivery should be reserved for standard obstetrical indications. The time interval between the diagnosis of clinical chorioamnionitis and delivery is not related to most adverse maternal and neonatal outcomes. Patients may require a higher dose of oxytocin to achieve adequate uterine activity or greater uterine activity to effect a given change in cervical dilation. The benefit of using continuous electronic fetal heart rate monitoring in these patients is unclear. We identified the following promising interventions for the management of clinical chorioamnionitis: (1) an antibiotic regimen including ceftriaxone, clarithromycin, and metronidazole that provides coverage against the most commonly identified microorganisms in patients with clinical chorioamnionitis; (2) vaginal cleansing with antiseptic solutions before cesarean delivery with the aim of decreasing the risk of endometritis and, possibly, postoperative wound infection; and (3) antenatal administration of N-acetylcysteine, an antioxidant and antiinflammatory agent, to reduce neonatal morbidity and mortality. Well-powered randomized controlled trials are needed to assess these interventions in patients with clinical chorioamnionitis.

Human neutrophils swim and phagocytise bacteria

BACKGROUND INFORMATION

Leukocytes migrate in an amoeboid fashion while patrolling our organism in the search for infection or tissue damage. Their capacity to migrate has been proven integrin independent, however, non-specific adhesion or confinement remain a requisite in current models of cell migration. This idea has been challenged twice within the last decade with human neutrophils and effector T lymphocytes, which were shown to migrate in free suspension, a phenomenon termed swimming. While the relevance of leukocyte swimming in vivo remains under judgment, a growing amount of clinical evidence demonstrates that leukocytes are indeed found in liquid-filled body cavities, occasionally with phagocyted pathogens, such as in the amniotic fluid, the cerebrospinal fluid (CSF), or the eye vitreous and aqueous humor.

RESULTS

We studied in vitro swimming of primary human neutrophils in the presence of live bacteria, in 2 and 3 dimensions. We show that swimming neutrophils perform phagocytosis of bacteria in suspension. By micropatterning live bacteria on a substrate with an optical technique, we further prove that they use chemotaxis to swim towards their targets. Moreover, we provide evidence that neutrophil navigation can alternate between adherent and non-adherent modes.

CONCLUSIONS

Our results suggest that human neutrophils do not rely on adhesion to carry out their functions, supporting a versatile phagocytic function adaptable to the various environmental conditions encountered in vivo, as already suggested by clinical data.

SIGNIFICANCE

We verified a claim stated 10 years ago and never reproduced, on the capacity of human neutrophils to swim and perform swimming chemotaxis. We further extended those results to prove that swimming neutrophils can phagocytise bacteria, disregarding adhesion nor confinement as a requisite for accomplishing their function, which differs with current paradigms of leukocyte migration.

RNA Sequencing Reveals Diverse Functions of Amniotic Fluid Neutrophils and Monocytes/Macrophages in Intra-Amniotic Infection

Intra-amniotic infection, the invasion of microbes into the amniotic cavity resulting in inflammation, is a clinical condition that can lead to adverse pregnancy outcomes for the mother and fetus as well as severe long-term neonatal morbidities. Despite much research focused on the consequences of intra-amniotic infection, there remains little knowledge about the innate immune cells that respond to invading microbes. We performed RNA-seq of sorted amniotic fluid neutrophils and monocytes/macrophages from women with intra-amniotic infection to determine the transcriptomic differences between these innate immune cells. Further, we sought to identify specific transcriptomic pathways that were significantly altered by the maternal or fetal origin of amniotic fluid neutrophils and monocytes/macrophages, the presence of a severe fetal inflammatory response, and pregnancy outcome (i.e., preterm or term delivery). We show that significant transcriptomic differences exist between amniotic fluid neutrophils and monocytes/macrophages from women with intra-amniotic infection, indicating the distinct roles these cells play. The transcriptome of amniotic fluid immune cells varies based on their maternal or fetal origin, and the significant transcriptomic differences between fetal and maternal monocytes/macrophages imply that those of fetal origin exhibit impaired functions. Notably, transcriptomic changes in amniotic fluid monocytes/macrophages suggest that these immune cells collaborate with neutrophils in the trafficking of fetal leukocytes throughout the umbilical cord (i.e., funisitis). Finally, amniotic fluid neutrophils and monocytes/macrophages from preterm deliveries display enhanced transcriptional activity compared to those from term deliveries, highlighting the protective role of these cells during this vulnerable period. Collectively, these findings demonstrate the underlying complexity of local innate immune responses in women with intra-amniotic infection and provide new insights into the functions of neutrophils and monocytes/macrophages in the amniotic cavity.

Comprehensive proteomic investigation of infectious and inflammatory changes in late preterm prelabour rupture of membranes

Preterm prelabour rupture of membranes beyond the 34th week of gestation (late PPROM) is frequently associated with the risk of the microbial invasion of the amniotic fluid (MIAC) and histological chorioamnionitis (HCA). Hence, we employed a Tandem Mass Tag-based approach to uncover amniotic fluid proteome response to the presence of MIAC and HCA in late PPROM. Protein dysregulation was associated with only five cases in the group of 15 women with confirmed MIAC and HCA. Altogether, 138 amniotic fluid proteins were changed in these five cases exclusively. These proteins were particularly associated with excessive neutrophil responses to infection, such as neutrophil degranulation and extracellular trap formation. We believe that the quantification of these proteins in amniotic fluid may assist in revealing women with the highest risk of excessive inflammatory response in late PPROM.

Cellular immune responses in amniotic fluid of women with a sonographic short cervix

Objectives A sonographic short cervix is one of the strongest predictors of preterm delivery. However, the cellular immune composition of amniotic fluid in women with a short cervix has not yet been described. Herein, we determined cellular and soluble immune responses in amniotic fluid from pregnant women with a mid-trimester asymptomatic short cervix. Methods Amniotic fluid samples (n=77) were collected from asymptomatic women with a cervical length between 15 and 25 mm (n=36, short cervix) or ≤15 mm (n=41, severely short cervix) diagnosed by ultrasound. Flow cytometry and multiplex measurement of cytokines/chemokines were performed. Results (1) The cellular immune composition of amniotic fluid did not differ between women with a severely short cervix (≤15 mm) and those with a short cervix 15-25 mm; (2) amniotic fluid concentrations of multiple cytokines/chemokines were higher in women with a severely short cervix (≤15 mm) than in those with a short cervix 15-25 mm; (3) the cellular immune composition of amniotic fluid did not differ between women with a severely short cervix (≤15 mm) who ultimately underwent preterm delivery and those who delivered at term; and (4) amniotic fluid concentrations of IL-2, but not other immune mediators, were increased in women with a severely short cervix (≤15 mm) who ultimately delivered preterm compared to those who delivered at term. Conclusions Women with a severely short cervix (≤15 mm) have increased concentrations of pro-inflammatory mediators in the amniotic cavity; yet, these do not translate to changes in the cellular immune response.

Periodontal disease and adverse pregnancy outcomes

Periodontal diseases are considered not only to affect tooth-supporting tissues but also to have a cause-and-effect relationship with various systemic diseases and conditions, such as adverse pregnancy outcomes. Mechanistic studies provide strong evidence that periodontal pathogens can translocate from infected periodontium to the feto-placental unit and initiate a metastatic infection. However, the extent and mechanisms by which metastatic inflammation and injury contribute to adverse pregnancy outcomes still remain unclear. The presence of oral bacteria in the placenta of women with term gestation further complicates our understanding of the biology behind the role of periodontal pathogens in pregnancy outcomes. Epidemiological studies demonstrate many methodological inconsistencies and flaws that render comparisons difficult and conclusions insecure. Therefore, despite the fact that a number of prospective studies show a positive association between periodontal diseases and various adverse pregnancy outcomes, the evidence behind it is still weak. Future well-designed explanatory studies are necessary to verify this relationship and, if present, determine its magnitude. The majority of high-quality randomized controlled trials reveal that nonsurgical periodontal therapy during the second trimester of gestation does not improve pregnancy outcomes. From a biological standpoint, this can be partially explained by the fact that therapy rendered at the fourth to sixth months of pregnancy is too late to prevent placental colonization by periodontal pathogens and consequently incapable of affecting pathogen-induced injury at the feto-placental unit. Thus, interventions during the preconception period may be more meaningful. With the increase in our understanding on the potential association between periodontal disease and adverse pregnancy outcomes, it is clear that dental practitioners should provide periodontal treatment to pregnant women that is safe for both the mother and the unborn child. Although there is not enough evidence that the anti-infective therapy alters pregnancy outcomes, it improves health-promoting behavior and periodontal condition, which in turn advance general health and risk factor control.

Maternal and fetal T cells in term pregnancy and preterm labor

Pregnancy is a state of immunological balance during which the mother and the developing fetus must tolerate each other while maintaining sufficient immunocompetence to ward off potential threats. The site of closest contact between the mother and fetus is the decidua, which represents the maternal-fetal interface. Many of the immune cell subsets present at the maternal-fetal interface have been well described; however, the importance of the maternal T cells in this compartment during late gestation and its complications, such as preterm labor and birth, has only recently been established. Moreover, pioneer and recent studies have indicated that fetal T cells are activated in different subsets of preterm labor and may elicit distinct inflammatory responses in the amniotic cavity, leading to preterm birth. In this review, we describe the established and proposed roles for maternal T cells at the maternal-fetal interface in normal term parturition, as well as the demonstrated contributions of such cells to the pathological process of preterm labor and birth. We also summarize the current knowledge of and proposed roles for fetal T cells in the pathophysiology of the preterm labor syndrome. It is our hope that this review provides a solid conceptual framework highlighting the importance of maternal and fetal T cells in late gestation and catalyzes new research questions that can further scientific understanding of these cells and their role in preterm labor and birth, the leading cause of neonatal mortality and morbidity worldwide.

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.

Cellular immune responses in amniotic fluid of women with preterm prelabor rupture of membranes

Background Preterm birth is the leading cause of perinatal morbidity and mortality. Preterm prelabor rupture of membranes (pPROM) occurs in 30% of preterm births; thus, this complication is a major contributor to maternal and neonatal morbidity. However, the cellular immune responses in amniotic fluid of women with pPROM have not been investigated. Methods Amniotic fluid samples were obtained from women with pPROM and a positive (n = 7) or negative (n = 10) microbiological culture. Flow cytometry was performed to evaluate the phenotype and number of amniotic fluid leukocytes. The correlation between amniotic fluid immune cells and an interleukin-6 (IL-6) concentration or a white blood cell (WBC) count in amniotic fluid was calculated. Results Women with pPROM and a positive amniotic fluid culture had (1) a greater number of total leukocytes in amniotic fluid, including neutrophils and monocytes/macrophages and (2) an increased number of total T cells in amniotic fluid, namely CD4+ T cells and CD8+ T cells, but not B cells. The numbers of neutrophils and monocytes/macrophages were positively correlated with IL-6 concentrations and WBC counts in amniotic fluid of women with pPROM. Conclusion Women with pPROM and a positive amniotic fluid culture exhibit a more severe cellular immune response than those with a negative culture, which is associated with well-known markers of intra-amniotic inflammation.

Amniotic fluid cell-free transcriptome: a glimpse into fetal development and placental cellular dynamics during normal pregnancy

Background

The amniotic fluid (AF) cell-free transcriptome is modulated by physiologic and pathologic processes during pregnancy. AF gene expression changes with advancing gestation reflect fetal development and organ maturation; yet, defining normal expression and splicing patterns for biomarker discovery in obstetrics requires larger heterogeneous cohorts, evaluation of potential confounding factors, and novel analytical approaches.

Methods

Women with a normal pregnancy who had an AF sample collected during midtrimester (n = 30) or at term gestation (n = 68) were included. Expression profiling at exon level resolution was performed using Human Transcriptome Arrays. Differential expression was based on moderated t-test adjusted p < 0.05 and fold change > 1.25; for differential splicing, a splicing index > 2 and adjusted p < 0.05 were required. Functional profiling was used to interpret differentially expressed or spliced genes. The expression of tissue-specific and cell-type specific signatures defined by single-cell genomics was quantified and correlated with covariates. In-silico validation studies were performed using publicly available datasets.

Results

1) 64,071 genes were detected in AF, with 11% of the coding and 6% of the non-coding genes being differentially expressed between midtrimester and term gestation. Expression changes were highly correlated with those previously reported (R > 0.79, p < 0.001) and featured increased expression of genes specific to the trachea, salivary glands, and lung and decreased expression of genes specific to the cardiac myocytes, uterus, and fetal liver, among others. 2) Single-cell RNA-seq signatures of the cytotrophoblast, Hofbauer cells, erythrocytes, monocytes, T and B cells, among others, showed complex patterns of modulation with gestation (adjusted p < 0.05). 3) In 17% of the genes detected, we found differential splicing with advancing gestation in genes related to brain development processes and immunity pathways, including some that were missed based on differential expression analysis alone.

Conclusions

This represents the largest AF transcriptomics study in normal pregnancy, reporting for the first time that single-cell genomic signatures can be tracked in the AF and display complex patterns of expression during gestation. We also demonstrate a role for alternative splicing in tissue-identity acquisition, organ development, and immune processes. The results herein may have implications for the development of fetal testing to assess placental function and fetal organ maturity.

Compartmentalized profiling of amniotic fluid cytokines in women with preterm labor

Objective

Amniotic fluid cytokines have been implicated in the mechanisms of preterm labor and birth. Cytokines can be packaged within or on the surface of extracellular vesicles. The main aim of this study was to test whether the protein abundance internal to and on the surface of extracellular vesicles changes in the presence of sterile intra-amniotic inflammation and proven intra-amniotic infection in women with preterm labor as compared to the women with preterm labor without either intra-amniotic inflammation or proven intra-amniotic infection.

Study design

Women who had an episode of preterm labor and underwent an amniocentesis for the diagnosis of intra-amniotic infection or intra-amniotic inflammation were classified into three groups: 1) preterm labor without either intra-amniotic inflammation or proven intra-amniotic infection, 2) preterm labor with sterile intra-amniotic inflammation, and 3) preterm labor with intra-amniotic infection. The concentrations of 38 proteins were determined on the extracellular vesicle surface, within the vesicles, and in the soluble fraction of amniotic fluid.

Results

1) Intra-amniotic inflammation, regardless of detected microbes, was associated with an increased abundance of amniotic fluid cytokines on the extracellular vesicle surface, within vesicles, and in the soluble fraction. These changes were most prominent in women with proven intra-amniotic infection. 2) Cytokine changes on the surface of extracellular vesicles were correlated with those determined in the soluble fraction; yet the magnitude of the increase was significantly different between these compartments. 3) The performance of prediction models of early preterm delivery based on measurements on the extracellular vesicle surface was equivalent to those based on the soluble fraction.

Conclusions

Differential packaging of amniotic fluid cytokines in extracellular vesicles during preterm labor with sterile intra-amniotic inflammation or proven intra-amniotic infection is reported herein for the first time. The current study provides insights into the biology of the intra-amniotic fluid ad may aid in the development of biomarkers for obstetrical disease.

Cellular immune responses in amniotic fluid of women with preterm clinical chorioamnionitis

OBJECTIVE

Preterm birth is the leading cause of neonatal morbidity and mortality worldwide. Some preterm births are associated with clinical chorioamnionitis; yet, this condition has been poorly investigated. Herein, we characterized the amniotic fluid cellular immune responses in women with preterm clinical chorioamnionitis.

METHODS AND SUBJECTS

Amniotic fluid samples were obtained from women with preterm clinical chorioamnionitis and a positive or negative microbiological culture (n = 17). The cellular composition of amniotic fluid was evaluated using fluorescence microscopy, scanning and transmission electron microscopy, and flow cytometry. Women without preterm clinical chorioamnionitis were also examined (n = 10).

RESULTS

Amniotic fluid from women with preterm clinical chorioamnionitis and a positive culture had: (1) abundant neutrophils associated with viable and non-viable bacteria, (2) neutrophils performing phagocytosis, (3) neutrophils forming NETs, (4) increased numbers of neutrophils, monocytes/macrophages, and CD4+ T cells, and (5) high expression of IL-1β by neutrophils and monocytes/macrophages. Amniotic fluid from women with preterm clinical chorioamnionitis and proven infection tended to have fewer monocytes/macrophages and CD4+ T cells compared to those without chorioamnionitis.

CONCLUSION

We provide the first morphologic and phenotypic characterization of the cellular immune responses in the amniotic cavity of women with preterm clinical chorioamnionitis, a condition associated with adverse neonatal outcomes.

Preterm labor is characterized by a high abundance of amniotic fluid prostaglandins in patients with intra-amniotic infection or sterile intra-amniotic inflammation

Objective: To distinguish between prostaglandin and prostamide concentrations in the amniotic fluid of women who had an episode of preterm labor with intact membranes through the utilisation of liquid chromatography-tandem mass spectrometry.Study design: Liquid chromatography-tandem mass spectrometry analysis of amniotic fluid of women with preterm labor and (1) subsequent delivery at term (2) preterm delivery without intra-amniotic inflammation; (3) preterm delivery with sterile intra-amniotic inflammation (interleukin (IL)-6>2.6 ng/mL without detectable microorganisms); and (4) preterm delivery with intra-amniotic infection [IL-6>2.6 ng/mL with detectable microorganisms].Results: (1) amniotic fluid concentrations of PGE₂, PGF_2α, and PGFM were higher in patients with intra-amniotic infection than in those without intra-amniotic inflammation; (2) PGE₂ and PGF_2α concentrations were also greater in patients with intra-amniotic infection than in those with sterile intra-amniotic inflammation; (3) patients with sterile intra-amniotic inflammation had higher amniotic fluid concentrations of PGE₂ and PGFM than those without intra-amniotic inflammation who delivered at term; (4) PGFM concentrations were also greater in women with sterile intra-amniotic inflammation than in those without intra-amniotic inflammation who delivered preterm; (5) amniotic fluid concentrations of prostamides (PGE₂-EA and PGF_2α-EA) were not different among patients with preterm labor; (6) amniotic fluid concentrations of prostaglandins, but no prostamides, were higher in cases with intra-amniotic inflammation; and (7) the PGE₂:PGE₂-EA and PGF_2α:PGF_2α-EA ratios were higher in patients with intra-amniotic infection compared to those without inflammation.Conclusions: Mass spectrometric analysis of amniotic fluid indicated that amniotic fluid concentrations of prostaglandins, but no prostamides, were higher in women with preterm labor and intra-amniotic infection than in other patients with an episode of preterm labor. Yet, women with intra-amniotic infection had greater amniotic fluid concentrations of PGE₂ and PGF_2α than those with sterile intra-amniotic inflammation, suggesting that these two clinical conditions may be differentiated by using mass spectrometric analysis of amniotic fluid.

Neutrophils in preterm birth: Friend or foe?

Preterm birth is a serious global health problem that affects 5-18% of pregnancies worldwide. In addition to being the major cause of neonatal mortality and morbidity, preterm birth is associated with short term and long term complications in the offspring. Despite this, the causes and pathogenesis of preterm birth remain unclear. Neutrophils are innate immune cells that infiltrate the maternal-fetal interface during normal parturition and their accumulation is dramatically increased during preterm birth, especially in the presence of an infection. Indeed, a defining feature of chorioamnionitis (inflammation of the chorioamnionic fetal membranes) that is associated with more than 40% of preterm births, is neutrophil accumulation. While these cells may play an important role during normal term parturition as well as preterm birth, their functions at the maternal-fetal interface are unclear. This review will provide a broad overview of the relevant studies to enable a better understanding of the roles of neutrophils during normal parturition and preterm birth.

Human Chorionic Gonadotropin-Mediated Immune Responses That Facilitate Embryo Implantation and Placentation

Human chorionic gonadotropin (hCG) serves as one of the first signals provided by the embryo to the mother. Exactly at the time when the first step of the implantation process is initiated and the blastocyst adheres to the maternal endometrium, the embryonic tissue starts to actively secrete hCG. Shortly thereafter, the hormone can be detected in the maternal circulation where its concentration steadily increases throughout early pregnancy as it is continuously released by the forming placenta. Accumulating evidence underlines the critical function of hCG for embryo implantation and placentation. hCG not only regulates biological aspects of these early pregnancy events but also supports maternal immune cells in their function as helpers in the establishment of an adequate embryo-endometrial relationship. In view of its early presence in the maternal circulation, hCG has the potential to influence both local uterine immune cell populations as well as peripheral ones. The current review aims to summarize recent literature on the participation of innate and adaptive immune cells in embryo implantation and placentation with a specific focus on their regulation by hCG.

Evidence that intra-amniotic infections are often the result of an ascending invasion - a molecular microbiological study

Background Microbial invasion of the amniotic cavity resulting in intra-amniotic infection is associated with obstetrical complications such as preterm labor with intact or ruptured membranes, cervical insufficiency, as well as clinical and histological chorioamnionitis. The most widely accepted pathway for intra-amniotic infection is the ascension of microorganisms from the lower genital tract. However, hematogenous dissemination of microorganisms from the oral cavity or intestine, retrograde seeding from the peritoneal cavity through the fallopian tubes, and introduction through invasive medical procedures have also been suggested as potential pathways for intra-amniotic infection. The primary reason that an ascending pathway is viewed as most common is that the microorganisms most often detected in the amniotic fluid are those that are typical inhabitants of the vagina. However, thus far, no studies have shown that microorganisms in the amniotic cavity are simultaneously present in the vagina of the woman from which they were isolated. The objective of the study was to determine the frequency with which microorganisms isolated from women with intra-amniotic infection are also present in the lower genital tract. Methods This was a cross-sectional study of women with intra-amniotic infection with intact membranes. Intra-amniotic infection was defined as a positive culture and elevated concentrations of interleukin-6 (IL-6) (>2.6 ng/mL) in amniotic fluid and/or acute histologic chorioamnionitis and funisitis. Microorganisms isolated from bacterial cultures of amniotic fluid were taxonomically identified through matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and 16S ribosomal RNA (rRNA) gene sequencing. Vaginal swabs were obtained at the time of amniocentesis for the identification of microorganisms in the lower genital tract. The overall bacterial profiles of amniotic fluids and vaginal swabs were characterized through 16S rRNA gene sequencing. The bacterial profiles of vaginal swabs were interrogated for the presence of bacteria cultured from amniotic fluid and for the presence of prominent (>1% average relative abundance) operational taxonomic units (OTUs) within the overall 16S rRNA gene bacterial profiles of amniotic fluid. Results (1) A total of 75% (6/8) of women had bacteria cultured from their amniotic fluid that are typical residents of the vaginal ecosystem. (2) A total of 62.5% (5/8) of women with bacteria cultured from their amniotic fluid also had these bacteria present in their vagina. (3) The microorganisms cultured from amniotic fluid and also detected in the vagina were Ureaplasma urealyticum, Escherichia coli, and Streptococcus agalactiae. (4) 16S rRNA gene sequencing revealed that the amniotic fluid of women with intra-amniotic infection had bacterial profiles dominated by Sneathia, Ureaplasma, Prevotella, Lactobacillus, Escherichia, Gardnerella, Peptostreptococcus, Peptoniphilus, and Streptococcus, many of which had not been cultured from the amniotic fluid samples. (5) Seventy percent (7/10) of the prominent (>1% average relative abundance) OTUs found in amniotic fluid were also prominent in the vagina. Conclusion The majority of women with intra-amniotic infection had bacteria cultured from their amniotic fluid that were typical vaginal commensals, and these bacteria were detected within the vagina at the time of amniocentesis. Molecular microbiological interrogation of amniotic fluid from women with intra-amniotic infection revealed that the bacterial profiles of amniotic fluid were largely consistent with those of the vagina. These findings indicate that ascension from the lower genital tract is the primary pathway for intra-amniotic infection.

The origin of amniotic fluid monocytes/macrophages in women with intra-amniotic inflammation or infection

Background Monocytes, after neutrophils, are the most abundant white blood cells found in the amniotic cavity of women with intra-amniotic inflammation/infection. However, the origin of such cells has not been fully investigated. Herein, we determined (1) the origin of amniotic fluid monocytes/macrophages from women with intra-amniotic inflammation/infection, (2) the relationship between the origin of amniotic fluid monocytes/macrophages and preterm or term delivery and (3) the localization of monocytes/macrophages in the placental tissues. Methods Amniotic fluid samples (n = 16) were collected from women with suspected intra-amniotic inflammation or infection. Amniotic fluid monocytes/macrophages were purified by fluorescence-activated cell sorting, and DNA fingerprinting was performed. Blinded placental histopathological evaluations were conducted. Immunohistochemistry was performed to detect CD14+ monocytes/macrophages in the placental tissues. Results DNA fingerprinting revealed that (1) 56.25% (9/16) of amniotic fluid samples had mostly fetal monocytes/macrophages, (2) 37.5% (6/16) had predominantly maternal monocytes/macrophages and (3) one sample (6.25% [1/16]) had a mixture of fetal and maternal monocytes/macrophages. (4) Most samples with predominantly fetal monocytes/macrophages were from women who delivered early preterm neonates (77.8% [7/9]), whereas all samples with mostly maternal monocytes/macrophages or a mixture of both were from women who delivered term or late preterm neonates (100% [7/7]). (5) Most of the women included in this study presented acute maternal and fetal inflammatory responses in the placenta (85.7% [12/14]). (6) Women who had mostly fetal monocytes/macrophages in amniotic fluid had abundant CD14+ cells in the umbilical cord and chorionic plate, whereas women with mostly maternal amniotic fluid monocytes/macrophages had abundant CD14+ cells in the chorioamniotic membranes. Conclusion Amniotic fluid monocytes/macrophages can be of either fetal or maternal origin, or a mixture of both, in women with intra-amniotic inflammation or infection. These immune cells could be derived from the fetal and maternal vasculature of the placenta.

Fetal T Cell Activation in the Amniotic Cavity during Preterm Labor: A Potential Mechanism for a Subset of Idiopathic Preterm Birth

Prematurity is the leading cause of perinatal morbidity and mortality worldwide. In most cases, preterm birth is preceded by spontaneous preterm labor, a syndrome that is associated with intra-amniotic inflammation, the most studied etiology. However, the remaining etiologies of preterm labor are poorly understood; therefore, most preterm births are categorized as idiopathic. In this study, we provide evidence showing that the fetal immune system undergoes premature activation in women with preterm labor without intra-amniotic inflammation, providing a potential new mechanism of disease for some cases of idiopathic preterm birth. First, we showed that fetal T cells are a predominant leukocyte population in amniotic fluid during preterm gestations. Interestingly, only fetal CD4+ T cells were increased in amniotic fluid of women who underwent idiopathic preterm labor and birth. This increase in fetal CD4+ T cells was accompanied by elevated amniotic fluid concentrations of T cell cytokines such as IL-2, IL-4, and IL-13, which are produced by these cells upon in vitro stimulation, but was not associated with the prototypical cytokine profile observed in women with intra-amniotic inflammation. Also, we found that cord blood T cells, mainly CD4+ T cells, obtained from women with idiopathic preterm labor and birth displayed enhanced ex vivo activation, which is similar to that observed in women with intra-amniotic inflammation. Finally, we showed that the intra-amniotic administration of activated neonatal CD4+ T cells induces preterm birth in mice. Collectively, these findings provide evidence suggesting that fetal T cell activation is implicated in the pathogenesis of idiopathic preterm labor and birth.

Gasdermin D: Evidence of pyroptosis in spontaneous preterm labor with sterile intra-amniotic inflammation or intra-amniotic infection

PROBLEM

Pyroptosis, inflammatory programmed cell death, is initiated through the inflammasome and relies on the pore-forming actions of the effector molecule gasdermin D. Herein, we investigated whether gasdermin D is detectable in women with spontaneous preterm labor and sterile intra-amniotic inflammation or intra-amniotic infection.

METHOD OF STUDY

Amniotic fluid samples (n = 124) from women with spontaneous preterm labor were subdivided into the following groups: (a) those who delivered at term (n = 32); and those who delivered preterm (b) without intra-amniotic inflammation (n = 41), (c) with sterile intra-amniotic inflammation (n = 32), or (d) with intra-amniotic infection (n = 19), based on amniotic fluid IL-6 concentrations and the microbiological status of amniotic fluid (culture and PCR/ESI-MS). Gasdermin D concentrations were measured using an ELISA kit. Multiplex immunofluorescence staining was also performed to determine the expression of gasdermin D, caspase-1, and interleukin-1β in the chorioamniotic membranes. Flow cytometry was used to detect pyroptosis (active caspase-1) in decidual cells from women with preterm labor and birth.

RESULTS

(a) Gasdermin D was detected in the amniotic fluid and chorioamniotic membranes from women who underwent spontaneous preterm labor/birth with either sterile intra-amniotic inflammation or intra-amniotic infection, but was rarely detected in those without intra-amniotic inflammation. (b) Amniotic fluid concentrations of gasdermin D were higher in women with intra-amniotic infection than in those with sterile intra-amniotic inflammation, and its expression in the chorioamniotic membranes was associated with caspase-1 and IL-1β (inflammasome mediators). (c) Decidual stromal cells and leukocytes isolated from women with preterm labor and birth are capable of undergoing pyroptosis given their expression of active caspase-1.

CONCLUSION

Pyroptosis can occur in the context of sterile intra-amniotic inflammation and intra-amniotic infection in patients with spontaneous preterm labor and birth.

Cellular immune responses in amniotic fluid of women with preterm labor and intra-amniotic infection or intra-amniotic inflammation

PROBLEM

Preterm birth is commonly preceded by preterm labor, a syndrome that is causally linked to both intra-amniotic infection and intra-amniotic inflammation. However, the stereotypical cellular immune responses in these two clinical conditions are poorly understood.

METHOD OF STUDY

Amniotic fluid samples (n = 26) were collected from women diagnosed with preterm labor and intra-amniotic infection (amniotic fluid IL-6 concentrations ≥2.6 ng/mL and culturable microorganisms, n = 10) or intra-amniotic inflammation (amniotic fluid IL-6 concentrations ≥2.6 ng/mL without culturable microorganisms, n = 16). Flow cytometry was performed to evaluate the phenotype and number of amniotic fluid leukocytes. Amniotic fluid concentrations of classical pro-inflammatory cytokines, type 1 and type 2 cytokines, and T-cell chemokines were determined using immunoassays.

RESULTS

Women with spontaneous preterm labor and intra-amniotic infection had (a) a greater number of total leukocytes, including neutrophils and monocytes/macrophages, in amniotic fluid; (b) a higher number of total T cells and CD4⁺ T cells, but not CD8⁺ T cells or B cells, in amniotic fluid; and (c) increased amniotic fluid concentrations of IL-6, IL-1β, and IL-10, compared to those with intra-amniotic inflammation. However, no differences in amniotic fluid concentrations of T-cell cytokines and chemokines were observed between these two clinical conditions.

CONCLUSION

The cellular immune responses observed in women with preterm labor and intra-amniotic infection are more severe than in those with intra-amniotic inflammation, and neutrophils, monocytes/macrophages, and CD4⁺ T cells are the main immune cells responding to microorganisms that invade the amniotic cavity. These findings provide insights into the intra-amniotic immune mechanisms underlying the human syndrome of preterm labor.

Innate Immune Cells and Toll-like Receptor-Dependent Responses at the Maternal-Fetal Interface

During pregnancy, the placenta, the mother and the fetus exploit several mechanisms in order to avoid fetal rejection and to maintain an immunotolerant environment throughout nine months. During this time, immune cells from the fetal and maternal compartments interact to provide an adequate defense in case of an infection and to promote a tolerogenic milieu for the fetus to develop peacefully. Trophoblasts and decidual cells, together with resident natural killer cells, dendritic cells, Hofbauer cells and other macrophages, among other cell types, contribute to the modulation of the uterine environment to sustain a successful pregnancy. In this review, the authors outlined some of the various roles that the innate immune system plays at the maternal-fetal interface. First, the cell populations that are recruited into gestational tissues and their immune mechanisms were examined. In the second part, the Toll-like receptor (TLR)-dependent immune responses at the maternal-fetal interface was summarized, in terms of their specific cytokine/chemokine/antimicrobial peptide expression profiles throughout pregnancy.

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.

Are B cells altered in the decidua of women with preterm or term labor?

PROBLEM

The immunophenotype of B cells at the maternal-fetal interface (decidua) in labor at term and preterm labor is poorly understood.

METHOD OF STUDY

Decidual tissues were obtained from women with preterm or term labor and from non-labor gestational age-matched controls. Immunophenotyping of decidual B cells was performed using multicolor flow cytometry.

RESULTS

(a) In the absence of acute or chronic chorioamnionitis, total B cells were more abundant in the decidua parietalis of women who delivered preterm than in those who delivered at term, regardless of the presence of labor; (b) decidual transitional and naïve B cells were the most abundant B-cell subsets; (c) decidual B1 B cells were increased in women with either labor at term or preterm labor and chronic chorioamnionitis compared to those without this placental lesion; (d) decidual transitional B cells were reduced in women with preterm labor compared to those without labor; (e) naïve, class-switched, and non-class-switched B cells in the decidual tissues underwent mild alterations with the process of preterm labor; (f) decidual plasmablasts seemed to increase in women with either labor at term or preterm labor with chronic chorioamnionitis; and (g) decidual B cells expressed high levels of interleukin (IL)-12, IL-6, and/or IL-35.

CONCLUSION

Total B cells are not increased with the presence of preterm or term labor; yet, specific subsets (B1 and plasmablasts) undergo alterations in women with chronic chorioamnionitis. Therefore, B cells are solely implicated in the pathological process of preterm labor in a subset of women with chronic inflammation of the placenta. These findings provide insight into the immunology of the maternal-fetal interface in preterm and term labor.

Effector and Activated T Cells Induce Preterm Labor and Birth That Is Prevented by Treatment with Progesterone

Preterm labor commonly precedes preterm birth, the leading cause of perinatal morbidity and mortality worldwide. Most research has focused on establishing a causal link between innate immune activation and pathological inflammation leading to preterm labor and birth. However, the role of maternal effector/activated T cells in the pathogenesis of preterm labor/birth is poorly understood. In this study, we first demonstrated that effector memory and activated maternal T cells expressing granzyme B and perforin are enriched at the maternal-fetal interface (decidua) of women with spontaneous preterm labor. Next, using a murine model, we reported that prior to inducing preterm birth, in vivo T cell activation caused maternal hypothermia, bradycardia, systemic inflammation, cervical dilation, intra-amniotic inflammation, and fetal growth restriction, all of which are clinical signs associated with preterm labor. In vivo T cell activation also induced B cell cytokine responses, a proinflammatory macrophage polarization, and other inflammatory responses at the maternal-fetal interface and myometrium in the absence of an increased influx of neutrophils. Finally, we showed that treatment with progesterone can serve as a strategy to prevent preterm labor/birth and adverse neonatal outcomes by attenuating the proinflammatory responses at the maternal-fetal interface and cervix induced by T cell activation. Collectively, these findings provide mechanistic evidence showing that effector and activated T cells cause pathological inflammation at the maternal-fetal interface, in the mother, and in the fetus, inducing preterm labor and birth and adverse neonatal outcomes. Such adverse effects can be prevented by treatment with progesterone, a clinically approved strategy.

Effects of antibiotic therapy in women with the amniotic fluid "sludge" at 15-24 weeks of gestation on pregnancy outcomes

Objective: The aim of this prospective study was to assess the efficacy of antibiotic therapy for the prevention of adverse pregnancy outcomes in women with the amniotic fluid "sludge" at 15-24 weeks of gestation.Methods: 245 women underwent transvaginal ultrasound cervical length measurement at 15-24 weeks of pregnancy and 29 out of them with amniotic fluid "sludge" were included in the study. Eight women with the "sludge" had cervical length >25 mm (Group I), seven-an asymptomatic short cervix (Group IIa) and 14 women with a short cervix had symptoms like low abdominal pain, back pain, and menstrual-like cramps (Group IIb). All participants received intravenous, oral and/or vaginal antibiotic therapy. Participants in Group IIa were additionally given vaginal progesterone (VP), and in Group IIb-VP and indomethacin. Placentas from women with preterm birth (PTB) underwent histological examination.Results: The amniotic fluid "sludge" detected at an ultrasound scan between 15-24 weeks of gestation was associated with long-term maternal infections, histological chorioamnionitis, and was viewed as a marker of intra-amniotic infection. Absence of intravenous antibiotic therapy during midtrimester of pregnancy in these women was associated with neonatal infection with intrauterine onset in 61.1%, postpartum endometritis in 23.1%, and rate of PTB 46.2%. Intravenous antibiotic therapy eliminated sonographic presence of the sludge and resulted in prevented of neonatal and postpartum infections, prevented the risk of PTB in women with the cervical length >25 mm, in those with an asymptomatic short cervix receiving VP, and in 70% of symptomatic women with a short cervix, who received them in combination VP/indomethacin. For those women whose approach was not fully beneficial, it allowed to delay delivery in 11-17 weeks.Conclusions: Although we found that intravenous antibiotic therapy at 15-24 weeks of gestation in women with amniotic fluid "sludge" can protect from infection-related complications and demonstrated high beneficial effects of adding antibiotics to anti-inflammatory drug (indomethacin) and/or VP in women with a short cervix, further larger studies are needed.

Innate Lymphoid Cells in the Maternal and Fetal Compartments

Pregnancy success is orchestrated by the complex balance between the maternal and fetal immune systems. Herein, we summarize the potential role of innate lymphoid cells (ILCs) in the maternal and fetal compartments. We reviewed published literature describing different ILC subsets [ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTi) cells] in the uterus, decidua, fetal tissues [liver, secondary lymphoid organs (SLO), intestine, and lung] and amniotic cavity. ILC1s, ILC2s, and ILC3s are present in the murine uterus prior to and during pregnancy but have only been detected in the non-pregnant endometrium in humans. Specifically, ILC2s reside in the murine uterus from mid-pregnancy to term, ILC1s increase throughout gestation, and ILC3s remain constant. Yet, LTi cells have only been detected in the non-pregnant murine uterus. In the human decidua, ILC1s, ILC3s, and LTi-like cells are more abundant during early gestation, whereas ILC2s increase at the end of pregnancy. Decidual ILC1s were also detected during mid-gestation in mice. Interestingly, functional decidual ILC2s and ILC3s increased in women who underwent spontaneous preterm labor, indicating the involvement of such cells in this pregnancy complication. Fetal ILCs exist in the liver, SLO, intestine, lung, and amniotic cavity. The fetal liver is thought to be the source of ILC progenitors since the differentiation of these cells from hematopoietic stem cells occurs at this site, and mature ILC subsets can be found in this compartment as well. The interaction between LTi cells and specialized stromal cells is important during the formation of SLO. Mature ILCs are found at the mucosal surfaces of the lung and intestine, from where they can extravasate into the amniotic cavity. Amniotic fluid ILCs express high levels of RORγt, CD161, and CD103, hallmarks of ILC3s. Such cells are more abundant in the second trimester than later in gestation. Although amniotic fluid ILC3s produce IL-17A and TNFα, indicating their functionality, their numbers in patients with intra-amniotic infection/inflammation remain unchanged compared to those without this pregnancy complication. Collectively, these findings suggest that maternal (uterine and decidual) ILCs play central roles in both the initiation and maintenance of pregnancy, and fetal ILCs participate in the development of immunity.

Ascending Vaginal Infection Using Bioluminescent Bacteria Evokes Intrauterine Inflammation, Preterm Birth, and Neonatal Brain Injury in Pregnant Mice

Preterm birth is a serious global health problem and the leading cause of infant death before 5 years of age. At least 40% of cases are associated with infection. The most common way for pathogens to access the uterine cavity is by ascending from the vagina. Bioluminescent pathogens have revolutionized the understanding of infectious diseases. We hypothesized that bioluminescent Escherichia coli can be used to track and monitor ascending vaginal infections. Two bioluminescent strains were studied: E. coli K12 MG1655-lux, a nonpathogenic laboratory strain, and E. coli K1 A192PP-lux2, a pathogenic strain capable of causing neonatal meningitis and sepsis in neonatal rats. On embryonic day 16, mice received intravaginal E. coli K12, E. coli K1, or phosphate-buffered saline followed by whole-body bioluminescent imaging. In both cases, intravaginal delivery of E. coli K12 or E. coli K1 led to bacterial ascension into the uterine cavity, but only E. coli K1 induced preterm parturition. Intravaginal administration of E. coli K1 significantly reduced the proportion of pups born alive compared with E. coli K12 and phosphate-buffered saline controls. However, in both groups of viable pups born after bacterial inoculation, there was evidence of comparable brain inflammation by postnatal day 6. This study ascribes specific mechanisms by which exposure to intrauterine bacteria leads to premature delivery and neurologic inflammation in neonates.

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.

Human β-defensin-1: A natural antimicrobial peptide present in amniotic fluid that is increased in spontaneous preterm labor with intra-amniotic infection

PROBLEM

Human β-defensins (HBDs) are antimicrobial peptides that participate in the soluble innate immune mechanisms against infection. Herein, we determined whether HBD-1 was present in amniotic fluid during normal pregnancy and whether its concentrations change with intra-amniotic inflammation and/or infection.

METHOD OF STUDY

Amniotic fluid was collected from 219 women in the following groups: (a) midtrimester who delivered at term (n = 35); (b) term with (n = 33) or without (n = 17) labor; (c) preterm labor with intact membranes who delivered at term (n = 29) or who delivered preterm with (n = 19) and without (n = 29) intra-amniotic inflammation and infection or with intra-amniotic inflammation but without infection (n = 21); and (d) preterm prelabor rupture of membranes (pPROM) with (n = 19) and without (n = 17) intra-amniotic inflammation/infection. Amniotic fluid HBD-1 concentrations were determined using a sensitive and specific ELISA kit.

RESULTS

(a) HBD-1 was detectable in all amniotic fluid samples; (b) amniotic fluid concentrations of HBD-1 were changed with gestational age (midtrimester vs term no labor), being higher in midtrimester; (c) amniotic fluid concentrations of HBD-1 were similar between women with and without spontaneous labor at term; (d) among patients with spontaneous preterm labor, amniotic fluid concentrations of HBD-1 in women with intra-amniotic inflammation/infection and in those with intra-amniotic inflammation without infection were greater than in women without intra-amniotic inflammation or infection who delivered preterm or at term; and (e) the presence of intra-amniotic inflammation and infection in patients with pPROM did not change amniotic fluid concentrations of HBD-1.

CONCLUSION

HBD-1 is a physiological constituent of amniotic fluid that is increased in midtrimester during normal pregnancy and in the presence of culturable microorganisms in the amniotic cavity. These findings provide insight into the soluble host defense mechanisms against intra-amniotic infection.

Innate lymphoid cells at the human maternal-fetal interface in spontaneous preterm labor

PROBLEM

Pathological inflammation is causally linked to preterm labor and birth, the leading cause of neonatal morbidity and mortality worldwide. Our aims were to investigate whether (i) the newly described family of innate lymphoid cells (ILCs) was present at the human maternal-fetal interface and (ii) ILC inflammatory subsets were associated with the pathological process of preterm labor.

METHODS OF STUDY

Decidual leukocytes were isolated from women with preterm or term labor as well as from gestational age-matched non-labor controls. ILCs (CD15- CD14- CD3- CD19- CD56- CD11b- CD127+ cells) and their subsets (ILC1, T-bet+ ILCs; ILC2, GATA3+ ILCs; and ILC3, RORγt+ ILCs) and cytokine expression were identified in the decidual tissues using immunophenotyping.

RESULTS

(i) The proportion of total ILCs was increased in the decidua parietalis of women with preterm labor; (ii) ILC1s were a minor subset of decidual ILCs during preterm and term gestations; (iii) ILC2s were the most abundant ILC subset in the decidua during preterm and term gestations; (iv) the proportion of ILC2s was increased in the decidua basalis of women with preterm labor; (v) the proportion of ILC3s was increased in the decidua parietalis of women with preterm labor; and (vi) during preterm labor, ILC3s had higher expression of IL-22, IL-17A, IL-13, and IFN-γ compared to ILC2s in the decidua.

CONCLUSION

ILC2s were the most abundant ILC subset at the human maternal-fetal interface during preterm and term gestations. Yet, during preterm labor, an increase in ILC2s and ILC3s was observed in the decidua basalis and decidua parietalis, respectively. These findings provide evidence demonstrating a role for ILCs at the maternal-fetal interface during the pathological process of preterm labor.

The immunophenotype of amniotic fluid leukocytes in normal and complicated pregnancies

PROBLEM

The immune cellular composition of amniotic fluid is poorly understood. Herein, we determined: 1) the immunophenotype of amniotic fluid immune cells during the second and third trimester in the absence of intra-amniotic infection/inflammation; 2) whether amniotic fluid T cells and ILCs display different phenotypical characteristics to that of peripheral cells; and 3) whether the amniotic fluid immune cells are altered in women with intra-amniotic infection/inflammation.

METHOD OF STUDY

Amniotic fluid samples (n = 57) were collected from 15 to 40 weeks of gestation in women without intra-amniotic infection/inflammation. Samples from women with intra-amniotic infection/inflammation were also included (n = 9). Peripheral blood mononuclear cells from healthy adults were used as controls (n = 3). Immunophenotyping was performed using flow cytometry.

RESULTS

In the absence of intra-amniotic infection/inflammation, the amniotic fluid contained several immune cell populations between 15 and 40 weeks. Among these immune cells: (i) T cells and ILCs were greater than B cells and natural killer (NK) cells between 15 and 30 weeks; (ii) T cells were most abundant between 15 and 30 weeks; (iii) ILCs were most abundant between 15 and 20 weeks; (iv) B cells were scarce between 15 and 20 weeks; yet, they increased and were constant after 20 weeks; (v) NK cells were greater between 15 and 30 weeks than at term; (vi) ILCs expressed high levels of RORγt, CD161, and CD103 (ie, group 3 ILCs); (vii) T cells expressed high levels of RORγt; (viii) neutrophils increased as gestation progressed; and (ix) monocytes/macrophages emerged after 20 weeks and remained constant until term. All of the amniotic fluid immune cells, except ILCs, were increased in the presence of intra-amniotic infection/inflammation.

CONCLUSION

The amniotic fluid harbors a diverse immune cellular composition during normal and complicated pregnancies.

CD71+ erythroid cells from neonates born to women with preterm labor regulate cytokine and cellular responses

Neonatal CD71+ erythroid cells are thought to have immunosuppressive functions. Recently, we demonstrated that CD71+ erythroid cells from neonates born to women who underwent spontaneous preterm labor (PTL) are reduced to levels similar to those of term neonates; yet, their functional properties are unknown. Herein, we investigated the functionality of CD71+ erythroid cells from neonates born to women who underwent spontaneous preterm or term labor. CD71+ erythroid cells from neonates born to women who underwent PTL displayed a similar mRNA profile to that of those from term neonates. The direct contact between preterm or term neonatal CD71+ erythroid cells and maternal mononuclear immune cells, but not soluble products from these cells, induced the release of proinflammatory cytokines and a reduction in the release of TGF-β. Moreover, PTL-derived neonatal CD71+ erythroid cells (1) modestly altered CD8+ T cell activation; (2) inhibited conventional CD4+ and CD8+ T-cell expansion; (3) suppressed the expansion of CD8+ regulatory T cells; (4) regulated cytokine responses mounted by myeloid cells in the presence of a microbial product; and (5) indirectly modulated T-cell cytokine responses. In conclusion, neonatal CD71+ erythroid cells regulate neonatal T-cell and myeloid responses and their direct contact with maternal mononuclear cells induces a proinflammatory response. These findings provide insight into the biology of neonatal CD71+ erythroid cells during the physiologic and pathologic processes of labor.

Are amniotic fluid neutrophils in women with intraamniotic infection and/or inflammation of fetal or maternal origin?

BACKGROUND

Neutrophils are the most abundant white blood cells found in the amniotic cavity of women with intraamniotic infection and/or inflammation. The current belief is that these neutrophils are of fetal origin. However, abundant neutrophils have been found in the amniotic fluid of women with a severe acute maternal inflammatory response but without a severe fetal inflammatory response in the placenta, suggesting that these innate immune cells can also be of maternal origin or a mixture of both fetal and maternal neutrophils.

OBJECTIVE

We sought to investigate the origin of amniotic fluid neutrophils from women with intraamniotic infection and/or inflammation and to correlate these findings with acute histologic maternal and fetal inflammatory responses in the placenta.

STUDY DESIGN

Amniotic fluid was collected from 15 women with suspected intraamniotic infection and/or inflammation (positive microbiological cultures and/or interleukin-6 concentrations ≥2.6 ng/mL). Amniotic fluid neutrophils were purified by fluorescence-activated cell sorting, DNA was extracted, and DNA fingerprinting was performed. DNA fingerprinting was also performed in the umbilical cord and maternal blood DNA. Fluorescence in situ hybridization was assayed in women with male neonates. Blinded placental histopathological evaluations were conducted.

RESULTS

First, DNA fingerprinting revealed that 43% (6/14) of women who underwent a single amniocentesis had mostly fetal neutrophils in the amniotic fluid. Second, DNA fingerprinting showed that 36% (5/14) of the women who underwent a single amniocentesis had predominantly maternal neutrophils in the amniotic fluid. Third, DNA fingerprinting indicated that 21% (3/14) of the women who underwent a single amniocentesis had an evident mixture of fetal and maternal neutrophils in the amniotic fluid. Fourth, DNA fingerprinting revealed that a woman who underwent 2 amniocenteses (patient 15) had fetal neutrophils first, and as infection progressed, abundant maternal neutrophils invaded the amniotic cavity. Fifth, fluorescence in situ hybridization confirmed DNA fingerprinting results by showing that both fetal and maternal neutrophils were present in the amniotic fluid. Sixth, most of the women who had predominantly amniotic fluid neutrophils of fetal origin at the time of collection delivered extremely preterm neonates (71% [5/7]). Seventh, all of the women who had predominantly amniotic fluid neutrophils of maternal origin at the time of collection delivered term or late preterm neonates (100% [6/6]). Eighth, 2 of the women who had an evident mixture of fetal and maternal neutrophils in the amniotic fluid at the time of collection delivered extremely preterm neonates (67% [2/3]), and the third woman delivered a term neonate (33% [1/3]). Finally, most of the women included in this study presented acute maternal and fetal inflammatory responses in the placenta (87% [13/15]).

CONCLUSION

Amniotic fluid neutrophils can be either predominantly of fetal or maternal origin, or a mixture of both fetal and maternal origin, in women with intraamniotic infection and/or inflammation. The findings herein provide evidence that both fetal and maternal neutrophils can invade the amniotic cavity, suggesting that both the fetus and the mother participate in the host defense mechanisms against intraamniotic infection.

Amniotic fluid neutrophils can phagocytize bacteria: A mechanism for microbial killing in the amniotic cavity

PROBLEM

Neutrophils are capable of performing phagocytosis, a primary mechanism for microbial killing. Intra-amniotic infection is characterized by an influx of neutrophils into the amniotic cavity. Herein, we investigated whether amniotic fluid neutrophils could phagocytize bacteria found in the amniotic cavity of women with intra-amniotic infection.

METHODS

Amniotic fluid neutrophils from women with intra-amniotic infection were visualized by transmission electron microscopy (n=6). The phagocytic activity of amniotic fluid neutrophils from women with intra-amniotic infection and/or inflammation (n=10) or peripheral neutrophils from healthy individuals (controls, n=3) was tested using ex vivo phagocytosis assays coupled with live imaging. Phagocytosis by amniotic fluid neutrophils was also visualized by confocal microscopy (n=10) as well as scanning and transmission electron microscopy (n=5).

RESULTS

(i) Intra-amniotic infection-related bacteria including cocci (eg Streptococcus agalactiae), bacilli (eg Bacteriodes fragilis and Prevotella spp.), and small bacteria without a cell wall (eg Ureaplasma urealyticum) were found inside of amniotic fluid neutrophils; (ii) peripheral neutrophils (controls) rapidly phagocytized S. agalactiae, U. urealyticum, Gardnerella vaginalis, and Escherichia coli; (iii) amniotic fluid neutrophils rapidly phagocytized S. agalactiae and G. vaginalis; and (iv) amniotic fluid neutrophils slowly phagocytized U. urealyticum and E. coli; yet, the process of phagocytosis of the genital mycoplasma was lengthier.

CONCLUSION

Amniotic fluid neutrophils can phagocytize bacteria found in the amniotic cavity of women with intra-amniotic infection, namely S. agalactiae, U. urealyticum, G. vaginalis, and E. coli. Yet, differences in the rapidity of phagocytosis were observed among the studied microorganisms. These findings provide a host defense mechanism whereby amniotic fluid neutrophils can kill microbes invading the amniotic cavity.