Chronic chorioamnionitis: a clinicopathologic and immunohistochemical study

Gestational Age, Infection, and Suboptimal Maternal Prepregnancy BMI Independently Associate with Placental Histopathology in a Cohort of Pregnancies without Major Maternal Comorbidities

Background: The placenta undergoes morphological and functional adaptations to adverse exposures during pregnancy. The effects ofsuboptimal maternal body mass index (BMI), preterm birth, and infection on placental histopathological phenotypes are not yet well understood, despite the association between these conditions and poor offspring outcomes. We hypothesized that suboptimal maternal prepregnancy BMI and preterm birth (with and without infection) would associate with altered placental maturity and morphometry, and that altered placental maturity would associate with poor birth outcomes. Methods: Clinical data and human placentae were collected from 96 pregnancies where mothers were underweight, normal weight, overweight, or obese, without other major complications. Placental histopathological characteristics were scored by an anatomical pathologist. Associations between maternal BMI, placental pathology (immaturity and hypermaturity), placental morphometry, and infant outcomes were investigated for term and preterm births with and without infection. Results: Fetal capillary volumetric proportion was decreased, whereas the villous stromal volumetric proportion was increased in placentae from preterm pregnancies with chorioamnionitis compared to preterm placentae without chorioamnionitis. At term and preterm, pregnancies with maternal overweight and obesity had a high percentage increase in proportion of immature placentae compared to normal weight. Placental maturity did not associate with infant birth outcomes. We observed placental hypermaturity and altered placental morphometry among preterm pregnancies with chorioamnionitis, suggestive of altered placental development, which may inform about pregnancies susceptible to preterm birth and infection. Conclusions: Our data increase our understanding of how common metabolic exposures and preterm birth, in the absence of other comorbidities or complications, potentially contribute to poor pregnancy outcomes and developmental programming.

Prevalence of Fetal Inflammatory Response Syndrome and Villitis of Unknown Etiology in the Placenta of Saudi Women and Their Association with Baby Sex

Long-term health consequences are influenced by circumstances that occur during pregnancy. The convergence of the maternal and fetal circulations occurs in the placenta, which is the first organ to develop. Placental pathology provides an accurate diagnosis of amniotic sac inflammation, and pathological alterations in preterm placentas provide evidence for the causes of numerous perinatal pathologies, including spontaneous preterm births. This retrospective study aimed to re-examine placentas regarded as normal by the Obstetrics and Gynecology Department at our institution. Thirty-seven male and forty-seven female placentas were collected following full-term delivery, and the grading and staging of any evident inflammatory responses were evaluated and correlated with the babies' sex. Full-thickness placental samples that were considered normal and not sent to the histopathology department were obtained from the central and marginal regions of placental discs. Morphological examination of the fresh placenta was conducted, and fetal and maternal inflammatory response syndromes were assessed. In addition, placental villitis of unknown etiology (VUE) and chronic deciduitis were evaluated. Immunohistochemistry was performed to evaluate the patterns of inflammation in the placenta using anti-CD8 and anti-CD68 antibodies. The correlation between silent pathologies and clinical complications or the development of fetal inflammatory response syndrome was measured. In this study, 17 (20%) maternal and 10 (12%) fetal samples showed inflammatory responses. The frequencies of chronic deciduitis and VUE were higher among pregnant Saudi women than previously reported, probably because fetal inflammatory response syndrome goes unnoticed in Saudi Arabia. In addition, the prevalence of fetal and maternal inflammatory responses was higher in the placentas of the mothers of males than in those of females, suggesting that differences occur in the inflammatory response in the placenta depending on the sex of the newborn. Grading placental inflammation (in cases of VUE) typically predicts the degree of maternal anti-fetal cellular rejection; therefore, increasing the number of placental samples sent for microscopic inspection may be preferable because of their significance in identifying the causes of chronic disorders.

Clinical and Histological Associations of Chronic Inflammatory Lesions in Preterm Placentas: Uncovering the Hidden Dangers

BACKGROUND

Chronic placental inflammatory lesions (CPIL) include chronic deciduitis (CD), villitis of unknown etiology (VUE), and chronic chorioamnionitis (CCA). The frequency of these lesions and their relationship with various clinicopathological parameters in preterm birth (PTB) is presented.

MATERIAL AND METHODS

Preterm placentas from April 2018 to December 2020 were reviewed for presence of CPIL. PTB was classified as spontaneous, indicated, or mixed phenotype. The association of CPIL with clinical parameters like gestational age, birth weight, obstetric complications, and placental parameters like placental dimensions, weight, vascular malperfusion, acute inflammatory lesions, and basal plate myometrial fibers were analyzed.

RESULTS

The study included 538 preterm placentas with 54.3% from indicated PTB. CD was more common (28.4%) than VUE (17.8%) and CCA (12.6%). CD showed significant association with VUE and CCA (both P = .0001) and VUE with CCA (P = .0001). CD was more common in indicated PTB (33.8%, P = .002) and associated with lower birth weight (1591 g vs 1705 g, P = .003), lower placental weight (270.7 g vs 296.9 g, P = .004), length (14.2 cm vs 14.8 cm, P = .006), breadth (11.7 cm vs 12.2 cm, P = .007), maternal vascular malperfusion (P = .004), and basal plate myometrial fibers (P = .02). High-grade and multifocal low-grade VUE was associated with reduced placental length (13.9 cm vs 14.6 cm, P = .02)and breadth (11.5 cm vs 12.1 cm, P = .01). CCA did not show any other association.

CONCLUSION

CPIL are common in PTB and their coexistence suggested a common pathogenic mechanism. Placental examination is the only definite way to identify as they lack clinical signs and symptoms. The smaller placental size associated with these lesions may suggest alter mechanisms for adverse pregnancy outcomes.

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.

Villitis of unknown etiology, chronic deciduitis, chronic chorioamnionitis and chronic histiocytic intervillositis in monozygotic and dizygotic twin pregnancies. A retrospective analysis of 16 cases

INTRODUCTION

Villitis of unknown etiology (VUE), chronic chorioamnionitis (CC), chronic deciduitis (CD) and chronic histiocytic intervillositis (CHI) are most likely the result of a pathologic immune reaction caused by maternal anti-fetal rejection. We analyzed placentas of twin pregnancies with manifestation of these lesions in monozygotic and dizygotic instances.

METHODS

Twin pregnancies from our archive with at least one chronic inflammatory lesion were selected for further analysis and assessed concerning zygosity (gender, chorionicity, short tandem repeat (STR)-analysis).

RESULTS

The cohort comprised sixteen twin placentas, monozygotic in five cases and dizygotic in 11 cases, respectively. VUE (n = 4), CC (n = 1) and CHI (n = 3) manifested concordantly in both placentas of the monozygotic pregnancies and affected discordantly one of the twin placentas in the dizygotic instances. CD (n = 10) manifested concordantly in two and discordantly in one of the monozygotic placentas, and concordantly in three and discordantly in four of the dizygotic instances. Intrauterine fetal demise (n = 3), preterm birth (n = 9) and low birth weight (n = 2) were recognized. Discordant fetal growth in live born children was recognized in two dizygotic cases with discordant manifestation of VUE and CHI.

DISCUSSION

The concordant manifestation of VUE, CC and CHI in monozygotic and the discordant pattern of inflammation in dizygotic pregnancies points to pathologic immune mechanisms against genetically determined fetal antigens being essential for the development of these entities. The heterogenous manifestation of CD could be a hint for diverse fetal or maternal etiologic factors that may contribute to this lesion.

Placental pathology is necessary to understand common pregnancy complications and achieve an improved taxonomy of obstetrical disease

The importance of a fully functioning placenta for a good pregnancy outcome is unquestioned. Loss of function can lead to pregnancy complications and is often detected by a thorough placental pathologic examination. Placental pathology has advanced the science and practice of obstetrics and neonatal-perinatal medicine by classifying diseases according to underlying biology and specific patterns of injury. Many past obstacles have limited the incorporation of placental findings into both clinical studies and day-to-day practice. Limitations have included variability in the nomenclature used to describe placental lesions, a shortage of perinatal pathologists fully competent to analyze placental specimens, and a troubling lack of understanding of placental diagnoses by clinicians. However, the potential use of placental pathology for phenotypic classification, improved understanding of the biology of adverse pregnancy outcomes, the development of treatment and prevention, and patient counseling has never been greater. This review, written partly in response to a recent critique published in a major obstetrics-gynecology journal, reexamines the role of placental pathology by reviewing current concepts of biology; explaining the most recent terminology; emphasizing the usefulness of specific diagnoses for obstetrician-gynecologists, neonatologists, and patients; previewing upcoming changes in recommendations for placental submission; and suggesting future improvements. These improvements should include further consideration of overall healthcare costs, cost-effectiveness, the clinical value added of placental assessment, improvements in placental pathology education and practice, and leveraging of placental pathology to identify new biomarkers of disease and evaluate novel therapies tailored to specific clinicopathologic phenotypes of both women and infants.

Toward a new taxonomy of obstetrical disease: improved performance of maternal blood biomarkers for the great obstetrical syndromes when classified according to placental pathology

BACKGROUND

The major challenge for obstetrics is the prediction and prevention of the great obstetrical syndromes. We propose that defining obstetrical diseases by the combination of clinical presentation and disease mechanisms as inferred by placental pathology will aid in the discovery of biomarkers and add specificity to those already known.

OBJECTIVE

To describe the longitudinal profile of placental growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1), and the PlGF/sFlt-1 ratio throughout gestation, and to determine whether the association between abnormal biomarker profiles and obstetrical syndromes is strengthened by information derived from placental examination, eg, the presence or absence of placental lesions of maternal vascular malperfusion.

STUDY DESIGN

This retrospective case cohort study was based on a parent cohort of 4006 pregnant women enrolled prospectively. The case cohort of 1499 pregnant women included 1000 randomly selected patients from the parent cohort and all additional patients with obstetrical syndromes from the parent cohort. Pregnant women were classified into six groups: 1) term delivery without pregnancy complications (n=540; control); 2) preterm labor and delivery (n=203); 3) preterm premature rupture of the membranes (n=112); 4) preeclampsia (n=230); 5) small-for-gestational-age neonate (n=334); and 6) other pregnancy complications (n=182). Maternal plasma concentrations of PlGF and sFlt-1 were determined by enzyme-linked immunosorbent assays in 7560 longitudinal samples. Placental pathologists, masked to clinical outcomes, diagnosed the presence or absence of placental lesions of maternal vascular malperfusion. Comparisons between mean biomarker concentrations in cases and controls were performed by utilizing longitudinal generalized additive models. Comparisons were made between controls and each obstetrical syndrome with and without subclassifying cases according to the presence or absence of placental lesions of maternal vascular malperfusion.

RESULTS

1) When obstetrical syndromes are classified based on the presence or absence of placental lesions of maternal vascular malperfusion, significant differences in the mean plasma concentrations of PlGF, sFlt-1, and the PlGF/sFlt-1 ratio between cases and controls emerge earlier in gestation; 2) the strength of association between an abnormal PlGF/sFlt-1 ratio and the occurrence of obstetrical syndromes increases when placental lesions of maternal vascular malperfusion are present (adjusted odds ratio [aOR], 13.6 vs 6.7 for preeclampsia; aOR, 8.1 vs 4.4 for small-for-gestational-age neonates; aOR, 5.5 vs 2.1 for preterm premature rupture of the membranes; and aOR, 3.3 vs 2.1 for preterm labor (all P<0.05); and 3) the PlGF/sFlt-1 ratio at 28 to 32 weeks of gestation is abnormal in patients who subsequently delivered due to preterm labor with intact membranes and in those with preterm premature rupture of the membranes if both groups have placental lesions of maternal vascular malperfusion. Such association is not significant in patients with these obstetrical syndromes who do not have placental lesions.

CONCLUSION

Classification of obstetrical syndromes according to the presence or absence of placental lesions of maternal vascular malperfusion allows biomarkers to be informative earlier in gestation and enhances the strength of association between biomarkers and clinical outcomes. We propose that a new taxonomy of obstetrical disorders informed by placental pathology will facilitate the discovery and implementation of biomarkers as well as the prediction and prevention of such disorders.

Congenital Herpes Simplex Virus: A Histopathological View of the Placenta

Congenital Herpes simplex virus (HSV) infection is considered a common pregnancy pathology that is not always easy to diagnose. This study aimed to present the spectrum of placental histopathological lesions in pregnancies complicated by HSV infection. MEDLINE and Google Scholar databases were searched using the keywords "HSV" and "placental histopathology" up to June 20, 2022. Study inclusion required presenting placental histopathological anomalies in pregnant women diagnosed with HSV infection antenatally, during labor, or postnatally. Herein, we briefly present placental pathogenesis conditions, which have been correlated with congenital HSV infection, providing clinicians with a short review describing herpetic placental pathology.

IL-27 Mediates Th1 Cells Infiltration in Fetal Membranes in Preterm Labor

The objective of this study is to investigate the effect of IL-27 on Th1 cells infiltration in human fetal membranes (FMs) in preterm labor (PL). The expression of Th1 cells specific transcription factor (T-bet), Th1 cells infiltration related molecules (CXCL9, CXCL10, CXCL11, and ICAM-1), and IL-27 receptor α subunit (IL-27Rα) was compared in human FMs from pregnant women in PL group and term labor (TL) group. In vitro, rhIL-27 was added to the culture medium of amniotic epithelial cells (WISH cells) to detect the expression of CXCL9, CXCL10, CXCL11, and ICAM-1. Furthermore, the underlying signaling pathway was detected by single-sample gene set enrichment analysis and western blot analysis. The expression of T-bet and CXCL9, CXCL10, CXCL11, and ICAM-1 as well as IL-27Rα was higher in human FMs from PL group than TL group. In vitro, rhIL-27 could upregulate the expression of CXCL9, CXCL10, CXCL11, and ICAM-1 in WISH cells. Using gene-set enrichment analysis of FMs, JAK/STAT signaling pathway was found to be activated by IL-27 signaling in PL. Using western blot analysis, JAK2/STAT1/STAT3 signaling pathway was confirmed to be enhanced in rhIL-27 treated WISH cells. In addition, AG490 (JAK2 inhibitor) could inhibit the secretion of CXCL9, CXCL10, and CXCL11 in WISH cells stimulated by rhIL-27. Our results suggested that IL-27 may promote Th1 cells infiltration in human FMs in PL, by promoting the expression of CXCL9, CXCL10, and CXCL11 at least partly through JAK2/STAT1/STAT3 signaling pathway.

The Role of Innate Immune System in the Human Amniotic Membrane and Human Amniotic Fluid in Protection Against Intra-Amniotic Infections and Inflammation

Intra-amniotic infection and inflammation (IAI) affect fetal development and are highly associated with preterm labor and premature rupture of membranes, which often lead to adverse neonatal outcomes. Human amniotic membrane (hAM), the inner part of the amnio-chorionic membrane, protects the embryo/fetus from environmental dangers, including microbial infection. However, weakened amnio-chorionic membrane may be breached or pathogens may enter through a different route, leading to IAI. The hAM and human amniotic fluid (hAF) respond by activation of all components of the innate immune system. This includes changes in 1) hAM structure, 2) presence of immune cells, 3) pattern recognition receptors, 4) cytokines, 5) antimicrobial peptides, 6) lipid derivatives, and 7) complement system. Herein we provide a comprehensive and integrative review of the current understanding of the innate immune response in the hAM and hAF, which will aid in design of novel studies that may lead to breakthroughs in how we perceive the IAI.

Hypertensive disease, preterm birth, fetal growth restriction and chronic inflammatory disorders of the placenta: experiences in a single institution with a standardized protocol of investigation

PURPOSE

Chronic inflammatory disorders of the placenta, in particular villitis of unknown etiology (VUE), chronic deciduitis (CD), chronic chorioamnionitis (CC), chronic histiocytic intervillositis (CHI), and eosinophilic/T-cell chorionic vasculitis (ETCV) can exclusively be diagnosed histologically. Using a standardized procedure for submission and pathological-anatomical examination of placentas in a single perinatal care center, we analyzed the association of chronic placental lesions to perinatal complications.

METHODS

We reviewed all singleton placentas and miscarriages that were examined histologically over a period of ten years after having implemented a standardized protocol for placental submission in our hospital. Cases with chronic inflammatory lesions were identified, and clinical data were analyzed and compared with a focus on preterm birth, hypertensive disorders, and fetal growth restriction and/or fetal demise.

RESULTS

In 174 placentas, at least one of the chronic inflammatory entities was diagnosed. CD was the most frequent disorder (n = 95), and had strong associations with preterm birth (47.3% of all cases with CD) and intrauterine fetal demise. VUE (n = 74) was exclusively diagnosed in the third trimester. This disorder was associated with a birth weight below the 10th percentile (45% of the cases) and hypertensive disease in pregnancy. Miscarriage and intrauterine fetal demise were associated with CHI (in 66.7% of cases, n = 18).

CONCLUSIONS

Chronic inflammatory disorders are frequently observed and contribute to major obstetric and perinatal complications. Further studies are needed to get a better picture of the connection between adverse obstetric outcomes and chronic inflammation to aid in the better counseling of patients.

Placental pathology in women with HIV

Recognizing the importance of placental features and their unique functions can provide insight into maternal health, the uterine environment during the course of pregnancy, birth outcomes and neonatal health. In the context of HIV and antiretroviral therapy (ART), there have been great strides in the prevention of mother to child transmission of HIV. However, there is still paucity of data on the impact of HIV/ART exposure on placental pathology and studies available only examine specific patterns of placental injury, further justifying the need for a more defined and comprehensive approach to the differential diagnoses of HIV/ART-exposed placentae. The purpose of this review is to consolidate findings from individual studies that have been reported on patterns of placental injury in the context of HIV/ART exposure. In both the pre- and post-ART eras HIV and/or ART has been associated with placental injury including maternal vascular malperfusion as well as acute and chronic inflammation. These patterns of injury are further associated with adverse birth outcomes including preterm birth and current evidence suggests an association between poor placental function and compromised fetal development. With the ever increasing number of pregnant women with HIV on ART, there is a compelling need for full incorporation of placental diagnoses into obstetric disease classification. It is also important to take into account key elements of maternal clinical history. Lastly, there is a need to standardize the reporting of placental pathology in order to glean additional insight into the elucidation of HIV/ART associated placental injury.

Histologic Chorioamnionitis in Pregnancies Complicated by Preeclampsia and the Effect on Neonatal Outcomes

Histological chorioamnionitis (HC) is a common placental finding that represents acute/chronic inflammation and can affect neonatal outcomes. We aimed to examine the effect of HC on neonatal outcomes in pregnancies complicated by preeclampsia. All pregnancies with the diagnosis of preeclampsia at 24-42 weeks between 2008 and 2019 were reviewed. Placental lesions were classified according to the "Amsterdam" criteria. Composite adverse neonatal outcome included ≥1 early complication. Maternal and neonatal outcomes were compared between cases with and without HC. Multivariable regression analysis was performed to identify independent associations with adverse neonatal outcome. Compared to preeclampsia without HC (n=517), preeclampsia with HC (n=55) was characterized by a more advanced gestational age (p<0.001) and a higher rate of nulliparity (p=0.02). Diabetes was more prevalent in preeclampsia without HC (p=0.039) as was a history of previous preeclampsia (p=0.048). Neonates in the preeclampsia with HC group had higher rates of adverse neonatal outcome (p<0.001) and Apgar scores <7 at 5 min (p=0.034) despite a higher birthweight (p=0.005). Preeclampsia without HC was associated with smaller placentas and a higher rate of placental maternal vascular malperfusion lesions (p=0.014 and p<0.001 respectively). By multivariate analysis, gestational age and HC were independently associated with adverse neonatal outcome (aOR 0.88 95% CI 0.76-0.96, and aOR 1.33, 95% CI 1.11-3.09, respectively). In preeclampsia, concomitant HC was associated with adverse neonatal outcome despite a more advanced gestational age and higher neonatal birthweight. This inflammatory mechanism probably plays a role in a more severe subgroup of preeclampsia cases, causing an additional risk for the developing fetus.

The transmembrane G protein-coupled CXCR3 receptor-ligand system and maternal foetal allograft rejection

Chronic placental inflammatory lesions lead to poor obstetric outcomes. These lesions often proceed undetected until examination of placental tissues after delivery and are mediated by CXCR3, a seven-transmembrane G protein-coupled receptor, and its chemokine ligands - CXCL9, CXCL10 and CXCL11. CXCR3-chemokine ligand interaction disrupts feto-maternal immune tolerance and activate obnoxious immunological responses similar to transplant rejection and graft-versus-host disease. The resultant chronic inflammatory responses manifest in different parts of the placenta characterised by the presence of incompatible immunocompetent cells from the feto-maternal unit i.e. maternal CD8⁺ T cells in the chorionic membrane or plate (chronic chorioamnionitis); foetal Hofbauer cells and maternal CD8⁺ T cells in the chorionic villous tree (villitis of unknown aetiology); maternal CD8⁺ T and plasma cells in the basal plate (chronic deciduitis); and maternal CD8⁺ T cells, histiocytes and T regulatory cells in the intervillous space (chronic intervillositis). This review critically examines how the CXCR3-chemokine ligand interaction disrupts feto-maternal immune tolerance, initiates a series of chronic placental inflammatory lesions, and consequently activates the pathways to intrauterine growth restriction, stillbirth, spontaneous abortion, preterm prelabour rupture of membranes, preterm labour and birth. The possibility of interrupting these signalling pathways through the use of CXCR3 chemokine inhibitors to prevent adverse reproductive sequelae as well as the potential clinical utility of CXCR3 chemokines as non-invasive predictive clinical biomarkers are also highlighted.

Maternal-Fetal Inflammation in the Placenta and the Developmental Origins of Health and Disease

Events in fetal life impact long-term health outcomes. The placenta is the first organ to form and is the site of juxtaposition between the maternal and fetal circulations. Most diseases of pregnancy are caused by, impact, or are reflected in the placenta. The purpose of this review is to describe the main inflammatory processes in the placenta, discuss their immunology, and relate their short- and long-term disease associations. Acute placental inflammation (API), including maternal and fetal inflammatory responses corresponds to the clinical diagnosis of chorioamnionitis and is associated with respiratory and neurodevelopmental diseases. The chronic placental inflammatory pathologies (CPI), include chronic villitis of unknown etiology, chronic deciduitis, chronic chorionitis, eosinophilic T-cell vasculitis, and chronic histiocytic intervillositis. These diseases are less-well studied, but have complex immunology and show mechanistic impacts on the fetal immune system. Overall, much work remains to be done in describing the long-term impacts of placental inflammation on offspring health.

Harmful and beneficial effects of inflammatory response on reproduction: sterile and pathogen-associated inflammation

In reproduction, inflammatory processes play important roles in the development of many pregnancy complications such as preterm labor/birth, recurrent pregnancy loss, recurrent implantation failure, and preeclampsia. Inflammation can be initiated by both microbial and non-microbial causes. Bacterial infection in the feto-maternal interface and uterus can provoke preterm labor/birth, miscarriage, and chronic endometritis. By contrast, inflammation without infection, or 'sterile inflammation,' can also lead to many kinds of complications, such as preterm labor/birth, miscarriage, or preeclampsia. Aberrant inflammation is facilitated by immune cells such as macrophages, dendritic cells, natural killer cells, and invariant natural killer T cells. In addition, cytokines, chemokines, and several kinds of inflammatory mediators are involved. On the other hand, appropriate inflammation is required for a successful offspring during the progression of the entire pregnancy. Herein, we discuss the relation between pregnancy and inflammation with immunological alterations. Understanding the role of inflammation in complications during pregnancy may establish new perspectives of the progress of normal pregnancy as well as treatments during pregnancy complications.

The fetal inflammatory response syndrome: the origins of a concept, pathophysiology, diagnosis, and obstetrical implications

The fetus can deploy a local or systemic inflammatory response when exposed to microorganisms or, alternatively, to non-infection-related stimuli (e.g., danger signals or alarmins). The term "Fetal Inflammatory Response Syndrome" (FIRS) was coined to describe a condition characterized by evidence of a systemic inflammatory response, frequently a result of the activation of the innate limb of the immune response. FIRS can be diagnosed by an increased concentration of umbilical cord plasma or serum acute phase reactants such as C-reactive protein or cytokines (e.g., interleukin-6). Pathologic evidence of a systemic fetal inflammatory response indicates the presence of funisitis or chorionic vasculitis. FIRS was first described in patients at risk for intraamniotic infection who presented preterm labor with intact membranes or preterm prelabor rupture of the membranes. However, FIRS can also be observed in patients with sterile intra-amniotic inflammation, alloimmunization (e.g., Rh disease), and active autoimmune disorders. Neonates born with FIRS have a higher rate of complications, such as early-onset neonatal sepsis, intraventricular hemorrhage, periventricular leukomalacia, and death, than those born without FIRS. Survivors are at risk for long-term sequelae that may include bronchopulmonary dysplasia, neurodevelopmental disorders, such as cerebral palsy, retinopathy of prematurity, and sensorineuronal hearing loss. Experimental FIRS can be induced by intra-amniotic administration of bacteria, microbial products (such as endotoxin), or inflammatory cytokines (such as interleukin-1), and animal models have provided important insights about the mechanisms responsible for multiple organ involvement and dysfunction. A systemic fetal inflammatory response is thought to be adaptive, but, on occasion, may become dysregulated whereby a fetal cytokine storm ensues and can lead to multiple organ dysfunction and even fetal death if delivery does not occur ("rescued by birth"). Thus, the onset of preterm labor in this context can be considered to have survival value. The evidence so far suggests that FIRS may compound the effects of immaturity and neonatal inflammation, thus increasing the risk of neonatal complications and long-term morbidity. Modulation of a dysregulated fetal inflammatory response by the administration of antimicrobial agents, anti-inflammatory agents, or cell-based therapy holds promise to reduce infant morbidity and mortality.

Immunomorphological Features of the Placenta in Allogeneic Pregnancy as the Background for the Development of Obstetric Complications

OBJECTIVE

To study the structural and immunohistochemical features of placentas in women after assisted reproductive technology (ART) with allogeneic eggs (oocyte donation and surrogate motherhood).

STUDY DESIGN

The study involved 89 women whose pregnancy occurred as a result of in vitro fertilization (IVF) with a donor egg in a surrogate motherhood program (IVF-SM, n = 47 patients) or oocyte donation (IVF-DO, n = 42). The comparison group consisted of 21 patients in whom pregnancy occurred as a result of IVF with their own egg (IVF-OE). A clinical and anamnestic analysis of the pregnant women was carried out. Morphological and immunohistochemical studies were performed on placental material. Immunohistochemical analysis of CD8, CD56, CD138, and CD25/CD4 markers indicating the processes of impaired tolerance in placenta was carried out. -Results: We observed a predominance of women aged >40 (range 42.7-3.91) years with a burdened somatic and obstetric-gynecological history and a high incidence of hypertensive pregnancy complications, such as gestational arterial hypertension (27.4%) and preeclampsia (28.5%), in the IVF-DO group. The IVF-SM group included mainly somatically healthy women aged <30 (29.4-3.19) years with a high risk of termination of pregnancy in the third trimester (49.6%) and premature birth (21.6%). Placentas taken from women after allogeneic pregnancy had pronounced signs of immune alteration, such as chronic histiocytic intervillositis, lymphoplasmacytic deciduitis, chronic chorioamnionitis, chronic villitis, and perivillous fibrinoid with lymphocytes (p [F] < 0.05). Immunohistochemical study of the placentas showed accumulation of CD138+ plasma cells, CD8+ T lymphocytes, and uterine natural killer cells, and a decrease in the number of CD25/CD4+ regulatory T cells (Tregs) in the structures of the uteroplacental region (Kruskal-Wallis test, p < 0.05).

CONCLUSION

Placentas after IVF with oocyte donation and surrogate motherhood programs are characterized by similar changes, associated with the development of chronic inflammation in the structures of the placenta and immunohistochemical signs of impaired immunological tolerance at the maternal-fetal interface. The data we obtained allow us to classify pregnancies under surrogate motherhood programs as a risk factor for the development of pregnancy complications with immune pathogenesis.

Immune responses in women with periodontitis and preterm low birth weight: Levels of CD4+ and CD8+ T cells in gingival granulation tissue

OBJECTIVE

Preterm Low-Birth-Weight (PLBW) is frequently associated with periodontal disease. However, the mechanism is still unknown. The present study was performed to examine the possible link between periodontal infections and PLBW in post-partum women utilizing clinical parameters and CD4+ and CD8 + T lymphocytes ratio in gingival granulation tissue.

MATERIALS

The tissues used in this study consisted of 35 gingival granulation tissue biopsies from 35 mothers of healthy infants (HTBW), 35 biopsies of gingival granulation tissue from 35 mothers of PLBW within one month postpartum and gingival tissue biopsies from 7 control individual with no periodontal disease (HC). CD4+ and CD8 + T lymphocyte ratios in a unit area of the gingival granulation tissue were determined by hystometrically. Statistical analysis was performed by using Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

CD8 + T lymphocytes were more prevalent in the PLBW group than in the HTBW and HC group (P < 0.05). The CD4+/CD8+ ratio in the PLBW group was lower than those of the other groups (p < 0.05). There were no statistically significant differences in CD4 + T lymphocytes counts between all groups (P > 0.05).

CONCLUSION

Within the limits of this study it can be concluded that CD8 + T lymphocytes in gingival tissue may play important roles in the pathogenesis of periodontitis and PLBW.

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

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

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

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

Chronic inflammatory lesions of the placenta are associated with an up-regulation of amniotic fluid CXCR3: A marker of allograft rejection

OBJECTIVE

The objective of this study is to determine whether the amniotic fluid (AF) concentration of soluble CXCR3 and its ligands CXCL9 and CXCL10 changes in patients whose placentas show evidence of chronic chorioamnionitis or other placental lesions consistent with maternal anti-fetal rejection.

METHODS

This retrospective case-control study included 425 women with (1) preterm delivery (n=92); (2) term in labor (n=68); and (3) term not in labor (n=265). Amniotic fluid CXCR3, CXCL9 and CXCL10 concentrations were determined by ELISA.

RESULTS

(1) Amniotic fluid concentrations of CXCR3 and its ligands CXCL9 and CXCL10 are higher in patients with preterm labor and maternal anti-fetal rejection lesions than in those without these lesions [CXCR3: preterm labor and delivery with maternal anti-fetal rejection placental lesions (median, 17.24 ng/mL; IQR, 6.79-26.68) vs. preterm labor and delivery without these placental lesions (median 8.79 ng/mL; IQR, 4.98-14.7; P=0.028)]; (2) patients with preterm labor and chronic chorioamnionitis had higher AF concentrations of CXCL9 and CXCL10, but not CXCR3, than those without this lesion [CXCR3: preterm labor with chronic chorioamnionitis (median, 17.02 ng/mL; IQR, 5.57-26.68) vs. preterm labor without chronic chorioamnionitis (median, 10.37 ng/mL; IQR 5.01-17.81; P=0.283)]; (3) patients with preterm labor had a significantly higher AF concentration of CXCR3 than those in labor at term regardless of the presence or absence of placental lesions.

CONCLUSION

Our findings support a role for maternal anti-fetal rejection in a subset of patients with preterm labor.

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

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

Fetal death: an extreme manifestation of maternal anti-fetal rejection

OBJECTIVE

The aim of this study was to determine the association between chronic placental inflammation and amniotic fluid (AF) markers of maternal anti-fetal rejection as well as the presence of microorganisms in the AF fluid of patients with fetal death.

STUDY DESIGN

This cohort study included 40 patients with fetal death whose placentas were examined for chronic inflammatory lesions and whose AF chemokine ligand (CXCL)10 and interleukin (IL)-6 concentrations were determined by immunoassays. AF was processed for bacteria, mycoplasmas and viruses using cultivation and molecular microbiologic techniques (i.e. PCR-ESI/MS).

RESULTS

(1) The most prevalent placental findings were maternal vascular underperfusion (63.2%, 24/38), followed by chronic inflammatory lesions (57.9%, 22/38); (2) chronic chorioamnionitis (18/38) was three times more frequent than villitis of unknown etiology (6/38); (3) an elevated AF CXCL10 concentration (above the 95th centile) was present in 60% of the cases, and a receiver operating characteristics (ROC)-derived cut-off of 2.9 ng/mL had a sensitivity of 73% and a specificity of 75% in the identification of chronic placental inflammatory lesions; (4) only five cases had microbial invasion of the amniotic cavity, and the presence of microorganisms did not correlate with chronic placental inflammation.

CONCLUSION

In women with unexplained fetal death, there is an association between elevated AF CXCL10 and chronic placental inflammatory lesions. Therefore, we conclude that a subset of patients with fetal death may have endured a breakdown of maternal-fetal tolerance, which cannot be attributed to microorganisms in the amniotic cavity.

Differential immunophenotype of macrophages in acute and chronic chorioamnionitis

AIM

The aim of this study was to investigate the involvement and immunophenotype of macrophages in acute chorioamnionitis (ACA) and chronic chorioamnionitis (CCA), marking amniotic fluid infection and anti-fetal rejection, respectively.

METHODS

Chorioamniotic membranes from (1) gestational age-matched cases without chorioamnionitis, (2) cases with ACA, and (3) cases with CCA were studied after immunohistochemical staining using antibodies against CD14, CD68, CD163, and DC-SIGN.

RESULTS

Macrophages increased prominently in the chorionic trophoblastic layer of both ACA and CCA cases in contrast to non-inflammatory cases. Macrophages in the decidua and the chorioamniotic membranes of ACA cases expressed CD14. Macrophages in the chorionic trophoblastic layer of CCA cases were characterized by CD68 positivity. DC-SIGN-positive cells were increased in the chorioamniotic mesodermal layer of CCA cases.

CONCLUSIONS

Macrophages participate in the inflammatory response in ACA and CCA. The differential immunophenotypes of macrophages in the decidua and chorioamniotic membranes of ACA and CCA cases suggest their disease-specific and region-specific roles at the feto-maternal interface.

In vivo T-cell activation by a monoclonal αCD3ε antibody induces preterm labor and birth

PROBLEM

Activated/effector T cells seem to play a role in the pathological inflammation associated with preterm labor. The aim of this study was to determine whether in vivo T-cell activation by a monoclonal αCD3ε antibody induces preterm labor and birth.

METHOD OF STUDY

Pregnant B6 mice were intraperitoneally injected with a monoclonal αCD3ε antibody or its isotype control. The gestational age, the rates of preterm birth and pup mortality at birth as well as the fetal heart rate and umbilical artery pulsatility index were determined.

RESULTS

Injection of a monoclonal αCD3ε antibody led to preterm labor/birth (αCD3ε 83 ± 16.97% [10/12] vs isotype 0% [0/8]) and increased the rate of pup mortality at birth (αCD3ε 87.30 ± 8.95% [77/85] vs isotype 4.91 ± 4.34% [3/59]). In addition, injection of a monoclonal αCD3ε antibody decreased the fetal heart rate and increased the umbilical artery pulsatility index when compared to the isotype control.

CONCLUSION

In vivo T-cell activation by a monoclonal αCD3ε antibody in late gestation induces preterm labor and birth.

Chronic Placental Inflammation in Twin Pregnancies

Background:

Chronic placental inflammation, such as villitis of unknown etiology (VUE) and chronic chorioamnionitis (CCA), is considered a placental manifestation of maternal anti-fetal rejection. The aim of this study is to investigate its frequency in twin pregnancies compared to singleton pregnancies.

Methods:

Three hundred twin placentas and 1,270 singleton placentas were consecutively collected at a tertiary medical center in Seoul, Republic of Korea from 2009 to 2012. Hematoxylin and eosin sections of tissue samples (full-thickness placental disc and chorioamniotic membranes) were reviewed.

Results:

Non-basal VUE was more frequent in twin placentas than in singleton placentas (6.0% vs 3.2%, p < .05). In preterm birth, CCA was found less frequently in twin placentas than in singleton placentas (9.6% vs 14.8%, p < .05), reaching its peak at an earlier gestational age in twin placentas (29–32 weeks) than in singleton placentas (33–36 weeks). CCA was more frequent in twin pregnancies with babies of a different sex than with those with the same sex (13.8% vs 6.9%, p=.052). Separate dichorionic diamniotic twin placentas were affected by chronic deciduitis more frequently than singleton placentas (16.9% vs 9.7%, p<.05).

Conclusions:

The higher frequency of non-basal VUE in twin placentas and of CCA in twin placentas with different fetal sex supports the hypothesis that the underlying pathophysiological mechanism is maternal anti-fetal rejection related to increased fetal antigens in twin pregnancies. The peak of CCA at an earlier gestational age in twin placentas than in singleton placentas suggests that CCA is influenced by placental maturation.

Chronic inflammation of the placenta: definition, classification, pathogenesis, and clinical significance

Chronic inflammatory lesions of the placenta are characterized by the infiltration of the organ by lymphocytes, plasma cells, and/or macrophages and may result from infections (viral, bacterial, parasitic) or be of immune origin (maternal anti-fetal rejection). The 3 major lesions are villitis (when the inflammatory process affects the villous tree), chronic chorioamnionitis (which affects the chorioamniotic membranes), and chronic deciduitis (which involves the decidua basalis). Maternal cellular infiltration is a common feature of the lesions. Villitis of unknown etiology (VUE) is a destructive villous inflammatory lesion that is characterized by the infiltration of maternal T cells (CD8+ cytotoxic T cells) into chorionic villi. Migration of maternal T cells into the villi is driven by the production of T-cell chemokines in the affected villi. Activation of macrophages in the villi has been implicated in the destruction of the villous architecture. VUE has been reported in association with preterm and term fetal growth restriction, preeclampsia, fetal death, and preterm labor. Infants whose placentas have VUE are at risk for death and abnormal neurodevelopmental outcome at the age of 2 years. Chronic chorioamnionitis is the most common lesion in late spontaneous preterm birth and is characterized by the infiltration of maternal CD8+ T cells into the chorioamniotic membranes. These cytotoxic T cells can induce trophoblast apoptosis and damage the fetal membranes. The lesion frequently is accompanied by VUE. Chronic deciduitis consists of the presence of lymphocytes or plasma cells in the basal plate of the placenta. This lesion is more common in pregnancies that result from egg donation and has been reported in a subset of patients with premature labor. Chronic placental inflammatory lesions can be due to maternal anti-fetal rejection, a process associated with the development of a novel form of fetal systemic inflammatory response. The syndrome is characterized by an elevation of the fetal plasma T-cell chemokine. The evidence that maternal anti-fetal rejection underlies the pathogenesis of many chronic inflammatory lesions of the placenta is reviewed. This article includes figures and histologic examples of all chronic inflammatory lesions of the placenta.

Characterization of the fetal blood transcriptome and proteome in maternal anti-fetal rejection: evidence of a distinct and novel type of human fetal systemic inflammatory response

BACKGROUND

The human fetus is able to mount a systemic inflammatory response when exposed to microorganisms. This stereotypic response has been termed the 'fetal inflammatory response syndrome' (FIRS), defined as an elevation of fetal plasma interleukin-6 (IL-6). FIRS is frequently observed in patients whose preterm deliveries are associated with intra-amniotic infection, acute inflammatory lesions of the placenta, and a high rate of neonatal morbidity. Recently, a novel form of fetal systemic inflammation, characterized by an elevation of fetal plasma CXCL10, has been identified in patients with placental lesions consistent with 'maternal anti-fetal rejection'. These lesions include chronic chorioamnionitis, plasma cell deciduitis, and villitis of unknown etiology. In addition, positivity for human leukocyte antigen (HLA) panel-reactive antibodies (PRA) in maternal sera can also be used to increase the index of suspicion for maternal anti-fetal rejection. The purpose of this study was to determine (i) the frequency of pathologic lesions consistent with maternal anti-fetal rejection in term and spontaneous preterm births; (ii) the fetal serum concentration of CXCL10 in patients with and without evidence of maternal anti-fetal rejection; and (iii) the fetal blood transcriptome and proteome in cases with a fetal inflammatory response associated with maternal anti-fetal rejection.

METHOD OF STUDY

Maternal and fetal sera were obtained from normal term (n = 150) and spontaneous preterm births (n = 150). A fetal inflammatory response associated with maternal anti-fetal rejection was diagnosed when the patients met two or more of the following criteria: (i) presence of chronic placental inflammation; (ii) ≥80% of maternal HLA class I PRA positivity; and (iii) fetal serum CXCL10 concentration >75th percentile. Maternal HLA PRA was analyzed by flow cytometry. The concentrations of fetal CXCL10 and IL-6 were determined by ELISA. Transcriptome analysis was undertaken after the extraction of total RNA from white blood cells with a whole-genome DASL assay. Proteomic analysis of fetal serum was conducted by two-dimensional difference gel electrophoresis. Differential gene expression was considered significant when there was a P < 0.01 and a fold-change >1.5.

RESULTS

(i) The frequency of placental lesions consistent with maternal anti-fetal rejection was higher in patients with preterm deliveries than in those with term deliveries (56% versus 32%; P < 0.001); (ii) patients with spontaneous preterm births had a higher rate of maternal HLA PRA class I positivity than those who delivered at term (50% versus 32%; P = 0.002); (iii) fetuses born to mothers with positive maternal HLA PRA results had a higher median serum CXCL10 concentration than those with negative HLA PRA results (P < 0.001); (iv) the median serum CXCL10 concentration (but not IL-6) was higher in fetuses with placental lesions associated with maternal anti-fetal rejection than those without such lesions (P < 0.001); (v) a whole-genome DASL assay of fetal blood RNA demonstrated differential expression of 128 genes between fetuses with and without lesions associated with maternal anti-fetal rejection; and (vi) comparison of the fetal serum proteome demonstrated 20 proteins whose abundance differed between fetuses with and without lesions associated with maternal anti-fetal rejection.

CONCLUSION

We describe a systemic inflammatory response in human fetuses born to mothers with evidence of maternal anti-fetal rejection. The transcriptome and proteome of this novel type of fetal inflammatory response were different from that of FIRS type I (which is associated with acute infection/inflammation).

Eosinophilic/T-cell chorionic vasculitis and chronic villitis involve regulatory T cells and often occur together

Eosinophilic/T-cell chorionic vasculitis (ETCV) is characterized by mixed T-cell, eosinophilic, and histiocytic infiltrates within the chorionic vessel wall. We sought to better characterize this lesion with respect to other pathologic correlates and the T-cell populations involved. Epidemiologic data and other pathologic diagnoses, including concurrent chronic villitis (CV), were tabulated for each case of ETCV diagnosed at our institution over a 6-year period. CD3, CD25, FOXP3, and dual FOXP3-CD3 immunostains were used to identify regulatory T-cell populations in ETCV and CV. Cells positive for CD3, FOXP3, and CD25 were quantitated by manual counts of ×40 fields at the sites of ETCV and CV, and FOXP3∶CD3 and CD25∶CD3 ratios were calculated. Digital analysis of ETCV and CV using the dual FOXP3-CD3 immunostain was also performed on select cases. Of 31 ETCV cases, 10 (32%) were accompanied by CV and 13 (42%) by a thrombus in the vessel affected by ETCV. The mean Treg cell marker∶CD3 ratios in ETCV ranged from 0.18 to 0.26 by manual count and digital analysis, but the counts did not statistically differ by method. The mean Treg cell marker∶CD3 ratios in CV ranged from 0.37 to 0.39 by manual count and 0.19 by digital analysis, but these counts also did not statistically differ by method. Chronic villitis was seen in one-third of ETCV cases. FOXP3+ and CD25+ regulatory T cells represent a significant subpopulation of T cells in ETCV and CV, suggesting that they may play a role in these entities.

Thrown off balance: the effect of antenatal inflammation on the developing lung and immune system

In recent years, translational research with various animal models has been helpful to answer basic questions about the effect of antenatal inflammation on maturation and development of the fetal lung and immune system. The fetal lung and immune systems are very plastic and their development can be conditioned and influenced by both endogenous and/or exogenous factors. Antenatal inflammation can induce pulmonary inflammation, leading to lung injury and remodeling in the fetal lung. Exposure to antenatal inflammation can induce interleukin-1α production, which enhances surfactant protein and lipid synthesis thereby promoting lung maturation. Interleukin-1α is therefore a candidate for the link between lung inflammation and lung maturation, preventing respiratory distress syndrome in preterm infants. Antenatal inflammation can, however, cause structural changes in the fetal lung and affect the expression of growth factors, such as transforming growth factor-beta, connective tissue growth factor, fibroblast growth factor-10, or bone morphogenetic protein-4, which are essential for branching morphogenesis. These alterations cause alveolar and microvascular simplification resembling the histology of bronchopulmonary dysplasia. Antenatal inflammation may also affect neonatal outcome by modulating the responsiveness of the immune system. Lipopolysaccharide-tolerance (endotoxin hyporesponsiveness/immunoparalysis), induced by exposure to inflammation in utero, may prevent fetal lung damage, but increases susceptibility to postnatal infections. Moreover, prenatal exposure to inflammation appears to be a predisposition for the development of adverse neonatal outcomes, like bronchopulmonary dysplasia, if the preterm infant is exposed to a second postnatal hit, such as mechanical ventilation oxygen exposure, infections, or steroids.

Chronic chorioamnionitis is the most common placental lesion in late preterm birth

OBJECTIVES

The pathogenesis of late preterm birth remains elusive for the mechanisms of disease responsible. Placental examination can often provide important clues for the pathogenesis of pregnancy complications. This study was conducted to determine placental pathologic findings according to the gestational age and the clinical circumstances of preterm birth.

STUDY DESIGN

Placental pathologic findings and obstetrical and neonatal outcomes were reviewed in a consecutive preterm birth cohort from a single tertiary center (N = 1206). Placentas of term births (N = 300) were used as normal controls.

RESULTS

Acute chorioamnionitis (22.7% vs. 16.7%), maternal vascular underperfusion (6.4% vs. 0.5%), and chronic chorioamnionitis (20.8% vs. 10.5%) were significantly more frequent in preterm births than in term births (P < 0.05, for each). Among preterm births, chronic chorioamnionitis was the most common pathology of late preterm birth (gestational age <37 and ≥34 weeks), while acute chorioamnionitis was the most common lesion of extremely preterm birth (gestational age <28 weeks). While the frequency of acute chorioamnionitis decreased with advancing gestation, that of chronic chorioamnionitis increased (P < 0.001, for each). The upward trend of the frequency of chronic chorioamnionitis was related to advancing gestation in both spontaneous and indicated preterm births (P < 0.001, for each).

CONCLUSIONS

Chronic chorioamnionitis is a common pathology of late preterm birth. It is suggested that chronic chorioamnionitis, a feature of maternal anti-fetal rejection, is an important etiology of preterm birth, especially of late preterm birth.

Distinct patterns of C4d immunoreactivity in placentas with villitis of unknown etiology, cytomegaloviral placentitis, and infarct

C4d deposition is considered to be evidence of antibody-mediated rejection. This study was conducted to compare C4d immunoreactivity between villitis of unknown etiology (VUE) and cytomegaloviral placentitis. C4d immunohistochemistry was performed in cases with VUE (n = 16) and cytomegaloviral placentitis (n = 5). Distinct, linear C4d immunoreactivity along the syncytiotrophoblast was found in all VUE cases. In cytomegaloviral placentitis, the intensity of C4d immunoreactivity along the syncytiotrophoblast was not prominent, but cytoplasmic C4d immunoreactivity of villous cytotrophoblasts was frequently observed. Further screening of the cases with placental infarcts (n = 5) demonstrated prominent C4d immunoreactivity in the chorionic villi adjacent to the infarct. We report the characteristic co-localization of VUE and C4d immunoreactivity. The overall findings in this study strongly suggest that the complement activation is a common mechanism of diverse placental injuries associated with rejection, infection, and ischemia.

Interleukin-33 in the human placenta

OBJECTIVE

Interleukin-33 (IL-33) is the newest member of the IL-1 cytokine family, a group of key regulators of inflammation. The purpose of this study was to determine whether IL-33 is expressed in the human placenta and to investigate its expression in the context of acute and chronic chorioamnionitis.

METHODS

Placental tissues were obtained from five groups of patients: 1) normal pregnancy at term without labor (n = 10); 2) normal pregnancy at term in labor (n = 10); 3) preterm labor without inflammation (n = 10); 4) preterm labor with acute chorioamnionitis and funisitis (n = 10); and 5) preterm labor with chronic chorioamnionitis (n = 10). Immunostaining was performed to determine IL-33 protein expression patterns in the placental disk, chorioamniotic membranes, and umbilical cord. mRNA expression of IL-33 and its receptor IL1RL1 (ST2) was measured in primary amnion epithelial and mesenchymal cells (AECs and AMCs, n = 4) and human umbilical vein endothelial cells (HUVECs, n = 4) treated with IL-1β (1 and 10 ng/ml) and CXCL10 (0.5 and 1 or 5 ng/ml).

RESULTS

1) Nuclear IL-33 expression was found in endothelial and smooth muscle cells in the placenta, chorioamniotic membranes, and umbilical cord; 2) IL-33 was detected in the nucleus of CD14+ macrophages in the chorioamniotic membranes, chorionic plate, and umbilical cord, and in the cytoplasm of myofibroblasts in the Wharton's jelly; 3) acute (but not chronic) chorioamnionitis was associated with the presence of IL-33+ macrophages in the chorioamniotic membranes and umbilical cord; 4) expression of IL-33 or IL1RL1 (ST2) mRNA in AECs was undetectable; 5) IL-33 mRNA expression increased in AMCs and HUVECs after IL-1β treatment but did not change with CXCL10 treatment; and 6) IL1RL1 (ST2) expression decreased in AMCs and increased in HUVECs after IL-1β but not CXCL10 treatment.

CONCLUSIONS

IL-33 is expressed in the nucleus of placental endothelial cells, CD14+ macrophages, and myofibroblasts in the Wharton's jelly. IL-1β can induce the expression of IL-33 and its receptor. Protein expression of IL-33 is detectable in macrophages of the chorioamniotic membranes in acute (but not chronic) chorioamnionitis.

Ascending Infection: Acute Chorioamnionitis

Acute chorioamnionitis is a major cause of spontaneous preterm birth, accounting for more than 40% of deliveries complicated by preterm premature rupture of membranes or preterm labor. In the majority of cases, especially in preterm births, acute chorioamnionitis is caused by ascending polymicrobial infection. Recent evidence suggests that in some cases acute chorioamnionitis may have a noninfectious cause. In addition to the nonspecific patterns of conventional acute chorioamnionitis, this article describes characteristic inflammatory patterns indicative of a specific infectious cause. Several inflammatory entities of putative immunologic (noninfectious) etiology are addressed, including eosinophilic/T-cell vasculitis and chronic chorioamnionitis.

Midtrimester amniotic fluid concentrations of interleukin-6 and interferon-gamma-inducible protein-10: evidence for heterogeneity of intra-amniotic inflammation and associations with spontaneous early (<32 weeks) and late (>32 weeks) preterm delivery

INTRODUCTION

Intra-amniotic inflammation is traditionally defined as an elevation of amniotic fluid interleukin (IL)-6. Previous case control studies have suggested an association between an elevated midtrimester amniotic fluid IL-6 and preterm delivery, although such an association has been recently challenged. Intra-amniotic inflammation can also be defined by an elevation of the T-cell chemokine, Interferon-gamma-inducible protein (IP)-10. An elevation in amniotic fluid IP-10 has been associated with chronic chorioamnionitis, a lesion frequently found in late spontaneous preterm birth and fetal death. In contrast, an elevation in amniotic fluid IL-6 is typically associated with acute chorioamnionitis and funisitis. This study was conducted to examine the relationship between an elevation in amniotic fluid IL-6 in the midtrimester and preterm delivery at or before 32 weeks of gestation, and the amniotic fluid concentration of IP-10 and preterm delivery after 32 weeks of gestation.

MATERIALS AND METHODS

This cohort study included 847 consecutive women undergoing genetic midtrimester amniocentesis; in 796 cases, amniotic fluid and pregnancy outcome was available for study after exclusion of abnormal karyotype and/or fetal congenital anomalies. Spontaneous preterm delivery was defined as early (≤32 weeks) or late (after 32 completed weeks of pregnancy). The amniotic fluid and maternal blood concentrations of IL-6 and IP-10 were measured by specific immunoassays.

RESULTS

1) The prevalence of preterm delivery was 8.3% (66/796), while those of early and late spontaneous preterm delivery were 1.5% (n=12), and 4.5% (n=36), respectively; 2) patients who had a spontaneous preterm delivery after 32 weeks of gestation had a higher median amniotic fluid IP-10 concentration than those who delivered at term [median 713 pg/mL, inter-quartile range (IQR) 509-1427 pg/mL vs. median 589 pg/mL, IQR 402-953 pg/mL; P=0.006] and an elevation of amniotic fluid IP-10 concentration above 502 pg/mL (derived from an ROC curve) was associated with late spontaneous preterm delivery [odds ratio 3.9 (95% CI 1.6-9.9)]; 3) patients who had a spontaneous preterm delivery ≤32 weeks of gestation had a higher median amniotic fluid IL-6 concentration than those who delivered at term [median 2052 pg/mL, IQR 435-3015 pg/mL vs. median 414 pg/mL, IQR 209-930 pg/mL; P=0.006], and an elevated amniotic fluid IL-6 concentration above 1740 pg/mL (derived from an ROC curve) was associated with early spontaneous preterm delivery [odds ratio 9.5 (95% CI 2.9-31.1)]; 4) subclinical intra-amniotic inflammation, defined as an elevation of IL-6 (≥2.9 ng/mL) or IP-10 (≥2.2 ng/mL) concentration above the 95th percentile of patients who had uncomplicated term delivery (n=652 for IL-6 and n=633 for IP-10), was observed in 6.3% (50/796) and 5.8% (45/770) of cases, respectively. Although each type of inflammation is a risk factor for spontaneous preterm delivery, many patients had a term delivery without complication; 5) the amniotic fluid in the midtrimester did not contain microorganisms detectable with cultivation techniques.

CONCLUSIONS

INTRA-amniotic inflammation is heterogeneous. Some patients have elevated amniotic fluid concentrations of IL-6, and are at risk for spontaneous preterm delivery before 32 weeks of gestation, while others have an elevated IP-10 (a chemotactic T-cell chemokine) and such patients are at risk for spontaneous preterm delivery after 32 weeks of gestation. A fraction of patients have subclinical intra-amniotic inflammation and deliver at term. The clinical significance of this condition remains to be determined.

Peripheral CD300a+CD8+ T lymphocytes with a distinct cytotoxic molecular signature increase in pregnant women with chronic chorioamnionitis

PROBLEM

  CD300a is an immunomodulatory molecule of the immunoglobulin receptor superfamily expressed in the leukocytes of myeloid and lymphoid lineages. However, its biological function on CD8+ T lymphocytes remains largely unknown. This study was conducted to assess the biological significance of CD300a expression in T lymphocytes and to determine whether its expression in peripheral T lymphocytes changes in pregnant women presenting with antifetal rejection.

METHODS OF STUDY

Microarray analysis was performed using total RNA isolated from peripheral CD300a+ and CD300a- T lymphocytes. Flow cytometric analysis of the peripheral blood samples of pregnant women and pathologic examination of the placentas were conducted.

RESULTS

  A large number of genes (N = 1245) were differentially expressed between CD300a- and CD300a+ subsets of CD8+ T lymphocytes, which included CCR7, CD244, CX3CR1, GLNY, GZMB, GZMK, IL15, ITGB1, KLRG1, PRF1, and SLAMF7. Gene ontology analysis of differentially expressed genes demonstrated enrichment of biological processes such as immune response, cell death, and signal transduction. CD300a expression in CD8+ T lymphocytes was coupled to a more cytotoxic molecular signature. Of note, the proportion of CD300a+CD8+ T lymphocytes increased in pregnant women with chronic chorioamnionitis (antifetal rejection of the chorioamniotic membranes; P < 0.05).

CONCLUSION

  The findings of this study strongly suggest an increase in systemic T-lymphocyte-mediated cytotoxicity in pregnant women with chronic chorioamnionitis as a manifestation of maternal antifetal rejection.

Inflammatory response in acute chorioamnionitis

Acute chorioamnionitis is the principal antecedent of premature birth and an important contributor to specific neonatal and other complications that may extend throughout subsequent life. A large number of studies have addressed surrogate markers of in-utero inflammation including cytokines, chemokines, pathogen-associated molecular patterns, and elicited host proteins. However, chorioamnionitis means inflammation occurring within the chorioamnion and the only practical direct measure available to assess this finding in most placentas is histopathology. The maternal and fetal inflammatory response to the presence of organisms within the placental membranes, so-called histologic chorioamnionitis, is the focus of this review. The issues addressed are the nature and origin of the eliciting antigen, mode of spread to the placenta, general characteristics of placental immunity, and a specific characterization of the spectrum of pathologic lesions observed in placentas with membrane infection.

Maternal HLA panel-reactive antibodies in early gestation positively correlate with chronic chorioamnionitis: evidence in support of the chronic nature of maternal anti-fetal rejection

PROBLEM

Maternal tolerance of the fetus is essential for viviparity, yet anti-fetal rejection occurs in several pregnancy complications. Chronic chorioamnionitis is a feature of anti-fetal cellular rejection. There is a robust association between chronic chorioamnionitis and maternal seropositivity for anti-human leukocyte antigen (HLA) panel-reactive antibodies (PRA) at the time of delivery. This longitudinal study was performed to assess maternal HLA PRA status in early gestation and the temporal evolution of maternal HLA PRA in the context of chronic chorioamnionitis and, thereby, to determine whether HLA PRA during the course of pregnancy is useful for the detection of anti-fetal rejection.

METHOD OF STUDY

Maternal sera obtained before 16 weeks of gestation and at delivery were analyzed for HLA PRA in cases with (N = 100) and without (N = 150) chronic chorioamnionitis.

RESULTS

IgG (but not IgM) HLA class I and II PRA positivity at delivery was higher in cases with chronic chorioamnionitis than in those without chronic chorioamnionitis. IgG HLA class I PRA positivity before 16 weeks of gestation was higher in cases with chronic chorioamnionitis than in those without (30.3 versus 13.3%; P = 0.001). Positive conversion (negative HLA PRA before 16 weeks of gestation but positive at delivery) of IgG HLA class I and II PRA was significantly associated with chronic chorioamnionitis. Fetal HLA class I antigen-specific antibodies were confirmed in 12 of 16 mothers tested who were sensitized to HLA class I antigens before 16 weeks of gestation.

CONCLUSION

Positive maternal HLA PRA before 16 weeks of gestation and the temporal evolution of maternal HLA PRA are associated with the presence of chronic chorioamnionitis at the time of delivery. Maternal IgG HLA PRA has the potential to be a monitoring tool of anti-fetal rejection. Furthermore, the findings herein indicate that subsets of fetuses are exposed to alloimmune HLA antibodies for months, especially in cases with chronic chorioamnionitis.

Unexplained fetal death has a biological signature of maternal anti-fetal rejection: chronic chorioamnionitis and alloimmune anti-human leucocyte antigen antibodies

AIMS

Chronic chorioamnionitis is a histological manifestation of maternal anti-fetal cellular rejection. As failure of graft survival is the most catastrophic event in organ transplantation, we hypothesized that fetal death could be a consequence of maternal rejection. The aim of this study was to assess whether there is evidence of cellular and antibody-mediated rejection in fetal death.

METHODS AND RESULTS

Placental histology was reviewed for the presence of chronic chorioamnionitis in unexplained preterm fetal death (n=30) and preterm live birth (n=103). Amniotic fluid CXCL10 concentrations were measured with a specific immunoassay. Chronic chorioamnionitis was more frequent in fetal death than in live birth (60.0% versus 37.9%; P<0.05) and fetal death had a higher median amniotic fluid CXCL10 concentration than live birth (2.0 versus 1.8 ng/ml, P<0.05), after adjusting for gestational age at amniocentesis. Maternal anti-human leucocyte antigen class II panel-reactive seropositivity determined by flow cytometry was higher in fetal death compared to live birth (35.7% versus 10.9%; P<0.05).

CONCLUSIONS

Chronic chorioamnionitis is a common pathologic feature in unexplained preterm fetal death. This novel finding suggests that cellular and antibody-mediated anti-fetal rejection of the mother is associated with fetal death (graft failure) in human pregnancy.

Eosinophilic/T-cell chorionic vasculitis: a clinicopathologic and immunohistochemical study of 51 cases

We report 51 placentas diagnosed with eosinophilic/T-cell chorionic vasculitis (E/TCV), an unusual form of chorionic vasculitis characterized by an infiltrate composed predominantly of CD3+ T cells and eosinophils. The placentas were all 3rd trimester, with 48 (94.1%) being term. Forty-seven (92.2%) were singleton placentas, and the remaining 4 were twins. The E/TCV was limited to 1 chorionic surface vessel in 40 (78.4%) and involved 50% or less of the vessel circumference in 30 (58.8%) placentas. The inflammation faced the intervillous space in 12 (23.5%) and the amniotic cavity in 8 (15.7%) and had no distinct predominant direction in the remaining 31 (60.8%) placentas. Twelve (25.5%) placentas showed mural thrombi or intramural fibrin in association with the E/TCV. One hundred six term singleton placentas were selected as the control group, and the 47 singleton placentas with E/TCV made up the study group for comparison of demographic and histopathologic features. Villitis of unknown etiology was identified more frequently in study group placentas (20 [42.6%]) compared with control group placentas (14 [13.2%]) (P < 0.001). Vascular changes of fetal vascular thrombo-occlusive disease were identified away from the E/TCV more frequently in study group placentas (8 [17.0%]) compared with control group placentas (4 [3.8%]) (P  =  0.008). There were no significant differences in the frequencies of other placental lesions studied, including acute inflammatory lesions and lesions related to maternal underperfusion. There were no significant differences in maternal age, race, parity, birth weight, allergy history, blood type, or medication use.

HISTOLOGICAL CHORIOAMNIONITIS: CURRENT CONCEPTS OF DIAGNOSIS, CLASSIFICATION AND CLINICAL SIGNIFICANCE

Interest in the clinical associations between maternal intrapartum fever and adverse neonatal outcome has been longstanding, with publications of a relationship between maternal fever and cerebral palsy dating from the 1950s. Further recognition of the associations between either clinically or histologically characterised chorioamnionitis, ascending infection and neonatal wellbeing followed, with numerous reports in the 1960s and 70s, particularly as the neonatal significance of group B streptococcal infections became apparent. Similarly, with the systematic introduction of diagnostic light microscopy into clinical medicine, chorioamnionitis (inflammation of the placental membranes) and funisitis (inflammation of the umbilical cord) were recognised as distinct histological entities, with increasing recognition that the aetiology was likely to be infective. There are numerous texts discussing in detail the pathogenesis and histological features of chorioamnionitis and funisitis. The aim of this review is to provide an overview of the salient associated issues for clinical practitioners and to highlight areas of ongoing uncertainty and recent developments in understanding.

A signature of maternal anti-fetal rejection in spontaneous preterm birth: chronic chorioamnionitis, anti-human leukocyte antigen antibodies, and C4d

Background

Chronic chorioamnionitis is found in more than one-third of spontaneous preterm births. Chronic chorioamnionitis and villitis of unknown etiology represent maternal anti-fetal cellular rejection. Antibody-mediated rejection is another type of transplantation rejection. We investigated whether there was evidence for antibody-mediated rejection against the fetus in spontaneous preterm birth.

Methods and Findings

This cross-sectional study included women with (1) normal pregnancy and term delivery (n = 140) and (2) spontaneous preterm delivery (n = 140). We analyzed maternal and fetal sera for panel-reactive anti-HLA class I and class II antibodies, and determined C4d deposition on umbilical vein endothelium by immunohistochemistry. Maternal anti-HLA class I seropositivity in spontaneous preterm births was higher than in normal term births (48.6% vs. 32.1%, p = 0.005). Chronic chorioamnionitis was associated with a higher maternal anti-HLA class I seropositivity (p<0.01), significant in preterm and term birth. Villitis of unknown etiology was associated with increased maternal and fetal anti-HLA class I and II seropositivity (p<0.05, for each). Fetal anti-HLA seropositivity was closely related to maternal anti-HLA seropositivity in both groups (p<0.01, for each). C4d deposition on umbilical vein endothelium was more frequent in preterm labor than term labor (77.1% vs. 11.4%, p<0.001). Logistic regression analysis revealed that chronic chorioamnionitis (OR = 6.10, 95% CI 1.29–28.83), maternal anti-HLA class I seropositivity (OR = 5.90, 95% CI 1.60–21.83), and C4d deposition on umbilical vein endothelium (OR = 36.19, 95% CI 11.42–114.66) were associated with preterm labor and delivery.

Conclusions

A major subset of spontaneous preterm births has a signature of maternal anti-fetal cellular and antibody-mediated rejections with links to fetal graft-versus-host disease and alloimmune reactions.

IL-6 trans-signaling system in intra-amniotic inflammation, preterm birth, and preterm premature rupture of the membranes

Classic IL-6 signaling is conditioned by the transmembrane receptor (IL-6R) and homodimerization of gp130. During trans-signaling, IL-6 binds to soluble IL-6R (sIL-6R), enabling activation of cells expressing solely gp130. Soluble gp130 (sgp130) selectively inhibits IL-6 trans-signaling. To characterize amniotic fluid (AF) IL-6 trans-signaling molecules (IL-6, sIL-6R, sgp130) in normal gestations and pregnancies complicated by intra-amniotic inflammation (IAI), we studied 301 women during second trimester (n = 39), third trimester (n = 40), and preterm labor with intact (n = 131, 85 negative IAI and 46 positive IAI) or preterm premature rupture of membranes (PPROM; n = 91, 61 negative IAI and 30 positive IAI). ELISA, Western blotting, and real-time RT-PCR were used to investigate AF, placenta, and amniochorion for protein and mRNA expression of sIL-6R, sgp130, IL-6R, and gp130. Tissues were immunostained for IL-6R, gp130, CD15(+) (polymorphonuclear), and CD3(+) (T cell) inflammatory cells. The ability of sIL-6R and sgp130 to modulate basal and LPS-stimulated release of amniochorion matrix metalloprotease-9 was tested ex vivo. We showed that in physiologic gestations, AF sgp130 decreases toward term. AF IL-6 and sIL-6R were increased in IAI, whereas sgp130 was decreased in PPROM. Our results suggested that fetal membranes are the probable source of AF sIL-6R and sgp130. Immunohistochemistry and RT-PCR revealed increased IL-6R and decreased gp130 expression in amniochorion of women with IAI. Ex vivo, sIL-6R and LPS augmented amniochorion matrix metalloprotease-9 release, whereas sgp130 opposed this effect. We conclude that IL-6 trans-signaling molecules are physiologic constituents of the AF regulated by gestational age and inflammation. PPROM likely involves functional loss of sgp130.