Inflammation in fetal sheep from intra-amniotic injection of Ureaplasma parvum

Bronchopulmonary Dysplasia: Pathogenesis and Pathophysiology

Bronchopulmonary dysplasia (BPD), also known as chronic lung disease, is the most common respiratory morbidity in preterm infants. "Old" or "classic" BPD, as per the original description, is less common now. "New BPD", which presents with distinct clinical and pathological features, is more frequently observed in the current era of advanced neonatal care, where extremely premature infants are surviving because of medical advancements. The pathogenesis of BPD is complex and multifactorial and involves both genetic and environmental factors. This review provides an overview of the pathology of BPD and discusses the influence of several prenatal and postnatal factors on its pathogenesis, such as maternal factors, genetic susceptibility, ventilator-associated lung injury, oxygen toxicity, sepsis, patent ductus arteriosus (PDA), and nutritional deficiencies. This in-depth review draws on existing literature to explore these factors and their potential contribution to the development of BPD.

Effects of multiple pro-inflammatory stimuli in utero on the ileum of extremely premature ovine fetuses

Introduction

Chorioamnionitis is common in preterm birth and associated with a higher risk of intestinal inflammation and necrotizing enterocolitis. The intestinal inflammation influences the enteric nervous system development. We hypothesized that inflammation and innervation in the fetal ileum may be modified by chorioamnionitis induced by repeated challenge with lipopolysaccharide and/or preexisting Ureaplasma parvum infection at very low gestational age equivalent to 60% of term.

Materials and methods

Time mated ovine fetuses were exposed by intraamniotic injections to chronic Ureaplasma parvum for 24 days and/or lipopolysaccharide for 7 days, 2 days, or 7 & 2 days before delivery at 94 +/-2 days of gestational age (term at approximately 150 days). Intestinal inflammation as well as structural changes of the enteric nervous system were assessed.

Results

Lipopolysaccharide exposure increased CD3 and myeloperoxidase-positive cells (p < 0.05). Repetitive exposure to lipopolysaccharide or combined Ureaplasma parvum & lipopolysaccharide exposure increased intestinal inflammation (p < 0.05). The reduction of nuclei of neurons was most significant with repetitive lipopolysaccharide exposures but could be detected in all other intervention groups compared to the control group. Astrocyte-like glial cells increased if exposure to lipopolysaccharide was only 2 days before delivery or chronic exposure to Ureaplasma parvum existed beforehand (p < 0.05).

Discussion

After exposure to chorioamnionitis induced by Ureaplasma parvum and/or lipopolysaccharide, inflammatory responses as well as structural changes of the enteric nervous system were more pronounced the longer and the more frequent the exposure to pro-inflammatory stimuli before birth. These changes may cause functional effects of clinical importance.

Placing Ureaplasma within the Context of Bronchopulmonary Dysplasia Endotypes and Phenotypes

Different pathophysiological pathways (endotypes), leading to very preterm birth may result in distinct clinical phenotypes of bronchopulmonary dysplasia (BPD). Ureaplasma is a unique player in the pathogenesis of BPD. The interaction between factors inherent to Ureaplasma (virulence, bacterial load, duration of exposure), and to the host (immune response, infection clearance, degree of prematurity, respiratory support, concomitant infections) may contribute to BPD development in a variable manner. The data reviewed herein support the hypothesis that Ureaplasma, as a representative of the infectious/inflammatory endotype, may produce pulmonary damage predominantly in parenchyma, interstitium, and small airways. In contrast, Ureaplasma may have a very limited role in the pathogenesis of the vascular phenotype of BPD. In addition, if Ureaplasma is a key factor in BPD pathogenesis, its eradication by macrolides should prevent BPD. However, various meta-analyses do not show consistent evidence that this is the case. The limitations of current definitions and classifications of BPD, based on respiratory support needs instead of pathophysiology and phenotypes, may explain this and other failures in strategies aimed to prevent BPD. The precise mechanisms through which Ureaplasma infection leads to altered lung development and how these pathways can result in different BPD phenotypes warrant further investigation.

Acute Lung Functional and Airway Remodeling Effects of an Inhaled Highly Selective Phosphodiesterase 4 Inhibitor in Ventilated Preterm Lambs Exposed to Chorioamnionitis

Phosphodiesterase (PDE) inhibition has been identified in animal studies as a new treatment option for neonatal lung injury, and as potentially beneficial for early lung development and function. However, our group could show that the inhaled PDE4 inhibitor GSK256066 could have dose-dependent detrimental effects and promote lung inflammation in the premature lung. In this study, the effects of a high and a low dose of GSK256066 on lung function, structure and alveolar development were investigated. In a triple hit lamb model of Ureaplasma-induced chorioamnionitis, prematurity, and mechanical ventilation, 21 animals were treated as unventilated (NOVENT) or 24 h ventilated controls (Control), or with combined 24 h ventilation and low dose (iPDE1) or high dose (iPDE10) treatment with inhaled GSK 256066. We found that high doses of an inhaled PDE4 inhibitor impaired oxygenation during mechanical ventilation. In this group, the budding of secondary septae appeared to be decreased in the preterm lung, suggesting altered alveologenesis. Ventilation-induced structural and functional changes were only modestly ameliorated by a low dose of PDE4 inhibitor. In conclusion, our findings indicate the narrow therapeutic window of PDE4 inhibitors in the developing lung.

Endotypes of Prematurity and Phenotypes of Bronchopulmonary Dysplasia: Toward Personalized Neonatology

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is increasingly recognized as the consequence of a pathological reparative response of the developing lung to both antenatal and postnatal injury. According to this view, the pathogenesis of BPD is multifactorial and heterogeneous with different patterns of antenatal stress (endotypes) that combine with varying postnatal insults and might distinctively damage the development of airways, lung parenchyma, interstitium, lymphatic system, and pulmonary vasculature. This results in different clinical phenotypes of BPD. There is no clear consensus on which are the endotypes of prematurity but the combination of clinical information with placental and bacteriological data enables the identification of two main pathways leading to birth before 32 weeks of gestation: (1) infection/inflammation and (2) dysfunctional placentation. Regarding BPD phenotypes, the following have been proposed: parenchymal, peripheral airway, central airway, interstitial, congestive, vascular, and mixed phenotype. In line with the approach of personalized medicine, endotyping prematurity and phenotyping BPD will facilitate the design of more targeted therapeutic and prognostic approaches.

Animal Models of Chorioamnionitis: Considerations for Translational Medicine

Preterm birth is defined as any birth occurring before 37 completed weeks of gestation by the World Health Organization. Preterm birth is responsible for perinatal mortality and long-term neurological morbidity. Acute chorioamnionitis is observed in 70% of premature labor and is associated with a heavy burden of multiorgan morbidities in the offspring. Unfortunately, chorioamnionitis is still missing effective biomarkers and early placento- as well as feto-protective and curative treatments. This review summarizes recent advances in the understanding of the underlying mechanisms of chorioamnionitis and subsequent impacts on the pregnancy outcome, both during and beyond gestation. This review also describes relevant and current animal models of chorioamnionitis used to decipher associated mechanisms and develop much needed therapies. Improved knowledge of the pathophysiological mechanisms underpinning chorioamnionitis based on preclinical models is a mandatory step to identify early in utero diagnostic biomarkers and design novel anti-inflammatory interventions to improve both maternal and fetal outcomes.

High Mobility Group Box 1 in Pig Amniotic Membrane Experimentally Infected with E. coli O55

Intra-amniotic infections (IAI) are one of the reasons for preterm birth. High mobility group box 1 (HMGB1) is a nuclear protein with various physiological functions, including tissue healing. Its excessive extracellular release potentiates inflammatory reaction and can revert its action from beneficial to detrimental. We infected the amniotic fluid of a pig on the 80th day of gestation with 1 × 10⁴ colony forming units (CFUs) of E. coli O55 for 10 h, and evaluated the appearance of HMGB1, receptor for glycation endproducts (RAGE), and Toll-like receptor (TLR) 4 in the amniotic membrane and fluid. Sham-infected amniotic fluid served as a control. The expression and release of HMGB1 were evaluated by Real-Time PCR, immunofluorescence, immunohistochemistry, and ELISA. The infection downregulated HMGB1 mRNA expression in the amniotic membrane, changed the distribution of HMGB1 protein in the amniotic membrane, and increased its level in amniotic fluid. All RAGE mRNA, protein expression in the amniotic membrane, and soluble RAGE level in the amniotic fluid were downregulated. TLR4 mRNA and protein expression and soluble TLR4 were all upregulated. HMGB1 is a potential target for therapy to suppress the exaggerated inflammatory response. This controlled expression and release can, in some cases, prevent the preterm birth of vulnerable infants. Studies on suitable animal models can contribute to the development of appropriate therapy.

Melatonin for the prevention of fetal injury associated with intrauterine inflammation

Intrauterine inflammation is shown to be associated with preterm birth, fetal inflammatory response syndrome, and other pregnancy-related comorbidities such as central nervous system diseases including cerebral palsy and periventricular leukomalacia, pulmonary diseases such as bronchopulmonary dysplasia and respiratory distress syndrome, and necrotizing enterocolitis, to name a few. Many animal studies on intrauterine inflammation demonstrate that ascending infection of reproductive organs or the production of proinflammatory cytokines by some stimuli in utero results in such manifestations. Melatonin, known for its primary function in maintaining circadian rhythm, is now recognized as one of the most potent antioxidant and anti-inflammatory drugs. In some studies, melatonin injection in pregnant animals with intrauterine inflammation significantly reduced the number of preterm births, the severity of structural disintegration of the fetal lungs observed in bronchopulmonary dysplasia, and perinatal brain injuries with improvement in neuromotor function. These implicated benefits of melatonin in pregnant women with intrauterine inflammation seem promising in many research studies, strongly supporting the hypothesis that melatonin has antioxidative and anti-inflammatory properties that can potentially be taken by pregnant women who are at risk of having intrauterine inflammation. In this review, the potential of melatonin for improving outcomes of the pregnancies with intrauterine inflammation will be discussed.

Detection of Volatile Organic Compounds as Potential Novel Biomarkers for Chorioamnionitis - Proof of Experimental Models

Background: Histologic chorioamnionitis is only diagnosed postnatally which prevents interventions. We hypothesized that volatile organic compounds (VOCs) in the amniotic fluid might be useful biomarkers for chorioamnionitis and that VOC profiles differ between amnionitis of different origins. Methods: Time-mated ewes received intra-amniotic injections of media or saline (controls), or live Ureaplasma parvum serovar 3 (Up) 14, 7 or 3d prior to c-section at day 124 gestational age (GA). 100 μg recombinant ovine IL-1α was instilled at 7, 3 or 1d prior to delivery. Headspace VOC profiles were measured from amniotic fluids at birth using ion mobility spectrometer coupled with multi-capillary columns. Results: 127 VOC peaks were identified. 27 VOCs differed between samples from controls and Up- or IL-1α induced amnionitis. The best discrimination between amnionitis by Up vs. IL-1α was reached by 2-methylpentane, with a sensitivity/specificity of 96/95% and a positive predictive value/negative predictive values of 96 and 95%. The concentration of 2-methylpentane in VOCs peaked 7d after intra-amniotic instillation of Up. Discussion: We established a novel method to study headspace VOC profiles of amniotic fluids. VOC profiles may be a useful tool to detect and to assess the duration of amnionitis induced by Up. 2-methylpentane was previously described in the exhalate of women with pre-eclampsia and might be a volatile biomarker for amnionitis. Amniotic fluids analyzed by ion mobility spectrometry coupled with multi-capillary columns may provide bedside diagnosis of amnionitis and understanding inflammatory mechanisms during pregnancy.

CD74, a novel predictor for bronchopulmonary dysplasia in preterm infants

Bronchopulmonary dysplasia (BPD) remains a major complication and accounts for high morbidity and mortality of preterm infants. The present study aimed to identify the key genes in the development of BPD and to provide some new insights into the pathogenesis of BPD. The GSE108754 dataset was downloaded from Gene Expression Omnibus database containing 5 samples of BPD patients and 6 of non-BPD infants. The differentially expressed genes (DEGs) between BPD and non-BPD patients were identified by R software. The pathway and function enrichment analyses were performed through Database for Annotation Visualization and Integrated Discovery website. The protein-protein interaction network for DEGs was established by Cytoscape software and the most highly connected module was selected through MCODE plugin. Furthermore, the clinical sample verification among 25 BPD patients and 10 non-BPD infants was carried out in our center. Finally, based on the results above, the gene set enrichment analysis focusing on CD74 upregulated status was employed. Totally, 189 DEGs including 147 upregulated genes and 42 downregulated genes between BPD and non-BPD patients were screened out. The pathway and function enrichments revealed these DEGs were mainly enriched in asthma, intestinal immune network for IgA production, antigen processing and presentation and immune response. Thirteen DEGs (CD74, HLA-DMA, HLA-DRA, HLA-DMB, HLA-DOB, HLA-DQA1, HLA-DRB5, HLA-DPA1, HLA-DOA, HLA-DPB1, HLA-DQB2, HLA-DQA2, and HLA-DQB1) were determined as hub genes. The mRNA expression levels of the 13 hub genes were tested by quantitative real-time polymerase chain reaction among our clinical samples. Eventually, CD74 was confirmed to be the most significant highly expressed in BPD samples (P < .001) and its expression level was negatively correlated with gestational age (r = -0.653) and birth weight (r = -0.675). The gene set enrichment analysis results showed the gene sets associated with lupus erythematosus, viral myocarditis, immune network for IgA production, graft versus host disease, cell adhesion molecules and so no were differentially enriched with the phenotype of high-expression CD74. In conclusion, CD74 may serve to predict the BPD development and provide a new therapeutic target for BPD.

Early origins of lung disease: towards an interdisciplinary approach

The prenatal and perinatal environments can have profound effects on the development of chronic inflammatory diseases. However, mechanistic insight into how the early-life microenvironment can impact upon development of the lung and immune system and consequent initiation and progression of respiratory diseases is still emerging. Recent studies investigating the developmental origins of lung diseases have started to delineate the effects of early-life changes in the lung, environmental exposures and immune maturation on the development of childhood and adult lung diseases. While the influencing factors have been described and studied in mostly animal models, it remains challenging to pinpoint exactly which factors and at which time point are detrimental in lung development leading to respiratory disease later in life. To advance our understanding of early origins of chronic lung disease and to allow for proper dissemination and application of this knowledge, we propose four major focus areas: 1) policy and education; 2) clinical assessment; 3) basic and translational research; and 4) infrastructure and tools, and discuss future directions for advancement. This review is a follow-up of the discussions at the European Respiratory Society Research Seminar "Early origins of lung disease: towards an interdisciplinary approach" (Lisbon, Portugal, November 2019).

Antenatal Infections and Respiratory Outcome in Preterm Infants

Fetal exposure to infection and inflammation can result in accelerated lung maturation and simultaneously altered lung development. This alteration is characterized by reduced alveolar and vascular formation that is one of the hallmarks of the changes observed in animal models and in infants with bronchopulmonary dysplasia (BPD). These opposite effects on maturation and on lung development can explain the reduced severity of respiratory distress syndrome (RDS) but increased incidence of BPD observed in infants exposed to antenatal infections. This also explains why infants born to mothers with chorioamnionitis or colonized with ureaplasma urealitycum have an increased risk of lung injury and BPD. Despite the negative effects of infection on lung development, there is no clear evidence that antibiotic therapy improves the respiratory course in these infants. While the administration of azithromycin to ureaplasma colonized infants is effective in eradicating airway colonization, the effect on BPD is inconclusive. One of the few interventions that have been shown to improve respiratory outcome and reduce BPD in infants with severe RDS is the modulation of inflammation by the administration of systemic or intratracheal steroids early after birth. KEY POINTS: · Antenatal infection can reduce RDS.. · Fetal exposure to infection can alter lung development and increase BPD.. · The detrimental effect of infection is enhanced by mechanical ventilation..

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.

Neonatal Mycoplasma and Ureaplasma Infections

Mycoplasma species (spp.) can be commensals or opportunistic pathogens of the urogenital tract, and they can be commonly isolated from amniotic fluid, placenta, and fetal/neonatal tissue or blood in mothers delivering prematurely or their preterm infants. Although the presence of Mycoplasma spp. has been associated with adverse maternal-fetal outcomes such as preterm birth and maternal chorioamnionitis, it is less clear whether vertical transmission to the neonate results in colonization or active infection/inflammation. Moreover, the presence of Mycoplasma spp. in neonatal blood, cerebrospinal fluid, or tissue has been variably associated with increased risk of neonatal comorbidities, especially bronchopulmonary dysplasia (BPD). Although the treatment of the mother or neonate with antibiotics is effective in eradicating ureaplasma, it is not clear that the treatment is effective in reducing the incidence of major morbidities of the preterm neonate (eg, BPD). In this article, we review the animal and clinical data for ureaplasma-related complications and treatment strategies. [Pediatr Ann. 2020;49(7):e305-e312.].

Pulmonary Consequences of Prenatal Inflammatory Exposures: Clinical Perspective and Review of Basic Immunological Mechanisms

Chorioamnionitis, a potentially serious inflammatory complication of pregnancy, is associated with the development of an inflammatory milieu within the amniotic fluid surrounding the developing fetus. When chorioamnionitis occurs, the fetal lung finds itself in the unique position of being constantly exposed to the consequent inflammatory meditators and/or microbial products found in the amniotic fluid. This exposure results in significant changes to the fetal lung, such as increased leukocyte infiltration, altered cytokine, and surfactant production, and diminished alveolarization. These alterations can have potentially lasting impacts on lung development and function. However, studies to date have only begun to elucidate the association between such inflammatory exposures and lifelong consequences such as lung dysfunction. In this review, we discuss the pathogenesis of and fetal immune response to chorioamnionitis, detail the consequences of chorioamnionitis exposure on the developing fetal lung, highlighting the various animal models that have contributed to our current understanding and discuss the importance of fetal exposures in regard to the development of chronic respiratory disease. Finally, we focus on the clinical, basic, and therapeutic challenges in fetal inflammatory injury to the lung, and propose next steps and future directions to improve our therapeutic understanding of this important perinatal stress.

Detrimental Effects of an Inhaled Phosphodiesterase-4 Inhibitor on Lung Inflammation in Ventilated Preterm Lambs Exposed to Chorioamnionitis Are Dose Dependent

Background: Treatment of bronchopulmonary dysplasia in preterm infants is challenging due to its multifactorial origin. In rodent models of neonatal lung injury, selective inhibition of phosphodiesterase 4 (PDE4) has been shown to exert anti-inflammatory properties in the lung. We hypothesized that GSK256066, a highly selective, inhalable PDE4 inhibitor, would have beneficial effects on lung injury and inflammation in a triple hit lamb model of Ureaplasma parvum (UP)-induced chorioamnionitis, prematurity, and mechanical ventilation. Methods: Twenty-one preterm lambs were surgically delivered preterm at 129 days after 7 days intrauterine exposure to UP. Sixteen animals were subsequently ventilated for 24 hours and received endotracheal surfactant and intravenous caffeine citrate. Ten animals were randomized to receive twice a high (10 μg/kg) or low dose (1 μg/kg) of nebulized PDE4 inhibitor. Results: Nebulization of high, but not low, doses of PDE4 inhibitor led to a significant decrease in pulmonary PDE activity, and was associated with lung injury and vasculitis, influx of neutrophils, and increased proinflammatory cytokine messenger RNA levels. Conclusion: Contrary to our hypothesis, we found in our model a dose-dependent proinflammatory effect of an inhaled highly selective PDE4 inhibitor in the lung. Our findings indicate the narrow therapeutic range of inhaled PDE4 inhibitors in the preterm population.

Differential modulation of pulmonary caspases: Is this the key to Ureaplasma-driven chronic inflammation?

Although accepted agents in chorioamnionitis and preterm birth, the role of Ureaplasma species (spp.) in inflammation-driven morbidities of prematurity, including the development of bronchopulmonary dysplasia, remains controversial. To add to scarce in vitro data addressing the pro-inflammatory capacity of Ureaplasma spp., pulmonary epithelial-like A549 cells and human pulmonary microvascular endothelial cells (HPMEC) were incubated with Ureaplasma (U.) urealyticum, U. parvum, and Escherichia coli lipopolysaccharide (LPS). Ureaplasma isolates down-regulated caspase mRNA levels in A549 cells (caspase 8: p<0.001, 9: p<0.001, vs. broth), while increasing caspase protein expression, enzyme activity, and cell death in HPMEC (active caspase 3: p<0.05, caspase 8: p<0.05, active caspase 9: p<0.05, viability: p<0.05). LPS, contrarily, induced caspase mRNA expression in HPMEC (caspase 3: p<0.01, 4: p<0.001, 5: p<0.001, 8: p<0.001, vs. control), but not in A549 cells, and did not affect enzyme activity or protein levels in either cell line. LPS, but neither Ureaplasma isolate, enhanced mRNA expression of pro-inflammatory interleukin (IL)-6 in both A549 (p<0.05, vs. control) and HPMEC (p<0.001) as well as tumor necrosis factor-α (p<0.01), IL-1β (p<0.001), and IL-8 (p<0.05) in HPMEC. We are therefore the first to demonstrate a differential modulation of pulmonary caspases by Ureaplasma spp. in vitro. Ureaplasma-driven enhanced protein expression and activity of caspases in pulmonary endothelial cells result in cell death and may cause structural damage. Down-regulated caspase mRNA in pulmonary epithelial cells, contrarily, may indicate Ureaplasma-induced inhibition of apoptosis and prevent effective immune responses. Both may ultimately contribute to chronic Ureaplasma colonization and long-term pulmonary inflammation.

Surfactant Components and Tracheal Aspirate Inflammatory Markers in Preterm Infants with Respiratory Distress Syndrome

In 93 preterm infants ≤32 weeks of gestational age and 12 control infants, epithelial lining fluid disaturated-phosphatidylcholine, surfactant protein A and B, albumin, and myeloperoxidase activity were assessed after intubation and before exogenous surfactant administration. We found that disaturated-phosphatidylcholine, surfactant protein B, and myeloperoxidase were significantly higher in preterms with chorioamnionitis.

Ureaplasma Species Differentially Modulate Pro- and Anti-Inflammatory Cytokine Responses in Newborn and Adult Human Monocytes Pushing the State Toward Pro-Inflammation

Background:Ureaplasma species have been associated with chorioamnionitis and preterm birth and have been implicated in the pathogenesis of neonatal short and long-term morbidity. However, being mostly commensal bacteria, controversy remains on the pro-inflammatory capacity of Ureaplasma. Discussions are ongoing on the incidence and impact of prenatal, perinatal, and postnatal infection. The present study addressed the impact of Ureaplasma isolates on monocyte-driven inflammation. Methods: Cord blood monocytes of term neonates and adult monocytes, either native or LPS-primed, were cultured with Ureaplasma urealyticum (U. urealyticum) serovar 8 (Uu8) and Ureaplasma parvum serovar 3 (Up3). Using qRT-PCR, cytokine flow cytometry, and multi-analyte immunoassay, we assessed mRNA and protein expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-8, IL-12p40, IL-10, and IL-1 receptor antagonist (IL-1ra) as well as Toll-like receptor (TLR) 2 and TLR4. Results: Uu8 and Up3 induced mRNA expression and protein release of TNF-α, IL-1β and IL-8 in term neonatal and adult monocytes (p < 0.01 and p < 0.05). Intracellular protein expression of TNF-α, IL-1β and IL-8 in Ureaplasma-stimulated cells paralleled those results. Ureaplasma-induced cytokine levels did not significantly differ from LPS-mediated levels except for lower intracellular IL-1β in adult monocytes (Uu8: p < 0.05). Remarkably, ureaplasmas did not induce IL-12p40 response and promoted lower amounts of anti-inflammatory IL-10 and IL-1ra than LPS, provoking a cytokine imbalance more in favor of pro-inflammation (IL-1β/IL-10, IL-8/IL-10 and IL-8/IL-1ra: p < 0.01, vs. LPS). In contrast to LPS, both isolates induced TLR2 mRNA in neonatal and adult cells (p < 0.001 and p < 0.05) and suppressed TLR4 mRNA in adult monocytes (p < 0.05). Upon co-stimulation, Uu8 and Up3 inhibited LPS-induced intracellular IL-1β (p < 0.001 and p < 0.05) and IL-8 in adult monocytes (p < 0.01), while LPS-induced neonatal cytokines were maintained or aggravated (p < 0.05). Conclusion: Our data demonstrate a considerable pro-inflammatory capacity of Ureaplasma isolates in human monocytes. Stimulating pro-inflammatory cytokine responses while hardly inducing immunomodulatory and anti-inflammatory cytokines, ureaplasmas might push monocyte immune responses toward pro-inflammation. Inhibition of LPS-induced cytokines in adult monocytes in contrast to sustained inflammation in term neonatal monocytes indicates a differential modulation of host immune responses to a second stimulus. Modification of TLR2 and TLR4 expression may shape host susceptibility to inflammation.

Bronchopulmonary dysplasia: A review of pathogenesis and pathophysiology

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of primarily premature infants that results from an imbalance between lung injury and repair in the developing lung. BPD is the most common respiratory morbidity in preterm infants, which affects nearly 10, 000 neonates each year in the United States. Over the last two decades, the incidence of BPD has largely been unchanged; however, the pathophysiology has changed with the substantial improvement in the respiratory management of extremely low birth weight (ELBW) infants. Here we have attempted to comprehensively review and summarize the current literature on the pathogenesis and pathophysiology of BPD. Our goal is to provide insight to help further progress in preventing and managing severe BPD in the ELBW infants.

Pulmonary vascular changes in extremely preterm sheep after intra-amniotic exposure to Ureaplasma parvum and lipopolysaccharide

Background

Chorioamnionitis can induce pulmonary inflammation and promote bronchopulmonary dysplasia development, distinguished by alveolar simplification and impaired vascular growth. Chorioamnionitis is more common during the extremely preterm canalicular lung stage (crucial for vascular development); and increases the risk for subsequent sepsis. We hypothesized that single/combined exposure to chronic and/or acute inflammation induces pulmonary inflammatory responses and vascular changes.

Methods

Ovine fetuses were intra-amniotically exposed to chronic Ureaplasma parvum (UP) at 24 days (d) before extreme preterm delivery at 94d (term 147d) and/or to lipopolysaccharide (LPS) 7 or 2d before delivery. Pulmonary inflammation, vascular remodeling and angiogenic factors were assessed.

Results

LPS exposure increased CD3-positive and myeloperoxidase-positive cells. Combined UP-LPS exposure increased pulmonary inflammation compared with 2d LPS or UP groups. The UP+2d LPS group had an increased adventitial fibrosis score when compared with UP-treated animals. A reduced wall-to-lumen ratio was found in the 7d LPS animals when compared to the 2d LPS-treated animals. Exposure to UP+2d LPS reduced VEGF and VEGFR-2 levels compared with 2d LPS-treated animals. Angiopoietin-1 (Ang1) and tunica interna endothelial cell kinase 2 (Tie-2) levels were decreased after UP+7d LPS as well as after 7d LPS, but not with UP alone.

Conclusion

Chronic UP and subsequent LPS exposure increased pulmonary inflammation and decreased expression of angiogenic growth factors and receptors when compared to single hit-exposed animals.

The Human Ureaplasma Species as Causative Agents of Chorioamnionitis

The human Ureaplasma species are the most frequently isolated microorganisms from the amniotic fluid and placentae of women who deliver preterm and are also associated with spontaneous abortions or miscarriages, neonatal respiratory diseases, and chorioamnionitis. Despite the fact that these microorganisms have been habitually found within placentae of pregnancies with chorioamnionitis, the role of Ureaplasma species as a causative agent has not been satisfactorily explained. There is also controversy surrounding their role in disease, particularly as not all women infected with Ureaplasma spp. develop chorioamnionitis. In this review, we provide evidence that Ureaplasma spp. are associated with diseases of pregnancy and discuss recent findings which demonstrate that Ureaplasma spp. are associated with chorioamnionitis, regardless of gestational age at the time of delivery. Here, we also discuss the proposed major virulence factors of Ureaplasma spp., with a focus on the multiple-banded antigen (MBA), which may facilitate modulation/alteration of the host immune response and potentially explain why only subpopulations of infected women experience adverse pregnancy outcomes. The information presented within this review confirms that Ureaplasma spp. are not simply "innocent bystanders" in disease and highlights that these microorganisms are an often underestimated pathogen of pregnancy.

Intra-amniotic Ureaplasma parvum-Induced Maternal and Fetal Inflammation and Immune Responses in Rhesus Macaques

BACKGROUND

Although Ureaplasma species are the most common organisms associated with prematurity, their effects on the maternal and fetal immune system remain poorly characterized.

METHODS

Rhesus macaque dams at approximately 80% gestation were injected intra-amniotically with 10⁷ colony-forming units of Ureaplasma parvum or saline (control). Fetuses were delivered surgically 3 or 7 days later. We performed comprehensive assessments of inflammation and immune effects in multiple fetal and maternal tissues.

RESULTS

Although U. parvum grew well in amniotic fluid, there was minimal chorioamnionitis. U. parvum colonized the fetal lung, but fetal systemic microbial invasion was limited. Fetal lung inflammation was mild, with elevations in CXCL8, tumor necrosis factor (TNF) α, and CCL2 levels in alveolar washes at day 7. Inflammation was not detected in the fetal brain. Significantly, U. parvum decreased regulatory T cells (Tregs) and activated interferon γ production in these Tregs in the fetus. It was detected in uterine tissue by day 7 and induced mild inflammation and increased expression of connexin 43, a gap junction protein involved with labor.

CONCLUSIONS

U. parvum colonized the amniotic fluid and caused uterine inflammation, but without overt chorioamnionitis. It caused mild fetal lung inflammation but had a more profound effect on the fetal immune system, decreasing Tregs and polarizing them toward a T-helper 1 phenotype.

Gastric fluid versus amniotic fluid analysis for the identification of intra-amniotic infection due to Ureaplasma species

OBJECTIVE

Early neonatal sepsis is often due to intra-amniotic infection. The stomach of the neonate contains fluid swallowed before and during delivery. The presence of bacteria as well as neutrophils detected by culture or Gram stain of the gastric fluid during the first day of life is suggestive of exposure to bacteria or inflammation. We undertook this study to determine the relationship between gastric fluid analysis and amniotic fluid obtained by transabdominal amniocentesis in the detection of Ureaplasma species, the most frequent microorganisms responsible for intra-amniotic infection.

MATERIALS AND METHODS

The study population consisted of 100 singleton pregnant women who delivered preterm neonates (<35 weeks) within 7 days of amniocentesis. Gastric fluid of newborns was obtained by nasogastric intubation on the day of birth. Amniotic fluid and gastric fluid were cultured for genital Mycoplasmas, and polymerase chain reaction (PCR) for Ureaplasma species was performed. Intra-amniotic inflammation was defined as an elevated amniotic fluid matrix metalloproteinase-8 concentration (>23 ng/mL).

RESULTS

(1) Ureaplasma species were detected by culture or PCR in 18% (18/100) of amniotic fluid samples and in 5% (5/100) of gastric fluid samples; (2) among the amniotic fluid cases positive for Ureaplasma species, these microorganisms were identified in 27.8% (5/18) of gastric fluid samples; (3) none of the cases negative for Ureaplasma species in the amniotic fluid were found to be positive for these microorganisms in the gastric fluid; (4) patients with amniotic fluid positive for Ureaplasma species but with gastric fluid negative for these microorganisms had a significantly higher rate of intra-amniotic inflammation, acute histologic chorioamnionitis, and neonatal death than those with both amniotic fluid and gastric fluid negative for Ureaplasma species; and (5) no significant differences were observed in the rate of intra-amniotic inflammation, acute histologic chorioamnionitis, and neonatal death between patients with amniotic fluid positive for Ureaplasma species but with gastric fluid negative for these microorganisms and those with both amniotic fluid and gastric fluid positive for Ureaplasma species.

CONCLUSIONS

Gastric fluid analysis has 100% specificity in the identification of intra-amniotic infection with Ureaplasma species. However, the detection of Ureaplasma species by culture or PCR in the gastric fluid of neonates at birth did not identify these microorganisms in two-thirds of cases with microbial invasion of the amniotic cavity. Thus, amniotic fluid analysis is superior to that of gastric fluid in the identification of intra-amniotic infection.

Role of Ureaplasma Respiratory Tract Colonization in Bronchopulmonary Dysplasia Pathogenesis: Current Concepts and Update

Respiratory tract colonization with the genital mycoplasma species Ureaplasma parvum and Ureaplasma urealyticum in preterm infants is a significant risk factor for bronchopulmonary dysplasia (BPD). Recent studies of the ureaplasmal genome, animal infection models, and human infants have provided a better understanding of specific virulence factors, pathogen-host interactions, and variability in genetic susceptibility that contribute to chronic infection, inflammation, and altered lung development. This review provides an update on the current evidence supporting a causal role of ureaplasma infection in BPD pathogenesis. The current status of antibiotic trials to prevent BPD in Ureaplasma-infected preterm infants is also reviewed.

Systemic interleukin-2 administration improves lung function and modulates chorioamnionitis-induced pulmonary inflammation in the ovine fetus

Chorioamnionitis, an inflammatory reaction of the fetal membranes to microbes, is an important cause of preterm birth and associated with inflammation-driven lung injury. However, inflammation in utero overcomes immaturity of the premature lung by inducing surfactant lipids and lung gas volume. Previously, we found that lipopolysaccharide (LPS)-induced chorioamnionitis resulted in pulmonary inflammation with increased effector T cells and decreased regulatory T cell (Treg) numbers. Because Tregs are crucial for immune regulation, we assessed the effects of interleukin (IL)-2-driven selective Treg expansion on the fetal lung in an ovine chorioamnionitis model. Instrumented fetuses received systemic prophylactic IL-2 treatment [118 days gestational age (dGA)] with or without subsequent exposure to intra-amniotic LPS (122 dGA). Following delivery at 129 dGA (term 147 dGA), pulmonary and systemic inflammation, morphological changes, lung gas volume, and phospholipid concentration were assessed. IL-2 pretreatment increased the FoxP3(+)/CD3(+) ratio, which was associated with reduced CD3-positive cells in the fetal lungs of LPS-exposed animals. Prophylactic IL-2 treatment did not prevent pulmonary accumulation of myeloperoxidase- and PU.1-positive cells or elevation of bronchoalveolar lavage fluid IL-8 and systemic IL-6 concentrations in LPS-exposed animals. Unexpectedly, IL-2 treatment improved fetal lung function of control lambs as indicated by increased disaturated phospholipids and improved lung gas volume. In conclusion, systemic IL-2 treatment in utero preferentially expanded Tregs and improved lung gas volume and disaturated phospholipids. These beneficial effects on lung function were maintained despite the moderate immunomodulatory effects of prophylactic IL-2 in the course of chorioamnionitis.

Acute chorioamnionitis and funisitis: definition, pathologic features, and clinical significance

Acute inflammatory lesions of the placenta consist of diffuse infiltration of neutrophils at different sites in the organ. These lesions include acute chorioamnionitis, funisitis, and chorionic vasculitis and represent a host response (maternal or fetal) to a chemotactic gradient in the amniotic cavity. While acute chorioamnionitis is evidence of a maternal host response, funisitis and chorionic vasculitis represent fetal inflammatory responses. Intraamniotic infection generally has been considered to be the cause of acute chorioamnionitis and funisitis; however, recent evidence indicates that "sterile" intraamniotic inflammation, which occurs in the absence of demonstrable microorganisms induced by "danger signals," is frequently associated with these lesions. In the context of intraamniotic infection, chemokines (such as interleukin-8 and granulocyte chemotactic protein) establish a gradient that favors the migration of neutrophils from the maternal or fetal circulation into the chorioamniotic membranes or umbilical cord, respectively. Danger signals that are released during the course of cellular stress or cell death can also induce the release of neutrophil chemokines. The prevalence of chorioamnionitis is a function of gestational age at birth, and present in 3-5% of term placentas and in 94% of placentas delivered at 21-24 weeks of gestation. The frequency is higher in patients with spontaneous labor, preterm labor, clinical chorioamnionitis (preterm or term), or ruptured membranes. Funisitis and chorionic vasculitis are the hallmarks of the fetal inflammatory response syndrome, a condition characterized by an elevation in the fetal plasma concentration of interleukin-6, and associated with the impending onset of preterm labor, a higher rate of neonatal morbidity (after adjustment for gestational age), and multiorgan fetal involvement. This syndrome is the counterpart of the systemic inflammatory response syndrome in adults: a risk factor for short- and long-term complications (ie, sterile inflammation in fetuses, neonatal sepsis, bronchopulmonary dysplasia, periventricular leukomalacia, and cerebral palsy). This article reviews the definition, pathogenesis, grading and staging, and clinical significance of the most common lesions in placental disease. Illustrations of the lesions and diagrams of the mechanisms of disease are provided.

Animal Models, Learning Lessons to Prevent and Treat Neonatal Chronic Lung Disease

Bronchopulmonary dysplasia (BPD) is a unique injury syndrome caused by prolonged injury and repair imposed on an immature and developing lung. The decreased septation and decreased microvascular development phenotype of BPD can be reproduced in newborn rodents with increased chronic oxygen exposure and in premature primates and sheep with oxygen and/or mechanical ventilation. The inflammation caused by oxidants, inflammatory agonists, and/or stretch injury from mechanical ventilation seems to promote the anatomic abnormalities. Multiple interventions targeted to specific inflammatory cells or pathways or targeted to decreasing ventilation-mediated injury can substantially prevent the anatomic changes associated with BPD in term rodents and in preterm sheep or primate models. Most of the anti-inflammatory therapies with benefit in animal models have not been tested clinically. None of the interventions that have been tested clinically are as effective as anticipated from the animal models. These inconsistencies in responses likely are explained by the antenatal differences in lung exposures of the developing animals relative to very preterm humans. The animals generally have normal lungs while the lungs of preterm infants are exposed variably to intrauterine inflammation, growth abnormalities, antenatal corticosteroids, and poorly understood effects from the causes of preterm delivery. The animal models have been essential for the definition of the mediators that can cause a BPD phenotype. These models will be necessary to develop and test future-targeted interventions to prevent and treat BPD.

Oral, nasal and pharyngeal exposure to lipopolysaccharide causes a fetal inflammatory response in sheep

Background

A fetal inflammatory response (FIR) in sheep can be induced by intraamniotic or selective exposure of the fetal lung or gut to lipopolysaccharide (LPS). The oral, nasal, and pharyngeal cavities (ONP) contain lymphoid tissue and epithelium that are in contact with the amniotic fluid. The ability of the ONP epithelium and lymphoid tissue to initiate a FIR is unknown.

Objective

To determine if FIR occurs after selective ONP exposure to LPS in fetal sheep.

Methods

Using fetal recovery surgery, we isolated ONP from the fetal lung, GI tract, and amniotic fluid by tracheal and esophageal ligation and with an occlusive glove fitted over the snout. LPS (5 mg) or saline was infused with 24 h Alzet pumps secured in the oral cavity (n = 7–8/group). Animals were delivered 1 or 6 days after initiation of the LPS or saline infusions.

Results

The ONP exposure to LPS had time-dependent systemic inflammatory effects with changes in WBC in cord blood, an increase in posterior mediastinal lymph node weight at 6 days, and pro-inflammatory mRNA responses in the fetal plasma, lung, and liver. Compared to controls, the expression of surfactant protein A mRNA increased 1 and 6 days after ONP exposure to LPS.

Conclusion

ONP exposure to LPS alone can induce a mild FIR with time-dependent inflammatory responses in remote fetal tissues not directly exposed to LPS.

The Maternal Serological Response to Intrauterine Ureaplasma sp. Infection and Prediction of Risk of Pre-Term Birth

Pre-term birth (PTB) associated with intrauterine infection and inflammation (IUI) is the major cause of early PTB less than 32 weeks of gestation. Ureaplasma spp. are common commensals of the urogenital tract in pregnancy and are the most commonly identified microorganisms in amniotic fluid of pre-term pregnancies. While we have an understanding of the causal relationship between intra-amniotic infection, inflammation and PTB, we are still unable to explain why vaginal Ureaplasma sp. colonization is tolerated in some women but causes PTB in others. It is now known that placental tissues are frequently colonized by bacteria even in apparently healthy pregnancies delivered at term; usually this occurs in the absence of a significant local inflammatory response. It appears, therefore, that the site, nature, and magnitude of the immune response to infiltrating microorganisms are key in determining pregnancy outcome. Some evidence exists that the maternal serological response to Ureaplasma sp. colonization may be predictive of adverse pregnancy outcome, although issues such as the importance of virulence factors (serovars) and the timing, magnitude, and functional consequences of the immune response await clarification. This mini-review discusses the evidence linking the maternal immune response to risk of PTB and the potential applications of maternal serological analysis for predicting obstetric outcome.

Preterm birth, intrauterine infection, and fetal inflammation

Preterm birth (PTB) (delivery before 37 weeks’ gestation) is a leading cause of neonatal death and disease in industrialized and developing countries alike. Infection (most notably in high-risk deliveries occurring before 28 weeks’ gestation) is hypothesized to initiate an intrauterine inflammatory response that plays a key role in the premature initiation of labor as well as a host of the pathologies associated with prematurity. As such, a better understanding of intrauterine inflammation in pregnancy is critical to our understanding of preterm labor and fetal injury, as well as on-going efforts to prevent PTB. Focusing on the fetal innate immune system responses to intrauterine infection, the present paper will review clinical and experimental studies to discuss the capacity for a fetal contribution to the intrauterine inflammation associated with PTB. Evidence from experimental studies to suggest that the fetus has the capacity to elicit a pro-inflammatory response to intrauterine infection is highlighted, with reference to the contribution of the lung, skin, and gastrointestinal tract. The paper will conclude that pathological intrauterine inflammation is a complex process that is modified by multiple factors including time, type of agonist, host genetics, and tissue.

Ventilation-induced increases in EGFR ligand mRNA are not altered by intra-amniotic LPS or ureaplasma in preterm lambs

Chorioamnionitis and mechanical ventilation are associated with bronchopulmonary dysplasia (BPD) in preterm infants. Mechanical ventilation at birth activates both inflammatory and acute phase responses. These responses can be partially modulated by previous exposure to intra-amniotic (IA) LPS or Ureaplasma parvum (UP). Epidermal growth factor receptor (EGFR) ligands participate in lung development, and angiotensin converting enzyme (ACE) 1 and ACE2 contribute to lung inflammation. We asked whether brief mechanical ventilation at birth altered EGFR and ACE pathways and if antenatal exposure to IA LPS or UP could modulate these effects. Ewes were exposed to IA injections of UP, LPS or saline multiple days prior to preterm delivery at 85% gestation. Lambs were either immediately euthanized or mechanically ventilated for 2 to 3 hr. IA UP and LPS cause modest changes in the EGFR ligands amphiregulin (AREG), epiregulin (EREG), heparin binding epidermal growth factor (HB-EGF), and betacellulin (BTC) mRNA expression. Mechanical ventilation greatly increased mRNA expression of AREG, EREG, and HB-EGF, with no additional increases resulting from IA LPS or UP. With ventilation AREG and EREG mRNA localized to cells in terminal airspace. EGFR mRNA also increased with mechanical ventilation. IA UP and LPS decreased ACE1 mRNA and increased ACE2 mRNA, resulting in a 4 fold change in the ACE1/ACE2 ratio. Mechanical ventilation with large tidal volumes increased both ACE1 and ACE2 expression. The alterations seen in ACE with IA exposures and EGFR pathways with mechanical ventilation may contribute to the development of BPD in preterm infants.

Effects of intra-amniotic lipopolysaccharide exposure on the fetal lamb lung as gestation advances

BACKGROUND

Intra-amniotic lipopolysaccharide (LPS) exposure may affect neonatal outcome by altering fetal lung and immune system development. We hypothesized that intra-amniotic LPS exposure would cause persistent fetal pulmonary responses as the lungs develop in utero.

METHODS

Fetal lambs were exposed to intra-amniotic LPS at 118 or at 118 and 123 d of gestational age (GA) with delivery at 125, 133, or 140 d (term = 147 d). Immune responses, PU.1 expression, Toll-like receptor (TLR)-1,2,4,6 mRNA levels, mast cell levels, and pulmonary elastin deposition were evaluated.

RESULTS

After a single dose of LPS, pulmonary inflammatory responses were observed with increases of (i) PU.1 and TLR1 at 125 d GA and (ii) monocytes, lymphocytes, TLR2, and TLR6 at 133 d GA. Repetitive LPS exposure resulted in (i) increases of neutrophils, monocytes, PU.1, and TLR1 at 125 d GA; (ii) increases of neutrophils, PU.1, and TLR2 at 133 d GA; and (iii) decreases of mast cells, elastin foci, TLR4, and TLR6 at early gestation. At 140 d GA, only PU.1 was increased after repetitive LPS exposure.

CONCLUSION

The preterm fetal lung can respond to a single exposure or repeated exposures from intra-amniotic LPS in multiple ways, but the absence of inflammatory and structural changes in LPS-exposed fetuses delivered near term suggest that the fetus can resolve an inflammatory stimulus in utero with time.

Immune profiling of BALB/C and C57BL/6 mice reveals a correlation between Ureaplasma parvum-Induced fetal inflammatory response syndrome-like pathology and increased placental expression of TLR2 and CD14

PROBLEM

Both BALB/c and C57BL/6 mice are susceptible to intrauterine infection with Ureaplasma parvum, but only protypical TH2/M2 BALB/c mice develop severe chorioamnionitis, fetal infection, and fetal inflammatory response syndrome-like (FIRS) pathology.

METHOD OF STUDY

Microscopy, gene expression analysis, and ELISA were used to identify placental innate immune responses relevant to macrophage polarity, severe chorioamnionitis, and fetal infection.

RESULTS

Both mouse strains exhibited a pro-M2 cytokine profile at the maternal/fetal interface. In BALB/c mice, expression of CD14 and TLRs 1, 2, 6 was increased in infected placentas; TLR2 and CD14 were localized to neutrophils. Increased TLR2/CD14 was also observed in BALB/c syncytiotrophoblasts in tissues with pathological evidence of FIRS. In contrast, expression in C57BL/6 placentas was either unchanged or down-regulated.

CONCLUSION

Our findings show a link between increased syncytiotrophoblast expression of CD14/TLR2 and FIRS-like pathology in BALB/c mice. Functional studies are required to determine if CD14 is contributing to fetal morbidity during chorioamnionitis.

Fetal immune response to chorioamnionitis

Chorioamnionitis is a frequent cause of preterm birth and is associated with an increased risk for injury responses in the lung, gastrointestinal tract, brain, and other fetal organs. Chorioamnionitis is a polymicrobial nontraditional infectious disease because the organisms causing chorioamnionitis are generally of low virulence and colonize the amniotic fluid often for extended periods, and the host (mother and the fetus) does not have typical infection-related symptoms such as fever. In this review, we discuss the effects of chorioamnionitis in experimental animal models that mimic the human disease. Our focus is on the immune changes in multiple fetal organs and the pathogenesis of chorioamnionitis-induced injury in different fetal compartments. As chorioamnionitis disproportionately affects preterm infants, we discuss the relevant developmental context for the immune system. We also provide a clinical context for the fetal responses.

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).

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.

Antenatal ureaplasma infection impairs development of the fetal ovine gut in an IL-1-dependent manner

Ureaplasma infection of the amniotic cavity is associated with adverse postnatal intestinal outcomes. We tested whether interleukin-1 (IL-1) signaling underlies intestinal pathology following ureaplasma exposure in fetal sheep. Pregnant ewes received intra-amniotic injections of ureaplasma or culture media for controls at 3, 7, and 14 d before preterm delivery at 124 d gestation (term 150 d). Intra-amniotic injections of recombinant human interleukin IL-1 receptor antagonist (rhIL-1ra) or saline for controls were given 3 h before and every 2 d after Ureaplasma injection. Ureaplasma exposure caused fetal gut inflammation within 7 d with damaged villus epithelium and gut barrier loss. Proliferation, differentiation, and maturation of enterocytes were significantly reduced after 7 d of ureaplasma exposure, leading to severe villus atrophy at 14 d. Inflammation, impaired development and villus atrophy of the fetal gut was largely prevented by intra-uterine rhIL-1ra treatment. These data form the basis for a clinical understanding of the role of ureaplasma in postnatal intestinal pathologies.

Ureaplasma and BPD

Ureaplasma is an organism with low virulence and is a commensal of the lower genito-urinary tract in females. From here, it can gain entry in the amniotic fluid to cause inflammation in the amniotic compartment during pregnancy. Ureaplasma spp. are the most common organisms isolated from women with chorioamnionitis. Ureaplasma spp. are associated with increased risk for preterm labor and morbidity in the preterm neonate. However, there is some controversy regarding the importance of Ureaplasma in the pathogenesis of bronchopulmonary dysplasia (BPD). This article will review the microbiology of Ureaplasma, host innate immune responses, and the pathology of lung injury in animal models of Ureaplasma chorioamnionitis. We will review epidemiological studies of Ureaplasma and BPD in preterm infants and efficacy of antibiotics in preventing preterm labor and BPD.

Repeated intrauterine exposures to inflammatory stimuli attenuated transforming growth factor-β signaling in the ovine fetal lung

BACKGROUND

Bronchopulmonary dysplasia (BPD) is one of the most common complications after preterm birth and is associated with intrauterine exposure to bacteria. Transforming growth factor-β (TGFβ) is implicated in the development of BPD.

OBJECTIVES

We hypothesized that different and/or multiple bacterial signals could elicit divergent TGFβ signaling responses in the developing lung.

METHODS

Time-mated pregnant Merino ewes received an intra-amniotic injection of lipopolysaccharide (LPS) and/or Ureaplasma parvum serovar 3 (UP) at 117 days' and/or 121/122 days' gestational age (GA). Controls received an equivalent injection of saline and or media. Lambs were euthanized at 124 days' GA (term = 150 days' GA). TGFβ1, TGFβ2, TGFβ3, TGFβ receptor (R)1 and TGFβR2 protein levels, Smad2 phosphorylation and elastin deposition were evaluated in lung tissue.

RESULTS

Total TGFβ1 and TGFβ2 decreased by 24 and 51% after combined UP+LPS exposure, whereas total TGFβ1 increased by 31% after 7 days' LPS exposure but not after double exposures. Alveolar expression of TGFβR2 decreased 75% after UP, but remained unaltered after double exposures. Decreased focal elastin deposition after single LPS exposure was prevented by double exposures.

CONCLUSIONS

TGFβ signaling components and elastin responded differently to intrauterine LPS and UP exposure. Multiple bacterial exposures attenuated TGFβ signaling and normalized elastin deposition.

LPS-induced chorioamnionitis and antenatal corticosteroids modulate Shh signaling in the ovine fetal lung

Chorioamnionitis and antenatal corticosteroids mature the fetal lung functionally but disrupt late-gestation lung development. Because Sonic Hedgehog (Shh) signaling is a major pathway directing lung development, we hypothesized that chorioamnionitis and antenatal corticosteroids modulated Shh signaling, resulting in an altered fetal lung structure. Time-mated ewes with singleton ovine fetuses received an intra-amniotic injection of lipopolysaccharide (LPS) and/or maternal intramuscular betamethasone 7 and/or 14 days before delivery at 120 days gestational age (GA) (term = 150 days GA). Intra-amniotic LPS exposure decreased Shh mRNA levels and Gli1 protein expression, which was counteracted by both betamethasone pre- or posttreatment. mRNA and protein levels of fibroblast growth factor 10 and bone morphogenetic protein 4, which are important mediators of lung development, increased 2-fold and 3.5-fold, respectively, 14 days after LPS exposure. Both 7-day and 14-day exposure to LPS changed the mRNA levels of elastin (ELN) and collagen type I alpha 1 (Col1A1) and 2 (Col1A2), which resulted in fewer elastin foci and increased collagen type I deposition in the alveolar septa. Corticosteroid posttreatment prevented the decrease in ELN mRNA and increased elastin foci and decreased collagen type I deposition in the fetal lung. In conclusion, fetal lung exposure to LPS was accompanied by changes in key modulators of lung development resulting in abnormal lung structure. Betamethasone treatment partially prevented the changes in developmental processes and lung structure. This study provides new insights into clinically relevant prenatal exposures and fetal lung development.

Effects of chorioamnionitis on the fetal lung

Very preterm infants are commonly exposed to a chronic, often asymptomatic, chorioamnionitis that is diagnosed by histologic evaluation of the placenta only after delivery. The reported effects of these exposures on fetal lungs are inconsistent because exposure to different organisms, durations of exposure, and fetal/maternal responses affect outcomes. In experimental models, chorioamnionitis can both injure and mature the fetal lung and cause immune nodulation. Postnatal care strategies also change how chorioamnionitis relates to clinical outcomes such as bronchopulmonary dysplasia.

Host genetic background impacts disease outcome during intrauterine infection with Ureaplasma parvum

Ureaplasma parvum, an opportunistic pathogen of the human urogenital tract, has been implicated in contributing to chorioamnionitis, fetal morbidity, and fetal mortality. It has been proposed that the host genetic background is a critical factor in adverse pregnancy outcome as sequela to U. parvum intra-amniotic infection. To test this hypothesis we assessed the impact of intrauterine U. parvum infection in the prototypical TH1/M1 C57BL/6 and TH2/M2 BALB/c mouse strain. Sterile medium or U. parvum was inoculated into each uterine horn and animals were evaluated for intra-amniotic infection, fetal infection, chorioamnionitis and fetal pathology at 72 hours post-inoculation. Disease outcome was assessed by microbial culture, in situ detection of U. parvum in fetal and utero-placental tissues, grading of chorioamnionitis, and placental gene expression of IL-1α, IL-1β, IL-6, TNF-α, S100A8, and S100A9. Placental infection and colonization rates were equivalent in both strains. The in situ distribution of U. parvum in placental tissues was also similar. However, a significantly greater proportion of BALB/c fetuses were infected (P<0.02). C57BL/6 infected animals predominantly exhibited mild to moderate chorioamnionitis (P<0.0001), and a significant reduction in placental expression of IL-1α, IL-1β, IL-6, TNF-α, S100A8, and S100A9 compared to sham controls (P<0.02). Conversely, severe protracted chorioamnionitis with cellular necrosis was the predominant lesion phenotype in BALB/c mice, which also exhibited a significant increase in placental expression of IL-1α, IL-1β, IL-6, TNF-α, S100A8, and S100A9 (P<0.01). Fetal pathology in BALB/c was multi-organ and included brain, lung, heart, liver, and intestine, whereas fetal pathology in C57BL/6 was only detected in the liver and intestines. These results confirm that the host genetic background is a major determinant in ureaplasmal induced chorioamnionitis with fetal infection and fetal inflammatory response.

In-vitro validation of cytokine neutralizing antibodies by testing with ovine mononuclear splenocytes

Cytokines have gained increasing attention as therapeutic targets in inflammation-related disorders and inflammatory conditions have been investigated in sheep. Monoclonal antibodies (mAbs) specific for the ovine pro-inflammatory cytokines interleukin (IL)-1β and IL-6 could be used to study the effects of blocking pro-inflammatory cytokines in sheep. Ovine-specific IL-1β and IL-6 proteins and mAbs specific for these molecules were produced and the ability of the mAbs to neutralize the proteins was tested in cultures of ovine splenic mononuclear cells. Expression of nuclear factor (NF)-κβ and signal transducer and activator of transcription (STAT)-3 was evaluated by western blotting and densitometric quantification. Treatment with purified IL-1β and IL-6 proteins increased NF-κβ (P < 0.001) and STAT-3 (P < 0.01) expression, respectively, in cell culture. Treatment with these proteins that were pre-incubated with IL-1β and IL-6 mAbs attenuated (P < 0.01) these effects. These results confirm the bioactivity of ovine IL-1β and IL-6 proteins and the neutralizing capacity of anti-ovine-IL-1β and -IL-6 mAbs in vitro. These mAbs could be used to investigate anti-inflammatory strategies for attenuation of the effects of these pro-inflammatory cytokines in sheep.

Interleukin-19 in fetal systemic inflammation

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is considered the fetal counterpart of the systemic inflammatory response syndrome (SIRS), which can be caused by infection and non-infection-related insults. Although the initial response is mediated by pro-inflammatory signals, the control of this response is achieved by anti-inflammatory mediators which are essential for the successful outcome of the affected individual. Interleukin (IL)-19 is capable of stimulating the production of IL-10, a major anti-inflammatory cytokine, and is a potent inducer of the T-helper 2 (Th2) response. The aim of this study was to determine if there is a change in umbilical cord plasma IL-19 and IL-10 concentrations in preterm neonates with and without acute funisitis, the histologic counterpart of FIRS.

METHODS

A case-control study was conducted including 80 preterm neonates born after spontaneous labor. Neonates were classified according to the presence (n = 40) or absence of funisitis (n = 40), which is the pathologic hallmark of FIRS. Neonates in each group were also matched for gestational age. Umbilical cord plasma IL-19 and IL-10 concentrations were determined by ELISA.

RESULTS

1) The median umbilical cord plasma IL-19 concentration was 2.5-fold higher in neonates with funisitis than in those without funisitis (median 87 pg/mL; range 20.6-412.6 pg/mL vs. median 37 pg/mL; range 0-101.7 pg/mL; p < 0.001); 2) newborns with funisitis had a significantly higher median umbilical cord plasma IL-10 concentration than those without funisitis (median 4 pg/mL; range 0-33.5 pg/mL vs. median 2 pg/mL; range 0-13.8 pg/mL; p < 0.001); and 3) the results were similar when we included only patients with funisitis who met the definition of FIRS by umbilical cord plasma IL-6 concentrations ≥ 17.5 pg/mL (p < 0.001).

CONCLUSION

IL-19 and IL-10 are parts of the immunologic response of FIRS. A subset of fetuses with FIRS had high umbilical cord plasma IL-19 concentrations. In utero exposure to high systemic concentrations of IL-19 may reprogram the immune response.

Antenatal exposure to Ureaplasma species exacerbates bronchopulmonary dysplasia synergistically with subsequent prolonged mechanical ventilation in preterm infants

INTRODUCTION

The presence of microorganisms in gastric fluid in neonates at birth is postulated to reflect antenatal infection and also to be associated with the development of bronchopulmonary dysplasia (BPD).

RESULTS

A logistic regression analysis, after controlling for other risk factors, indicated that Ureaplasma-positive infants were not at increased risk for moderate/severe BPD (adjusted odds ratio (OR): 2.58, 95% confidence interval (CI): 0.57-6.89, P = 0.12). However, the association between the presence of Ureaplasma species and the risk for moderate/severe BPD increased significantly in infants on mechanical ventilation (MV) ≥2 wk (adjusted OR: 4.17, 95% CI: 1.62-44.1, P = 0.009). An analysis using a lung injury marker indicated that Ureaplasma-positive infants with MV ≥2 wk, but not other infants, showed higher serum KL-6 levels in samples taken from cord blood, and that KL-6 levels increased time-dependently up to 4 wk of age.

DISCUSSION

Antenatal exposure to Ureaplasma species induces lung injury prior to birth and synergistically contributes to the development of BPD in infants requiring prolonged MV (≥2 wk).

METHODS

We recovered gastric fluid specimens from 122 infants with gestational age (GA) <29 wk or birth weight <1,000 g to investigate whether these microorganisms influence respiratory outcome of BPD. A PCR analysis was used to detect urease and 16S ribosomal RNA (rRNA) genes to classify neonates into Ureaplasma-positive or Ureaplasma-negative infants.

Perinatal inflammation and lung injury

Bronchopulmonary dysplasia (BPD) remains the major morbidity of extreme preterm birth. The incidence of BPD has remained stable despite recent efforts to reduce postnatal exposures to volutrauma and hyperoxia. This review will focus on recent clinical and experimental insights that provide support for the concept that the 'new BPD' is the result of inflammation-mediated injury and altered lung development during a window of vulnerability in genetically susceptible infants that is modified by maternal and postnatal exposures.

Intra-amniotic LPS and antenatal betamethasone: inflammation and maturation in preterm lamb lungs

The proinflammatory stimulus of chorioamnionitis is commonly associated with preterm delivery. Women at risk of preterm delivery receive antenatal glucocorticoids to functionally mature the fetal lung. However, the effects of the combined exposures of chorioamnionitis and antenatal glucocorticoids on the fetus are poorly understood. Time-mated ewes with singleton fetuses received an intra-amniotic injection of lipopolysaccharide (LPS) either preceding or following maternal intramuscular betamethasone 7 or 14 days before delivery, and the fetuses were delivered at 120 days gestational age (GA) (term = 150 days GA). Gestation matched controls received intra-amniotic and maternal intramuscular saline. Compared with saline controls, intra-amniotic LPS increased inflammatory cells in the bronchoalveolar lavage and myeloperoxidase, Toll-like receptor 2 and 4 mRNA, PU.1, CD3, and Foxp3-positive cells in the fetal lung. LPS-induced lung maturation measured as increased airway surfactant and improved lung gas volumes. Intra-amniotic LPS-induced inflammation persisted until 14 days after exposure. Betamethasone treatment alone induced modest lung maturation but, when administered before intra-amniotic LPS, suppressed lung inflammation. Interestingly, betamethasone treatment after LPS did not counteract inflammation but enhanced lung maturation. We conclude that the order of exposures of intra-amniotic LPS or maternal betamethasone had large effects on fetal lung inflammation and maturation.