Inflammation-induced immune suppression of the fetus: a potential link between chorioamnionitis and postnatal early onset sepsis

Multipotent adult progenitor cells prevent functional impairment and improve development in inflammation driven detriment of preterm ovine lungs

Background

Perinatal inflammation increases the risk for bronchopulmonary dysplasia in preterm neonates, but the underlying pathophysiological mechanisms remain largely unknown. Given their anti-inflammatory and regenerative capacity, multipotent adult progenitor cells (MAPC) are a promising cell-based therapy to prevent and/or treat the negative pulmonary consequences of perinatal inflammation in the preterm neonate. Therefore, the pathophysiology underlying adverse preterm lung outcomes following perinatal inflammation and pulmonary benefits of MAPC treatment at the interface of prenatal inflammatory and postnatal ventilation exposures were elucidated.

Methods

Instrumented ovine fetuses were exposed to intra-amniotic lipopolysaccharide (LPS 5 mg) at 125 days gestation to induce adverse systemic and peripheral organ outcomes. MAPC (10 × 106 cells) or saline were administered intravenously two days post LPS exposure. Fetuses were delivered preterm five days post MAPC treatment and either killed humanely immediately or mechanically ventilated for 72 h.

Results

Antenatal LPS exposure resulted in inflammation and decreased alveolar maturation in the preterm lung. Additionally, LPS-exposed ventilated lambs showed continued pulmonary inflammation and cell junction loss accompanied by pulmonary edema, ultimately resulting in higher oxygen demand. MAPC therapy modulated lung inflammation, prevented loss of epithelial and endothelial barriers and improved lung maturation in utero. These MAPC-driven improvements remained evident postnatally, and prevented concomitant pulmonary edema and functional loss.

Conclusion

In conclusion, prenatal inflammation sensitizes the underdeveloped preterm lung to subsequent postnatal inflammation, resulting in injury, disturbed development and functional impairment. MAPC therapy partially prevents these changes and is therefore a promising approach for preterm infants to prevent adverse pulmonary outcomes.

Tdap vaccination during pregnancy and risk of chorioamnionitis and related infant outcomes

INTRODUCTION

An increased risk of chorioamnionitis in people receiving tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine during pregnancy has been reported. The importance of this association is unclear as additional study has not demonstrated increased adverse infant outcomes associated with Tdap vaccination in pregnancy.

METHODS

We conducted a retrospective observational cohort study of pregnant people ages 15-49 years with singleton pregnancies ending in live birth who were members of 8 Vaccine Safety Datalink (VSD) sites during October 2016-September 2018. We used a time-dependent covariate Cox model with stabilized inverse probability weights applied to evaluate associations between Tdap vaccination during pregnancy and chorioamnionitis and preterm birth outcomes. We used Poisson regression with robust variance with stabilized inverse probability weights applied to evaluate the association of Tdap vaccination with adverse infant outcomes. We performed medical record reviews on a random sample of patients with ICD-10-CM-diagnosed chorioamnionitis to determine positive predictive values (PPV) of coded chorioamnionitisfor "probable clinical chorioamnionitis," "possible clinical chorioamnionitis," or "histologic chorioamnionitis."

RESULTS

We included 118,211 pregnant people; 103,258 (87%) received Tdap vaccine during pregnancy; 8098 (7%) were diagnosed with chorioamnionitis. The adjusted hazard ratio for chorioamnionitis in the Tdap vaccine-exposed group compared to unexposed was 0.96 (95% CI 0.90-1.03). There was no association between Tdap vaccine and preterm birth or adverse infant outcomes associated with chorioamnionitis. Chart reviews were performed for 528 pregnant people with chorioamnionitis. The PPV for clinical (probable or possible clinical chorioamnionitis) was 48% and 59% for histologic chorioamnionitis. The PPV for the combined outcome of clinical or histologic chorioamnionitis was 81%.

CONCLUSIONS AND RELEVANCE

Tdap vaccine exposure during pregnancy was not associated with chorioamnionitis, preterm birth, or adverse infant outcomes. ICD-10 codes for chorioamnionitis lack specificity for clinical chorioamnionitis and should be a recognized limitation when interpreting results.

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.

Antenatal diagnosis of chorioamnionitis: A review of the potential role of fetal and placental imaging

Chorioamnionitis is present in up to 70% of spontaneous preterm births. It is defined as an acute inflammation of the chorion, with or without involvement of the amnion, and is evidence of a maternal immunological response to infection. A fetal inflammatory response can coexist and is diagnosed on placental histopathology postnatally. Fetal inflammatory response syndrome (FIRS) is associated with poorer fetal and neonatal outcomes. The only antenatal diagnostic test is amniocentesis which carries risks of miscarriage or preterm birth. Imaging of the fetal immune system, in particular the thymus and the spleen, and the placenta may give valuable information antenatally regarding the diagnosis of fetal inflammatory response. While ultrasound is largely limited to structural information, MRI can complement this with functional information that may provide insight into the metabolic activities of the fetal immune system and placenta. This review discusses fetal and placental imaging in pregnancies complicated by chorioamnionitis and their potential future use in achieving non-invasive antenatal diagnosis. This article is protected by copyright. All rights reserved.

Potential Benefits of Bovine Colostrum in Pediatric Nutrition and Health

Bovine colostrum (BC), the first milk produced from cows after parturition, is increasingly used as a nutritional supplement to promote gut function and health in other species, including humans. The high levels of whey and casein proteins, immunoglobulins (Igs), and other milk bioactives in BC are adapted to meet the needs of newborn calves. However, BC supplementation may improve health outcomes across other species, especially when immune and gut functions are immature in early life. We provide a review of BC composition and its effects in infants and children in health and selected diseases (diarrhea, infection, growth-failure, preterm birth, necrotizing enterocolitis (NEC), short-bowel syndrome, and mucositis). Human trials and animal studies (mainly in piglets) are reviewed to assess the scientific evidence of whether BC is a safe and effective antimicrobial and immunomodulatory nutritional supplement that reduces clinical complications related to preterm birth, infections, and gut disorders. Studies in infants and animals suggest that BC should be supplemented at an optimal age, time, and level to be both safe and effective. Exclusive BC feeding is not recommended for infants because of nutritional imbalances relative to human milk. On the other hand, adverse effects, including allergies and intolerance, appear unlikely when BC is provided as a supplement within normal nutrition guidelines for infants and children. Larger clinical trials in infant populations are needed to provide more evidence of health benefits when patients are supplemented with BC in addition to human milk or formula. Igs and other bioactive factors in BC may work in synergy, making it critical to preserve bioactivity with gentle processing and pasteurization methods. BC has the potential to become a safe and effective nutritional supplement for several pediatric subpopulations.

Chorioamnionitis induces hepatic inflammation and time-dependent changes of the enterohepatic circulation in the ovine fetus

Chorioamnionitis, inflammation of fetal membranes, is an important cause of preterm birth and a risk factor for the development of adverse neonatal outcomes including sepsis and intestinal pathologies. Intestinal bile acids (BAs) accumulation and hepatic cytokine production are involved in adverse intestinal outcomes. These findings triggered us to study the liver and enterohepatic circulation (EHC) following intra-amniotic (IA) lipopolysaccharide (LPS) exposure. An ovine chorioamnionitis model was used in which circulatory cytokines and outcomes of the liver and EHC of preterm lambs were longitudinally assessed following IA administration of 10 mg LPS at 5, 12 or 24h or 2, 4, 8 or 15d before preterm birth. Hepatic inflammation was observed, characterized by increased hepatic cytokine mRNA levels (5h - 2d post IA LPS exposure) and increased erythropoietic clusters (at 8 and 15 days post IA LPS exposure). Besides, 12h after IA LPS exposure, plasma BA levels were increased, whereas gene expression levels of several hepatic BA transporters were decreased. Initial EHC alterations normalized over time. Concluding, IA LPS exposure induces significant time-dependent changes in the fetal liver and EHC. These chorioamnionitis induced changes have potential postnatal consequences and the duration of IA LPS exposure might be essential herein.

Sex-Specific Survival, Growth, Immunity and Organ Development in Preterm Pigs as Models for Immature Newborns

Background: After very preterm birth, male infants show higher mortality than females, with higher incidence of lung immaturity, neurological deficits, infections, and growth failure. In modern pig production, piglets dying in the perinatal period (up to 20%) often show signs of immature organs, but sex-specific effects are not clear. Using preterm pigs as model for immature infants and piglets, we hypothesized that neonatal survival and initial growth and immune development depend on sex. Methods: Using data from a series of previous intervention trials with similar delivery and rearing procedures, we established three cohorts of preterm pigs (90% gestation), reared for 5, 9, or 19 days before sample collection (total n = 1,938 piglets from 109 litters). Partly overlapping endpoints among experiments allowed for multiple comparisons between males and females for data on mortality, body and organ growth, gut, immunity, and brain function. Results: Within the first 2 days, males showed higher mortality than females (18 vs. 8%, P < 0.001), but less severe immune response to gram-positive infection. No effect of sex was observed for thermoregulation or plasma cortisol. Later, infection resistance did not differ between sexes, but growth rate was reduced for body (up to -40%) and kidneys (-6%) in males, with higher leucocyte counts (+15%) and lower CD4 T cell fraction (-5%) on day 9 and lower monocyte counts (-18%, day 19, all P < 0.05). Gut structure, function and necrotizing enterocolitis (NEC) incidence were similar between groups, but intestinal weight (-3%) and brush-border enzyme activities were reduced at day 5 (lactase, DPP IV, -8%) in males. Remaining values for blood biochemistry, hematology, bone density, regional brain weights, and visual memory (tested in a T maze) were similar. Conclusion: Following preterm birth, male pigs show higher mortality and slower growth than females, despite limited differences in organ growth, gut, immune, and brain functions. Neonatal intensive care procedures may be particularly important for compromised newborns of the male sex. Preterm pigs can serve as good models to study the interactions of sex- and maturation-specific survival and physiological adaptation in mammals.

Association of Histological and Clinical Chorioamnionitis With Neonatal Sepsis Among Preterm Infants: A Systematic Review, Meta-Analysis, and Meta-Regression

Chorioamnionitis (CA) is considered a key risk factor for very preterm birth and for developing early onset sepsis (EOS) in preterm infants, but recent data suggest that CA might be protective against late onset sepsis (LOS). We performed a systematic review and meta-analysis of studies exploring the association between CA and sepsis. A comprehensive literature search was performed in PubMed/MEDLINE and EMBASE, from their inception to December 1, 2018. A random-effects model was used to calculate odds ratios (OR) and 95% confidence intervals (CI). Sources of heterogeneity were analyzed by subgroup and meta-regression analyses. The following categories of sepsis were analyzed: EOS, LOS, unspecified onset sepsis (UOS), culture-proven, and clinical sepsis. CA was subdivided into clinical and histological chorioamnionitis. Funisitis was also analyzed. We found 3,768 potentially relevant studies, of which 107 met the inclusion criteria (387,321 infants; 44,414 cases of CA). Meta-analysis showed an association between any CA and any EOS (OR 4.29, CI 3.63-5.06), any LOS (OR 1.29, CI 1.11-1.54), and any UOS (OR 1.59, CI 1.11-1.54). Subgroup analysis showed that CA was associated with culture-proven EOS (OR 4.69, CI 3.91-5.56), clinical EOS (OR 3.58, CI 1.90-6.76), and culture-proven LOS (OR 1.31, CI 1.12-1.53), but not with clinical LOS (OR 1.52, CI 0.78-2.96). The presence of funisitis did not increase the risk of either EOS or LOS when compared with CA without funisitis. CA-exposed infants had lower gestational age (-1.11 weeks, CI -1.37 to -0.84) than the infants not exposed to CA. Meta-regression analysis showed that the lower gestational age of the CA group correlated with the association between CA and LOS but not with the association between CA and EOS. In conclusion, our data suggest that the positive association between chorioamnionitis and LOS may be modulated by the effect of chorioamnionitis on gestational age.

Chronic Intra-Uterine Ureaplasma parvum Infection Induces Injury of the Enteric Nervous System in Ovine Fetuses

Background: Chorioamnionitis, inflammation of the fetal membranes during pregnancy, is often caused by intra-amniotic (IA) infection with single or multiple microbes. Chorioamnionitis can be either acute or chronic and is associated with adverse postnatal outcomes of the intestine, including necrotizing enterocolitis (NEC). Neonates with NEC have structural and functional damage to the intestinal mucosa and the enteric nervous system (ENS), with loss of enteric neurons and glial cells. Yet, the impact of acute, chronic, or repetitive antenatal inflammatory stimuli on the development of the intestinal mucosa and ENS has not been studied. The aim of this study was therefore to investigate the effect of acute, chronic, and repetitive microbial exposure on the intestinal mucosa, submucosa and ENS in premature lambs. Materials and Methods: A sheep model of pregnancy was used in which the ileal mucosa, submucosa, and ENS were assessed following IA exposure to lipopolysaccharide (LPS) for 2 or 7 days (acute), Ureaplasma parvum (UP) for 42 days (chronic), or repetitive microbial exposure (42 days UP with 2 or 7 days LPS). Results: IA LPS exposure for 7 days or IA UP exposure for 42 days caused intestinal injury and inflammation in the mucosal and submucosal layers of the gut. Repetitive microbial exposure did not further aggravate injury of the terminal ileum. Chronic IA UP exposure caused significant structural ENS alterations characterized by loss of PGP9.5 and S100β immunoreactivity, whereas these changes were not found after re-exposure of chronic UP-exposed fetuses to LPS for 2 or 7 days. Conclusion: The in utero loss of PGP9.5 and S100β immunoreactivity following chronic UP exposure corresponds with intestinal changes in neonates with NEC and may therefore form a novel mechanistic explanation for the association of chorioamnionitis and NEC.

Protection of the Ovine Fetal Gut against Ureaplasma-Induced Chorioamnionitis: A Potential Role for Plant Sterols

Chorioamnionitis, clinically most frequently associated with Ureaplasma, is linked to intestinal inflammation and subsequent gut injury. No treatment is available to prevent chorioamnionitis-driven adverse intestinal outcomes. Evidence is increasing that plant sterols possess immune-modulatory properties. Therefore, we investigated the potential therapeutic effects of plant sterols in lambs intra-amniotically (IA) exposed to Ureaplasma. Fetal lambs were IA exposed to Ureaplasma parvum (U. parvum, UP) for six days from 127 d-133 d of gestational age (GA). The plant sterols β-sitosterol and campesterol, dissolved with β-cyclodextrin (carrier), were given IA every two days from 122 d-131 d GA. Fetal circulatory cytokine levels, gut inflammation, intestinal injury, enterocyte maturation, and mucosal phospholipid and bile acid profiles were measured at 133 d GA (term 150 d). IA plant sterol administration blocked a fetal inflammatory response syndrome. Plant sterols reduced intestinal accumulation of proinflammatory phospholipids and tended to prevent mucosal myeloperoxidase-positive (MPO) cell influx, indicating an inhibition of gut inflammation. IA administration of plant sterols and carrier diminished intestinal mucosal damage, stimulated maturation of the immature epithelium, and partially prevented U. parvum-driven reduction of mucosal bile acids. In conclusion, we show that β-sitosterol and campesterol administration protected the fetus against adverse gut outcomes following UP-driven chorioamnionitis by preventing intestinal and systemic inflammation.

Repeated lipopolysaccharide exposure leads to placental endotoxin tolerance

PROBLEM

Placental infection induces increased levels of pro-inflammatory cytokines, which have been implicated in the pathogenesis of pre-term labor. Endotoxin tolerance is a phenomenon in which exposure to a dose of endotoxin makes tissue less responsive to subsequent exposures. The objective of our study was to determine whether repeated exposure to endotoxin will induce a tolerant phenotype in normal human second-trimester placental tissue.

METHODS OF STUDY

Human second-trimester placental explants from elective termination of pregnancy were cultured and exposed to endotoxin (LPS). After 24 hours, the media was collected for analysis, and the explants were re-exposed to LPS after adding fresh media for another 24 hours. This process was repeated for a total of 4 LPS doses. The media was collected from each day and analyzed for cytokine levels.

RESULTS

The first LPS treatment stimulated the secretion of the pro-inflammatory cytokines IL-1β and TNF-α. However, their production was significantly diminished with repeated LPS doses. Production of the anti-inflammatory cytokines, IL-1ra and IL-10, was also stimulated by the first LPS treatment, but secretion was more gradually and moderately decreased with repeated LPS doses compared to the pro-inflammatory cytokines. The ratios of the anti-inflammatory/pro-inflammatory mediators (IL-1ra/IL-1β and IL-10/TNF-α) indicate a progressively more anti-inflammatory milieu with repeated LPS doses.

CONCLUSION

Repeated LPS exposure of human second-trimester placental tissues induced endotoxin tolerance. We speculate that endotoxin tolerance at the maternal-fetal interface will protect the fetus from exaggerated inflammatory responses after repeated infectious exposure.

Prenatal Intra-Amniotic Endotoxin Induces Fetal Gut and Lung Immune Responses and Postnatal Systemic Inflammation in Preterm Pigs

Prenatal inflammation is a major risk for preterm birth and neonatal morbidity, but its effects on postnatal immunity and organ functions remain unclear. Using preterm pigs as a model for preterm infants, we investigated whether prenatal intra-amniotic (IA) inflammation modulates postnatal systemic immune status and organ functions. Preterm pigs exposed to IA lipopolysaccharide (LPS) for 3 days were compared with controls at birth and postnatal day 5 after formula feeding. IA LPS induced mild chorioamnionitis but extensive intra-amniotic inflammation. There were minor systemic effects at birth (increased blood neutrophil counts), but a few days later, prenatal LPS induced delayed neonatal arousal, systemic inflammation (increased blood leukocytes, plasma cytokines, and splenic bacterial counts), altered serum biochemistry (lower albumin and cholesterol and higher iron and glucose values), and increased urinary protein and sodium excretion. In the gut and lungs, IA LPS-induced inflammatory responses were observed mainly at birth (increased LPS, CXCL8, and IL-1β levels and myeloperoxidase-positive cell density, multiple increases in innate immune gene expressions, and reduced villus heights), but not on postnatal day 5 (except elevated lung CXCL8 and diarrhea symptoms). Finally, IA LPS did not affect postnatal gut brush-border enzymes, hexose absorption, permeability, or sensitivity to necrotizing enterocolitis on day 5. Short-term IA LPS exposure predisposes preterm pigs to postnatal systemic inflammation after acute fetal gut and lung inflammatory responses.

Infections in Pregnancy

Infections during pregnancy may affect a developing fetus. If left untreated, these infections can lead to the death of the mother, fetus, or neonate and other adverse sequelae. There are many factors that impact infection during pregnancy, such as the immune system changes during pregnancy, hormonal flux, stress, and the microbiome. We review some of the outcomes of infection during pregnancy, such as preterm birth, chorioamnionitis, meningitis, hydrocephaly, developmental delays, microcephaly, and sepsis. Transmission routes are discussed regarding how a pregnant woman may pass her infection to her fetus. This is followed by examples of infection during pregnancy: bacterial, viral, parasitic, and fungal infections. There are many known organisms that are capable of producing similar congenital defects during pregnancy; however, whether these infections share common mechanisms of action is yet to be determined. To protect the health of pregnant women and their offspring, additional research is needed to understand how these intrauterine infections adversely affect pregnancies and/or neonates in order to develop prevention strategies and treatments.

Genome-Wide Epigenetic Characterization of Tissues from Three Germ Layers Isolated from Sheep Fetuses

DNA methylation of regulatory and growth-related genes contributes to fetal programming which is important for maintaining the correct development of three germ layers of the embryo that develope into different tissues and organs, and which persists into adult life. In this study, a preliminary epigenetic screen was performed to define genomic regions that are involved in fetal epigenome remodeling. Embryonic ectodermic tissues (origin of nervous tissue), mesenchymal tissues (origin of connective and muscular tissues), and foregut endoderm tissues (origin of epithelial tissue), from day 28 sheep fetuses were collected and the distribution of methylated CpGs was analyzed using whole-genome bisulfite sequencing. Patterns of methylation among the three tissues showed a high level of conservation of hypo-methylated CpG islands CGIs, and a consistent level of methylation in regulatory genetic elements. Analysis of tissue specific differentially methylated regions, revealed that 20% of the total CGIs differed between tissues. A proportion of the methylome was remodeled in gene bodies, 5′ UTRs and 3′ UTRs (7, 11, and 11%, respectively). Genes with overlapping differentially methylated regions in gene bodies and CGIs showed a significant enrichment for tissue morphogenesis and development pathways. The data presented here provides a “reference” for the epigenetic status of genes potentially involved in the maintenance and regulation of fetal developmental during early life, a period expected to be particularly prone to epigenetic alterations induced by environmental and nutritional stressors.

Classic Galactosemia: Study on the Late Prenatal Development of GALT Specific Activity in a Sheep Model

Classic galactosemia results from deficient activity of galactose-1-phosphate uridylyltransferase (GALT), a key enzyme of galactose metabolism. Despite early diagnosis and early postnatal therapeutic intervention, patients still develop neurologic and fertility impairments. Prenatal developmental toxicity has been hypothesized as a determinant factor of disease. In order to shed light on the importance of prenatal GALT activity, several studies have examined GALT activity throughout development. GALT was shown to increase with gestational age in 7-28 weeks human fetuses; later stages were not investigated. Prenatal studies in animals focused exclusively on brain and hepatic GALT activity. In this study, we aim to examine GALT specific activity in late prenatal and adult stages, using a sheep model. Galactosemia acute target-organs-liver, small intestine and kidney-had the highest late prenatal activity, whereas the chronic target-organs-brain and ovary-did not exhibit a noticeable pre- or postnatal different activity compared with nontarget organs. This is the first study on GALT specific activity in the late prenatal stage for a wide variety of organs. Our findings suggest that GALT activity cannot be the sole pathogenic factor accounting for galactosemia long-term complications, and that some organs/cells might have a greater susceptibility to galactose toxicity. Anat Rec, 300:1570-1575, 2017. © 2017 Wiley Periodicals, Inc.

Maternal Tdap vaccination and risk of infant morbidity

INTRODUCTION

An increased risk of diagnosed chorioamnionitis in women vaccinated with Tdap during pregnancy was previously detected at two Vaccine Safety Datalink (VSD) sites. The clinical significance of this finding related to infant outcomes remains uncertain.

METHODS

Retrospective cohort study of singleton live births born to women who were continuously insured from 6months prior to their last menstrual period through 6weeks postpartum, with ≥1 outpatient visit during pregnancy from January 1, 2010 to November 15, 2013 at seven integrated United States health care systems part of the VSD. We re-evaluated the association between maternal Tdap and chorioamnionitis and evaluated whether specific infant morbidities differ among infants born to mothers who did and did not receive Tdap during pregnancy. We focused on 2 Tdap exposure windows: the recommended 27-36weeks gestation or anytime during pregnancy. We identified inpatient diagnostic codes for transient tachypnea of the newborn (TTN), neonatal sepsis, neonatal pneumonia, respiratory distress syndrome (RDS), and newborn convulsions associated with an infant's first hospitalization. A generalized linear model with Poisson distribution and log-link was used to estimate propensity score adjusted rate ratios (ARR) with 95% confidence intervals (CI).

RESULTS

The analyses included 197,564 pregnancies. Chorioamnionitis was recorded in 6.4% of women who received Tdap vaccination any time during pregnancy and 5.2% of women who did not (ARR [95% CI]: 1.23 [1.17, 1.28]). Compared with unvaccinated women, there were no significant increased risks (ARR [95% CI]) for TTN (1.04 [0.98, 1.11]), neonatal sepsis (1.06 [0.91, 1.23]), neonatal pneumonia (0.94 [0.72, 1.22]), RDS (0.91 [0.66, 1.26]), or newborn convulsions (1.16 [0.87, 1.53]) in infants born to Tdap-vaccinated women.

CONCLUSIONS AND RELEVANCE

Despite an observed association between maternal Tdap vaccination and maternal chorioamnionitis, we did not find increased risk for clinically significant infant outcomes associated with maternal chorioamnionitis.

Augmented Th17-type immune responses in preterm neonates exposed to histologic chorioamnionitis

BACKGROUND

Histologic chorioamnionitis (HCA) is a placental inflammatory disorder that frequently precedes preterm delivery. HCA increases risk for long-standing inflammatory injury and may influence immune programming, particularly in preterm (PT) neonates. We hypothesized that HCA exposure is associated with an increased circulating frequency of proinflammatory, Th17-type responses.

METHODS

Placental cord blood was collected from HCA-exposed or control neonates (23-41 wk gestation). Frequencies of Th17 and T regulatory (Treg) cells and assessments of Th17-type features in CD4 and Treg cells were determined by flow cytometric analysis.

RESULTS

Cord blood samples from 31 PT and 17 term neonates were analyzed by flow cytometry. A diagnosis of HCA in extremely PT (EPT, GA ≤ 30 wk) gestations was associated with the highest cord blood frequencies of progenitor (pTh17, CD4⁺CD161⁺) and mature (mTh17, CD4⁺CD161⁺CCR6⁺) Th17 cells. Preterm neonates exposed to HCA also exhibited elevated cord blood frequencies of IL-17⁺ Treg cells, as well as T cells with effector memory phenotype (TEM) that coexpressed Th17-type surface antigens.

CONCLUSION

Th17-type responses are amplified in preterm neonates exposed to HCA. We speculate that a Th17 bias may potentiate the inflammatory responses and related morbidity observed in preterm neonates whose immune systems have been "primed" by HCA exposure.

Fully automated predictive intelligent control of oxygenation (PRICO) in resuscitation and ventilation of preterm lambs

BACKGROUND

Hyperoxia and hypoxia influence morbidity and mortality of preterm infants. Automated closed-loop control of the fraction of inspired oxygen (FiO(2)) has been shown to facilitate oxygen supplementation in the neonatal intensive care unit (NICU), but has not yet been tested during preterm resuscitation. We hypothesized that fully automated FiO(2) control based on predefined oxygen saturation (SpO(2)) targets was applicable in both preterm resuscitation and ventilation.

METHODS

Twenty-two preterm lambs were operatively delivered and intubated in a modified EXIT procedure. They were randomized to receive standardized resuscitation with either automated or manual FiO(2) control, targeting SpO(2) according to the Dawson curve in the first 10 min and SpO(2) 90-95% hereafter. Automated FiO(2) control also was applied during surfactant replacement therapy and subsequent ventilation.

RESULTS

Time within target range did not differ significantly between manual and automated FiO(2) control during resuscitation, however automated FiO(2) control significantly avoided hyperoxia. Automated FiO(2) control was feasible during surfactant replacement and kept SpO(2) within target range significantly better than manual control during subsequent ventilation.

CONCLUSION

In our model, fully automated FiO(2) control was feasible in rapidly changing physiologic conditions during postnatal resuscitation and prevented hyperoxia. We conclude that closed loop FiO(2) control is a promising tool for the delivery room.

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.

Prophylactic Interleukin-2 Treatment Prevents Fetal Gut Inflammation and Injury in an Ovine Model of Chorioamnionitis

BACKGROUND

Chorioamnionitis results from an infection of the fetal membranes and is associated with fetal adverse outcomes notably in the intestine. Using a translational ovine model, we showed that intra-amniotic exposure to inflammatory stimuli decreased the regulatory/effector T (Treg/Teff) cell balance in the gut, which was accompanied by intestinal inflammation and mucosal injury. We thus aimed to augment the Treg/Teff cell ratio in the fetal gut by prophylactic IL-2 treatment and evaluate whether it is sufficient to prevent chorioamnionitis-induced intestinal inflammation and mucosal injury.

METHODS

Fetal sheep (122 d of gestation) were intra-amniotically exposed to lipopolysaccharide for 2 or 7 days with or without prophylactic IL-2 treatment (4 d). We evaluated the infiltration of inflammatory cells in the ileum and mesenteric lymph nodes. Cytokine gene expression was analyzed in fetal ileum and the inflammatory changes were correlated with gut wall integrity.

RESULTS

IL-2 administration preferentially increased intestinal Treg cells and thus the Treg/Teff cell ratio. Prophylactic IL-2 treatment reduced the lipopolysaccharide-induced influx of neutrophils and CD3(+) T cells and decreased the messenger RNA levels of proinflammatory cytokines including IL-6 and IL-17 in the fetal ileum. Importantly, prophylactic IL-2 treatment prevented mucosal damage without inducing fetal adverse treatment outcomes.

CONCLUSIONS

Our data show that prophylactic IL-2 treatment prevents fetal intestinal inflammation and mucosal injury in the context of experimental chorioamnionitis. Modulation of the Treg/Teff cell balance may contribute to the protective effects of IL-2.

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.

Propofol administration to the maternal-fetal unit improved fetal EEG and influenced cerebral apoptotic pathway in preterm lambs suffering from severe asphyxia

BACKGROUND

Term and near-term infants are at high risk of developing brain injury and life-long disability if they have suffered from severe perinatal asphyxia. We hypothesized that propofol administration to the maternal-fetal unit can diminish cerebral injury in term and near-term infant fetuses in states of progressive severe asphyxia.

METHODS

Forty-four late preterm lambs underwent total umbilical cord occlusion (UCO) or sham treatment in utero. UCO resulted in global asphyxia and cardiac arrest. After emergency cesarean section under either maternal propofol or isoflurane anesthesia, the fetuses were resuscitated and subsequently anesthetized the same way as their mothers.

RESULTS

Asphyctic lambs receiving isoflurane showed a significant increase of total and low-frequency spectral power in bursts indicating seizure activity and more burst-suppression with a marked increase of interburst interval length during UCO. Asphyctic lambs receiving propofol showed less EEG changes. Propofol increased levels of anti-apoptotic B-cell lymphoma-extra large (Bcl-xL) and phosphorylated STAT-3 and reduced the release of cytochrome c from the mitochondria and the protein levels of activated cysteinyl aspartate-specific protease (caspase)-3, -9, and N-methyl-d-aspartate (NMDA) receptor.

CONCLUSIONS

Improvement of fetal EEG during and after severe asphyxia could be achieved by propofol treatment of the ovine maternal-fetal unit. The underlying mechanism is probably the reduction of glutamate-induced cytotoxicity by down-regulation of NMDA receptors and an inhibition of the mitochondrial apoptotic pathway.

Comparison of airway responses in sheep of different age in precision-cut lung slices (PCLS)

Background

Animal models should display important characteristics of the human disease. Sheep have been considered particularly useful to study allergic airway responses to common natural antigens causing human asthma. A rationale of this study was to establish a model of ovine precision-cut lung slices (PCLS) for the in vitro measurement of airway responses in newborn and adult animals. We hypothesized that differences in airway reactivity in sheep are present at different ages.

Methods

Lambs were delivered spontaneously at term (147d) and adult sheep lived till 18 months. Viability of PCLS was confirmed by the MTT-test. To study airway provocations cumulative concentration-response curves were performed with different allergic response mediators and biogenic amines. In addition, electric field stimulation, passive sensitization with house dust mite (HDM) and mast cells staining were evaluated.

Results

PCLS from sheep were viable for at least three days. PCLS of newborn and adult sheep responded equally strong to methacholine and endothelin-1. The responses to serotonin, leukotriene D₄ and U46619 differed with age. No airway contraction was evoked by histamine, except after cimetidine pretreatment. In response to EFS, airways in PCLS from adult and newborn sheep strongly contracted and these contractions were atropine sensitive. Passive sensitization with HDM evoked a weak early allergic response in PCLS from adult and newborn sheep, which notably was prolonged in airways from adult sheep. Only few mast cells were found in the lungs of non-sensitized sheep at both ages.

Conclusion

PCLS from sheep lungs represent a useful tool to study pharmacological airway responses for at least three days. Sheep seem well suited to study mechanisms of cholinergic airway contraction. The notable differences between newborn and adult sheep demonstrate the importance of age in such studies.

Intestinal fatty acid-binding protein: a possible marker for gut maturation

BACKGROUND

Gut immaturity is linked with postnatal intestinal disorders. However, biomarkers to assess the intestinal developmental stage around birth are lacking. The aim of this study was to gain more insight on intestinal fatty acid-binding protein (I-FABP) as an indicator of gut maturity.

METHODS

Antenatal I-FABP distribution and release was investigated in extremely premature, moderately premature, and term lambs, and these findings were verified in human urinary samples. Ileal I-FABP distribution was confirmed in autopsy material within 24 h postnatally.

RESULTS

Median (range) serum I-FABP levels were lower in extremely premature lambs compared with moderately premature lambs (156 (50.0-427) vs. 385 (100-1,387) pg/ml; P = 0.02). Contrarily, median early postnatal urine I-FABP levels in human infants were higher in extremely premature compared with moderately premature and term neonates (1,219 (203-15,044) vs. 256 (50-1,453) and 328 (96-1,749) pg/ml; P = 0.008 and P = 0.04, respectively). I-FABP expression was most prominent in nonvacuolated enterocytes and increased with rising gestational age (GA) in ovine and human tissue samples. The epithelial distribution pattern changed from a phenotype displaying I-FABP-positive enterocytes merely in the crypts early in gestation into a phenotype with I-FABP expressing cells exclusively present in the villus tips at term in ovine and human tissue.

CONCLUSION

In this ovine and human study, increasing GA is accompanied by an increase in I-FABP tissue content. Cord I-FABP levels correlate with gestation in ovine fetuses, identifying I-FABP as a marker for gut maturation. Raised postnatal urine I-FABP levels in preterm human infants may indicate intestinal injury and/or inflammation in utero.

Prenatal inflammation is associated with adverse neonatal outcomes

OBJECTIVE

The purpose of this study was to determine whether prenatal inflammation (as assessed by clinical chorioamnionitis, maternal temperature >38°C, or histologic chorioamnionitis) is associated with a composite adverse neonatal outcome.

STUDY DESIGN

We performed a prospective cohort study of women at 22 weeks to 33 weeks 6 days' gestation with symptoms of labor (April 2009 to March 2012). Relevant maternal and neonatal exposures and outcomes were recorded. Multivariable logistic regression was performed to determine the association between prenatal inflammation and neonatal outcomes that were controlled for potential confounders.

RESULTS

We analyzed 871 mother-infant pairs. The preterm birth rate was 42.0%. When we controlled for infant sex and modified the data by gestational age at delivery, prenatal inflammation remains a significant risk factor for adverse neonatal outcomes, despite advancing gestational age: clinical chorioamnionitis at 32 weeks' gestation (odds ratio [OR], 3.12; 95% confidence interval [CI], 1.02-9.52], at 36 weeks' gestation (OR, 8.88; 95% CI, 4.32-18.25), and at 40 weeks' gestation (OR, 25.30; 95% CI, 9.25-69.19); maternal temperature >38°C at 32 weeks' gestation (OR, 3.18; 95% CI, 0.66-15.42), at 36 weeks gestation (OR, 8.40; 95% CI, 3.60-19.61), and at 40 weeks gestation (OR, 22.19; 95% CI, 8.15-60.44); histologic chorioamnionitis at 32 weeks gestation (OR, 1.25; 95% CI, 0.64-2.46), at 36 weeks gestation (OR, 2.56; 95% CI, 1.54-4.23), and at 40 weeks gestation (OR, 5.23; 95% CI, 1.95-13.99).

CONCLUSION

The protective association with advancing gestational age is diminished when prenatal inflammation is present.

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.

Altered canonical Wingless-Int signaling in the ovine fetal lung after exposure to intra-amniotic lipopolysaccharide and antenatal betamethasone

BACKGROUND

Antenatal inflammation and maternal corticosteroids induce fetal lung maturation but interfere with late lung development. Canonical Wingless-Int (Wnt) signaling directs lung development and repair. We showed that intra-amniotic (IA) lipopolysaccharide (LPS) exposure disrupted developmental signaling pathways in the preterm lamb lungs. Therefore, we hypothesized that pulmonary Wnt signaling was altered by exposure to IA LPS and/or antenatal corticosteroids.

METHODS

Ovine fetuses were exposed to IA LPS, maternal intramuscular betamethasone, a control saline injection, or a combination thereof at 107 and/or 114 d gestational age (term = 150 d gestational age) before delivery at 121 d gestational age.

RESULTS

IA LPS exposure decreased the lung expression of lymphoid enhancer-binding factor 1 (LEF1), a major Wnt pathway effector. WNT1, WNT4, and downstream messenger β-catenin decreased after LPS exposure. WNT7b mRNA increased fourfold 14 d post-LPS exposure. Betamethasone treatment 7 d before LPS exposure prevented the reduction in LEF1 expression, whereas betamethasone administration after LPS normalized the LPS-induced increase in Wnt7b mRNA.

CONCLUSION

IA LPS exposure decreased canonical Wnt signaling in the developing lung. Antenatal corticosteroids before or after IA inflammation had different effects on pulmonary Wnt signaling. This study provides new insights into possible mechanisms by which prenatal inflammation affects lung development and how corticosteroid can be beneficial in this setting.

Soluble ST2, a modulator of the inflammatory response, in preterm and term labor

OBJECTIVE

Intra-amniotic infection/inflammation (IAI) is causally linked with spontaneous preterm labor and delivery. The ST2L receptor and its soluble form (sST2) are capable of binding to interleukin (IL)-33, a member of the IL-1 superfamily. Members of this cytokine family have been implicated in the onset of spontaneous preterm labor in the context of infection. Soluble ST2 has anti-inflammatory properties, and plasma concentrations are elevated in systemic inflammation, such as sepsis, acute pyelonephritis in pregnancy and the fetal inflammatory response syndrome. The aims of this study were to examine: (1) whether amniotic fluid concentrations of sST2 change with IAI, preterm, and term parturition; and (2) if mRNA expression of ST2 in the chorioamniotic membranes changes with acute histologic chorioamnionitis in women who deliver preterm.

METHOD

A cross-sectional study was conducted to determine amniotic fluid concentrations of sST2 in: (1) women with preterm labor (PTL) who delivered at term (n=49); (2) women with PTL who delivered preterm without IAI (n=21); (3) women with PTL who delivered preterm with IAI (n=31); (4) term pregnancies not in labor (n=13); and (5) term pregnancies in labor (n=43). The amniotic fluid concentration of sST2 was determined by ELISA. The mRNA expression of ST2 in the chorioamniotic membranes of women who delivered preterm with (n=24), and without acute histologic chorioamnionitis (n=19) was determined by qRT-PCR.

RESULTS

(1) Patients with PTL who delivered preterm with IAI had a lower median amniotic fluid concentration of sST2 compared to those with PTL who delivered preterm without IAI [median 410 ng/mL, inter-quartile range (IQR) 152-699 ng/mL versus median 825 ng/mL, IQR 493-1216 ng/mL; p=0.0003] and those with PTL who delivered at term [median 410 ng/mL, IQR 152-699 ng/mL versus median 673 ng/mL, IQR 468-1045 ng/mL; p=0.0003]; (2) no significant differences in the median amniotic fluid concentration of sST2 were observed between patients with PTL who delivered at term and those who delivered preterm without IAI (p=0.4), and between women at term in labor and those at term not in labor (p=0.9); (3) the mean mRNA expression of ST2 was 4-fold lower in women who delivered preterm with acute histologic chorioamnionitis than in those without this lesion (p=0.008).

CONCLUSIONS

The median sST2 amniotic fluid concentration and mRNA expression of ST2 by chorioamniotic membranes is lower in PTL associated with IAI and acute histologic chorioamnionitis than in PTL without these conditions. Changes in the median amniotic fluid sST2 concentration are not observed in preterm and term parturition without IAI. Thus, amniotic fluid sST2 in the presence of IAI behaves differently when compared to sST2 in the plasma of individuals affected by fetal inflammatory response syndrome, acute pyelonephritis in pregnancy, and adult sepsis. Decreased concentrations of sST2 in IAI are likely to promote a pro-inflammatory response, which is important for parturition in the context of infection.

Systemic G-CSF attenuates cerebral inflammation and hypomyelination but does not reduce seizure burden in preterm sheep exposed to global hypoxia-ischemia

Hypoxic-ischemic encephalopathy (HIE) is common in preterm infants, but currently no curative therapy is available. Cell-based therapy has a great potential in the treatment of hypoxic-ischemic preterm brain injury. Granulocyte-colony stimulating factor (G-CSF) is known to mobilize endogenous hematopoietic stem cells (HSC) and promotes proliferation of endogenous neural stem cells. On these grounds, we hypothesized that systemic G-CSF would be neuroprotective in a large translational animal model of hypoxic-ischemic injury in the preterm brain. Global hypoxia-ischemia (HI) was induced by transient umbilical cord occlusion in instrumented preterm sheep. G-CSF treatment (100μg/kg intravenously, during five consecutive days) was started one day before the global HI insult to ascertain mobilization of endogenous stem cells within the acute phase after global HI. Mobilization of HSC and neutrophils was studied by flow cytometry. Brain sections were stained for microglia (IBA-1), myelin basic protein (MBP) and myeloperoxidase (MPO) to study microglial proliferation, white matter injury and neutrophil invasion respectively. Electrographic seizure activity was analyzed using amplitude-integrated electroencephalogram (aEEG). G-CSF effectively mobilized CD34-positive HSC in the preterm sheep. In addition, G-CSF caused marked mobilization of neutrophils, but did not influence enhanced invasion of neutrophils into the preterm brain after global HI. Microglial proliferation and hypomyelination following global HI were reduced as a result of G-CSF treatment. G-CSF did not cause a reduction of the electrographic seizure activity after global HI. In conclusion, G-CSF induced mobilization of endogenous stem cells which was associated with modulation of the cerebral inflammatory response and reduced white matter injury in an ovine model of preterm brain injury after global HI. G-CSF treatment did not improve neuronal function as shown by seizure analysis. Our study shows that G-CSF treatment has neuroprotective potential following hypoxic-ischemic injury in the preterm brain.

Mesenchymal stem cells induce T-cell tolerance and protect the preterm brain after global hypoxia-ischemia

Hypoxic-ischemic encephalopathy (HIE) in preterm infants is a severe disease for which no curative treatment is available. Cerebral inflammation and invasion of activated peripheral immune cells have been shown to play a pivotal role in the etiology of white matter injury, which is the clinical hallmark of HIE in preterm infants. The objective of this study was to assess the neuroprotective and anti-inflammatory effects of intravenously delivered mesenchymal stem cells (MSC) in an ovine model of HIE. In this translational animal model, global hypoxia-ischemia (HI) was induced in instrumented preterm sheep by transient umbilical cord occlusion, which closely mimics the clinical insult. Intravenous administration of 2 x 10(6) MSC/kg reduced microglial proliferation, diminished loss of oligodendrocytes and reduced demyelination, as determined by histology and Diffusion Tensor Imaging (DTI), in the preterm brain after global HI. These anti-inflammatory and neuroprotective effects of MSC were paralleled by reduced electrographic seizure activity in the ischemic preterm brain. Furthermore, we showed that MSC induced persistent peripheral T-cell tolerance in vivo and reduced invasion of T-cells into the preterm brain following global HI. These findings show in a preclinical animal model that intravenously administered MSC reduced cerebral inflammation, protected against white matter injury and established functional improvement in the preterm brain following global HI. Moreover, we provide evidence that induction of T-cell tolerance by MSC might play an important role in the neuroprotective effects of MSC in HIE. This is the first study to describe a marked neuroprotective effect of MSC in a translational animal model of HIE.

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).

Functional impairment of the auditory pathway after perinatal asphyxia and the short-term effect of perinatal propofol anesthesia in lambs

BACKGROUND

Sensorineural hearing loss (SNHL) is a common feature in the postasphyxial syndrome in newborns. Several anesthetic drugs have been proposed to attenuate secondary neuronal injury elicited by hypoxia-ischemia. We hypothesized that propofol anesthesia reduces auditory impairment after perinatal asphyxia in comparison with isoflurane.

METHODS

Twenty-three pregnant ewes were randomized to propofol or isoflurane anesthesia and sedation. The lambs underwent in utero umbilical cord occlusion (isoflurane n = 5; propofol n = 7) and were compared with sham-treated animals (isoflurane n = 5; propofol n = 6) at a gestational age of 133 d. For 8 h after delivery by cesarean section, repeated auditory brainstem responses (ABRs) were recorded to obtain hearing thresholds, peak amplitudes, latencies, and interpeak latencies.

RESULTS

Significantly elevated mean thresholds, diminished amplitudes, and elevated latencies were observed in the asphyxia group relative to the control group through the observation period. Comparison of anesthetic treatment in the asphyxia group revealed a significantly lower elevation in threshold and less impairment in the ABR amplitudes and latencies during propofol anesthesia as compared with isoflurane anesthesia.

CONCLUSION

Our results support the hypothesis that anesthesia with propofol has a preventive effect on the functional changes to the auditory pathway in the event of perinatal asphyxia.

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.

Cerebral inflammation and mobilization of the peripheral immune system following global hypoxia-ischemia in preterm sheep

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most important causes of brain injury in preterm infants. Preterm HIE is predominantly caused by global hypoxia-ischemia (HI). In contrast, focal ischemia is most common in the adult brain and known to result in cerebral inflammation and activation of the peripheral immune system. These inflammatory responses are considered to play an important role in the adverse outcomes following brain ischemia. In this study, we hypothesize that cerebral and peripheral immune activation is also involved in preterm brain injury after global HI.

METHODS

Preterm instrumented fetal sheep were exposed to 25 minutes of umbilical cord occlusion (UCO) (n = 8) at 0.7 gestation. Sham-treated animals (n = 8) were used as a control group. Brain sections were stained for ionized calcium binding adaptor molecule 1 (IBA-1) to investigate microglial proliferation and activation. The peripheral immune system was studied by assessment of circulating white blood cell counts, cellular changes of the spleen and influx of peripheral immune cells (MPO-positive neutrophils) into the brain. Pre-oligodendrocytes (preOLs) and myelin basic protein (MBP) were detected to determine white matter injury. Electro-encephalography (EEG) was recorded to assess functional impairment by interburst interval (IBI) length analysis.

RESULTS

Global HI resulted in profound activation and proliferation of microglia in the hippocampus, periventricular and subcortical white matter. In addition, non-preferential mobilization of white blood cells into the circulation was observed within 1 day after global HI and a significant influx of neutrophils into the brain was detected 7 days after the global HI insult. Furthermore, global HI resulted in marked involution of the spleen, which could not be explained by increased splenic apoptosis. In concordance with cerebral inflammation, global HI induced severe brain atrophy, region-specific preOL vulnerability, hypomyelination and persistent suppressed brain function.

CONCLUSIONS

Our data provided evidence that global HI in preterm ovine fetuses resulted in profound cerebral inflammation and mobilization of the peripheral innate immune system. These inflammatory responses were paralleled by marked injury and functional loss of the preterm brain. Further understanding of the interplay between preterm brain inflammation and activation of the peripheral immune system following global HI will contribute to the development of future therapeutic interventions in preterm HIE.

Intraamniotic lipopolysaccharide exposure changes cell populations and structure of the ovine fetal thymus

RATIONALE

Chorioamnionitis induces preterm delivery and acute involution of the fetal thymus which is associated with postnatal inflammatory disorders. We studied the immune response, cell composition, and architecture of the fetal thymus following intraamniotic lipopolysaccharide (LPS) exposure.

METHODS

Time-mated ewes received an intraamniotic injection of LPS 5, 12, or 24 hours or 2, 4, 8, or 15 days before delivery at 125 days gestational age (term = 150 days).

RESULTS

The LPS exposure resulted in decreased blood lymphocytes within 5 hours and decreased thymic corticomedullary ratio within 24 hours. Thymic interleukin 6 (IL6) and IL17 messenger RNA (mRNA) increased 5-fold 24 hours post-LPS exposure. Increased toll-like receptor 4 (TLR4) mRNA and nuclear factor κB positive cells at 24 hours after LPS delivery demonstrated acute thymic activation. Both TLR4 and IL1 mRNA increased by 5-fold and the number of Foxp3-positive cells (Foxp3+ cells) decreased 15 days after exposure.

CONCLUSION

Intraamniotic LPS exposure caused a proinflammatory response, involution, and a persistent depletion of thymic Foxp3+ cells indicating disturbance of the fetal immune homeostasis.