Pathogenesis of bronchopulmonary dysplasia

Mitochondrial DNA mutations in extremely preterm infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a serious chronic lung disease affecting extremely preterm infants. While mitochondrial dysfunction has been investigated in various medical conditions, limited research has explored mitochondrial DNA (mtDNA) gene mutations, specifically in BPD. This study aimed to evaluate mitochondrial mtDNA gene mutations in extremely preterm infants with BPD. In this prospective observational study, we enrolled a cohort of extremely preterm infants diagnosed with BPD. Clinical data were collected to provide comprehensive patient profiles. Peripheral blood mononuclear cells were isolated from whole-blood samples obtained within a defined timeframe. Subsequently, mtDNA extraction and sequencing using next-generation sequencing technology were performed to identify mtDNA gene mutations. Among the cohort of ten extremely preterm infants with BPD, mtDNA sequencing revealed the presence of mutations in seven patients, resulting in a total of twenty-one point mutations. Notably, many of these mutations were identified in loci associated with critical components of the respiratory chain complexes, vital for proper mitochondrial function and cellular energy production. This pilot study provides evidence of mtDNA point mutations in a subset of extremely preterm infants with BPD. These findings suggest a potential association between mitochondrial dysfunction and the pathogenesis of BPD. Further extensive investigations are warranted to unravel the mechanisms underlying mtDNA mutations in BPD.

Mechanical ventilation in special populations

Optimal respiratory support can only be achieved if the ventilator strategy utilized for each individual patient at any given point in the evolution of their disease process is tailored to the underlying pathophysiology. The critically ill newborn infant requires individualized patient care when it comes to mechanical ventilation. This can only occur if the clinician has a good understanding of the different pathophysiologies of a variety of conditions that can lead to respiratory failure. In this chapter we describe the key pathophysiological features of bronchopulmonary dysplasia, meconium aspiration syndrome and lung hypoplasia syndromes with emphasis on congenital diaphragmatic hernia. We review available evidence to guide management an provide specific recommendations for pathophysiologically-based mechanical ventilation support.

A clinical informatics approach to bronchopulmonary dysplasia: current barriers and future possibilities

Bronchopulmonary dysplasia (BPD) is a complex, multifactorial lung disease affecting preterm neonates that can result in long-term pulmonary and non-pulmonary complications. Current therapies mainly focus on symptom management after the development of BPD, indicating a need for innovative approaches to predict and identify neonates who would benefit most from targeted or earlier interventions. Clinical informatics, a subfield of biomedical informatics, is transforming healthcare by integrating computational methods with patient data to improve patient outcomes. The application of clinical informatics to develop and enhance clinical therapies for BPD presents opportunities by leveraging electronic health record data, applying machine learning algorithms, and implementing clinical decision support systems. This review highlights the current barriers and the future potential of clinical informatics in identifying clinically relevant BPD phenotypes and developing clinical decision support tools to improve the management of extremely preterm neonates developing or with established BPD. However, the full potential of clinical informatics in advancing our understanding of BPD with the goal of improving patient outcomes cannot be achieved unless we address current challenges such as data collection, storage, privacy, and inherent data bias.

A Systematic Review: Is Early Fluid Restriction in Preterm Neonates Going to Prevent Bronchopulmonary Dysplasia?

Preterm birth causes constant challenges, with bronchopulmonary dysplasia (BPD) being a major concern. Immediately after birth, it takes time to establish feeding between the mother and the premature baby. During this time, the telological shifting of fluid from extracellular space to intracellular space will help the baby; this transition should be smooth. Both normal physiologic changes and pathophysiologic events are capable of disrupting this delicate fluid shifting that occurs in very low-birth-weight infants during the first week of life. The immaturity of the renal system and evaporative losses complicate this process. This lack of fluid displacement can be associated with an increased amount of water in the lungs and reduced lung compliance. This can lead to the need for more ventilatory support and a higher oxygen requirement, which, in turn, leads to lung damage. The fluid restriction is also associated with complications such as severe dehydration, intracranial hemorrhage, and bilirubin toxicity. However, the administration of large amounts of fluid and salt is associated with an increased incidence of patent ductus arteriosus, BPD, necrotizing enterocolitis, and intraventricular hemorrhage. There were studies conducted in both the pre-surfactant and surfactant eras that were inconclusive regarding fluid restriction in BPD. We only included very recent studies. This systematic review attempts to summarize the current evidence, focusing on the efficacy and safety of early fluid management in preterm infants. This reduces the risk of BPD and improves outcomes for premature infants. As we know, intact survival is very important. Our review supported the early fluid restriction.

Prevention of Chronic Morbidities in Extremely Premature Newborns with LISA-nCPAP Respiratory Therapy and Adjuvant Perinatal Strategies

Less invasive surfactant administration techniques, together with nasal continuous airway pressure (LISA-nCPAP) ventilation, an emerging noninvasive ventilation (NIV) technique in neonatology, are gaining more significance, even in extremely premature newborns (ELBW), under 27 weeks of gestational age. In this review, studies on LISA-nCPAP are compiled with an emphasis on short- and long-term morbidities associated with prematurity. Several perinatal preventative and therapeutic investigations are also discussed in order to start integrated therapies as numerous organ-saving techniques in addition to lung-protective ventilations. Two thirds of immature newborns can start their lives on NIV, and one third of them never need mechanical ventilation. With adjuvant intervention, these ratios are expected to be increased, resulting in better outcomes. Optimized cardiopulmonary transition, especially physiologic cord clamping, could have an additively beneficial effect on patient outcomes gained from NIV. Organ development and angiogenesis are strictly linked not only in the immature lung and retina, but also possibly in the kidney, and optimized interventions using angiogenic growth factors could lead to better morbidity-free survival. Corticosteroids, caffeine, insulin, thyroid hormones, antioxidants, N-acetylcysteine, and, moreover, the immunomodulatory components of mother's milk are also discussed as adjuvant treatments, since immature newborns deserve more complex neonatal interventions.

Impact of early screening echocardiography and targeted PDA treatment on neonatal outcomes in "22-23" week and "24-26" infants

The hemodynamically significant patent ductus arteriosus (hsPDA) is a controversial topic in neonatology, particularly among neonates at the earliest gestational ages of 22+0-23+6 weeks. There is little, to no data on the natural history or impact of the PDA in extremely preterm babies. In addition, these high-risk patients have typically been excluded from randomized clinical trials of PDA treatment. In this work, we present the impact of early hemodynamic screening (HS) of a cohort of patients born 22+0-23+6 weeks gestation who either were diagnosed with hsPDA or died in the first postnatal week as compared to a historical control (HC) cohort. We also report a comparator population of 24+0-26+6 weeks gestation. All patients in the HS epoch were evaluated between 12-18h postnatal age and treated based on disease physiology whereas the HC patients underwent echocardiography at the discretion of the clinical team. We demonstrate a two-fold reduction in the composite primary outcome of death prior to 36 weeks or severe BPD and report a lower incidence of severe intraventricular hemorrhage (n=5, 7% vs n=27, 27%), necrotizing enterocolitis (n=1, 1% vs n=11, 11%) and first-week vasopressor use (n=7, 11% vs n=40, 39%) in the HS cohort. HS was also associated with an increase in survival free of severe morbidity from the already high rate of 50% to 73% among neonates <24 weeks gestation. We present a biophysiological rationale behind the potential modulator role of hsPDA on these outcomes and review the physiology relevant to neonates born at these extremely preterm gestations. These data highlight the need for further interrogation of the biological impact of hsPDA and impact of early echocardiography directed therapy in infants born less than 24 weeks gestation.

Postnatal abnormality in brainstem neural conduction in neonatal bronchopulmonary dysplasia survivors

OBJECTIVE

To investigate postnatal neural conduction in the auditory brainstem in neonatal bronchopulmonary dysplasia (BPD) survivors.

METHODS

Thirty-two very preterm BPD survivors were studied at 57-58 weeks of postconceptional age. Brainstem auditory-evoked response was studied using maximum length sequence. Wave latencies and intervals were analyzed in detail. The controls were 37 normal term infants and 35 very preterm non-BPD infants.

RESULTS

Compared with normal term controls, BPD survivors showed significantly shortened I-III interval but significantly prolonged III-V interval and greater III-V/I-III interval ratio. Compared with very preterm non-BPD controls, BPD survivors showed a significant shortening in waves III latency and I-III interval, moderate prolonged III-V interval, and significantly greater III-V/I-III interval ratio. These differences were generally similar at all click rates used. The slopes of latency- and interval-click rate functions in BPD survivors did not differ significantly from the two control groups.

CONCLUSIONS

Brainstem neural conduction in BPD survivors differed from normal term and age-matched non-BPD infants; neural maturation is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions, which may constitute an important risk for postnatal neurodevelopment in BPD survivors.

IMPACT

We found that brainstem neural conduction at PCA 57-58 weeks in neonatal BPD survivors differs from normal term and age-matched non-BPD infants. No major differences were found between normal term and very preterm non-BPD infants in brainstem auditory conduction. Neural conduction in BPD survivors is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions. The abnormality may constitute an important risk for postnatal neurodevelopment in BPD survivors.

A Quality Improvement Initiative to Reduce Bronchopulmonary Dysplasia in a Level 4 NICU-Golden Hour Management of Respiratory Distress Syndrome in Preterm Newborns

BACKGROUND

Prevention of chronic lung disease (CLD) requires a multidisciplinary approach spanning from the delivery room to Neonatal Intensive Care Unit (NICU) discharge. In 2018, a quality improvement (QI) initiative commenced in a level 4 NICU with the goal of decreasing chronic lung disease rates below the Vermont Oxford Network (VON) average of 24%.

METHODS

Improvement strategies focused on addressing the primary drivers of ventilation strategies, surfactant administration, non-invasive ventilation, medication use, and nutrition/fluid management. The primary outcome was VON CLD, defined as need for mechanical ventilation and/or supplemental oxygen use at 36 weeks postmenstrual age. Statistical process control charts were used to display and analyze data over time.

RESULTS

The overall CLD rate decreased from 33.5 to 16.5% following several interventions, a 51% reduction that has been sustained for >18 months. Changes most attributable to this include implementation of the "golden hour" gestational age (GA) based delivery room protocol that encourages early surfactant administration and timely extubation. Fewer infants were intubated across all GA groups with the largest improvement among infants 26-27 weeks GA.

CONCLUSIONS

Our efforts significantly decreased CLD through GA-based respiratory guidelines and a comprehensive, rigorous QI approach that can be applicable to other teams focused on improvement.

Prenatal indole-3-carbinol administration activates aryl hydrocarbon receptor-responsive genes and attenuates lung injury in a bronchopulmonary dysplasia model

Hyperoxia-hypoxia exposure is a proposed cause of alveolar developmental arrest in bronchopulmonary dysplasia in preterm infants, where mitochondrial reactive oxygen species and oxidative stress vulnerability are increased. The aryl hydrocarbon receptor (AhR) is one of the main activators of the antioxidant enzyme system that protects tissues and systems from damage. The present study aimed to determine if the activation of the AhR signaling pathway by prenatal administration of indole-3-carbinol (I3C) protects rat pups from hyperoxia-hypoxia-induced lung injury. To assess the activation of protein-encoding genes related to the AhR signaling pathway (Cyp1a1, Cyp1b1, Ugt1a6, Nqo1, and Gsta1), pup lungs were excised at 0, 24, and 72 h after birth, and mRNA expression levels were quantified by reverse transcription-quantitative polymerase chain reaction assays (RT-qPCR). An adapted Ratner's method was used in rats to evaluate radial alveolar counts (RACs) and the degree of fibrosis. The results reveal that the relative expression of AhR-related genes in rat pups of prenatally I3C-treated dams was significantly different from that of untreated dams. The RAC was significantly lower in the hyperoxia-hypoxia group (4.0 ± 1.0) than that in the unexposed control group (8.0 ± 2.0; P < 0.01). When rat pups of prenatally I3C-treated dams were exposed to hyperoxia-hypoxia, an RAC recovery was observed, and the fibrosis index was similar to that of the unexposed control group. A cytokine antibody array revealed an increase in the NF-κB signaling cascade in I3C-treated pups, suggesting that the pathway could regulate the inflammatory process under the stimulus of this compound. In conclusion, the present study demonstrates that I3C prenatal treatment activates AhR-responsive genes in pup's lungs and hence attenuates lung damage caused by hyperoxia-hypoxia exposure in newborns.

Predictors of Developmental and Respiratory Outcomes Among Preterm Infants With Bronchopulmonary Dysplasia

Objectives: To examine the importance of perinatal and postnatal environmental factors on developmental and respiratory outcomes among preterm infants with bronchopulmonary dysplasia (BPD). Methods: Preterm infants (<32 weeks of gestation) born at a single tertiary medical center between 2012 and 2015 were included. Development was assessed at 12 months corrected age. Parents retrospectively completed a health and lifestyle questionnaire reviewing their child's health during the first 2 years of life. A linear regression model was applied to assess the effect of various perinatal and postnatal factors on development. A machine-learning algorithm was trained to assess factors affecting inhaler use. Results: Of 398 infants meeting the inclusion criteria, 208 qualified for the study: 152 (73.1%) with no BPD, 40 (19.2%) with mild BPD, and 16 (7.7%) with moderate-severe BPD. Those in the moderate-severe group were more likely to be male, have mothers who were less educated, and require longer ventilation periods and less time to regain birth weight. They were also more likely to have mothers with asthma/allergies and to have a parent who smoked. Those in the moderate-severe BPD group exhibited significantly lower developmental scores (85.2 ± 16.4) than the no-BPD group (99.3 ± 10.9) and the mild BPD group (97.8 ± 11.7, p < 0.008) as well as more frequent inhaler use (p = 0.0014) than those with no or mild BPD. In addition to perinatal factors, exposure to breast milk, income level and daycare attendance positively affected development. Exposure to cigarette smoke, allergies among family members and daycare attendance proved to be important factors in inhaler use frequency. Conclusions: Postnatal environmental factors are important in predicting and modifying early childhood outcomes among preterm infants.

Weighted Gene Co-expression Network Analysis of Key Biomarkers Associated With Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a complex disorder resulting from interactions between genes and the environment. The accurate molecular etiology of BPD remains largely unclear. This study aimed to identify key BPD-associated genes and pathways functionally enriched using weighted gene co-expression network analysis (WGCNA). We analyzed microarray data of 62 pre-term patients with BPD and 38 pre-term patients without BPD from Gene Expression Omnibus (GEO). WGCNA was used to construct a gene expression network, and genes were classified into definite modules. In addition, the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of BPD-related hub genes were performed. Firstly, we constructed a weighted gene co-expression network, and genes were divided into 10 modules. Among the modules, the yellow module was related to BPD progression and severity and included the following hub genes: MMP25, MMP9, SIRPA, CKAP4, SLCO4C1, and SLC2A3; and the red module included some co-expression molecules that displayed a continuous decline in expression with BPD progression and included the following hub genes: LEF1, ITK, CD6, RASGRP1, IL7R, SKAP1, CD3E, and ICOS. GO and KEGG analyses showed that high expression of inflammatory response-related genes and low expression of T cell receptor activation-related genes are significantly correlated with BPD progression. The present WGCNA-based study thus provides an overall perspective of BPD and lays the foundation for identifying potential pathways and hub genes that contribute to the development of BPD.

Oxygen Therapy for Neonatal Resuscitation in the Delivery Room

Oxygen is commonly used in the delivery room during neonatal resuscitation. The transition from intrauterine to extrauterine life is a challenge to newborns, and exposure to too much oxygen can cause an increase in oxidative stress. The goal of resuscitation is to achieve normal oxygen levels as quickly as possible while avoiding excessive oxygen exposure and preventing inadequate oxygen supplementation. Although it has been shown that room air resuscitation is as effective as using 100% oxygen, often preterm infants need some degree of oxygen supplementation. The ideal concentration of oxygen with which to initiate resuscitation is yet to be determined. Current delivery room resuscitation guidelines recommend the use of room air for term newborns and preterm newborns of greater than or equal to 35 weeks' gestation and the use of a fraction of inspired oxygen of 0.21 to 0.3 for preterm infants of less than 35 weeks' gestation. Further recommendations include titrating oxygen supplementation as needed to obtain goal saturations. However, there is no current consensus on an intermediate oxygen concentration to start resuscitation or goal range saturations for preterm and asphyxiated term infants.

Early Neonatal Oxygen Exposure Predicts Pulmonary Morbidity and Functional Deficits at 1 Year

OBJECTIVE

To evaluate the predictive value of cumulative oxygen exposure thresholds over the first 2 postnatal weeks, linking them to bronchopulmonary dysplasia (BPD) and 1-year pulmonary morbidity and lung function in extremely low gestational age newborns.

STUDY DESIGN

Infants (N = 704) enrolled in the Prematurity and Respiratory Outcomes Program, a multicenter prospective cohort study, that survived to discharge were followed through their neonatal intensive care unit hospitalization to 1-year corrected age. Cumulative oxygen exposure (Oxygen_AUC14) thresholds were derived from univariate models of BPD, stratifying infants into high-, intermediate-, and low-oxygen exposure groups. These groups were then used in multivariate logistic regressions to prospectively predict post-prematurity respiratory disease (PRD), respiratory morbidity score (RMS) in the entire cohort, and pulmonary function z scores (N = 108 subset of infants) at 1-year corrected age.

RESULTS

Over the first 14 postnatal days, infants exposed to high oxygen averaged ≥33.1% oxygen, infants exposed to intermediate oxygen averaged 29.1%-33.1%, and infants exposed to low oxygen were below both cutoffs. In multivariate models, infants exposed to high oxygen showed increased PRD and RMS, whereas infants exposed to intermediate oxygen demonstrated increased moderate/severe RMS. Infants in the high/intermediate groups had decreased forced expiratory volume at 0.5 seconds/forced vital capacity ratio.

CONCLUSIONS

Oxygen_AUC14 establishes 3 thresholds of oxygen exposure that risk stratify infants early in their neonatal course, thereby predicting short-term (BPD) and 1-year (PRD, RMS) respiratory morbidity. Infants with greater Oxygen_AUC14 have altered pulmonary function tests at 1 year of age, indicating early evidence of obstructive lung disease and flow limitation, which may predispose extremely low gestational age newborns to increased long-term pulmonary morbidity.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01435187.

Repair of isolated atrial septal defect in infants less than 12 months improves symptoms of chronic lung disease or shunt-related pulmonary hypertension

INTRODUCTION

Infants with isolated atrial septal defects are usually minimally symptomatic, and repair is typically performed after infancy. Early repair may be considered if there is high pulmonary blood flow and reduced respiratory reserve or early signs of pulmonary hypertension. Our aim was to review the characteristics and outcomes of a cohort of patients who underwent infant repair at our institute.

METHODS

The study included 56 infants (28 female, 19 trisomy 21) with isolated atrial septal defect (age: 8 months (1.5-12), weight: 6 kg (2.8-7.5), echo Qp/Qs: 1.9 ± 0.1) who underwent surgical closure (20 fenestrated). Three groups were identified: 1) chronic lung disease and pulmonary hypertension (group A: n = 28%); 2) acutely unwell infants with pulmonary hypertension but no chronic lung disease (group B: n = 20, 36%); and 3) infants with refractory congestive heart failure without either pulmonary hypertension or chronic lung disease (group C: n = 9, 16%).

RESULTS

Post-operatively, pulmonary hypertension infants (47/56) showed improvement in tricuspid annular plane systolic excursion z-score (p < 0.001) and right ventricular systolic/diastolic duration ratio (p < 0.05). All ventilator (14.3%) or oxygen-dependent (31.6%) infants could be weaned within 2 weeks after repair. One year later, weight z-score increased in all patients and by +1 in group A, +1.3 in group B and +2 in group C. Over a median follow-up of 1.4 years, three patients died, four patients continued to have pulmonary hypertension evidence and two remained on targeted pulmonary hypertension therapy.

CONCLUSION

Atrial septal defect repair within the first year may improve the clinical status and growth in infants with early signs of pulmonary hypertension or those requiring respiratory support and facilitate respiratory management.

Bone marrow stem cells accelerate lung maturation and prevent the LPS-induced delay of morphological and functional fetal lung development in the presence of ErbB4

ErbB4 is a regulator in lung development and disease. Prenatal infection is an important risk factor for the delay of morphologic lung development, while promoting the maturation of the surfactant system. Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to prevent lung injury. We hypothesized that BMSCs in comparison with hematopoietic control stem cells (HPSCs) minimize the lipopolysaccharide (LPS)-induced lung injury only when functional ErbB4 receptor is present. We injected LPS and/or murine green fluorescent protein-labeled BMSCs or HPSCs into the amniotic cavity of transgenic ErbB4^heart mothers at gestational day 17. Fetal lungs were analyzed 24 h later. BMSCs minimized significantly LPS-induced delay in morphological lung maturation consisting of a stereologically measured increase in mesenchyme and septal thickness and a decrease of future airspace and septal surface. This effect was more prominent and significant in the ErbB4^heart+/- lungs, suggesting that the presence of functioning ErbB4 signaling is required. BMSC also diminished the LPS induced increase in surfactant protein (Sftp)a mRNA and decrease in Sftpc mRNA is only seen if ErbB4 is present. The reduction of morphological delay of lung development and of levels of immune-modulating Sftp was more pronounced in the presence of the ErbB4 receptor. Thus, ErbB4 may be required for the protective signaling of BMSCs.

Intranasal delivery of human umbilical cord Wharton's jelly mesenchymal stromal cells restores lung alveolarization and vascularization in experimental bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating lung condition that develops in premature newborns exposed to prolonged mechanical ventilation and supplemental oxygen. Significant morbidity and mortality are associated with this costly disease and effective therapies are limited. Mesenchymal stem/stromal cells (MSCs) are multipotent cells that can repair injured tissue by secreting paracrine factors known to restore the function and integrity of injured lung epithelium and endothelium. Most preclinical studies showing therapeutic efficacy of MSCs for BPD are administered either intratracheally or intravenously. The purpose of this study was to examine the feasibility and effectiveness of human cord tissue-derived MSC administration given via the intranasal route. Human umbilical cord tissue MSCs were isolated, characterized, and given intranasally (500 000 cells per 20 μL) to a hyperoxia-induced rat model of BPD. Lung alveolarization, vascularization, and pulmonary vascular remodeling were restored in animals receiving MSC treatment. Gene and protein analysis suggest the beneficial effects of MSCs were attributed, in part, to a concerted effort targeting angiogenesis, immunomodulation, wound healing, and cell survival. These findings are clinically significant, as neonates who develop BPD have altered alveolar development, decreased pulmonary vascularization and chronic inflammation, all resulting in impaired tissue healing. Our study is the first to report the intranasal delivery of umbilical cord Wharton's jelly MSCs in experimental BPD is feasible, noninvasive, and an effective route that may bear clinical applicability.

Conservative Non-intervention Approach for Hemodynamically Significant Patent Ductus Arteriosus in Extremely Preterm Infants

While persistent patent ductus arteriosus (PDA) in preterm infants has been known to be associated with increased mortality and morbidities including bronchopulmonary dysplasia, and necrotizing enterocolitis, there is minimal evidence supporting their causal relationships, and most traditional medical and/or surgical treatments have failed to show improvements in these outcomes. As such, the pendulum has swung toward the conservative non-intervention approach for the management of persistent PDA during the last decade; however, the benefits and risks of this approach are unclear. In this mini review, we focused on whom, when, and how to apply the conservative non-intervention approach for persistent PDA, especially in extremely preterm infants.

Determinants of the lung microbiome in intubated premature infants at risk for bronchopulmonary dysplasia

BACKGROUND

Airway dysbiosis in premature infants may be associated with bronchopulmonary dysplasia (BPD). Early oropharyngeal colostrum (OPC) administration alters the oral microbiome, which may impact the lung microbiome. We aim to compare the oral and tracheal microbiota during the first week of life, and to determine whether early OPC administration affects microbial diversity or leukocyte inflammatory activity in the lung.

METHODS

Intubated premature infants (n = 42) were evaluated. The oral microbiome was characterized on day of life (DOL) 3, and the tracheal microbiome on DOL 3 and DOL 7, using 16S ribosomal DNA sequencing. Gene expression for inflammatory markers was quantified in airway leukocytes by real-time q-PCR.

RESULTS

The oral and tracheal microbiota were significantly different on DOL 3, but the tracheal microbiome on DOL 7 was more similar to the oral from DOL 3. Tracheal bacterial diversity decreased from DOL 3 to DOL 7. Longer time to first OPC administration tended to be associated with lower bacterial diversity in the airways.

CONCLUSIONS

The tracheal microbiome in intubated premature infants in the first week is likely determined, in part, by the composition of the oral microbiome. Bacterial diversity in intubated babies decreases during the first week of life, a pattern that could be consistent with risk for BPD. Decreased bacterial diversity and increased inflammatory activity in the lung may also be associated with delayed administration of OPC.

Effects of hyperoxia on alveolar and pulmonary vascular development in germ-free mice

Airway microbial dysbiosis is associated with subsequent bronchopulmonary dysplasia (BPD) development in very preterm infants. However, the relationship of airway microbiome in normal pulmonary development has not been defined. To better understand the role of the airway microbiome, we compared normal and abnormal alveolar and pulmonary vascular development in mice with or without a microbiome. We hypothesized that the lungs of germ-free (GF) mice would have an exaggerated phenotypic response to hyperoxia compared with non-germ-free (NGF) mice. With the use of a novel gnotobiotic hyperoxia chamber, GF and NGF mice were exposed to either normoxia or hyperoxia. Alveolar morphometry, pulmonary mechanics, echocardiograms, inflammatory markers, and measures of pulmonary hypertension were studied. GF and NGF mice in normoxia showed no difference, whereas GF mice in hyperoxia showed protected lung structure and mechanics and decreased markers of inflammation compared with NGF mice. We speculate that an increase in abundance of pathogenic bacteria in NGF mice may play a role in BPD pathogenesis by regulating the proinflammatory signaling and neutrophilic inflammation in lungs. Manipulation of the airway microbiome may be a potential therapeutic intervention in BPD and other lung diseases.

Evaluating the use of corticosteroids in preventing and treating bronchopulmonary dysplasia in preterm neonates

Approximately 15 million babies worldwide are born premature, and complications of prematurity are one of the leading causes of death in neonates. Neonatal respiratory distress syndrome (NRDS) and bronchopulmonary dysplasia (BPD) are two of the most common and serious consequences of prematurity. Synthetic corticosteroids, including dexamethasone, have been central in efforts to treat and prevent BPD. There is strong evidence to show that prenatal corticosteroids reduce infant mortality and the incidence of NRDS, leading to their widespread use in obstetric units. However, data suggest that they are not as effective in reducing the incidence of BPD as NRDS, which may be due to the multifactorial pathogenesis of BPD. On the other hand, the use of postnatal corticosteroids in preterm infants is much more controversial. They have been shown to improve lung function and help in reducing the need for mechanical ventilation. These benefits, however, are associated with a range of adverse short- and long-term effects. This review will discuss the benefits and consequences of corticosteroids in treating BPD and will examine alternative treatments and future research that may improve the understanding of BPD and inform clinical practice.

Effects of Hyperoxia on the Developing Airway and Pulmonary Vasculature

Although it is necessary and part of standard practice, supplemental oxygen (40-90% O₂) or hyperoxia is a significant contributing factor to development of bronchopulmonary dysplasia, persistent pulmonary hypertension, recurrent wheezing, and asthma in preterm infants. This chapter discusses hyperoxia and the role of redox signaling in the context of neonatal lung growth and disease. Here, we discuss how hyperoxia promotes dysfunction in the airway and the known redox-mediated mechanisms that are important for postnatal vascular and alveolar development. Whether in the airway or alveoli, redox pathways are important and greatly influence the neonatal lung.

Loss of CD73-mediated extracellular adenosine production exacerbates inflammation and abnormal alveolar development in newborn mice exposed to prolonged hyperoxia

BackgroundHyperoxic lung injury is characterized by cellular damage from high oxygen concentrations that lead to an inflammatory response and it disrupts normal alveolarization in the developing newborn lung. Adenosine is a signaling molecule that is generated extracellularly by ecto-5'-nucleotidase (CD73) in response to injury. Extracellular adenosine signals through cell surface receptors and has been found to have a protective role in acute injury situations; however, chronic elevations have been associated with detrimental changes in chronic lung diseases. We hypothesized that hyperoxia-induced lung injury leads to CD73-mediated increases in extracellular adenosine, which are detrimental to the newborn lung.MethodsC57Bl/6 and CD73-/- mice were exposed to 95% oxygen, 70% oxygen, or room air. Adenosine concentration and markers of pulmonary inflammation and lung development were measured.ResultsExposure to hyperoxia caused pulmonary inflammation and disrupted normal alveolar development in association with increased pulmonary adenosine levels. Loss of CD73-mediated extracellular adenosine production led to decreased survival with exposure to 95% oxygen, and exacerbated pulmonary inflammation and worsened lung development with 70% oxygen exposure.ConclusionExposure to hyperoxia causes lung injury associated with an increase in adenosine concentration, and loss of CD73-mediated adenosine production leads to worsening of hyperoxic lung injury.Pediatric Research advance online publication, 23 August 2017; doi:10.1038/pr.2017.176.

Influence of prenatal hypoxia and postnatal hyperoxia on morphologic lung maturation in mice

Background

Oxygen supply as a lifesaving intervention is frequently used to treat preterm infants suffering additionally from possible prenatal or perinatal pathogen features. The impact of oxygen and/or physical lung injury may influence the morphological lung development, leading to a chronic postnatal lung disease called bronchopulmonary dysplasia (BPD). At present different experimental BPD models are used. However, there are no systematic comparative studies regarding different influences of oxygen on morphological lung maturation.

Objective

We investigated the influence of prenatal hypoxia and/or postnatal hyperoxia on morphological lung maturation based on stereological parameters, to find out which model best reflects morphological changes in lung development comparable with alterations found in BPD.

Methods

Pregnant mice were exposed to normoxia, the offspring to normoxia (No/No) or to hyperoxia (No/Hyper). Furthermore, pregnant mice were exposed to hypoxia and the offspring to normoxia (Hypo/No) or to hyperoxia (Hypo/Hyper). Stereological investigations were performed on all pups at 14 days after birth.

Results

Compared to controls (No/No) 1) the lung volume was significantly reduced in the No/Hyper and Hypo/Hyper groups, 2) the volume weighted mean volume of the parenchymal airspaces was significantly higher in the Hypo/Hyper group, 3) the total air space volume was significantly lower in the No/Hyper and Hypo/Hyper groups, 4) the total septal surface showed significantly lower values in the No/Hyper and Hypo/Hyper groups, 5) the wall thickness of septa showed the highest values in the Hypo/Hyper group without reaching significance, 6) the volume density and the volume weighted mean volume of lamellar bodies in alveolar epithelial cells type II (AEII) were significantly lower in the Hypo/Hyper group.

Conclusion

Prenatal hypoxia and postnatal hyperoxia differentially influence the maturation of lung parenchyma. In 14 day old mice a significant retardation of morphological lung development leading to BPD-like alterations indicated by different parameters was only seen after hypoxia and hyperoxia.

[Interstitial processes of the lungs in childhood]

Interstitial processes in the lungs of children can be due to several underlying diseases. Knowledge of the child's age is important as genetic aberrations play a major role in diseases in the first 2 years, whereas immunological diseases are more common starting in kindergarden age. In general lung diseases are rare in children, which makes the diagnostics difficult and results in a delayed diagnosis. In addition, pediatric pulmonologists are often very reluctant to perform lung biopsies due to a lack of a specialized pathologist. In order to make a contribution to the diagnostics of pediatric pulmonary diseases, pathologists should be specialized in pulmonary pathology, have a good knowledge of genetic methods and fetal lung development, which includes the genetic factors involved in lung growth and differentiation. A close cooperation with the pediatric pulmonologist is necessary and each patient should be discussed jointly on an interstitial lung disease board to promote the quality of diagnostics. The pathologist should be aware that the developing lungs of children are not just a smaller form of adult lungs and often react very differently. In this article, we mainly focus on diffuse infiltration patterns, such as ground glass and reticulonodular infiltrations as described in high-resolution computed tomography (HRCT). Localized interstitial processes, which can sometimes be tumor-like and malformations are not dealt with; however, vascular malformations are included as these often manifest as diffuse interstitial infiltrations and must therefore be taken into consideration for the differential diagnostics.

Oxidative injury of the pulmonary circulation in the perinatal period: Short- and long-term consequences for the human cardiopulmonary system

Development of the pulmonary circulation is a complex process with a spatial pattern that is tightly controlled. This process is vulnerable for disruption by various events in the prenatal and early postnatal periods. Disruption of normal pulmonary vascular development leads to abnormal structure and function of the lung vasculature, causing neonatal pulmonary vascular diseases. Premature babies are especially at risk of the development of these diseases, including persistent pulmonary hypertension and bronchopulmonary dysplasia. Reactive oxygen species play a key role in the pathogenesis of neonatal pulmonary vascular diseases and can be caused by hyperoxia, mechanical ventilation, hypoxia, and inflammation. Besides the well-established short-term consequences, exposure of the developing lung to injurious stimuli in the perinatal period, including oxidative stress, may also contribute to the development of pulmonary vascular diseases later in life, through so-called "fetal or perinatal programming." Because of these long-term consequences, it is important to develop a follow-up program tailored to adolescent survivors of neonatal pulmonary vascular diseases, aimed at early detection of adult pulmonary vascular diseases, and thereby opening the possibility of early intervention and interfering with disease progression. This review focuses on pathophysiologic events in the perinatal period that have been shown to disrupt human normal pulmonary vascular development, leading to neonatal pulmonary vascular diseases that can extend even into adulthood. This knowledge may be particularly important for ex-premature adults who are at risk of the long-term consequences of pulmonary vascular diseases, thereby contributing disproportionately to the burden of adult cardiovascular disease in the future.

Abnormal findings in brainstem auditory evoked response at 36-37weeks of postconceptional age in babies with neonatal chronic lung disease

AIM

To examine brainstem auditory function at 36-37weeks of postconceptional age in preterm infants who are diagnosed to have neonatal chronic lung disease (CLD).

STUDY DESIGN

Preterm infants, born at 31 and less weeks of gestation, were studied at 36-37weeks of postconceptional age when they were diagnosed to have neonatal CLD. Brainstem auditory evoked response (BAER) was recorded and analyzed at different click rates.

RESULTS

Compared with healthy controls at the same postconceptional age, the CLD infants showed a slightly increase in BAER wave V latency. However, the I-V, and III-V interpeak intervals in the CLD infants were significantly increased. The III-V/I-III interval ratio was also significantly increased. The amplitudes of BAER waves III and V in the CLD infants tended to be reduced. These BAER findings were similar at all 21, 51 and 91/s clicks, although the abnormalities tended to be more significant at higher than at low click rates.

CONCLUSION

At 36-37weeks of postconceptional age, BAER was abnormal in preterm infants who were diagnosed to have neonatal CLD. This suggests that at time when the diagnosis of CLD is made there is functional impairment, reflecting poor myelination, in the brainstem auditory pathway in preterm infants with neonatal CLD.

Mandatory Closure Versus Nonintervention for Patent Ductus Arteriosus in Very Preterm Infants

OBJECTIVE

To determine whether a nonintervention approach for treating hemodynamically significant patent ductus arteriosus (PDA) is associated with decreased mortality and/or morbidity compared with a mandatory closure approach in extremely low birth weight infants.

STUDY DESIGN

We reviewed the medical records of 178 infants of 23-26 weeks' gestational age with PDA, requiring ventilator treatment, and with hemodynamically significant PDA ≥2 mm in size. Mandatory closure was used during period I (July 2009 to December 2011, n = 81), and nonintervention was used during period II (January 2012 to June 2014, n = 97).

RESULTS

During period I, 64% of infants were first treated with indomethacin, and 82% were ultimately ligated surgically. During period II, no infant was treated with indomethacin and/or ligation. The average postnatal day of PDA closure was day 13 and day 44 during periods I and II, respectively. There was significantly more use of diuretics and fluid restriction during period II compared with period I. There was no difference in mortality or morbidities such as necrotizing enterocolitis or intraventricular hemorrhage. The incidence of bronchopulmonary dysplasia (BPD) and the propensity score adjusted OR of BPD were significantly lower during period II compared with period I.

CONCLUSIONS

Despite longer PDA exposure, nonintervention was associated with significantly less BPD compared with mandatory closure. Additional study is warranted to determine the benefits and risks of non-intervention for the hemodynamically significant PDA in extremely low birth weight infants.

Nasal High-Flow Therapy for Primary Respiratory Support in Preterm Infants

BACKGROUND

Treatment with nasal high-flow therapy has efficacy similar to that of nasal continuous positive airway pressure (CPAP) when used as postextubation support in neonates. The efficacy of high-flow therapy as the primary means of respiratory support for preterm infants with respiratory distress has not been proved.

METHODS

In this international, multicenter, randomized, noninferiority trial, we assigned 564 preterm infants (gestational age, ≥28 weeks 0 days) with early respiratory distress who had not received surfactant replacement to treatment with either nasal high-flow therapy or nasal CPAP. The primary outcome was treatment failure within 72 hours after randomization. Noninferiority was determined by calculating the absolute difference in the risk of the primary outcome; the chosen margin of noninferiority was 10 percentage points. Infants in whom high-flow therapy failed could receive rescue CPAP; infants in whom CPAP failed were intubated and mechanically ventilated.

RESULTS

Trial recruitment stopped early at the recommendation of the independent data and safety monitoring committee because of a significant difference in the primary outcome between treatment groups. Treatment failure occurred in 71 of 278 infants (25.5%) in the high-flow group and in 38 of 286 infants (13.3%) in the CPAP group (risk difference, 12.3 percentage points; 95% confidence interval [CI], 5.8 to 18.7; P<0.001). The rate of intubation within 72 hours did not differ significantly between the high-flow and CPAP groups (15.5% and 11.5%, respectively; risk difference, 3.9 percentage points; 95% CI, -1.7 to 9.6; P=0.17), nor did the rate of adverse events.

CONCLUSIONS

When used as primary support for preterm infants with respiratory distress, high-flow therapy resulted in a significantly higher rate of treatment failure than did CPAP. (Funded by the National Health and Medical Research Council and others; Australian New Zealand Clinical Trials Registry number, ACTRN12613000303741 .).

Proton-pump inhibitor omeprazole attenuates hyperoxia induced lung injury

Background

The administration of supplemental oxygen to treat ventilatory insufficiency may lead to the formation of reactive oxygen species and subsequent tissue damage. Cytochrome P4501A1 (CYP1A1) can modulate hyperoxic lung injury by a currently unknown mechanism. Our objective was to evaluate the effect of administration of omeprazole on the induction of CYP1A1 and its influence on hyperoxic lung injury in an established preterm rabbit model.

Methods

Omeprazole was administered either (1) directly to the fetus, (2) to the mother or (3) after birth to the pups in different doses (2–10 or 20 mg/kg). Controls were injected with the same amount of saline. Pups were housed in normoxia (21 %) or hyperoxia (>95 %) for 5 days. Outcome parameters were induction of CYP1A1 measured by real-time polymerase chain reaction (RT-PCR) immediately after delivery, at day 3 and day 5 as well as lung function, morphometry and immunohistochemistry assessed at day 5 of life. Transcriptome analysis was used to define the targeted pathways.

Results

Daily neonatal injections demonstrated a dose-dependent increase in CYP1A1. Lung function tests showed a significant improvement in tissue damping, tissue elasticity, total lung capacity, static compliance and elastance. Morphometry revealed a more developed lung architecture with thinned septae in animals treated with the highest dose (20 mg/kg) of omeprazole. Surfactant protein B, vascular endothelial growth factor and its receptor were significantly increased on immunohistochemical stainings after omeprazole treatment.

Conclusions

Neonatal administration of omeprazole induces CYP1A1 in a dose-dependent matter and combined pre- and postnatal administration attenuates hyperoxic lung injury in preterm rabbits, even with the lowest dose of omeprazole without clear CYP1A1 induction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1009-3) contains supplementary material, which is available to authorized users.

Caveolin-1 regulates the expression of tight junction proteins during hyperoxia-induced pulmonary epithelial barrier breakdown

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common complication in preterm infants that involves the downregulation of tight junction (TJ) proteins. However, the mechanism underlying downregulation of the expression of TJ proteins during at the early stages of hyperoxia-induced BPD remains to be understood. Here, we aimed to identify the role of caveolin-1 (Cav-1) in hyperoxia-induced pulmonary epithelial barrier breakdown.

METHODS

First, we established an in vitro pulmonary epithelial barrier models using primary type II alveolar epithelial cells (AEC-II) from newborn rats. AEC-II was assigned to the hyperoxic (85 % O2/5 % CO2) or normoxic (21 % O2/5 % CO2) groups. Second, AEC-II was transfected with Cav-1-siRNA to downregulate Cav-1 under normoxic exposure. Third, AEC-II was transfected with a cDNA encoding Cav-1 to upregulate Cav-1 expression under hyperoxic exposure. Then, expression levels of Cav-1 and TJ proteins were examined by immunofluorescence staining, reverse transcription-polymerase chain reaction, and Western blotting. The TJ structures visualized using a transmission electron microscope, and transepithelial resistance and apparent permeability coefficient of fluorescein isothiocyanate-dextran, which are indicators of barrier function, were measured.

RESULTS

Our data showed that exposure to hyperoxia disrupted the structure and function of the pulmonary epithelial barrier and decreased the ZO-1, occludin, claudin-4, and Cav-1 expression levels. Moreover, Cav-1 knockdown attenuated the expression of the other three genes and disrupted pulmonary epithelial barrier structure and function under normoxic exposure. However, Cav-1 upregulation markedly antagonized the hyperoxia-induced pulmonary epithelial barrier destruction and TJ protein loss.

CONCLUSIONS

This is the first study to present evidence illustrating the novel role of Cav-1 downregulation-mediated TJ protein loss in pulmonary epithelial barrier destruction during BPD.

Oxygen Saturation Targeting and Bronchopulmonary Dysplasia

Oxygen saturation targeting is widely used in neonatal intensive care, but the optimal target range in very preterm infants has been uncertain and is the subject of recent debate and research. This review briefly discusses the technology of oxygen monitoring and the role of oxygen toxicity in preterm infants. The background to the recent trials of oxygen saturation targeting in acute and continuing care of very preterm infants is reviewed, and the findings and implications of the recent trials, particularly with respect to bronchopulmonary dysplasia, are discussed.

The NLRP3 inflammasome is critically involved in the development of bronchopulmonary dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD), a devastating lung disease in preterm infants, includes inflammation, the mechanisms of which are not fully characterized. Here we report that the activation of the NLRP3 inflammasome is associated with the development of BPD. Hyperoxia-exposed neonatal mice have increased caspase-1 activation, IL1β and inflammation, and decreased alveolarization. Nlrp3(-/-) mice have no caspase-1 activity, no IL1β, no inflammatory response and undergo normal alveolarization. Treatment of hyperoxia-exposed mice with either IL1 receptor antagonist to block IL1β or glyburide to block the Nlrp3 inflammasome results in decreased inflammation and increased alveolarization. Ventilated preterm baboons show activation of the NLRP3 inflammasome with increased IL1β:IL1ra ratio. The IL1β:IL1ra ratio in tracheal aspirates from preterm infants with respiratory failure is predictive of the development of BPD. We conclude that early activation of the NLRP3 inflammasome is a key mechanism in the development of BPD, and represents a novel therapeutic target for BPD.

Recent Changes in the Incidence of Bronchopulmonary Dysplasia among Very-Low-Birth-Weight Infants in Korea

We investigated the incidence of bronchopulmonary dysplasia (BPD) in very-low-birth-weight (VLBW) infants in Korea using the Korean Neonatal Network (KNN) data. In total, 2,386 VLBW infants born from January 2013 to June 2014 were prospectively registered. BPD was defined as supplemental oxygen or positive pressure support at 36 weeks postmenstrual age (PMA). The overall incidence of BPD was 28.9%, and the overall mortality rate in the neonatal intensive care units (NICUs) was 11.9%. To investigate recent changes in the incidence of BPD among VLBW infants, we compared the BPD rate in the present study with the latest nationwide retrospective survey conducted between 2007 and 2008. For comparison, we selected infants (23-31 weeks of gestation) (n=1,990) to adjust for the same conditions with the previous survey in 2007-2008 (n=3,841). Among the limited data on VLBW infants (23-31 weeks of gestation), the incidence of BPD increased by 85% (from 17.8% to 33.0%) and the mortality rate in the NICU decreased by 31.4% (from 18.8% to 12.9%) compared to those in the study conducted in 2007-2008. The current trend of increase in the incidence of BPD among infants can be attributed to the increase in the survival rate of VLBW infants.

cAMP-mediated secretion of brain-derived neurotrophic factor in developing airway smooth muscle

Moderate hyperoxic exposure in preterm infants contributes to subsequent airway dysfunction and to risk of developing recurrent wheeze and asthma. The regulatory mechanisms that can contribute to hyperoxia-induced airway dysfunction are still under investigation. Recent studies in mice show that hyperoxia increases brain-derived neurotrophic factor (BDNF), a growth factor that increases airway smooth muscle (ASM) proliferation and contractility. We assessed the mechanisms underlying effects of moderate hyperoxia (50% O2) on BDNF expression and secretion in developing human ASM. Hyperoxia increased BDNF secretion, but did not alter endogenous BDNF mRNA or intracellular protein levels. Exposure to hyperoxia significantly increased [Ca2+]i responses to histamine, an effect blunted by the BDNF chelator TrkB-Fc. Hyperoxia also increased ASM cAMP levels, associated with reduced PDE4 activity, but did not alter protein kinase A (PKA) activity or adenylyl cyclase mRNA levels. However, 50% O2 increased expression of Epac2, which is activated by cAMP and can regulate protein secretion. Silencing RNA studies indicated that Epac2, but not Epac1, is important for hyperoxia-induced BDNF secretion, while PKA inhibition did not influence BDNF secretion. In turn, BDNF had autocrine effects of enhancing ASM cAMP levels, an effect inhibited by TrkB and BDNF siRNAs. Together, these novel studies suggest that hyperoxia can modulate BDNF secretion, via cAMP-mediated Epac2 activation in ASM, resulting in a positive feedback effect of BDNF-mediated elevation in cAMP levels. The potential functional role of this pathway is to sustain BDNF secretion following hyperoxic stimulus, leading to enhanced ASM contractility and proliferation.

Association of vitamin D binding protein polymorphisms with bronchopulmonary dysplasia: a case-control study of gc globulin and bronchopulmonary dysplasia

OBJECTIVE

The pathophysiologies of bronchopulmonary dysplasia (BPD) are inflammation, infection, tissue damage, angiogenesis defects and genetic susceptibility. Because of the role of the vitamin D binding protein (Gc globulin) on these factors, we investigated the relationship between Gc globulin polymorphisms and BPD.

STUDY DESIGN

This case-control study was performed with 160 neonates (⩽32 gestational ages, ⩽1500 g). PCR DNA sequence analyses were used for GC gene rs4588 and rs7041 single-nucleotide polymorphisms.

RESULT

In the univariate analyses, it was observed that Gc2 was the only variant that was protective against BPD (Odd ratio (OR)=0.47, 95% coinfidence interval (CI)=0.24 to 0.89, P=0.020). In the multivariate analyses, Gc2 decreased the risk of disease (OR=0.15, 95% CI=0.029 to 0.79, P=0.026) independent of gestational age, birth weight, 5-min Appearance, Pulse, Grimace, Activity, and Respiration scores, respiratory distress syndrome and sepsis.

CONCLUSION

The Gc2 variant was, after adjusting for confounders, associated with a decrease in the frequency of BPD. Our study adds Gc globulin to the list of candidate genes that potentially contribute to the etiology of the disease.

Transcriptome Analysis of the Preterm Rabbit Lung after Seven Days of Hyperoxic Exposure

The neonatal management of preterm born infants often results in damage to the developing lung and subsequent morbidity, referred to as bronchopulmonary dysplasia (BPD). Animal models may help in understanding the molecular processes involved in this condition and define therapeutic targets. Our goal was to identify molecular pathways using the earlier described preterm rabbit model of hyperoxia induced lung-injury. Transcriptome analysis by mRNA-sequencing was performed on lungs from preterm rabbit pups born at day 28 of gestation (term: 31 days) and kept in hyperoxia (95% O₂) for 7 days. Controls were preterm pups kept in normoxia. Transcriptomic data were analyzed using Array Studio and Ingenuity Pathway Analysis (IPA), in order to identify the central molecules responsible for the observed transcriptional changes. We detected 2217 significantly dysregulated transcripts following hyperoxia, of which 90% could be identified. Major pathophysiological dysregulations were found in inflammation, lung development, vascular development and reactive oxygen species (ROS) metabolism. To conclude, amongst the many dysregulated transcripts, major changes were found in the inflammatory, oxidative stress and lung developmental pathways. This information may be used for the generation of new treatment hypotheses for hyperoxia-induced lung injury and BPD.

Affect of Early Life Oxygen Exposure on Proper Lung Development and Response to Respiratory Viral Infections

Children born preterm often exhibit reduced lung function and increased severity of response to respiratory viruses, suggesting that premature birth has compromised proper development of the respiratory epithelium and innate immune defenses. Increasing evidence suggests that premature birth promotes aberrant lung development likely due to the neonatal oxygen transition occurring before pulmonary development has matured. Given that preterm infants are born at a point of time where their immune system is also still developing, early life oxygen exposure may also be disrupting proper development of innate immunity. Here, we review current literature in hopes of stimulating research that enhances understanding of how the oxygen environment at birth influences lung development and host defense. This knowledge may help identify those children at risk for disease and ideally culminate in the development of novel therapies that improve their health.

Does chronic oxygen dependency in preterm infants with bronchopulmonary dysplasia at NICU discharge predict respiratory outcomes at 3 years of age?

OBJECTIVE

To determine whether chronic oxygen dependency at the time of discharge from the neonatal intensive care unit (NICU) in infants with bronchopulmonary dysplasia (BPD) predicts respiratory outcomes at 3 years.

STUDY DESIGN

Preterm infants ⩽1250 g without BPD, BPD and BPD with chronic oxygen dependency were identified from the Southern Alberta Perinatal Follow-up clinic database (1995-2007). Respiratory outcomes at 4, 8, 18 and 36 months corrected age following NICU discharge were examined. Univariate analyses were done.

RESULTS

Out of 1563 infants admitted to the NICU, 1212 survived. Complete follow-up data at 36 months were available for 1030 (85%) children. Children with BPD with or without chronic oxygen dependency had significantly (P<0.001) lower birth weights and gestational ages, and greater post-natal steroid use, compared with those with no BPD. At 4, 8 and 18 months follow-up, the use of respiratory medications and supplemental oxygen were both significantly higher in the BPD infants with chronic oxygen dependency group compared with the no-BPD group and BPD group. At 36 months, children in the BPD with chronic oxygen dependency group were more likely to use respiratory medications and supplemental oxygen vs the no-BPD or the BPD groups. At 4, 8 and 36 months of age, more children in the BPD with chronic oxygen dependency group had post-neonatal chronic lung disease (PNCLD) than children in the other groups, but at 36 months the difference was significant only for the BPD with chronic oxygen dependency vs no-BPD group (P<0.001).

CONCLUSIONS

At 36 months, children diagnosed with BPD with chronic oxygen dependency at NICU discharge were more likely to need respiratory medications and supplemental oxygen in the previous 12 months, as compared with no-BPD or BPD groups. They were also more likely to require frequent physician visits and have PNCLD at 3 years, as compared with the no-BPD group.

A multicentre, randomised controlled, non-inferiority trial, comparing high flow therapy with nasal continuous positive airway pressure as primary support for preterm infants with respiratory distress (the HIPSTER trial): study protocol

INTRODUCTION

High flow (HF) therapy is an increasingly popular mode of non-invasive respiratory support for preterm infants. While there is now evidence to support the use of HF to reduce extubation failure, there have been no appropriately designed and powered studies to assess the use of HF as primary respiratory support soon after birth. Our hypothesis is that HF is non-inferior to the standard treatment--nasal continuous positive airway pressure (NCPAP)--as primary respiratory support for preterm infants.

METHODS AND ANALYSIS

The HIPSTER trial is an unblinded, international, multicentre, randomised, non-inferiority trial. Eligible infants are preterm infants of 28-36(+6) weeks' gestational age (GA) who require primary non-invasive respiratory support for respiratory distress in the first 24 h of life. Infants are randomised to treatment with either HF or NCPAP. The primary outcome is treatment failure within 72 h after randomisation, as determined by objective oxygenation, blood gas, and apnoea criteria, or the need for urgent intubation and mechanical ventilation. Secondary outcomes include the incidence of intubation, pneumothorax, bronchopulmonary dysplasia, nasal trauma, costs associated with hospital care and parental stress. With a specified non-inferiority margin of 10%, using a two-sided 95% CI and 90% power, the study requires 375 infants per group (total 750 infants).

ETHICS AND DISSEMINATION

Ethical approval has been granted by the relevant human research ethics committees at The Royal Women's Hospital (13/12), The Royal Children's Hospital (33144A), The Mercy Hospital for Women (R13/34), and the South-Eastern Norway Regional Health Authority (2013/1657). The trial is currently recruiting at 9 centres in Australia and Norway. The trial results will be published in peer-reviewed international journals, and presented at national and international conferences.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry ID: ACTRN12613000303741.

Role of microRNA-150 and glycoprotein nonmetastatic melanoma protein B in angiogenesis during hyperoxia-induced neonatal lung injury

Glycoprotein nonmetastatic melanoma protein B (GPNMB), a transmembrane protein, has been reported to have an important role in tissue repair and angiogenesis. Recently, we have demonstrated that hyperoxia exposure down-regulates microRNA (miR)-150 expression and concurrent induction of its target gene, GPNMB, in neonatal rat lungs. This study aimed to test the hypothesis that soluble GPNMB (sGPNMB) promotes angiogenesis in the hyperoxic neonatal lungs. Wild-type (WT) or miR-150 knockout (KO) neonates, exposed to 95% O2 for 3, 6, and 10 days, were evaluated for lung phenotypes, GPNMB protein expression in the lungs, and sGPNMB levels in the bronchoalveolar lavage. Angiogenic effects of sGPNMB were examined both in vitro and in vivo. After a 6-day exposure, similar analyses were performed in WT and miR-150 KO neonates during recovery at 7, 14, and 21 days. miR-150 KO neonates displayed an increased capillary network, decreased inflammation, and less alveolar damage compared with WT neonates after hyperoxia exposure. The early induction of GPNMB and sGPNMB were found in miR-150 KO neonates. The recombinant GPNMB, which contained a soluble portion of GPNMB, promoted endothelial tube formation in vitro and enhanced angiogenesis in vivo. The increased capillaries in the hyperoxic lungs of miR-150 KO neonates appeared dysmorphic. They were abnormally enlarged in size and occasionally laid at subepithelial regions in the alveoli. However, the lung architecture returned to normal during recovery, suggesting that abnormal vascularity during hyperoxia does not affect postnatal lung development. GPNMB plays an important role in angiogenesis during hyperoxia injury. Treatment with GPNMB may offer a novel therapeutic approach in reducing pathologic complications in bronchopulmonary dysplasia.

Cathepsin K overexpression modifies lung development in newborn mice

Cathepsin K (CatK), contributes to the development of chronic lung disease in newborn infants, but the impact of CatK for the lungs may be multifaceted. We have previously demonstrated that low level of CatK is associated with newborn lung injury and CatK deficiency aggravates lung injury in hyperoxia-exposed newborn mice. Thus, we hypothesized that sustained/higher expression of CatK could ameliorate hyperoxia-induced injury and restrain the development of pulmonary fibrosis. We studied the lungs of newborn wild-type (WT) and CatK overexpressing transgenic mice (TG) that were exposed to hyperoxia or room air for 7 or 14 days after birth. Fourfold pulmonary overexpression of CatK did not affect the growth or lung weight in room-air bred TG mice. The distal airspaces in TG mice were, however, enlarged on postnatal days (PN) 7 and 14, the latter together with increased apoptosis, compared with WT controls. Survival rate was normal and no respiratory distress was observed in air-bred TG mice. Hyperoxia inhibited alveolarization and increased collagen accumulation in WT mice. In TG mice, hyperoxia for 1 week did not aggravate the lung injury, and the lung morphology and already enlarged alveoli remained unchanged in TG mice at PN7. Prolonged hyperoxic exposure caused significant lung injury and mortality similarly in both group of mice, and only few mice survived until PN14. In summary, CatK overexpression slightly enlarges distal airways in infant mice, but hyperoxic environment is initially better tolerated when compared to WT mice. These findings suggest multifaceted role for CatK in lung development and newborn lung injury.

Bacillus Calmette-Guerín vaccination: a novel therapeutic approach to preventing hyperoxic lung injury

OBJECTIVE

A growing body of evidence suggests that vaccinations play a role in the normal maturation of the immune system and in both the development and balance of immune regulatory pathways that can impact health later in life. This study aimed to evaluate the effects of Bacillus Calmette-Guerín (BCG) vaccine on the hyperoxia-induced neonatal rat lung injury.

METHODS

Four groups were defined as hyperoxia-exposed BCG-vaccinated, hyperoxia-exposed placebo, room air-exposed control and room air-exposed BCG-vaccinated group. The validity of the hyperoxia-induced lung injury model used in this study was confirmed by histological and immunohistochemical test. Gene expression related with cytokine and growth factor was evaluated by real-time reverse transcription polymerase chain reaction.

RESULT

The mean alveolar surface area and quantification of secondary crest formation in the oxygen-exposed placebo group was significantly lower than that of the oxygen-exposed BCG-vaccinated group. Compared to the oxygen-exposed placebo group, the oxygen-exposed BCG-vaccinated group showed a significantly decreased alveolar septal fibrosis and smooth muscle actin expression. The expression of genes VEGF, FGF-BP1, IL-13, and NFκB1 (p50) in the lungs of the hyperoxia-exposed BCG-vaccinated group was significantly higher than that of the hyperoxia-exposed placebo group.

CONCLUSION

Results suggest that BCG vaccination can protect against neonatal hyperoxic lung injury. These benefits may be interpreted to coincide with its immunomodulatory effects on pro-inflammatory and anti-inflammatory cytokine balance and expression of growth factors.

Effects of Wharton's jelly-derived mesenchymal stem cells on neonatal neutrophils

Background

Mesenchymal stem cells (MSCs) have been proposed as autologous therapy for inflammatory diseases in neonates. MSCs from umbilical cord Wharton’s jelly (WJ-MSCs) are accessible, with high proliferative capacity. The effects of WJ-MSCs on neutrophil activity in neonates are not known. We compared the effects of WJ-MSCs on apoptosis and the expression of inflammatory, oxidant, and antioxidant mediators in adult and neonatal neutrophils.

Methods

WJ-MSCs were isolated, and their purity and function were confirmed by flow cytometry. Neutrophils were isolated from cord and adult blood by density centrifugation. The effects of neutrophil/WJ-MSC co-culture on apoptosis and gene and protein expression were measured.

Results

WJ-MSCs suppressed neutrophil apoptosis in a dose-dependent manner. WJ-MSCs decreased gene expression of NADPH oxidase-1 in both adult and neonatal neutrophils, but decreased heme oxygenase-1 and vascular endothelial growth factor and increased catalase and cyclooxygenase-2 in the presence of lipopolysaccharide only in adult cells. Similarly, generation of interleukin-8 was suppressed in adult but not neonatal neutrophils. Thus, WJ-MSCs dampened oxidative, vascular, and inflammatory activity by adult neutrophils, but neonatal neutrophils were less responsive. Conversely, Toll-like receptor-4, and cyclooxygenase-2 were upregulated in WJ-MSCs only in the presence of adult neutrophils, suggesting an inflammatory MSC phenotype that is not induced by neonatal neutrophils.

Conclusion

Whereas WJ-MSCs altered gene expression in adult neutrophils in ways suggesting anti-inflammatory and antioxidant effects, these responses were attenuated in neonatal cells. In contrast, inflammatory gene expression in WJ-MSCs was increased in the presence of adult but not neonatal neutrophils. These effects should be considered in clinical trial design before WJ-MSC-based therapy is used in infants.

Animal models of bronchopulmonary dysplasia. The preterm and term rabbit models

Bronchopulmonary dysplasia (BPD) is an important lung developmental pathophysiology that affects many premature infants each year. Newborn animal models employing both premature and term animals have been used over the years to study various components of BPD. This review describes some of the neonatal rabbit studies that have contributed to the understanding of BPD, including those using term newborn hyperoxia exposure models, premature hyperoxia models, and a term newborn hyperoxia model with recovery in moderate hyperoxia, all designed to emulate aspects of BPD in human infants. Some investigators perturbed these models to include exposure to neonatal infection/inflammation or postnatal malnutrition. The similarities to lung injury in human premature infants include an acute inflammatory response with the production of cytokines, chemokines, and growth factors that have been implicated in human disease, abnormal pulmonary function, disordered lung architecture, and alveolar simplification, development of fibrosis, and abnormal vascular growth factor expression. Neonatal rabbit models have the drawback of limited access to reagents as well as the lack of readily available transgenic models but, unlike smaller rodent models, are able to be manipulated easily and are significantly less expensive than larger animal models.

Adenosine promotes vascular barrier function in hyperoxic lung injury

Hyperoxic lung injury is characterized by cellular damage from high oxygen concentrations that lead to an inflammatory response in the lung with cellular infiltration and pulmonary edema. Adenosine is a signaling molecule that is generated extracellularly by CD73 in response to injury. Extracellular adenosine signals through cell surface receptors and has been found to be elevated and plays a protective role in acute injury situations. In particular, ADORA2B activation is protective in acute lung injury. However, little is known about the role of adenosine signaling in hyperoxic lung injury. We hypothesized that hyperoxia-induced lung injury leads to CD73-mediated increases in extracellular adenosine, which is protective through ADORA2B signaling pathways. To test this hypothesis, we exposed C57BL6, CD73(-/-), and Adora2B(-/-) mice to 95% oxygen or room air and examined markers of pulmonary inflammation, edema, and monitored lung histology. Hyperoxic exposure caused pulmonary inflammation and edema in association with elevations in lung adenosine levels. Loss of CD73-mediated extracellular adenosine production exacerbated pulmonary edema without affecting inflammatory cell counts. Furthermore, loss of the ADORA2B had similar results with worsening of pulmonary edema following hyperoxia exposure without affecting inflammatory cell infiltration. This loss of barrier function correlated with a decrease in occludin in pulmonary vasculature in CD73(-/-) and Adora2B(-/-) mice following hyperoxia exposure. These results demonstrate that exposure to a hyperoxic environment causes lung injury associated with an increase in adenosine concentration, and elevated adenosine levels protect vascular barrier function in hyperoxic lung injury through the ADORA2B-dependent regulation of occludin.

High surgical burden for infants with severe chronic lung disease (sCLD)

BACKGROUND/PURPOSE

Infants with severe chronic lung disease (sCLD) may require surgical procedures to manage their medical problems; however, the scope of these interventions is undefined. The purpose of this study was to characterize the frequency, type, and timing of operative interventions performed in hospitalized infants with sCLD.

METHODS

The Children's Hospital Neonatal Database was used to identify infants with sCLD from 24 children's hospital's NICUs hospitalized over a recent 16-month period.

RESULTS

556 infants were diagnosed with sCLD; less than 3% of infants had operations prior to referral and 30% were referred for surgical evaluation. In contrast, 71% of all sCLD infants received ≥1 surgical procedure during the CHND NICU hospitalization, with a mean of 3 operations performed per infant. Gastrostomy insertion (24%), fundoplication (11%), herniorrhaphy (13%), and tracheostomy placement (12%) were the most commonly performed operations. The timing of gastrostomy (PMA 48±10 wk) and tracheostomy (PMA 47±7 wk) insertions varied, and for infants who received both devices, only 33% were inserted concurrently (13/40 infants).

CONCLUSIONS

A striking majority of infants with sCLD received multiple surgical procedures during hospitalizations at participating NICUs. Further work regarding the timing, coordination, perioperative complications, and clinical outcomes for these infants is warranted.