Endotoxin-induced lung maturation in preterm lambs is not mediated by cortisol

LPCAT1 levels in the placenta, the maternal plasma and the fetal plasma do not predict fetal lung responses to glucocorticoids in a sheep model of pregnancy

INTRODUCTION

Lysophosphatidylcholine acyltransferase 1 (LPCAT1) is important for saturated phosphatidylcholine (Sat-PC) production in the lung. Sat-PC is a critical component of pulmonary surfactant, which maintains low alveolar surface tension, facilitating respiration. Previous studies have reported an association between maternal and fetal LPCAT1 levels and neonatal lung function. Using a sheep model of pregnancy, we investigated a potential correlation between glucocorticoid-induced lung maturation and LPCAT1 mRNA and/or protein levels in the fetal lung, the placenta, the fetal plasma, and the maternal plasma.

METHODS

Eighty seven single pregnant ewes received maternal intramuscular injections of betamethasone. A sub-group of five animals had both maternal and fetal catheters installed to allow for sequential sampling from both plasma compartments. Lambs were surgically delivered under terminal anaesthesia between 2 and 8 days after initial ANS treatment, at a gestational age of 121-123 days. Lambs were ventilated for 30 min to determine functional lung maturation before being euthanized for necropsy and sample collection. Fetal lung, placenta, and fetal and maternal plasma samples were used to analyse LPCAT1 gene expression and protein levels.

RESULTS

The expression of LPCAT1 mRNA in the fetal lung was significantly corelated to Sat-PC levels at 8 days (R² = 0.23, p < 0.001) and lung maturation status overall (gas exchange efficiency as determined by measurements of lamb PaCO₂ during ventilation, R² = 0.20, p < 0.001). Similarly, fetal lung LPCAT1 mRNA was also significantly correlated with the individual durability of ANS effects on fetal lung maturation (R² = 0.20, p < 0.001). Although ANS therapy altered LPCAT1 mRNA expression in the placenta, observed changes were independent of fetal lung maturation outcomes. Neither maternal nor fetal plasma LPCAT1 levels were changed by ANS therapy over the period, including in analysis of serial maternal and fetal samples from chronically catheterised animals.

DISCUSSION

LPCAT1 expression in the fetal lung was associated with the durability of glucocorticoid effects on fetal lung maturation. However, LPCAT1 expression in the placenta, the fetal plasma, and the maternal plasma was neither associated with, nor predictive of fetal lung maturation after glucocorticoid treatment in a sheep model of pregnancy.

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

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

Lamellar body count: Marker for foetal lung maturation promoted by intra-amniotic infection and/or inflammation

OBJECTIVE

There is evidence indicating that the risk of respiratory distress syndrome is reduced in preterm neonates exposed to intra-amniotic infection and/or inflammation. We hypothesised that foetal lung maturation promoted by intra-amniotic infection and/or inflammation results in elevated lamellar body count (LBC) in amniotic fluid (AF). This study aimed to determine the relationship between LBC in AF and intra-amniotic infection and/or inflammation in patients with threatened preterm birth.

STUDY DESIGN

This was a retrospective cohort study of patients with threatened preterm birth. A total of 104 consecutive pregnant women underwent amniocentesis in the early preterm period [gestational age < 34 weeks] to evaluate intra-amniotic infection and/or inflammation and foetal lung maturity. Intra-amniotic infection was confirmed by positive AF culture results for aerobic/anaerobic bacteria, fungi, and genital mycoplasma. Intra-amniotic inflammation was defined as a positive AF matrix metalloproteinase-8 rapid test. Outcomes of the study population were compared according to LBC in AF using a cut-off of 15,000/mm³.

RESULTS

The rates of elevated LBC and intra-amniotic infection and/or inflammation were 23% (24/104) and 52% (54/104), respectively. The median LBC was significantly higher in patients with intra-amniotic infection and/or inflammation than in those without [median LBC, 9,000/mm³ (interquartile range, IQR: 3,000-39,000) vs. 3,000/mm³ (IQR: 2,750-5,000), p < 0.001]. Intra-amniotic infection and/or inflammation was observed in 96% (23/24) of patients with elevated LBC and 39% (31/80) of patients without elevated LBC (p < 0.001). On multivariable analysis, the presence of intra-amniotic infection and/or inflammation was significantly associated with elevated LBC with an odds ratio (OR) of 66.0 [95% confidence interval (CI) 6.6-664.4, p < 0.001], even after accounting for gestational age at amniocentesis being a significantly related factor for predicting elevated LBC with an OR of 1.5 (95% CI 1.1-2.0, p = 0.004).

CONCLUSION

LBC elevation was independently associated with the presence of intra-amniotic infection and/or inflammation in women with early threatened preterm birth (gestational age < 34 weeks). This finding may support the view that an intra-amniotic inflammatory response promotes foetal lung maturation that can be detected by elevated LBC in AF.

Continuous but not pulsed low-dose fetal betamethasone exposures extend the durability of antenatal steroid therapy

Antenatal steroid (ANS) therapy is standard care for women at imminent risk of preterm labor. Despite extensive and long-standing use, 40-50% of babies exposed antenatally to steroids do not derive benefit; remaining undelivered 7d or more after ANS treatment is associated with a lack of treatment benefit, and increased risk of harms. We used a pregnant sheep model to evaluate the impact of continuous vs. pulsed ANS treatments on fetal lung maturation at an extended, eight-day treatment to delivery interval. Continuous low-dose ANS treatments for more than 72 hours in duration improved fetal lung maturation at eight days after treatment initiation. If fetal ANS exposure was interrupted, the beneficial ANS effect was lost. Truncated treatments, including that simulating the current clinical treatment regimen, did not improve lung function. Variable fetal lung maturation was correlated to the amount of saturated phosphatidylcholine present in the lung fluid. These data demonstrate that: i) the durability of ANS therapy may be enhanced by employing an extended, low-dose treatment regimen with reducing total dose; and ii) interrupting the continuity of fetal exposure by allowing it to fall below a minimal threshold was associated with comparably poor functional maturation of the preterm ovine lung.

Chorioamnionitis alters lung surfactant lipidome in newborns with respiratory distress syndrome

BACKGROUND

Chorioamnionitis is associated with preterm delivery and morbidities; its role in lung disease is controversial. The aim of this study is to assess the effect of chorioamnionitis on metabolite and lipid profiles of epithelial lining fluid in preterm newborns with respiratory distress syndrome (RDS).

METHODS

The study involved 30 newborns with RDS, born from mothers with or without histological chorioamnionitis (HCA): HCA+, N = 10; HCA-, N = 20. Patients had a gestational age ≤30 weeks; the groups were matched for age and birth weights. Tracheal aspirates were collected within 24 h after birth and analyzed using liquid chromatography/mass spectrometry-based untargeted lipidomics.

RESULTS

According to Mann-Whitney U tests, 570 metabolite features had statistically significantly higher or lower concentrations (p < 0.05) in tracheal aspirates of HCA+ compared to HCA-, and 241 metabolite features were putatively annotated and classified. The most relevant changes involved higher levels of glycerophospholipids (fold change 2.42-17.69) and sphingolipids, with lower concentration of all annotated sphingomyelins in HCA+ (fold change 0.01-0.50).

CONCLUSIONS

Untargeted lipidomics of tracheal aspirates suggested the production of lipid mediators in the context of an ongoing inflammatory status in HCA+ babies. However, the effect of chorioamnionitis on epithelial lining fluid composition deserves further investigations on a larger group of infants.

IMPACT

Our lipidomics investigation on tracheal aspirates of preterm newborns at birth suggested that exposure to maternal histological chorioamnionitis may cause changes in epithelial lining fluid composition. This is the first description of epithelial lining fluid lipidomic profiles in preterm infants with and without exposition to chorioamnionitis. These results could provide novel link between placental membrane inflammation and newborns' respiratory outcome.

Sequential Exposure to Antenatal Microbial Triggers Attenuates Alveolar Growth and Pulmonary Vascular Development and Impacts Pulmonary Epithelial Stem/Progenitor Cells

Perinatal inflammatory stress is strongly associated with adverse pulmonary outcomes after preterm birth. Antenatal infections are an essential perinatal stress factor and contribute to preterm delivery, induction of lung inflammation and injury, pre-disposing preterm infants to bronchopulmonary dysplasia. Considering the polymicrobial nature of antenatal infection, which was reported to result in diverse effects and outcomes in preterm lungs, the aim was to examine the consequences of sequential inflammatory stimuli on endogenous epithelial stem/progenitor cells and vascular maturation, which are crucial drivers of lung development. Therefore, a translational ovine model of antenatal infection/inflammation with consecutive exposures to chronic and acute stimuli was used. Ovine fetuses were exposed intra-amniotically to Ureaplasma parvum 42 days (chronic stimulus) and/or to lipopolysaccharide 2 or 7 days (acute stimulus) prior to preterm delivery at 125 days of gestation. Pulmonary inflammation, endogenous epithelial stem cell populations, vascular modulators and morphology were investigated in preterm lungs. Pre-exposure to UP attenuated neutrophil infiltration in 7d LPS-exposed lungs and prevented reduction of SOX-9 expression and increased SP-B expression, which could indicate protective responses induced by re-exposure. Sequential exposures did not markedly impact stem/progenitors of the proximal airways (P63+ basal cells) compared to single exposure to LPS. In contrast, the alveolar size was increased solely in the UP+7d LPS group. In line, the most pronounced reduction of AEC2 and proliferating cells (Ki67+) was detected in these sequentially UP + 7d LPS-exposed lambs. A similar sensitization effect of UP pre-exposure was reflected by the vessel density and expression of vascular markers VEGFR-2 and Ang-1 that were significantly reduced after UP exposure prior to 2d LPS, when compared to UP and LPS exposure alone. Strikingly, while morphological changes of alveoli and vessels were seen after sequential microbial exposure, improved lung function was observed in UP, 7d LPS, and UP+7d LPS-exposed lambs. In conclusion, although sequential exposures did not markedly further impact epithelial stem/progenitor cell populations, re-exposure to an inflammatory stimulus resulted in disturbed alveolarization and abnormal pulmonary vascular development. Whether these negative effects on lung development can be rescued by the potentially protective responses observed, should be examined at later time points.

Budesonide with surfactant decreases systemic responses in mechanically ventilated preterm lambs exposed to fetal intra-amniotic lipopolysaccharide

BACKGROUND

Chorioamnionitis is associated with increased rates of bronchopulmonary dysplasia (BPD) in ventilated preterm infants. Budesonide when added to surfactant decreased lung and systemic inflammation from mechanical ventilation in preterm lambs and decreased the rates and severity of BPD in preterm infants. We hypothesized that the addition of budesonide to surfactant will decrease the injury from mechanical ventilation in preterm lambs exposed to intra-amniotic (IA) lipopolysaccharide (LPS).

METHODS

Lambs at 126 ± 1 day GA received LPS 10 mg IA 48 h prior to injurious mechanical ventilation. After 15 min, lambs received either surfactant mixed with: (1) saline or (2) Budesonide 0.25 mg/kg, then ventilated with normal tidal volumes for 4 h. Injury markers in the lung, liver, and brain were compared.

RESULTS

Compared with surfactant alone, the addition of budesonide improved blood pressures, dynamic compliance, and ventilation, while decreasing mRNA for pro-inflammatory cytokines in the lung, liver, and multiple areas of the brain. LPS caused neuronal activation and structural changes in the brain that were not altered by budesonide. Budesonide was not retained within the lung beyond 4 h.

CONCLUSIONS

In preterm lambs exposed to IA LPS, the addition of budesonide to surfactant improved physiology and markers of lung and systemic inflammation.

IMPACT

The addition of budesonide to surfactant decreases the lung and systemic responses to injurious mechanical ventilation preterm lambs exposed to fetal LPS. Budesonide was present in the plasma by 15 min and the majority of the budesonide is no longer in the lung at 4 h of ventilation. IA LPS and mechanical ventilation caused structural changes in the brain that were not altered by short-term exposure to budesonide. The budesonide dose of 0.25 mg/kg being used clinically seems likely to decrease lung inflammation in preterm infants with chorioamnionitis.

The protective effect of CXC chemokine receptor 2 antagonist on experimental bronchopulmonary dysplasia induced by postnatal systemic inflammation

BACKGROUND

Animal studies have shown that a leukocyte influx precedes the development of bronchopulmonary dysplasia (BPD) in premature sheep. The CXC chemokine receptor 2 (CXCR2) pathway has been implicated in the pathogenesis of BPD because of the predominance of CXCR2 ligands in tracheal aspirates of preterm infants who later developed BPD.

PURPOSE

To test the effect of CXCR2 antagonist on postnatal systemic and pulmonary inflammation and alveolarization in a newborn Sprague-Dawley rat model of BPD.

METHODS

Lipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into the newborn rats on postnatal day 1 (P1), P3, and P5 to induce systemic inflammation and inhibit alveolarization. In the same time with LPS administration, CXCR2 antagonist (SB-265610) or vehicle was injected i.p. to investigate whether CXCR2 antagonist can alleviate the detrimental effect of LPS on alveolarization by attenuating inflammation. On P7 and P14, bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) were collected from the pups. To assess alveolarization, mean cord length and alveolar surface area were measured on 4 random nonoverlapping fields per animal in 2 distal lung sections at ×100 magnification.

RESULTS

Early postnatal LPS administration significantly increased neutrophil counts in BALF and PB and inhibited alveolarization, which was indicated by a greater mean cord length and lesser alveolar surface area. CXCR2 antagonist significantly attenuated the increase of neutrophil counts in BALF and PB and restored alveolarization as indicated by a decreased mean cord length and increased alveolar surface area in rat pups exposed to early postnatal systemic LPS.

CONCLUSION

CXCR2 antagonist preserved alveolarization by alleviating pulmonary and systemic inflammation induced by early postnatal systemic LPS administration. These results suggest that CXCR2 antagonist can be considered a potential therapeutic agent for BPD that results from disrupted alveolarization induced by inflammation.

Prenatal inflammation enhances antenatal corticosteroid-induced fetal lung maturation

Respiratory complicˆations are the major cause of morbidity and mortality among preterm infants, which is partially prevented by the administration of antenatal corticosteroids (ACS). Most very preterm infants are exposed to chorioamnionitis, but short- and long-term effects of ACS treatment in this setting are not well defined. In low-resource settings, ACS increased neonatal mortality by perhaps increasing infection. We report that treatment with low-dose ACS in the setting of inflammation induced by intraamniotic lipopolysaccharide (LPS) in rhesus macaques improves lung compliance and increases surfactant production relative to either exposure alone. RNA sequencing shows that these changes are mediated by suppression of proliferation and induction of mesenchymal cellular death via TP53. The combined exposure results in a mature-like transcriptomic profile with inhibition of extracellular matrix development by suppression of collagen genes COL1A1, COL1A2, and COL3A1 and regulators of lung development FGF9 and FGF10. ACS and inflammation also suppressed signature genes associated with proliferative mesenchymal progenitors similar to the term gestation lung. Treatment with ACS in the setting of inflammation may result in early respiratory advantage to preterm infants, but this advantage may come at a risk of abnormal extracellular matrix development, which may be associated with increased risk of chronic lung disease.

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

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

Dose of budesonide with surfactant affects lung and systemic inflammation after normal and injurious ventilation in preterm lambs

BACKGROUND

The addition of budesonide (Bud) 0.25 mg/kg to surfactant decreased the lung and systemic responses to mechanical ventilation in preterm sheep and the rates and severity of bronchopulmonary dysplasia (BPD) in preterm infants. We hypothesized that lower budesonide concentrations in surfactant will decrease injury while decreasing systemic corticosteroid exposure.

METHODS

Preterm lambs received either (1) protective tidal volume (V_T) ventilation with surfactant from birth or (2) injurious V_T ventilation for 15 min and then surfactant treatment. Lambs were further assigned to surfactant mixed with (i) Saline, (ii) Bud 0.25 mg/kg, (iii) Bud 0.1 mg/kg, or (iv) Bud 0.04 mg/kg. All lambs were then ventilated with protective V_T for 6 h.

RESULTS

Plasma Bud levels were proportional to the dose received and decreased throughout ventilation. In both protective and injurious V_T ventilation, <4% of Bud remained in the lung at 6 h. Some of the improvements in physiology and markers of injury with Bud 0.25 mg/kg were also found with 0.1 mg/kg, whereas 0.04 mg/kg had only minimal effects.

CONCLUSIONS

Lower doses of Bud were less effective at decreasing lung and systemic inflammation from mechanical ventilation. The plasma Bud levels were proportional to dose given and the majority left the lung.

The duration of fetal antenatal steroid exposure determines the durability of preterm ovine lung maturation

BACKGROUND

Antenatal corticosteroids (ACS) are the standard of care for maturing the fetal lung and improving outcomes for preterm infants. Antenatal corticosteroid dosing remains nonoptimized, and there is little understanding of how different treatment-to-delivery intervals may affect treatment efficacy. The durability of a lung maturational response is important because the majority of women treated with antenatal corticosteroids do not deliver within the widely accepted 1- to 7-day window of treatment efficacy.

OBJECTIVE

We used a sheep model to test the duration of fetal exposures for efficacy at delivery intervals from 1 to 10 days.

MATERIALS AND METHODS

For infusion studies, ewes with single fetuses were randomized to receive an intravenous bolus and maintenance infusion of betamethasone phosphate to target 1-4 ng/mL fetal plasma betamethasone for 36 hours, with delivery at 2, 4 ,or 7 days posttreatment or sterile saline solution as control. Animals receiving the clinical treatment were randomised to receive either a single injection of 0.25 mg/kg with a 1:1 mixture of betamethasone phosphate + betamethasone acetate with delivery at either 1 or 7 days posttreatment, or 2 treatments of 0.25 mg/kg betamethasone phosphate + betamethasone acetate spaced at 24 hours (giving ∼48 hours of fetal steroid exposure) with delivery at 2, 5, 7, or 10 days posttreatment. Negative control animals were treated with saline solution. All lambs were delivered at 121 ± 3 days gestational age and ventilated for 30 minutes to assess lung function.

RESULTS

Preterm lambs delivered at 1 or 2 days post-antenatal corticosteroid treatment had significant improvements in lung maturation for both intravenous and single-dose intramuscular treatments. After 2 days, the efficacy of 36-hour betamethasone phosphate infusions was lost. The single dose of 1:1 betamethasone phosphate + betamethasone acetate also was ineffective at 7 days. In contrast, animals treated with 2 doses had significant improvements in lung maturation at 2, 5, and 7 days, with treatment efficacy reduced by 10 days.

CONCLUSION

In preterm lambs, the durability of antenatal corticosteroids treatment depends on the duration of fetal exposure and is independent of the intravenous or intramuscular maternal route of administration. For acute 24- to 48-hour posttreatment deliveries, a 24-hour fetal antenatal corticosteroids exposure was sufficient for lung maturation. A fetal exposure duration of at least 48 hours was necessary to maintain long-term treatment durability. A single-dose ACS treatment should be sufficient for women delivering within <48 hours of antenatal corticosteroids treatment.

Surfactant plus budesonide decreases lung and systemic responses to injurious ventilation in preterm sheep

Mechanical ventilation from birth with normal tidal volumes (VT) causes lung injury and systemic responses in preterm sheep. The addition of budesonide to surfactant therapy decreases these injury markers. Budesonide and surfactant will decrease the injury from injurious VT ventilation in preterm sheep. Lambs at 126 ± 1 day gestational age were ventilated from birth with either: 1) Normal VT [surfactant 200 mg/kg before ventilation, positive end expiratory pressure (PEEP) 5 cmH2O, VT 8 mL/kg] or 2) Injury VT (high pressure, 100% oxygen, no PEEP) for 15 min, then further randomized to surfactant + saline or surfactant + 0.25 mg/kg budesonide with Normal VT for 6 h. Lung function and lung, liver, and brain tissues were evaluated for indicators of injury. Injury VT + saline caused significant injury and systemic responses, and Injury VT + budesonide improved lung physiology. Budesonide decreased lung inflammation and decreased pro-inflammatory cytokine mRNA in the lung, liver, and brain to levels similar to Normal VT + saline. Budesonide was present in plasma within 15 min of treatment in both ventilation groups, and less than 5% of the budesonide remained in the lung at 6 h. mRNA sequencing of liver and periventricular white matter demonstrated multiple pathways altered by both Injury VT and budesonide and the combination exposure. In lambs receiving Injury VT, the addition of budesonide to surfactant improved lung physiology and decreased pro-inflammatory cytokine responses in the lung, liver, and brain to levels similar to lambs receiving Normal VT.

Oral dosing for antenatal corticosteroids in the Rhesus macaque

Antenatal corticosteroids (ACS) are standard of care for women at risk of preterm delivery, although choice of drug, dose or route have not been systematically evaluated. Further, ACS are infrequently used in low resource environments where most of the mortality from prematurity occurs. We report proof of principle experiments to test betamethasone-phosphate (Beta-P) or dexamethasone-phosphate (Dex-P) given orally in comparison to the clinical treatment with the intramuscular combination drug beta-phosphate plus beta-acetate in a Rhesus Macaque model. First, we performed pharmacokinetic studies in non-pregnant monkeys to compare blood levels of the steroids using oral dosing with Beta-P, Dex-P and an effective maternal intramuscular dose of the beta-acetate component of the clinical treatment. We then evaluated maternal and fetal blood steroid levels with limited fetal sampling under ultrasound guidance in pregnant macaques. We found that oral Beta is more slowly cleared from plasma than oral Dex. The blood levels of both drugs were lower in maternal plasma of pregnant than in non-pregnant macaques. Using the pharmacokinetic data, we treated groups of 6–8 pregnant monkeys with oral Beta-P, oral Dex-P, or the maternal intramuscular clinical treatment and saline controls and measured pressure-volume curves to assess corticosteroid effects on lung maturation at 5d. Oral Beta-P improved the pressure-volume curves similarly to the clinical treatment. Oral Dex-P gave more variable and nonsignificant responses. We then compared gene expression in the fetal lung, liver and hippocampus between oral Beta-P and the clinical treatment by RNA-sequencing. The transcriptomes were largely similar with small gene expression differences in the lung and liver, and no differences in the hippocampus between the groups. As proof of principle, ACS therapy can be effective using inexpensive and widely available oral drugs. Clinical dosing strategies must carefully consider the pharmacokinetics of oral Beta-P or Dex-P to minimize fetal exposure while achieving the desired treatment responses.

Dosing and formulation of antenatal corticosteroids for fetal lung maturation and gene expression in rhesus macaques

Antenatal corticosteroids (ANS) are the major intervention to decrease respiratory distress syndrome and mortality from premature birth and are standard of care. The use of ANS is expanding to include new indications and gestational ages, although the recommended dosing was never optimized. The most widely used treatment is two intramuscular doses of a 1:1 mixture of betamethasone-phosphate (Beta-P) and betamethasone-acetate (Beta-Ac) - the clinical drug. We tested in a primate model the efficacy of the slow release Beta-Ac alone for enhancing fetal lung maturation and to reduce fetal corticosteroid exposure and potential toxic effects. Pregnant rhesus macaques at 127 days of gestation (80% of term) were treated with either the clinical drug (0.25 mg/kg) or Beta-Ac (0.125 mg/kg). Beta-Ac alone increased lung compliance and surfactant concentration in the fetal lung equivalently to the clinical drug. By transcriptome analyses the early suppression of genes associated with immune responses and developmental pathways were less affected by Beta-Ac than the clinical drug. Promoter and regulatory analysis prediction identified differentially expressed genes targeted by the glucocorticoid receptor in the lung. At 5 days the clinical drug suppressed genes associated with neuronal development and differentiation in the fetal hippocampus compared to control, while low dose Beta-Ac alone did not. A low dose ANS treatment with Beta-Ac should be assessed for efficacy in human trials.

Gestational Age-Dependent Fetal Fluid Dynamics in the Ovine Developmental Model: Establishment of Surrogate Markers for the Differentiation of Stem Cell Origin

The ovine developmental model represents the standard in vivo model for studies involving maternofetal physiology, amniotic fluid (AF) research, and fetal cell therapy prior to human clinical use. Although being close to the human fetal anatomy, 2 separate extraembryonic fluid compartments remain during gestation, known as the amnion and the allantois. A clear distinction between AF versus allantoic fluid (AL) is therefore indispensable for correct scientific conclusions with regard to human translation. In the presented study, the biochemical composition of AF and AL was evaluated in ovine gravid uteri postmortem (n = 31) over the entire gestation. Four parameters, consisting of Na+, Cl-, Mg2+, and total protein, have been found to allow for specific discrimination of the 2 fetal fluids at all gestational phases and therefore as potential surrogate parameters for gestational age. In addition, volumetric changes of the developing fetus and the 2 fetal fluid cavities were analyzed by contrast-enhanced computed tomography (n = 12). AF showed a significant, linear volumetric increase over gestation, whereas AL volume maintained relatively static independent of gestational age. These results serve as a basis for future studies by providing surrogate markers enabling a reliable distinction of isolated fetal fluids and contained cells in the ovine developmental model over the entire gestation.

Bronchopulmonary dysplasia: Pathophysiology and potential anti-inflammatory therapies

Inflammation of the preterm lungs is key to the pathogenesis of bronchopulmonary dysplasia (BPD), whether it arises as a consequence of intrauterine inflammation or postnatal respiratory management. This review explores steroidal and non-steroidal therapies for reducing neonatal pulmonary inflammation, aimed at treating or preventing BPD.

Inflammation-mediated fetal injury by maternal granulocyte-colony stimulating factor and high-dose intraamniotic endotoxin in the caprine model

Objective:

To define a novel experimental model with maternal intravenous (i.v.) granulocyte-colony stimulating factor (G-CSF) followed by a single- and high-dose of 20 mg intra-amniotic (IA) endotoxin to induce fetal brain injury in the preterm fetal goat.

Materials and Methods:

Pregnant goats (n=4) were given 50 microg/day G-CSF into the maternal jugular vein through gestational days 110-115 (term, 150 days). At gestational day 115, 20 mg of IA endotoxin was administered. Following preterm delivery at day 120 by cesarean section umbilical cord, fetal lung and brain tissues were harvested for histopathology, immunohistochemistry, and electron microscopy. Inflammatory markers were evaluated in the amniotic fluid and fetal plasma.

Results:

Necrotizing funisitis with abundant leukocyte infiltration and fetal brain injury was induced in all the fetuses in the experimental group.

Conclusion:

Maternal i.v. G-CSF for 5 days followed by 20 mg of IA endotoxin is a feasible caprine model to exacerbate intrauterine inflammation.

Oral antenatal corticosteroids evaluated in fetal sheep

BACKGROUND

The use of antenatal corticosteroids (ACS) in low-resource environments is sporadic. Further, drug choice, dose, and route of ACS are not optimized. We report the pharmacokinetics and pharmacodynamics of oral dosing of ACS using a preterm sheep model.

METHODS

We measured pharmacokinetics of oral betamethasone-phosphate (Beta-P) and dexamethasone-phosphate (Dex-P) using catheterized pregnant sheep. We compared fetal lung maturation responses of oral Beta-P and Dex-P to the standard treatment with 2 doses of the i.m. mixture of Beta-P and betamethasone-acetate at 2, 5, and 7 days after initiation of ACS.

RESULTS

Oral Dex-P had lower bioavailability than Beta-P, giving a lower maximum maternal and fetal concentration. A single oral dose of 0.33 mg/kg of Beta-P was equivalent to the standard clinical treatment assessed at 2 days; 2 doses of 0.16 mg/kg of oral Beta-P were equivalent to the standard clinical treatment at 7 days as assessed by lung mechanics and gas exchange after preterm delivery and ventilation. In contrast, oral Dex-P was ineffective because of its decreased bioavailability.

CONCLUSION

Using a sheep model, we demonstrate the use of pharmacokinetics to develop oral dosing strategies for ACS. Oral dosing is feasible and may facilitate access to ACS in low-resource environments.

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.

Animal models in neonatal resuscitation research: What can they teach us?

Animal models have made and continue to make important contributions to neonatal medicine. For example, studies in fetal sheep have taught us much about the physiology of the fetal-to-neonatal transition. However, whereas animal models allow multiple factors to be investigated in a logical and systematic manner, no animal model is perfect for humans and so we need to understand the fundamental differences in physiology between the species in question and humans. Although most physiological systems are well conserved between species, some small differences exist and so wherever possible the knowledge generated from preclinical studies in animals should be tested in clinical trials. However, with the rise of evidence-based medicine the distinction between scientific knowledge generation and evidence gathering has been confused and the two have been lumped together. This misunderstands the contribution that scientific knowledge can provide. Science should be used to guide the gathering of evidence by informing the design of clinical trials, thereby increasing their likelihood of success. While scientific knowledge is not evidence, in the absence of evidence it is likely to be the best option for guiding clinical practice.

Epidermal growth factor receptor inhibition with Gefitinib does not alter lung responses to mechanical ventilation in fetal, preterm lambs

BACKGROUND

Epidermal growth factor receptor (EGFR) is important for airway branching and lung maturation. Mechanical ventilation of preterm lambs causes increases in EGFR and EGFR ligand mRNA in the lung. Abnormal EGFR signaling may contribute to the development of bronchopulmonary dysplasia.

HYPOTHESIS

Inhibition of EGFR signaling will decrease airway epithelial cell proliferation and lung inflammation caused by mechanical ventilation in preterm, fetal sheep.

METHODS

Following exposure of the fetal head and chest at 123±1 day gestational age and with placental circulation intact, fetal lambs (n = 4-6/group) were randomized to either: 1) Gefitinib 15 mg IV and 1 mg intra-tracheal or 2) saline IV and IT. Lambs were further assigned to 15 minutes of either: a) Injurious mechanical ventilation (MV) or b) Continuous positive airway pressure (CPAP) 5 cmH2O. After the 15 minute intervention, the animals were returned to the uterus and delivered after i) 6 or ii) 24 hours in utero.

RESULTS

MV caused lung injury and inflammation, increased lung mRNA for cytokines and EGFR ligands, caused airway epithelial cell proliferation, and decreased airway epithelial phosphorylated ERK1/2. Responses to MV were unchanged by Gefitinib. Gefitinib altered expression of EGFR mRNA in the lung and liver of both CPAP and MV animals. Gefitinib decreased the liver SAA3 mRNA response to MV at 6 hours. There were no differences in markers of lung injury or inflammation between CPAP animals receiving Gefitinib or saline.

CONCLUSION

Inhibition of the EGFR pathway did not alter acute lung inflammation or injury from mechanical ventilation in preterm sheep.

Effects of budesonide and surfactant in preterm fetal sheep

Mechanical ventilation causes lung injury and systemic inflammatory responses in preterm sheep and is associated with bronchopulmonary dysplasia (BPD) in preterm infants. Budesonide added to surfactant decreased BPD by 20% in infants. We wanted to determine the effects of budesonide and surfactant on injury from high tidal volume (V_T) ventilation in preterm lambs. Ewes at 125 ± 1 days gestational age had fetal surgery to expose fetal head and chest with placental circulation intact. Lambs were randomized to 1) mechanical ventilation with escalating V_T to target 15 ml/kg by 15 min or 2) continuous positive airway pressure (CPAP) of 5 cmH₂O. After the 15-min intervention, lambs were given surfactant 100 mg/kg with saline, budesonide 0.25 mg/kg, or budesonide 1 mg/kg. The fetuses were returned to the uterus for 24 h and then delivered and ventilated for 30 min to assess lung function. Budesonide levels were low in lung and plasma. CPAP groups had improved oxygenation, ventilation, and decreased injury markers compared with fetal V_T lambs. Budesonide improved ventilation in CPAP lambs. Budesonide decreased lung weights and lung liquid and increased lung compliance and surfactant protein mRNA. Budesonide decreased proinflammatory and acute-phase responses in lung. Airway thickness increased in animals not receiving budesonide. Systemically, budesonide decreased monocyte chemoattractant protein-1 mRNA and preserved glycogen in liver. Results with 0.25 and 1 mg/kg budesonide were similar. We concluded that budesonide with surfactant matured the preterm lung and decreased the liver responses but did not improve lung function after high V_T injury in fetal sheep.

Extremely preterm fetal sheep lung responses to antenatal steroids and inflammation

BACKGROUND

The efficacy of antenatal steroids for fetal lung maturation in the periviable period is not fully understood.

OBJECTIVE

We sought to determine the lung maturational effects of antenatal steroids and inflammation in early gestation sheep fetuses, similar to the periviable period in human beings.

STUDY DESIGN

Date-mated ewes with singleton fetuses were randomly assigned to 1 of 4 treatment groups (n = 8/group): (1) maternal intramuscular injection of betamethasone; (2) intraamniotic lipopolysaccharide; (3) betamethasone + lipopolysaccharide; and (4) intraamniotic + intramuscular saline (controls). Fetuses were delivered surgically 48 hours later at 94 days' gestation (63% term gestation) for comprehensive evaluations of lung maturation, and lung and systemic inflammation.

RESULTS

Relative to controls, first, betamethasone increased the fetal lung air space to mesenchymal area ratio by 47% but did not increase the messenger RNAs for the surfactant proteins-B and -C that are important for surfactant function or increase the expression of pro-surfactant protein-C in the alveolar type II cells. Second, betamethasone increased expression of 1 of the 4 genes in surfactant lipid synthetic pathways. Third, betamethasone increased genes involved in epithelium sodium channel transport, but not sodium-potassium adenosine triphosphatase or Aquaporin 5. Fourth, lipopolysaccharide increased proinflammatory genes in the lung but did not effectively recruit activated inflammatory cells. Last, betamethasone incompletely suppressed lipopolysaccharide-induced lung inflammation. In the liver, betamethasone when given alone increased the expression of serum amyloid A3 and C-reactive protein messenger RNAs.

CONCLUSION

Compared the more mature 125-day gestation sheep, antenatal steroids do not induce pulmonary surfactants during the periviable period, indicating a different response.

The combined exposure to intra-amniotic inflammation and neonatal respiratory distress syndrome increases the risk of intraventricular hemorrhage in preterm neonates

OBJECTIVE

To evaluate the impact of combined exposure to intra-amniotic inflammation and neonatal respiratory distress syndrome (RDS) on the development of intraventricular hemorrhage (IVH) in preterm neonates.

METHODS

This retrospective cohort study includes 207 consecutive preterm births (24.0-33.0 weeks of gestation). Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. According to McMenamin's classification, IVH was defined as grade II or higher when detected by neurosonography within the first weeks of life.

RESULTS

(1) IVH was diagnosed in 6.8% (14/207) of neonates in the study population; (2) IVH was frequent among newborns exposed to intra-amniotic inflammation when followed by postnatal RDS [33% (6/18)]. The frequency of IVH was 7% (8/115) among neonates exposed to either of these conditions - intra-amniotic inflammation or RDS - and 0% (0/64) among those who were not exposed to these conditions; and (3) Neonates exposed to intra-amniotic inflammation and postnatal RDS had a significantly higher risk of IVH than those with only intra-amniotic inflammation [odds ratio (OR) 4.6, 95% confidence interval (CI) 1.1-19.3] and those with RDS alone (OR 5.6, 95% CI 1.0-30.9), after adjusting for gestational age.

CONCLUSION

The combined exposure to intra-amniotic inflammation and postnatal RDS markedly increased the risk of IVH in preterm neonates.

Ventilation Prior to Umbilical Cord Clamping Improves Cardiovascular Stability and Oxygenation in Preterm Lambs After Exposure to Intrauterine Inflammation

Background: Delaying umbilical cord clamping until after aeration of the lung (physiological-based cord clamping; PBCC) maintains cardiac output and oxygenation in preterm lambs at birth, however, its efficacy after intrauterine inflammation is not known. Given the high incidence of chorioamnionitis in preterm infants, we investigated whether PBCC conferred any benefits compared to immediate cord clamping (ICC) in preterm lambs exposed antenatally to 7 days of intrauterine inflammation. Methods: Ultrasound guided intraamniotic injection of 20 mg Lipopolysaccharide (from E. coli:055:B5) was administered to pregnant ewes at 0.8 gestation. Seven days later, ewes were anesthetized, preterm fetuses exteriorised via cesarean section, and instrumented for continuous measurement of pulmonary, systemic and cerebral pressures and flows, and systemic, and cerebral oxygenation. Lambs were then randomized to either PBCC, whereupon ventilation was initiated and maintained for 3 min prior to umbilical cord clamping, or ICC where the umbilical cord was cut and ventilation initiated 30 s later. Ventilation was maintained for 30 min. Results: ICC caused a rapid fall in systemic (by 25%) and cerebral (by 11%) oxygen saturation in ICC lambs, concurrent with a rapid increase in carotid arterial pressure and heart rate. The overshoot in carotid arterial pressure was sustained in ICC lambs for the first 20 min of the study. PBCC maintained cardiac output and prevented the fall in cerebral oxygen delivery at birth. PBCC lambs had lower respiratory compliance and higher respiratory requirements throughout the study. Conclusion: PBCC mitigated the adverse effects of ICC on oxygenation and cardiac output, and therefore could be more beneficial in preterm babies exposed to antenatal inflammation as it maintains cardiac output and oxygen delivery. The increased respiratory requirements require further investigation in this sub-group of preterm infants.

Effects of Intrauterine Inflammation on Cortical Gray Matter of Near-Term Lambs

Introduction: Ventilation causes cerebral white matter inflammation and injury, which is exacerbated by intrauterine inflammation. However, the effects on cortical gray matter are not well-known. Our aim was to examine the effect of ventilation on the cerebral cortex of near-term lambs exposed to intrauterine inflammation. Method:Pregnant ewes at 119 ± 1 days gestation received an intra-amniotic injection of saline or lipopolysaccharide (LPS; 10 mg). Seven days later, lambs were randomized to either a high tidal volume injurious ventilation strategy (INJ_SALN = 6, INJ_LPSN = 5) or a protective ventilation strategy (PROT_SALN = 5, PROT_LPSN = 6). Respiratory parameters, heart rate and blood gases were monitored during the neonatal period. At post-mortem, the brain was collected and processed for immunohistochemical assessment. Neuronal density (NeuN), apoptotic cell death (caspase 8 and TUNEL), microglial density (Iba-1), astrocytic density (GFAP), and vascular protein extravasation (sheep serum) were assessed within the frontal, parietal, temporal and occipital lobes of the cerebral cortex. Results:A significant reduction in the number of neurons in all cortical layers except 4 was observed in LPS-exposed lambs compared to controls (layer #1: p = 0.041; layers #2 + 3: p = 0.023; layers #5 + 6: p = 0.016). LPS treatment caused a significant increase in gray matter area, indicative of edema. LPS+ventilation did not cause apoptotic cell death in the gray matter. Astrogliosis was not observed following PROT or INJ ventilation, with or without LPS exposure. LPS exposure was associated with vascular protein extravasation. Conclusion:Ventilation had little effect on gray matter inflammation and injury. Intrauterine inflammation reduced neuronal cell density, caused edema of the cortical gray matter, and blood vessel extravasation in the brain of near-term lambs.

Effect of Human Amnion Epithelial Cells on the Acute Inflammatory Response in Fetal Sheep

Intra-amniotic (IA) lipopolysaccharide (LPS) injection in sheep induces inflammation in the fetus. Human amnion epithelial cells (hAECs) moderate the effect of IA LPS on fetal development, but their influence on the acute inflammatory response to IA LPS is unknown. We aimed to determine the effects of hAECs on the acute fetal inflammatory response to IA LPS. After surgical instrumentation at 116 days' gestation (d) ewes were randomized to 1 of 4 groups at 123 d: IA LPS (10 mg) and intravenous (IV) saline (n = 8), IA LPS and IV hAECs (n = 6), IA saline and IV saline (n = 5) or IA saline and IV hAECs (n = 5). IV injections were administered immediately after IA injections. Serial fetal blood samples were collected. At 125 d, placental, fetal lung and liver samples were collected. IA LPS increased inflammatory cell recruitment in the placenta and lungs, increased IL-1β and IL-8 mRNA levels in the lungs and increased serum amyloid A3 (SAA3) and C-reactive protein (CRP) mRNA levels in the liver. IV hAECs reduced fetal lung inflammatory cell recruitment but did not otherwise alter indices of placental, fetal lung or liver inflammation. The acute fetal inflammatory response to IA LPS is not substantially altered by IV hAEC treatment.

Inflammation-induced preterm lung maturation: lessons from animal experimentation

Intrauterine inflammation, or chorioamnionitis, is a major contributor to preterm birth. Prematurity per se is associated with considerable morbidity and mortality resulting from lung immaturity but exposure to chorioamnionitis reduces the risk of neonatal respiratory distress syndrome (RDS) in preterm infants. Animal experiments have identified that an increase in pulmonary surfactant production by the preterm lungs likely underlies this decreased risk of RDS in infants exposed to chorioamnionitis. Further animal experimentation has shown that infectious or inflammatory agents in amniotic fluid exert their effects on lung development by direct effects within the developing respiratory tract, and probably not by systemic pathways. Differences in the effects of intrauterine inflammation and glucocorticoids demonstrate that canonical glucocorticoid-mediated lung maturation is not responsible for inflammation-induced changes in lung development. Animal experimentation is identifying alternative lung maturational pathways, and transgenic animals and cell culture techniques will allow identification of novel mechanisms of lung maturation that may lead to new treatments for the prevention of RDS.

Chronic Exposure to Intra-Amniotic Lipopolysaccharide Affects the Ovine Fetal Brain

OBJECTIVE

Fetal brain injury is associated with chorioamnionitis, which is often present without signs of overt infection or fetal compromise. We aimed to determine if prolonged exposure to intrauterine inflammation caused by intra-amniotic infusion of lipopolysaccharide (LPS) would affect the fetal brain.

METHODS

At 80 days of pregnancy ewes bearing singletons had osmotic pumps implanted intra-amniotically to infuse Escherichia coli LPS (055:B5; n = 8) or saline (n = 7) for 28 days. At delivery (110 days), umbilical arterial blood and chorioamnion were assessed for inflammation; cytokine concentrations (interleukin [IL]-6 and IL-8) in amniotic fluid and fetal and maternal plasma were measured. The fetal cerebral hemispheres were examined for gross anatomical changes and the number of activated microglia/macrophages, astrocytes, and oligodendrocytes estimated after immunohistochemical staining.

RESULTS

Intra-amniotic administration of LPS caused chorioamnionitis, fetal leucocytosis, and a moderate to extensive infiltration of activated microglia/macrophages in the subcortical white matter in six of eight fetuses; the remaining two fetuses were less affected. Within these focal regions of damage there was an attenuation of astrocytic processes, axonal injury, and a reduction in the number of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) immunoreactive oligodendrocytes in areas of extensive focal damage. In control fetuses there was mild (3/7) or no infiltration of activated microglia/macrophages in the subcortical white matter. Overall the infiltration of activated microglia/macrophages in the white matter was significantly greater in LPS-exposed fetuses compared to controls. In regions devoid of injury, the number of oligodendrocytes and astrocytes was not different between groups, nor was there a difference in the volume of cerebral white matter or density of blood vessels within the white matter. Amniotic fluid IL-6 and IL-8, and maternal plasma IL-8 concentrations were significantly increased by LPS infusion.

CONCLUSIONS

An increase in inflammatory cells and axonal disruption in the subcortical white matter of the fetal brain can accompany chorioamnionitis induced by intra-amniotic administration of LPS, but cystic lesions do not occur. Thus, the effect on the fetal brain is milder than that reported from animal models of acute fetal/intrauterine infection.

Distending Pressure Did Not Activate Acute Phase or Inflammatory Responses in the Airways and Lungs of Fetal, Preterm Lambs

Background

Mechanical ventilation at birth causes airway injury and lung inflammation in preterm sheep. Continuous positive airway pressure (CPAP) is being increasingly used clinically to transition preterm infants at birth.

Objective

To test if distending pressures will activate acute phase reactants and inflammatory changes in the airways of fetal, preterm lambs.

Methods

The head and chest of fetal lambs at 128±1 day GA were surgically exteriorized. With placental circulation intact, fetal lambs were then randomized to one of five 15 minute interventions: PEEP of 0, 4, 8, 12, or 16 cmH₂O. Recruitment volumes were recorded. Fetal lambs remained on placental support for 30 min after the intervention. The twins of each 0 cmH₂O animal served as controls. Fetal lung fluid (FLF), bronchoalveolar lavage fluid (BAL), right mainstem bronchi and peripheral lung tissue were evaluated for inflammation.

Results

Recruitment volume increased from 0.4±0.04 mL/kg at 4 cmH₂O to 2.4±0.3 mL/kg at 16 cmH₂O. The lambs were surfactant deficient, and all pressures were below the opening inflection pressure on pressure-volume curve. mRNA expression of early response genes and pro-inflammatory cytokines did not increase in airway tissue or lung tissue at any pressure compared to controls. FLF and BAL also did not have increases in early response proteins. No histologic changes or Egr-1 activation was present at the pressures used.

Conclusion

Distending pressures as high as 16 cmH₂O did not recruit lung volume at birth and did not increase markers of injury in the lung or airways in non-breathing preterm fetal sheep.

Brief mechanical ventilation causes differential epithelial repair along the airways of fetal, preterm lambs

Mechanical ventilation of preterm lambs causes lung inflammation and injury to the airway epithelium, which is repaired by 15 days after ventilation. In mice, activated basal cells (p63+, KRT14+, KRT8+) initiate injury repair to the trachea, whereas club cells coordinate distal airway repair. In both human and sheep, basal cells line the pseudostratified airways to the distal bronchioles with club cells only present in terminal bronchioles. Mechanical ventilation causes airway epithelial injury that is repaired through basal cell activation in the fetal lung. Ewes at 123 ± 1 day gestational age had the head and chest of the fetus exteriorized and tracheostomy placed. With placental circulation intact, fetal lambs were mechanically ventilated with up to 15 ml/kg for 15 min with 95% N2/5% CO2 Fetal lambs were returned to the uterus for up to 24 h. The trachea, left mainstem bronchi, and peripheral lung were evaluated for epithelial injury and cellular response consistent with repair. Peripheral lung tissue had inflammation, pro-inflammatory cytokine production, epithelial growth factor receptor ligand upregulation, increased p63 expression, and proliferation of pro-SPB, TTF-1 positive club cells. In bronchi, KRT14 and KRT8 mRNA increased without increases in Notch pathway mRNA or proliferation. In trachea, mRNA increased for Notch ligands, SAM pointed domain-containing Ets transcription factor and mucin 5B, but not for basal cell markers. A brief period of mechanical ventilation causes differential epithelial activation between trachea, bronchi, and peripheral lung. The repair mechanisms identified in adult mice occur at different levels of airway branching in fetal sheep with basal and club cell activation.

Ventilation-induced lung injury is not exacerbated by growth restriction in preterm lambs

Intrauterine growth restriction (IUGR) and preterm birth are frequent comorbidities and, combined, increase the risk of adverse respiratory outcomes compared with that in appropriately grown (AG) infants. Potential underlying reasons for this increased respiratory morbidity in IUGR infants compared with AG infants include altered fetal lung development, fetal lung inflammation, increased respiratory requirements, and/or increased ventilation-induced lung injury. IUGR was surgically induced in preterm fetal sheep (0.7 gestation) by ligation of a single umbilical artery. Four weeks later, preterm lambs were euthanized at delivery or delivered and ventilated for 2 h before euthanasia. Ventilator requirements, lung inflammation, early markers of lung injury, and morphological changes in lung parenchymal and vascular structure and surfactant composition were analyzed. IUGR preterm lambs weighed 30% less than AG preterm lambs, with increased brain-to-body weight ratio, indicating brain sparing. IUGR did not induce lung inflammation or injury or alter lung parenchymal and vascular structure compared with AG fetuses. IUGR and AG lambs had similar oxygenation and respiratory requirements after birth and had significant, but similar, increases in proinflammatory cytokine expression, lung injury markers, gene expression, and surfactant phosphatidylcholine species compared with unventilated controls. IUGR does not induce pulmonary structural changes in our model. Furthermore, IUGR and AG preterm lambs have similar ventilator requirements in the immediate postnatal period. This study suggests that increased morbidity and mortality in IUGR infants is not due to altered lung tissue or vascular structure, or to an altered response to early ventilation.

Protective effect of chorioamnionitis on the development of bronchopulmonary dysplasia triggered by postnatal systemic inflammation in neonatal rats

BACKGROUND

Prenatal or postnatal systemic inflammation can contribute to the development of bronchopulmonary dysplasia (BPD). We investigated whether prenatal intra-amniotic (i.a.) inflammation or early postnatal systemic inflammation can induce BPD in a rat model.

METHODS

One microgram of lipopolysaccharide (LPS) or vehicle was injected into the amniotic sacs 2 d before delivery (E20). After birth, 0.25 mg/kg of LPS or vehicle was injected into the peritoneum of pups on postnatal day (P)1, P3, and P5. On P7 and P14, peripheral blood (PB), bronchoalveolar lavage fluid (BALF), and lung tissue were obtained and analyzed.

RESULTS

Postnatal i.p. injections of LPS significantly increased neutrophil counts in PB and BALF on P7 and P14. Similarly, proinflammatory cytokine and angiogenic factor transcript levels were increased in the lung by i.p. LPS on P7. Alveolar and pulmonary vascular development was markedly disrupted by i.p. LPS on P14. However, pretreatment with i.a. LPS significantly negated the detrimental effects of postnatal i.p. LPS on PB and BALF neutrophil counts and on lung proinflammatory cytokine expression and histopathological changes.

CONCLUSION

Exposure to early postnatal systemic LPS induces BPD, an arrest in alveolarization, in neonatal rats. Preceding exposure to i.a. LPS protects the lungs against BPD triggered by postnatal systemic inflammation.

Nebulization of Poractant alfa via a vibrating membrane nebulizer in spontaneously breathing preterm lambs with binasal continuous positive pressure ventilation

BACKGROUND

Surfactant replacement therapy is the gold standard treatment of neonatal respiratory distress (RDS). Nebulization is a noninvasive mode of surfactant administration. We administered Poractant alfa (Curosurf) via a vibrating perforated membrane nebulizer (eFlow Neonatal Nebulizer) to spontaneously breathing preterm lambs during binasal continuous positive pressure ventilation (CPAP).

METHODS

Sixteen preterm lambs were operatively delivered at a gestational age of 133 ± 1 d (term ~150 d), and connected to CPAP applied via customized nasal prongs. Nebulization was performed (i) with saline or (ii) with surfactant for 3 h in humidified or (iii) nonhumidified air, and with surfactant (iv) for 60 min or (v) for 30 min. We measured arterial oxygenation, lung gas volumes and surfactant pool size and deposition.

RESULTS

Nebulization of surfactant in humidified air for 3 h improved oxygenation and lung function, and surfactant was preferentially distributed to the lower lung lobes. Shorter nebulization times and 3 h nebulization in dry air did not show these effects. Nebulized surfactant reached all lung lobes, however the increase of surfactant pool size missed statistical significance.

CONCLUSION

Positive effects of surfactant nebulization to spontaneously breathing preterm lambs depend on treatment duration, surfactant dose, air humidity, and surfactant distribution within the lung.

Ex-Vivo Uterine Environment (EVE) Therapy Induced Limited Fetal Inflammation in a Premature Lamb Model

Introduction

Ex-vivo uterine environment (EVE) therapy uses an artificial placenta to provide gas exchange and nutrient delivery to a fetus submerged in an amniotic fluid bath. Development of EVE may allow us to treat very premature neonates without mechanical ventilation. Meanwhile, elevations in fetal inflammation are associated with adverse neonatal outcomes. In the present study, we analysed fetal survival, inflammation and pulmonary maturation in preterm lambs maintained on EVE therapy using a parallelised umbilical circuit system with a low priming volume.

Methods

Ewes underwent surgical delivery at 115 days of gestation (term is 150 days), and fetuses were transferred to EVE therapy (EVE group; n = 5). Physiological parameters were continuously monitored; fetal blood samples were intermittently obtained to assess wellbeing and targeted to reference range values for 2 days. Age-matched animals (Control group; n = 6) were surgically delivered at 117 days of gestation. Fetal blood and tissue samples were analysed and compared between the two groups.

Results

Fetal survival time in the EVE group was 27.0 ± 15.5 (group mean ± SD) hours. Only one fetus completed the pre-determined study period with optimal physiological parameters, while the other 4 animals demonstrated physiological deterioration or death prior to the pre-determined study end point. Significant elevations (p<0.05) in: i) inflammatory proteins in fetal plasma; ii) selected cytokine/chemokine mRNA expression levels in fetal tissues; and iii) histological inflammatory score in fetal lung, were observed in the EVE group compared to the Control group. There was no significant difference (p>0.05) in surfactant protein mRNA expression level between the two groups.

Conclusion

In this study, we achieved limited fetal survival using EVE therapy. Despite this, EVE therapy only induced a modest fetal inflammatory response and did not promote lung maturation. These data provide additional insight into markers of treatment efficacy for the assessment of future studies.

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.

Fluconazole treatment of intrauterine Candida albicans infection in fetal sheep

BACKGROUND

Intrauterine Candida albicans infection causes severe fetal inflammatory responses and fetal injury in an ovine model. We hypothesized that intra-amniotic antifungal therapy with fluconazole would decrease the adverse fetal effects of intra-amniotic C. albicans in sheep.

METHODS

Sheep received an intra-amniotic injection of 10(7) colony-forming units C. albicans. After 2 d, animals were then randomized to: (i) intra-amniotic and fetal intraperitoneal saline with delivery after 24 h (3 d C. albicans group); (ii) intra-amniotic and fetal intraperitoneal injections of fluconazole with delivery after either 24 h (3 d C. albicans plus 1 d fluconazole group) or 72 h (5 d C. albicans plus 3 d fluconazole group). Controls received intra-amniotic injections of saline followed by intra-amniotic and fetal intraperitoneal fluconazole injections.

RESULTS

Intra-amniotic C. albicans caused severe fetal inflammatory responses characterized by decreases in lymphocytes and platelets, an increase in posterior mediastinal lymph node weight and proinflammatory mRNA responses in the fetal lung, liver, and spleen. Fluconazole treatment temporarily decreased the pulmonary and chorioamnion inflammatory responses.

CONCLUSION

The severe fetal inflammatory responses caused by intra-amniotic C. albicans infection were transiently decreased with fluconazole. A timely fetal delivery of antimicrobial agents may prevent fetal injury associated with intrauterine infection.

The effect of prenatal maternal infection on respiratory function in mouse offspring: evidence for enhanced chemosensitivity

Systemic maternal inflammation is implicated in preterm birth and bronchopulmonary dysplasia (BPD) and may induce morbidities including reduced pulmonary function, sleep-disordered breathing, and cardiovascular disorders. Here we test the hypothesis that antenatal maternal inflammation per se causes altered alveolar development and increased chemoreflex sensitivity that persists beyond infancy. Pregnant C57BL/6 mice were administered lipopolysaccharide (LPS) (150 μg/kg ip) to induce maternal inflammation or saline (SHAM) at embryonic day 16 (randomized). Pups were weighed daily. On days 7, 28, and 60 (D07, D28, and D60), unrestrained wholebody plethysmography quantified ventilation and chemoreflex responses to hypoxia (10%), hypercapnia (7%), and asphyxia (hypoxic hypercapnia). Lungs were harvested to quantify alveolar number, size, and septal thickness. LPS pups had reduced baseline ventilation per unit bodyweight (∼40%, P < 0.001) vs. SHAM. LPS increased ventilatory responses to hypoxia (D07: 66% vs. 28% increase in ventilation; P < 0.001) hypercapnia (170% vs. 88%; P < 0.001), and asphyxia (249% vs. 154%; P < 0.001); hypersensitive hypoxic responsiveness persisted until D60 (P < 0.001). LPS also increased apnea frequency (P < 0.01). LPS caused thicker alveolar septae (D07, P < 0.001), diminished alveolar number (D28, P < 0.001) vs. SHAM, but effects were minimal by D60. Pups delivered from mothers exposed to antenatal inflammation exhibit deficits in lung structure and hypersensitive responses to respiratory stimuli that persist beyond the newborn period. Antenatal inflammation may contribute to impaired gas exchange and unstable breathing in newborn infants and adversely affect long-term health.

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.

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.

Sustained inflation at birth did not alter lung injury from mechanical ventilation in surfactant-treated fetal lambs

Background

Sustained inflations (SI) are used with the initiation of ventilation at birth to rapidly recruit functional residual capacity and may decrease lung injury and the need for mechanical ventilation in preterm infants. However, a 20 second SI in surfactant-deficient preterm lambs caused an acute phase injury response without decreasing lung injury from subsequent mechanical ventilation.

Hypothesis

A 20 second SI at birth will decrease lung injury from mechanical ventilation in surfactant-treated preterm fetal lambs.

Methods

The head and chest of fetal sheep at 126±1 day GA were exteriorized, with tracheostomy and removal of fetal lung fluid prior to treatment with surfactant (300 mg in 15 ml saline). Fetal lambs were randomized to one of four 15 minute interventions: 1) PEEP 8 cmH₂O; 2) 20 sec SI at 40 cmH₂O, then PEEP 8 cmH₂O; 3) mechanical ventilation with 7 ml/kg tidal volume; or 4) 20 sec SI then mechanical ventilation at 7 ml/kg. Fetal lambs remained on placental support for the intervention and for 30 min after the intervention.

Results

SI recruited a mean volume of 6.8±0.8 mL/kg. SI did not alter respiratory physiology during mechanical ventilation. Heat shock protein (HSP) 70, HSP60, and total protein in lung fluid similarly increased in both ventilation groups. Modest pro-inflammatory cytokine and acute phase responses, with or without SI, were similar with ventilation. SI alone did not increase markers of injury.

Conclusion

In surfactant treated fetal lambs, a 20 sec SI did not alter ventilation physiology or markers of lung injury from mechanical ventilation.

Protective ventilation of preterm lambs exposed to acute chorioamnionitis does not reduce ventilation-induced lung or brain injury

Background

The onset of mechanical ventilation is a critical time for the initiation of cerebral white matter (WM) injury in preterm neonates, particularly if they are inadvertently exposed to high tidal volumes (V_T) in the delivery room. Protective ventilation strategies at birth reduce ventilation-induced lung and brain inflammation and injury, however its efficacy in a compromised newborn is not known. Chorioamnionitis is a common antecedent of preterm birth, and increases the risk and severity of WM injury. We investigated the effects of high V_T ventilation, after chorioamnionitis, on preterm lung and WM inflammation and injury, and whether a protective ventilation strategy could mitigate the response.

Methods

Pregnant ewes (n = 18) received intra-amniotic lipopolysaccharide (LPS) 2 days before delivery, instrumentation and ventilation at 127±1 days gestation. Lambs were either immediately euthanased and used as unventilated controls (LPS_UVC; n = 6), or were ventilated using an injurious high V_T strategy (LPS_INJ; n = 5) or a protective ventilation strategy (LPS_PROT; n = 7) for a total of 90 min. Mean arterial pressure, heart rate and cerebral haemodynamics and oxygenation were measured continuously. Lungs and brains underwent molecular and histological assessment of inflammation and injury.

Results

LPS_INJ lambs had poorer oxygenation than LPS_PROT lambs. Ventilation requirements and cardiopulmonary and systemic haemodynamics were not different between ventilation strategies. Compared to unventilated lambs, LPS_INJ and LPS_PROT lambs had increases in pro-inflammatory cytokine expression within the lungs and brain, and increased astrogliosis (p<0.02) and cell death (p<0.05) in the WM, which were equivalent in magnitude between groups.

Conclusions

Ventilation after acute chorioamnionitis, irrespective of strategy used, increases haemodynamic instability and lung and cerebral inflammation and injury. Mechanical ventilation is a potential contributor to WM injury in infants exposed to chorioamnionitis.

Chorioamnionitis-induced fetal gut injury is mediated by direct gut exposure of inflammatory mediators or by lung inflammation

Intra-amniotic exposure to proinflammatory agonists causes chorioamnionitis and fetal gut inflammation. Fetal gut inflammation is associated with mucosal injury and impaired gut development. We tested whether this detrimental inflammatory response of the fetal gut results from a direct local (gut derived) or an indirect inflammatory response mediated by the chorioamnion/skin or lung, since these organs are also in direct contact with the amniotic fluid. The gastrointestinal tract was isolated from the respiratory tract and the amnion/skin epithelia by fetal surgery in time-mated ewes. Lipopolysaccharide (LPS) or saline (controls) was selectively infused in the gastrointestinal tract, trachea, or amniotic compartment at 2 or 6 days before preterm delivery at 124 days gestation (term 150 days). Gastrointestinal and intratracheal LPS exposure caused distinct inflammatory responses in the fetal gut. Inflammatory responses could be distinguished by the influx of leukocytes (MPO(+), CD3(+), and FoxP3(+) cells), tumor necrosis factor-α, and interferon-γ expression and differential upregulation of mRNA levels for Toll-like receptor 1, 2, 4, and 6. Fetal gut inflammation after direct intestinal LPS exposure resulted in severe loss of the tight junctional protein zonula occludens protein 1 (ZO-1) and increased mitosis of intestinal epithelial cells. Inflammation of the fetal gut after selective LPS instillation in the lungs caused only mild disruption of ZO-1, loss in epithelial cell integrity, and impaired epithelial differentiation. LPS exposure of the amnion/skin epithelia did not result in gut inflammation or morphological, structural, and functional changes. Our results indicate that the detrimental consequences of chorioamnionitis on fetal gut development are the combined result of local gut and lung-mediated inflammatory responses.

A novel molecular microbiologic technique for the rapid diagnosis of microbial invasion of the amniotic cavity and intra-amniotic infection in preterm labor with intact membranes

PROBLEM

The diagnosis of microbial invasion of the amniotic cavity (MIAC) has been traditionally performed using traditional cultivation techniques, which require growth of microorganisms in the laboratory. Shortcomings of culture methods include the time required (days) for identification of microorganisms, and that many microbes involved in the genesis of human diseases are difficult to culture. A novel technique combines broad-range real-time polymerase chain reaction with electrospray ionization time-of-flight mass spectrometry (PCR/ESI-MS) to identify and quantify genomic material from bacteria and viruses.

METHOD OF STUDY

AF samples obtained by transabdominal amniocentesis from 142 women with preterm labor and intact membranes (PTL) were analyzed using cultivation techniques (aerobic, anaerobic, and genital mycoplasmas) as well as PCR/ESI-MS. The prevalence and relative magnitude of intra-amniotic inflammation [AF interleukin 6 (IL-6) concentration ≥ 2.6 ng/mL], acute histologic chorioamnionitis, spontaneous preterm delivery, and perinatal mortality were examined.

RESULTS

(i) The prevalence of MIAC in patients with PTL was 7% using standard cultivation techniques and 12% using PCR/ESI-MS; (ii) seven of ten patients with positive AF culture also had positive PCR/ESI-MS [≥17 genome equivalents per PCR reaction well (GE/well)]; (iii) patients with positive PCR/ESI-MS (≥17 GE/well) and negative AF cultures had significantly higher rates of intra-amniotic inflammation and acute histologic chorioamnionitis, a shorter interval to delivery [median (interquartile range-IQR)], and offspring at higher risk of perinatal mortality, than women with both tests negative [90% (9/10) versus 32% (39/122) OR: 5.6; 95% CI: 1.4-22; (P < 0.001); 70% (7/10) versus 35% (39/112); (P = 0.04); 1 (IQR: <1-2) days versus 25 (IQR: 5-51) days; (P = 0.002), respectively]; (iv) there were no significant differences in these outcomes between patients with positive PCR/ESI-MS (≥17 GE/well) who had negative AF cultures and those with positive AF cultures; and (v) PCR/ESI-MS detected genomic material from viruses in two patients (1.4%).

CONCLUSION

(i) Rapid diagnosis of intra-amniotic infection is possible using PCR/ESI-MS; (ii) the combined use of biomarkers of inflammation and PCR/ESI-MS allows for the identification of specific bacteria and viruses in women with preterm labor and intra-amniotic infection; and (iii) this approach may allow for administration of timely and specific interventions to reduce morbidity attributed to infection-induced preterm birth.

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

BACKGROUND

Meconium-stained amniotic fluid (MSAF) is a common occurrence among women in spontaneous labor at term, and has been associated with adverse outcomes in both mother and neonate. MSAF is a risk factor for microbial invasion of the amniotic cavity (MIAC) and preterm birth among women with preterm labor and intact membranes. We now report the frequency of MIAC and the presence of bacterial endotoxin in the amniotic fluid of patients with MSAF at term.

MATERIALS AND METHODS

We conducted a cross-sectional study including women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and were later determined to be at term (n = 108). Patients were allocated into two groups: (1) MSAF (n = 66) and (2) clear amniotic fluid (n = 42). The presence of bacteria was determined by microbiologic techniques, and endotoxin was detected using the Limulus amebocyte lysate (LAL) gel clot assay. Statistical analyses were performed to test for normality and bivariate comparisons.

RESULTS

Bacteria were more frequently present in patients with MSAF compared to those with clear amniotic fluid [19.6% (13/66) versus 4.7% (2/42); p < 0.05]. The microorganisms were Gram-negative rods (n = 7), Ureaplasma urealyticum (n = 4), Gram-positive rods (n = 2) and Mycoplasma hominis (n = 1). The LAL gel clot assay was positive in 46.9% (31/66) of patients with MSAF, and in 4.7% (2/42) of those with clear amniotic fluid (p < 0.001). After heat treatment, the frequency of a positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) versus 2.3% (1/42), p < 0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher [1.3 (0.7-1.9) versus 0.6 (0.3-1.2), p = 0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) versus 9 (7.4-12.6), p < 0.001] in the MSAF group, than in those with clear amniotic fluid.

CONCLUSION

MSAF at term was associated with an increased incidence of MIAC. The index of suspicion for an infection-related process in postpartum women and their neonates should be increased in the presence of MSAF.

IL-1β expression in the distal lung epithelium disrupts lung morphogenesis and epithelial cell differentiation in fetal mice

Perinatal inflammation and the inflammatory cytokine IL-1 can modify lung morphogenesis. To examine the effects of antenatal expression of IL-1β in the distal airway epithelium on fetal lung morphogenesis, we studied lung development and surfactant expression in fetal mice expressing human IL-1β under the control of the surfactant protein (SP)-C promoter. IL-1β-expressing pups suffered respiratory failure and died shortly after birth. IL-1β caused fetal lung inflammation and enhanced the expression of keratinocyte-derived chemokine (KC/CXCL1) and monocyte chemoattractant protein 3 (MCP-3/CCL7), the calgranulins S100A8 and S100A9, the acute-phase protein serum amyloid A3, the chitinase-like proteins Ym1 and Ym2, and pendrin. IL-1β decreased the percentage of the total distal lung area made up of air saccules and the number of air saccules in the lungs of fetal mice. IL-1β inhibited the expression of VEGF-A and its receptors VEGFR-1 and VEGFR-2. The percentage of the cellular area of the distal lung made up of capillaries was decreased in IL-1β-expressing fetal mice. IL-1β suppressed the production of SP-B and pro-SP-C and decreased the amount of phosphatidylcholine and the percentage of palmitic acid in the phosphatidylcholine fraction of lung phospholipids, indicating that IL-1β prevented the differentiation of type II epithelial cells. The production of Clara cell secretory protein in the nonciliated bronchiolar (Clara) cells was likewise suppressed by IL-1β. In conclusion, expression of IL-1β in the epithelium of the distal airways disrupted the development of the airspaces and capillaries in the fetal lung and caused fatal respiratory failure at birth.