Bronchopulmonary dysplasia: new insights

Management of bronchopulmonary dysplasia in Japan: A nationwide survey

BACKGROUND

The incidence of bronchopulmonary dysplasia (BPD) and respiratory management practices for extremely low birth weight infants (ELBWIs) widely vary among institutions and countries.

AIMS

To clarify the variation and characteristics of the current practices of Japanese neonatologists managing patients with BPD.

STUDY DESIGN

Questionnaire-based survey.

PARTICIPANTS

Level II and III perinatal centers certified by the Japan Society of Perinatal and Neonatal Medicine.

OUTCOME MEASURES

Policies of the neonatal intensive care units (NICUs) regarding respiratory care and medications for BPD prevention and treatment.

RESULTS

A total of 76 % of facilities (207/274) responded to our survey. The response rates of level III and II facilities were 91 % (102/112) and 35 % (105/296), respectively. INtubation-SURfactant-Extubation and Less Invasive Surfactant Administration methods were performed in 23 % (47/206) and 1 % (3/206) of facilities, respectively. For the prophylactic purpose, systemic and inhaled steroids were administered "frequently" or "occasionally" in 14 % (28/205) and 42 % (86/204) of NICUs, respectively. For the therapeutic purpose, systemic and inhaled steroids were administered "frequently" or "occasionally" in 84 % (171/204) and 29 % (59/204) of NICUs, respectively. Approximately half of the NICUs (99/202) used volume-targeted ventilation (VTV) "frequently" or "occasionally" in progressing BPD. High-frequency oscillation ventilation (HFOV) was used for progressing BPD "frequently" and "occasionally" in 89 % (180/202) of the facilities.

CONCLUSIONS

Our study provided an overview and characteristics of BPD management in Japan in recent years. Noninvasive approaches with surfactant administration remain not widely used in Japan. HFOV is a widely accepted management for progressing BPD.

Thyroid hormone modulates hyperoxic neonatal lung injury and mitochondrial function

Mitochondrial dysfunction at birth predicts bronchopulmonary dysplasia (BPD) in extremely low-birth weight (ELBW) infants. Recently, nebulized thyroid hormone (TH), given as triiodothyronine (T3), was noted to decrease pulmonary fibrosis in adult animals through improved mitochondrial function. In this study, we tested the hypothesis that TH may have similar effects on hyperoxia-induced neonatal lung injury and mitochondrial dysfunction by testing whether i.n. T3 decreases neonatal hyperoxic lung injury in newborn mice; whether T3 improves mitochondrial function in lung homogenates, neonatal murine lung fibroblasts (NMLFs), and umbilical cord-derived mesenchymal stem cells (UC-MSCs) obtained from ELBW infants; and whether neonatal hypothyroxinemia is associated with BPD in ELBW infants. We found that inhaled T3 (given i.n.) attenuated hyperoxia-induced lung injury and mitochondrial dysfunction in newborn mice. T3 also reduced bioenergetic deficits in UC-MSCs obtained from both infants with no or mild BPD and those with moderate to severe BPD. T3 also increased the content of peroxisome proliferator-activated receptor γ coactivator 1α in lung homogenates of mice exposed to hyperoxia as well as mitochondrial potential in both NMLFs and UC-MSCs. ELBW infants who died or developed moderate to severe BPD had lower total T4 (TT4) compared with survivors with no or mild BPD. In conclusion, TH signaling and function may play a critical role in neonatal lung injury, and inhaled T3 supplementation may be useful as a therapeutic strategy for BPD.

Distinct lung function and bronchodilator responses between term and preterm young children with recurrent wheezing

BACKGROUND

Recurrent or unresolved wheezing is a common complaint in certain young children populations, especially those born preterm. Using infant lung function testing, we aimed to distinguish the differences between term and preterm young children with recurrent wheezing.

METHODS

Children under 2 years of corrected age were enrolled if they had 3 or more wheezing episodes during the enrollment period. Healthy term controls of comparable age were also recruited for reference. Measurements of lung function were made, including tidal breathing, passive respiratory mechanics, and forced tidal and raised-volume expiration. For children with recurrent wheezing, raised-volume forced expiration was repeated after an adequate delivery of bronchodilator nebulization was achieved.

RESULTS

In total, 68 young children (40 with recurrent wheezing and 28 healthy controls) were recruited. Among children with recurrent wheezing, 23 preterm children (preterm group), and 17 term children (term group) were enrolled. Compared with healthy controls, both the term and preterm groups had lower lung function as measured by absolute values and z scores. The term group performed worse than the preterm group with regard to forced vital capacity, forced expiratory volume at 0.5 s (FEV_0.5), and peak expiratory flow. Following bronchodilator nebulization, the term group had significantly higher increases in FEV_0.5 and forced mid-expiratory flow than the preterm group.

CONCLUSION

Young children with recurrent wheezing, especially term infants, demonstrated lower lung function than healthy controls. Moreover, the term group evidenced greater responsiveness to bronchodilators than the preterm group. The distinct bronchodilator responses may offer further information to guide the diagnosis and treatment of young children with recurrent wheezing.

Lung tissue engineering: An update

Pulmonary disease is a worldwide public health problem that reduces the life quality and increases the need for hospital admissions as well as the risk of premature death. A common problem is the significant shortage of lungs for transplantation as well as patients must also take immunosuppressive drugs for the rest of their lives to keep the immune system from attacking transplanted organs. Recently, a new strategy has been proposed in the cellular engineering of lung tissue as decellularization approaches. The main components for the lung tissue engineering are: (1) A suitable biological or synthetic three-dimensional (3D) scaffold, (2) source of stem cells or cells, (3) growth factors required to drive cell differentiation and proliferation, and (4) bioreactor, a system that supports a 3D composite biologically active. Although a number of synthetic as well biological 3D scaffold suggested for lung tissue engineering, the current favorite scaffold is decellularized extracellular matrix scaffold. There are a large number of commercial and academic made bioreactors, the favor has been, the one easy to sterilize, physiologically stimuli and support active cell growth as well as clinically translational. The challenges would be to develop a functional lung will depend on the endothelialized microvascular network and alveolar-capillary surface area to exchange gas. A critical review of the each components of lung tissue engineering is presented, following an appraisal of the literature in the last 5 years. This is a multibillion dollar industry and consider unmet clinical need.

Thioredoxin Reductase-1 Inhibition Augments Endogenous Glutathione-Dependent Antioxidant Responses in Experimental Bronchopulmonary Dysplasia

Background

Aurothioglucose- (ATG-) mediated inhibition of thioredoxin reductase-1 (TXNRD1) improves alveolarization in experimental murine bronchopulmonary dysplasia (BPD). Glutathione (GSH) mediates susceptibility to neonatal and adult oxidative lung injury. We have previously shown that ATG attenuates hyperoxic lung injury and enhances glutathione- (GSH-) dependent antioxidant defenses in adult mice.

Hypothesis

The present studies evaluated the effects of TXNRD1 inhibition on GSH-dependent antioxidant defenses in newborn mice in vivo and lung epithelia in vitro.

Methods

Newborn mice received intraperitoneal ATG or saline prior to room air or 85% hyperoxia exposure. Glutamate-cysteine ligase (GCL) catalytic (Gclc) and modifier (Gclm) mRNA levels, total GSH levels, total GSH peroxidase (GPx) activity, and Gpx2 expression were determined in lung homogenates. In vitro, murine transformed club cells (mtCCs) were treated with the TXNRD1 inhibitor auranofin (AFN) or vehicle in the presence or absence of the GCL inhibitor buthionine sulfoximine (BSO).

Results

In vivo, ATG enhanced hyperoxia-induced increases in Gclc mRNA levels, total GSH contents, and GPx activity. In vitro, AFN increased Gclm mRNA levels, intracellular and extracellular GSH levels, and GPx activity. BSO prevented AFN-induced increases in GSH levels.

Conclusions

Our data are consistent with a model in which TXNRD1 inhibition augments hyperoxia-induced GSH-dependent antioxidant responses in neonatal mice. Discrepancies between in vivo and in vitro results highlight the need for methodologies that permit accurate assessments of the GSH system at the single-cell level.

Modulators of inflammation in Bronchopulmonary Dysplasia

Over 50 years after its first description, Bronchopulmonary Dysplasia (BPD) remains a devastating pulmonary complication in preterm infants with respiratory failure and develops in 30-50% of infants less than 1000-gram birth weight. It is thought to involve ventilator- and oxygen-induced damage to an immature lung that results in an inflammatory response and ends in aberrant lung development with dysregulated angiogenesis and alveolarization. Significant morbidity and mortality are associated with this most common chronic lung disease of childhood. Thus, any therapies that decrease the incidence or severity of this condition would have significant impact on morbidity, mortality, human costs, and healthcare expenditure. It is clear that an inflammatory response and the elaboration of growth factors and cytokines are associated with the development of BPD. Numerous approaches to control the inflammatory process leading to the development of BPD have been attempted. This review will examine the anti-inflammatory approaches that are established or hold promise for the prevention or treatment of BPD.

Iloprost attenuates hyperoxia-mediated impairment of lung development in newborn mice

Cyclooxygenase-2 (COX-2/PTGS2) mediates hyperoxia-induced impairment of lung development in newborn animals and is increased in the lungs of human infants with bronchopulmonary dysplasia (BPD). COX-2 catalyzes the production of cytoprotective prostaglandins, such as prostacyclin (PGI2), as well as proinflammatory mediators, such as thromboxane A2. Our objective was to determine whether iloprost, a synthetic analog of PGI2, would attenuate hyperoxia effects in the newborn mouse lung. To test this hypothesis, newborn C57BL/6 mice along with their dams were exposed to normoxia (21% O2) or hyperoxia (85% O2) from 4 to 14 days of age in combination with daily intraperitoneal injections of either iloprost 200 µg·kg-1·day-1, nimesulide (selective COX-2 antagonist) 100 mg·kg-1·day-1, or vehicle. Alveolar development was estimated by radial alveolar counts and mean linear intercepts. Lung function was determined on a flexiVent, and multiple cytokines and myeloperoxidase (MPO) were quantitated in lung homogenates. Lung vascular and microvascular morphometry was performed, and right ventricle/left ventricle ratios were determined. We determined that iloprost (but not nimesulide) administration attenuated hyperoxia-induced inhibition of alveolar development and microvascular density in newborn mice. Iloprost and nimesulide both attenuated hyperoxia-induced, increased lung resistance but did not improve lung compliance that was reduced by hyperoxia. Iloprost and nimesulide reduced hyperoxia-induced increases in MPO and some cytokines (IL-1β and TNF-α) but not others (IL-6 and KC/Gro). There were no changes in pulmonary arterial wall thickness or right ventricle/left ventricle ratios. We conclude that iloprost improves lung development and reduces lung inflammation in a newborn mouse model of BPD.

Exosomal microRNA predicts and protects against severe bronchopulmonary dysplasia in extremely premature infants

Premature infants are at high risk for developing bronchopulmonary dysplasia (BPD), characterized by chronic inflammation and inhibition of lung development, which we have recently identified as being modulated by microRNAs (miRNAs) and alterations in the airway microbiome. Exosomes and exosomal miRNAs may regulate cell differentiation and tissue and organ development. We discovered that tracheal aspirates from infants with severe BPD had increased numbers of, but smaller, exosomes compared with term controls. Similarly, bronchoalveolar lavage fluid from hyperoxia-exposed mice (an animal model of BPD) and supernatants from hyperoxia-exposed human bronchial epithelial cells (in vitro model of BPD) had increased exosomes compared with air controls. Next, in a prospective cohort study of tracheal aspirates obtained at birth from extremely preterm infants, utilizing independent discovery and validation cohorts, we identified unbiased exosomal miRNA signatures predictive of severe BPD. The strongest signal of reduced miR-876-3p in BPD-susceptible compared with BPD-resistant infants was confirmed in the animal model and in vitro models of BPD. In addition, based on our recent discovery of increased Proteobacteria in the airway microbiome being associated with BPD, we developed potentially novel in vivo and in vitro models for BPD combining Proteobacterial LPS and hyperoxia exposure. Addition of LPS led to a larger reduction in exosomal miR 876-3p in both hyperoxia and normoxia compared with hyperoxia alone, thus indicating a potential mechanism by which alterations in microbiota can suppress miR 876-3p. Gain of function of miR 876-3p improved the alveolar architecture in the in vivo BPD model, demonstrating a causal link between miR 876-3p and BPD. In summary, we provide evidence for the strong predictive biomarker potential of miR 876-3p in severe BPD. We also provide insights on the pathogenesis of neonatal lung disease, as modulated by hyperoxia and microbial product-induced changes in exosomal miRNA 876-3p, which could be targeted for future therapeutic development.

Extracellular matrix in lung development, homeostasis and disease

The lung's unique extracellular matrix (ECM), while providing structural support for cells, is critical in the regulation of developmental organogenesis, homeostasis and injury-repair responses. The ECM, via biochemical or biomechanical cues, regulates diverse cell functions, fate and phenotype. The composition and function of lung ECM become markedly deranged in pathological tissue remodeling. ECM-based therapeutics and bioengineering approaches represent promising novel strategies for regeneration/repair of the lung and treatment of chronic lung diseases. In this review, we assess the current state of lung ECM biology, including fundamental advances in ECM composition, dynamics, topography, and biomechanics; the role of the ECM in normal and aberrant lung development, adult lung diseases and autoimmunity; and ECM in the regulation of the stem cell niche. We identify opportunities to advance the field of lung ECM biology and provide a set recommendations for research priorities to advance knowledge that would inform novel approaches to the pathogenesis, diagnosis, and treatment of chronic lung diseases.

Phytochemicals in Human Milk and Their Potential Antioxidative Protection

Diets contain secondary plant metabolites commonly referred to as phytochemicals. Many of them are believed to impact human health through various mechanisms, including protection against oxidative stress and inflammation, and decreased risks of developing chronic diseases. For mothers and other people, phytochemical intake occurs through the consumption of foods such as fruits, vegetables, and grains. Research has shown that some these phytochemicals are present in the mother’s milk and can contribute to its oxidative stability. For infants, human milk (HM) represents the primary and preferred source of nutrition because it is a complete food. Studies have reported that the benefit provided by HM goes beyond basic nutrition. It can, for example, reduce oxidative stress in infants, thereby reducing the risk of lung and intestinal diseases in infants. This paper summarizes the phytochemicals present in HM and their potential contribution to infant health.

Biomarkers associated with bronchopulmonary dysplasia/mortality in premature infants

BACKGROUND

Bronchopulmonary dysplasia (BPD) portends lifelong organ impairment and death. Our ability to predict BPD in first days of life is limited, but could be enhanced using novel biomarkers.

METHODS

Using an available clinical and urine biomarker database obtained from a prospective 113 infant cohort (birth weight ≤1,200 g and/or gestational age ≤31 wk), we evaluated the independent association of 14 urine biomarkers with BPD/mortality.

RESULTS

Two of the 14 urine biomarkers were independently associated with BPD/mortality after controlling for gestational age (GA), small for gestational age (SGA), and intubation status. The best performing protein was clusterin, a ubiquitously expressed protein and potential sensor of oxidative stress associated with lung function in asthma patients. When modeling for BPD/mortality, the independent odds ratio for maximum adjusted urine clusterin was 9.2 (95% CI: 3.3-32.8, P < 0.0001). In this model, clinical variables (GA, intubation status, and SGA) explained 38.3% of variance; clusterin explained an additional 9.2%, while albumin explained an additional 3.4%. The area under the curve incorporating clinical factors and biomarkers was 0.941.

CONCLUSION

Urine clusterin and albumin may improve our ability to predict BPD/mortality. Future studies are needed to validate these findings and determine their clinical usefulness.

Mitochondrial dysfunction in alveolar and white matter developmental failure in premature infants

At birth, some organs in premature infants are not developed enough to meet challenges of the extra-uterine life. Although growth and maturation continues after premature birth, postnatal organ development may become sluggish or even arrested, leading to organ dysfunction. There is no clear mechanistic concept of this postnatal organ developmental failure in premature neonates. This review introduces a concept-forming hypothesis: Mitochondrial bioenergetic dysfunction is a fundamental mechanism of organs maturation failure in premature infants. Data collected in support of this hypothesis are relevant to two major diseases of prematurity: white matter injury and broncho-pulmonary dysplasia. In these diseases, totally different clinical manifestations are defined by the same biological process, developmental failure of the main functional units-alveoli in the lungs and axonal myelination in the brain. Although molecular pathways regulating alveolar and white matter maturation differ, proper bioenergetic support of growth and maturation remains critical biological requirement for any actively developing organ. Literature analysis suggests that successful postnatal pulmonary and white matter development highly depends on mitochondrial function which can be inhibited by sublethal postnatal stress. In premature infants, sublethal stress results mostly in organ maturation failure without excessive cellular demise.

Attenuation of miR-17∼92 Cluster in Bronchopulmonary Dysplasia

RATIONALE

Bronchopulmonary dysplasia remains a significant cause of neonatal morbidity; however, the identification of novel targets to predict or prevent the development of bronchopulmonary dysplasia remains elusive. Proper microRNA (miR)-17∼92 cluster is necessary for normal lung development, and alterations in expression are reported in other pulmonary diseases. The overall hypothesis for our work is that altered miR-17∼92 cluster expression contributes to the molecular pathogenesis of bronchopulmonary dysplasia.

OBJECTIVES

The current studies tested the hypothesis that alterations in miR-17∼92 cluster and DNA methyltransferase expression are present in bronchopulmonary dysplasia.

METHODS

miR-17∼92 cluster expression, promoter methylation, and DNA methyltransferase expression were determined in autopsy lung samples obtained from premature infants who died with bronchopulmonary dysplasia, or from term/near-term infants who died from nonrespiratory causes. Expression of miR-17∼92 cluster members miR-17 and -19b was measured in plasma samples collected in the first week of life from a separate cohort of preterm infants at a second institution in whom bronchopulmonary dysplasia was diagnosed subsequently.

MEASUREMENTS AND MAIN RESULTS

Autopsy tissue data indicated that miR-17∼92 expression is significantly lower in bronchopulmonary dysplasia lungs and is inversely correlated with promoter methylation and DNA methyltransferase expression when compared with that of control subjects without bronchopulmonary dysplasia. Plasma sample analyses indicated that miR-17 and -19b expression was decreased in infants who subsequently developed bronchopulmonary dysplasia.

CONCLUSIONS

Our data are the first to demonstrate altered expression of the miR-17∼92 cluster in bronchopulmonary dysplasia. The consistency between our autopsy and plasma findings further support our working hypothesis that the miR-17∼92 cluster contributes to the molecular pathogenesis of bronchopulmonary dysplasia.

Regulation of alveolar septation by microRNA-489

MicroRNAs (miRs) are small conserved RNA that regulate gene expression. Bioinformatic analysis of miRNA profiles during mouse lung development indicated a role for multiple miRNA, including miRNA-489. miR-489 increased on completion of alveolar septation [postnatal day 42 (P42)], associated with decreases in its conserved target genes insulin-like growth factor-1 (Igf1) and tenascin C (Tnc). We hypothesized that dysregulation of miR-489 and its target genes Igf1 and Tnc contribute to hyperoxia-induced abnormal lung development. C57BL/6 mice were exposed to normoxia (21%) or hyperoxia (85% O2) from P4 to P14, in combination with intranasal locked nucleic acid against miR-489 to inhibit miR-489, cytomegalovirus promoter (pCMV)-miR-489 to overexpress miR-489, or empty vector. Hyperoxia reduced miR-489 and increased Igf1 and Tnc. Locked nucleic acid against miR-489 improved lung development during hyperoxia and did not alter it during normoxia, whereas miR-489 overexpression inhibited lung development during normoxia. The 3' untranslated region in vitro reporter studies confirmed Igf1 and Tnc as targets of miR-489. While miR-489 was of epithelial origin and present in exosomes, its targets Igf1 and Tnc were produced by fibroblasts. Infants with bronchopulmonary dysplasia (BPD) had reduced lung miR-489 and increased Igf1 and Tnc compared with normal preterm or term infants. These results suggest increased miR-489 is an inhibitor of alveolar septation. During hyperoxia or BPD, reduced miR-489 and increased Igf1 and Tnc may be inadequate attempts at compensation. Further inhibition of miR-489 may permit alveolar septation to proceed. The use of specific miRNA antagonists or agonists may be a therapeutic strategy for inhibited alveolarization, such as in BPD.

Early exposure to hyperoxia or hypoxia adversely impacts cardiopulmonary development

Preterm infants are at high risk for long-term abnormalities in cardiopulmonary function. Our objectives were to determine the long-term effects of hypoxia or hyperoxia on cardiopulmonary development and function in an immature animal model. Newborn C57BL/6 mice were exposed to air, hypoxia (12% oxygen), or hyperoxia (85% oxygen) from Postnatal Day 2-14, and then returned to air for 10 weeks (n = 2 litters per condition; > 10/group). Echocardiography, blood pressure, lung function, and lung development were evaluated at 12-14 weeks of age. Lungs from hyperoxia- or hypoxia-exposed mice were larger and more compliant (compliance: air, 0.034 ± 0.001 ml/cm H2O; hypoxia, 0.049 ± 0.002 ml/cm H2O; hyperoxia, 0.053 ± 0.002 ml/cm H2O; P < 0.001 air versus others). Increased airway reactivity, reduced bronchial M2 receptor staining, and increased bronchial α-smooth muscle actin content were noted in hyperoxia-exposed mice (maximal total lung resistance with methacholine: air, 1.89 ± 0.17 cm H2O ⋅ s/ml; hypoxia, 1.52 ± 0.34 cm H2O ⋅ s/ml; hyperoxia, 4.19 ± 0.77 cm H2O ⋅ s/ml; P < 0.004 air versus hyperoxia). Hyperoxia- or hypoxia-exposed mice had larger and fewer alveoli (mean linear intercept: air, 40.2 ± 0. 0.8 μm; hypoxia, 76.4 ± 2.4 μm; hyperoxia, 95.6 ± 4.6 μm; P < 0.001 air versus others; radial alveolar count [n]: air, 11.1 ± 0.4; hypoxia, 5.7 ± 0.3; hyperoxia, 5.6 ± 0.3; P < 0.001 air versus others). Hyperoxia-exposed adult mice had left ventricular dysfunction without systemic hypertension. In conclusion, exposure of newborn mice to hyperoxia or hypoxia leads to cardiopulmonary abnormalities in adult life, similar to that described in ex-preterm infants. This animal model may help to identify underlying mechanisms and to develop therapeutic strategies for pulmonary morbidity in former preterm infants.

VARA attenuates hyperoxia-induced impaired alveolar development and lung function in newborn mice

We have recently shown that a combination of vitamin A (VA) and retinoic acid (RA) in a 10:1 molar ratio (VARA) synergistically increases lung retinoid content in newborn rodents, more than either VA or RA alone in equimolar amounts. We hypothesized that the increase in lung retinoids would reduce oxidative stress and proinflammatory cytokines, resulting in attenuation of alveolar simplification and abnormal lung function in hyperoxia-exposed newborn mice. Newborn C57BL/6 mice were exposed to 85% O₂ (hyperoxia) or air (normoxia) for 7 or 14 days from birth and given vehicle or VARA every other day. Lung retinol content was measured by HPLC, function was assessed by flexiVent, and development was evaluated by radial alveolar counts, mean linear intercept, and secondary septal crest density. Mediators of oxidative stress, inflammation, and alveolar development were evaluated in lung homogenates. We observed that VARA increased lung retinol stores and attenuated hyperoxia-induced alveolar simplification while increasing lung compliance and lowering resistance. VARA attenuated hyperoxia-induced increases in DNA damage and protein oxidation accompanied with a reduction in nuclear factor (erythroid-derived 2)-like 2 protein but did not alter malondialdehyde adducts, nitrotyrosine, or myeloperoxidase concentrations. Interferon-γ and macrophage inflammatory protein-2α mRNA and protein increased with hyperoxia, and this increase was attenuated by VARA. Our study suggests that the VARA combination may be a potential therapeutic strategy in conditions characterized by VA deficiency and hyperoxia-induced lung injury during lung development, such as bronchopulmonary dysplasia in preterm infants.

Tension pneumothorax at anaesthetic induction in an ex-premature infant with bronchopulmonary dysplasia

ME, a 12-week-old premature infant with a history of complicated ventilatory support at birth, was referred to as a large tertiary centre for urgent retinal laser photocoagulation for retinopathy of prematurity. Following routine induction by a consultant paediatric anaesthetist, immediate ventilation difficulties were encountered, associated with a distended abdomen. Rapid assessment and escalation of the situation occurred, including assistance from several consultants. ME was diagnosed as having a pneumothorax. Rapid intervention, including needle decompression and insertion of a chest drain stabilised the patient. The procedure was cancelled, and the patient returned to intensive care. Over the next few days the patient gradually improved, and was gradually stepped down. The patient continued to improve, successfully overcoming the pneumothorax, pneumonia and insertion of a ventriculoperitoneal shunt, and eventually was discharged back to the referring hospital.

Chorioamnionitis, respiratory distress syndrome and bronchopulmonary dysplasia in extremely low birth weight infants

OBJECTIVE

To determine if histologic chorioamnionitis (HC) in the presence of respiratory distress syndrome (RDS) augments adverse pulmonary outcomes in extremely low birth weight (ELBW) infants.

STUDY DESIGN

We retrospectively identified 184 ELBW infants who were born at and admitted to the neonatal intensive care units between June 2005 and June 2009.

RESULTS

The mean gestational age of the cases was 27 ± 2 weeks, and the mean birth weight was 791 ± 147 g. A total of 88% (161/184) of patients developed bronchopulmonary dysplasia (BPD). HC was observed in 71 of 238 infants (39%). When infants were divided on the basis of the presence or absence of HC and RDS, the incidence of moderate or severe BPD and duration of oxygen requirement were greater in the HC+RDS+ group than in the HC-RDS+ or HC+RDS- groups. The combination of prenatal (HC) and postnatal (RDS) injuries increased significantly the risk for BPD. In the multivariate analysis, the significant predictors of developing BPD were low gestational age (odds ratio (OR), 0.6; confidence interval (CI), 0.4 to 0.7) and exposure to both HC and RDS (OR, 4.7; CI, 1.1 to 20.2).

CONCLUSION

The HC and RDS work synergistically to induce lung injury in ELBW infants. Chorioamnionitis may interact with RDS to further increase the risk of BPD, despite either HC or RDS could not show independent significant association with BPD.

Signaling pathways in the epithelial origins of pulmonary fibrosis

Pulmonary fibrosis complicates a number of disease processes and leads to substantial morbidity and mortality. Idiopathic pulmonary fibrosis (IPF) is perhaps the most pernicious and enigmatic form of the greater problem of lung fibrogenesis with a median survival of three years from diagnosis in affected patients. In this review, we will focus on the pathology of IPF as a model of pulmonary fibrotic processes, review possible cellular mechanisms, review current treatment approaches and review two transgenic mouse models of lung fibrosis to provide insight into processes that cause lung fibrosis. We will also summarize the potential utility of signaling pathway inhibitors as a future treatment in pulmonary fibrosis. Finally, we will present data demonstrating a minimal contribution of epithelial-mesenchymal transition in the development of fibrotic lesions in the transforming growth factor-alpha transgenic model of lung fibrosis.

Vitamin A and retinoic acid act synergistically to increase lung retinyl esters during normoxia and reduce hyperoxic lung injury in newborn mice

We have shown that vitamin A (VA) and retinoic acid (RA) synergistically increase lung retinyl ester content in neonatal rats. To confirm whether this biochemical synergism attenuates early neonatal hyperoxic lung injury in mice, we exposed newborn C57BL/6 mice to 95% O2 or air from birth to 4 d. The agent [vehicle, VA, RA, or the combination vitamin A+retinoic acid (VARA)] was given orally daily. Lung and liver retinyl ester content was measured, and lung injury and development were evaluated. We observed that lung, but not liver, retinyl ester levels were increased more by VARA than by VA or RA alone. Hyperoxic lung injury was reduced by VA and RA, and more so by VARA. VARA attenuated the hyperoxia-induced increases in macrophage inflammatory protein (MIP)-2 mRNA and protein expression, but did not alter hyperoxia-induced effects on peptide growth factors (PDGF, VEGF, and TGF-beta1). The 4-d exposure to hyperoxia or retinoids did not lead to observable differences in lung development. We conclude that the VARA combination has synergistic effects on lung retinyl ester concentrations and on the attenuation of hyperoxia-induced lung injury in newborn mice, possibly by modulation of inflammatory mediators.

Early alterations of growth factor patterns in bronchoalveolar lavage fluid from preterm infants developing bronchopulmonary dysplasia

Chronic lung disease of prematurity (bronchopulmonary dysplasia; BPD) is characterized by an arrest in lung development. We hypothesized that early alterations in pulmonary expression of growth factors important for normal lung development would precede development of BPD. Bronchoalveolar lavage fluid (BALF) was obtained from ventilated preterm infants (n = 62) on postnatal d 0, 1, 3, and 7 and analyzed for total phospholipids (PL), VEGF, PDGF-BB, TGF-alpha and -beta1, granulocyte macrophage colony stimulating factor (GM-CSF), and keratinocyte growth factor (KGF). Levels (Ln transformed) were compared between infants developing BPD and BPD-free survivors, adjusted for potential confounders. BPD was associated with higher overall GM-CSF (beta (95% CI) = 0.69 (0.13;1.25); p < 0.05), lower overall latent TGF-beta1 (beta (95% CI) = -1.19 (-1.87, -0.39); p < 0.01) and total PL (beta (95% CI) = -0.64 (-1.23, -0.05); p < 0.05), and lower d 0 and 3 levels of VEGF (mean difference (95% CI) = -1.75 (-2.72, -0.77), p < 0.001; and -1.18 (-2.30, -0.06), p < 0.05, respectively) and TGF-alpha (mean difference (95% CI) = -0.73 (-1.42, -0.04), p < 0.05; and -1.01 (-1.64, -0.38), p < 0.01, respectively). Day 0 VEGF levels had the highest predictive value for BPD (area under receiver operating characteristic curve = 0.87; p < 0.01). In conclusion, substantial alterations in BALF growth factor levels are present in infants developing BPD. An early imbalance in pulmonary growth factors may contribute to the developmental arrest of the lung seen in BPD.

Shielding parenteral nutrition from light: does the available evidence support a randomized, controlled trial?

BACKGROUND

Exposure of total parenteral nutrition to ambient light induces the generation of peroxides, creating oxidant stress, which potentially compounds complications of prematurity. Photograph protection of total parenteral nutrition reduces the peroxide load and has been shown to be associated with nutritional and biochemical benefits in animals and humans. It is unclear whether this reduction in peroxides from total parenteral nutrition leads to a reduction in the complications of prematurity, such as bronchopulmonary dysplasia. Our hypothesis was that shielding total parenteral nutrition from ambient light is linked to clinical benefits.

OBJECTIVE

The purpose of this work was to determine whether photograph protection of total parenteral nutrition (light protected), as compared with no photoprotection (light exposed), reduces the occurrence of bronchopulmonary dysplasia or death in preterm infants.

METHODS

The Canadian Neonatal Network provided data for infants born in 2006 at <28 weeks' gestation admitted to level 3 NICUs in Canada. A retrospective analysis was performed comparing bronchopulmonary dysplasia and death in infants who received light-exposed or light-protected parenteral nutrition. Data were analyzed by using logistic regression models. RESULTS. Thirteen NICUs offered partial light-protected (total parenteral nutrition bag only, intravenous tubing exposed) and 13 offered light-exposed parenteral nutrition; not a single NICU offered complete light-protected parenteral nutrition (total parenteral nutrition bag plus intravenous tubing). The incidence of bronchopulmonary dysplasia or death was 66% with light-protected (n = 428) vs 59% with light-exposed (n = 438) parenteral nutrition.

CONCLUSIONS

Partial photograph protection of total parenteral nutrition was not associated with a reduction in bronchopulmonary dysplasia or death as compared with no photograph protection; this relationship is confounded by covariates with strong associations with bronchopulmonary dysplasia. Partial photograph protection of total parenteral nutrition solutions confers no clinical benefit, while consuming valuable resources. A randomized, controlled trial is justified to determine whether there is a true "cause-and-effect" relationship between complete photoprotection of total parenteral nutrition and bronchopulmonary dysplasia or death.

Pathogenesis and prevention of chronic lung disease in the neonate

Often used interchangeably, chronic lung disease (CLD) or bronchopulmonary dysplasia (BPD) develops primarily in extremely low birth weight infants weighing <1000 g who receive prolonged oxygen therapy and or positive pressure ventilation. CLD, which occurs in as many as 30 percent of infants born weighing <1000 g, contributes significantly to the morbidity and mortality seen in very low birth weight infants. Despite extensive research aimed at identifying risk factors and devising preventative therapies, many questions about the etiology and pathogenesis of BPD remain. This article reviews the embryologic development of the lung and the pathogenesis of CLD or BPD. The authors discuss some of the measures that have been used in an attempt to both prevent and treat BPD.

Cytokines associated with bronchopulmonary dysplasia or death in extremely low birth weight infants

OBJECTIVE

The goal was to develop multivariate logistic regression models for the outcome of bronchopulmonary dysplasia and/or death at postmenstrual age of 36 weeks by using clinical and cytokine data from the first 28 days.

METHODS

For 1067 extremely low birth weight infants in the Neonatal Research Network of the National Institute of Child Health and Human Development, levels of 25 cytokines were measured in blood collected within 4 hours after birth and on days 3, 7, 14, and 21. Stepwise regression analyses using peak levels of the 25 cytokines and 15 clinical variables identified variables associated with bronchopulmonary dysplasia/death. Multivariate logistic regression analysis was performed for bronchopulmonary dysplasia/death by using variables selected through stepwise regression. Similar analyses were performed by using average cytokine values from days 0 to 21, days 0 to 3, and days 14 to 21.

RESULTS

Of 1062 infants with available data, 606 infants developed bronchopulmonary dysplasia or died. On the basis of results from all models combined, bronchopulmonary dysplasia/death was associated with higher concentrations of interleukin 1beta, 6, 8, and 10 and interferon gamma and lower concentrations of interleukin 17, regulated on activation, normal T cell expressed and secreted, and tumor necrosis factor beta. Compared with models with only clinical variables, the addition of cytokine data improved predictive ability by a statistically significant but clinically modest magnitude.

CONCLUSIONS

The overall cytokine pattern suggests that bronchopulmonary dysplasia/death may be associated with impairment in the transition from the innate immune response mediated by neutrophils to the adaptive immune response mediated by T lymphocytes.

Sucking behavior of preterm neonates as a predictor of developmental outcomes

OBJECTIVES

The relationship between the pattern of sucking behavior of preterm infants during the early weeks of life and neurodevelopmental outcomes during the first year of life was evaluated.

METHODS

The study sample consisted of 105 preterm infants (postmenstrual age [PMA] at birth = 30.5 +/- 2.8 weeks [mean +/- SD]; birth weight = 1476 +/- 460 g; mean length of hospital stay = 41.6 +/- 31.4 days). All infants received a 5-minute sucking test at 34 and at 40 weeks PMA, with outcomes evaluated at 6 and/or 12 months corrected gestational age via the Bayley Scales of Infant Development.

RESULTS

As expected, 6- and 12-month values for the Psychomotor Developmental Index (PDI) and Mental Developmental Index (MDI) of the Bayley Scales of Infant Development were significantly below the normative levels established for infants delivered at term. A significant association between neonatal sucking pattern at 40 weeks PMA and developmental outcome at 12 months corrected gestational age was obtained. Each of the 3 simple sucking parameters evaluated (number of sucks, mean number of sucks per bursts and mean sucking pressure peaks), as well as a composite parameter (average of the respective parameter z-scores), was significantly related to both PDI and MDI at 12 months.

CONCLUSIONS

Multivariable models, adjusting for PMA at birth, length of hospital stay, and other predictors, affirmed that sucking performance at 40 weeks PMA was a significant, independent predictor of developmental status 1 year later. Standardization of an instrument for neonatal sucking assessment may offer a cost-effective early screening strategy for preterm infants at greatest risk for developmental delay.

Wilson-Mikity syndrome: updated diagnostic criteria based on nine cases and a review of the literature

BACKGROUND

Nearly 50 years ago, Wilson and Mikity described a syndrome (WMS) of chronic lung disease (CLD) in premature infants, characterized by early development of cystic interstitial emphysema (PIE), despite minimal ventilatory support. The validity of the diagnosis is currently unclear; now considered either an anachronism, part of BPD spectrum or included within various poorly defined diagnoses such as chronic pulmonary insufficiency of prematurity (CPIP).

OBJECTIVES

To define clinically useful diagnostic criteria for WMS so its position in the spectrum of CLD of infancy can be established.

METHODS

We studied nine patients who fulfilled WMS criteria, combining this data with a detailed review of the available literature.

RESULTS

Despite minimal respiratory support at birth, all developed generalized or lobar cystic PIE by 3 weeks of age, followed by slow inflammatory progression over a further 2-3 months. Final outcome was variable but most were left with some degree of CLD.

CONCLUSIONS

WMS is a rare but clearly identifiable syndrome with significant morbidity, predominantly affecting infants below 1,500 g birth weight. The earliest pathology appears to be alveolar air leak. Inflammatory activation induced by cystic interstitial air may cause the subsequent progressive respiratory disease. Management is supportive but should include investigation for pulmonary hypertension.

Influence of lung oxidant and antioxidant status on alveolarization: role of light-exposed total parenteral nutrition

Parenteral multivitamins (MVP) are linked to the generation of peroxides, which cause oxidant injury in lungs associated with alveolar remodelling linked to lung disease of prematurity. This study was to investigate the relationship between alveolar development and lung oxidant-antioxidant status as modulated by the mode of administration of multivitamins with total parenteral nutrition (TPN). Four groups of guinea pig pups received parenteral nutrition differing by 1) mode of MVP admixture: with amino acid solution (AA-MVP) or lipid emulsion (LIP-MVP); 2) light exposure: TPN exposed (LE) or shielded from light (LP). After 2 or 4 days of TPN, vitamins C and E, 8-isoprostaneF2alpha and alveolarization index were determined in lungs and GSSG/GSH in lungs and blood. Exposure to light and the mode of MVP admixture did not influence vitamin E and isoprostane levels. Blood glutathione redox potential was more oxidized in LE and LIP-MVP groups after 4-day infusions, whereas lung redox potential was more reduced in LE groups. LP and LIP-MVP had a beneficial effect, with higher number of alveoli. Globally, results indicate that in this model, alveolarization and modifications in lung redox potential are two independent events induced by light exposed TPN.

Glucocorticoid regulation of human pulmonary surfactant protein-B mRNA stability involves the 3'-untranslated region

Expression of pulmonary surfactant, a complex mixture of lipids and proteins that acts to reduce alveolar surface tension, is developmentally regulated and restricted to lung alveolar type II cells. The hydrophobic protein surfactant protein-B (SP-B) is essential in surfactant function, and insufficient levels of SP-B result in severe respiratory dysfunction. Glucocorticoids accelerate fetal lung maturity and surfactant synthesis both experimentally and clinically. Glucocorticoids act transcriptionally and post-transcriptionally to increase steady-state levels of human SP-B mRNA; however, the mechanism(s) by which glucocorticoids act post-transcriptionally is unknown. We hypothesized that glucocorticoids act post-transcriptionally to increase SP-B mRNA stability via sequence-specific mRNA-protein interactions. We found that glucocorticoids increase SP-B mRNA stability in isolated human type II cells and in nonpulmonary cells, but do not alter mouse SP-B mRNA stability in a mouse type II cell line. Deletion analysis of an artificially-expressed SP-B mRNA indicates that the SP-B mRNA 3'-untranslated region (UTR) is necessary for stabilization, and the region involved can be restricted to a 126-nucleotide-long region near the SP-B coding sequence. RNA electrophoretic mobility shift assays indicate that cytosolic proteins bind to this region in the absence or presence of glucocorticoids. The formation of mRNA:protein complexes is not seen in other regions of the SP-B mRNA 3'-UTR. These results indicate that a specific 126-nucleotide region of human SP-B 3'-UTR is necessary for increased SP-B mRNA stability by glucocorticoids by a mechanism that is not lung cell specific and may involve mRNA-protein interactions.

A tissue-engineered model of fetal distal lung tissue

In extending our previous studies toward development of an engineered distal lung tissue construct (M. J. Mondrinos, S. Koutzaki, E. Jiwanmall, M. Li, J. P. Dechadarevian, P. I. Lelkes, and C. M. Finck. Tissue Eng 12: 717-728, 2006), we studied the effects of exogenous fibroblast growth factors FGF10, FGF7, and FGF2 on mixed populations of embryonic day 17.5 murine fetal pulmonary cells cultured in three-dimensional collagen gels. The morphogenic effects of the FGFs alone and in various combinations were assessed by whole mount immunohistochemistry and confocal microscopy. FGF10/7 significantly increased epithelial budding and proliferation; however, only FGF10 alone induced widespread budding. FGF7 alone induced dilation of epithelial structures but not widespread budding. FGF2 alone had a similar dilation, but not budding, effect in epithelial structures, and, in addition, significantly enhanced endothelial tubular morphogenesis and network formation, as well as mesenchymal proliferation. The combination of FGF10/7/2 induced robust budding of epithelial structures and the formation of uniform endothelial networks in parallel. These data suggest that appropriate combinations of exogenous FGFs chosen to target specific FGF receptor isoforms will allow for control of lung epithelial and mesenchymal cell behavior in the context of an engineered system. We propose that tissue-engineered fetal distal lung constructs could provide a potential source of tissue or cells for lung augmentation in pediatric pulmonary pathologies, such as pulmonary hypoplasia and bronchopulmonary dysplasia. In addition, engineered systems will provide alternative in vitro venues for the study of lung developmental biology and pathobiology.

Does bronchopulmonary dysplasia change the postoperative outcome of herniorrhaphy in premature babies?

BACKGROUND

Inguinal hernia is a common surgical condition in premature neonates. Because of physiological immaturity, they can present with lung-related diseases, such as bronchopulmonary dysplasia (BPD), which may influence the time for operation and the postoperative outcome after hernia repair. The aim of this study was to analyze the role of BPD in the outcome of premature infants who underwent herniorrhaphy.

METHODS

Fifty-two premature infants who underwent hernia repair from 1996 to 2004 at CAISM-UNICAMP were included in this study. Seventeen babies had BPD and 35 did not. The features reviewed included: (i) associated preoperative morbidity; (ii) birth data and the hernia; and (iii) hernia diagnosis, surgery and postoperative outcome data. Three sets of analysis were undertaken. The first compared features with and without BPD. The second was an univariate analysis to detect associations between those features and postoperative complications. Finally, a multivariate analysis to determine the effect of BPD when adjusted for other factors.

RESULTS

Some features were different between the studied groups, such as birth weight, age at herniorrhaphy and time of preoperative mechanical ventilation. There was no statistical difference in weight at surgery, duration of postoperative ventilation and weight at discharge between those with BPD and those without. Univariate and multivariate analysis found no association between different studied variables, including BPD, and incidence of postoperative respiratory complications.

CONCLUSION

These data suggest that all premature infants, with or without BPD, should be treated with equal concern regarding the possibility of postoperative pulmonary complications.

A rational approach to home oxygen use in infants and children

The provision of supplemental oxygen for infants and children with hypoxaemia is expensive but advantageous because it facilitates earlier discharge from hospital and enhances quality of life in the home setting. It is seen as potentially cost effective and family friendly. However, the prescription of supplemental oxygen varies greatly between neonatologists, paediatric respiratory physicians and paediatric cardiologists. There is a lack of consensus on appropriate indications for prescribing oxygen, desirable oxygen targets and clinically significant immediate and longer-term outcome measures. Of the limited studies available, most are small studies reporting the treatment of infants with chronic neonatal lung disease with inconsistent outcome measures. Such data are not readily extrapolated to older children, who are also poorly served by existing data in adult studies. Further delineation of the indications for home oxygen therapy is required together with appropriately designed and funded multicentre trials to provide evidence for optimal oxygen therapy.

The genetics of bronchopulmonary dysplasia

Over the last 15 years, neonatal morbidity and mortality has changed little for very low birth weight babies despite significant technological and therapeutic advances. Bronchopulmonary dysplasia (BPD) continues to be a major problem despite antenatal steroid use, surfactant replacement therapy, gentle noninvasive ventilation techniques, permissive hypercarbia, and judicious use of oxygen. Current evidence supports multiple contributing factors. Prematurity is the cardinal factor; others include pulmonary baro/volutrauma, hyperoxia, and inflammation. BPD is an end product of pulmonary inflammatory response and lung repair with impaired alveolarization and vascularization in response to lung injury. These sequences involve multiple morphoregulatory molecules, which have a range of activities largely determined by genetic variability. A clearer understanding of genetic susceptibility for BPD has recently emerged. Twin studies have shown that the BPD status of one twin, even after correcting for contributing factors, is a highly significant predictor of BPD in the second twin. After controlling for covariates, genetic factors account for 53% (P = 0.004, 95% CI = 16%-89%) of the variance in liability for BPD. Incremental improvements will likely depend on identification of these genetic components for targeting specific therapies.

Lung inflammation in preterm infants with respiratory distress syndrome: effects of ventilation with different tidal volumes

Ventilation with an inappropriate tidal volume (Vt) triggers lung inflammation, an important predisposing factor of bronchopulmonary dysplasia. It still remains uncertain what the appropriate starting target Vt should be during the acute phase of respiratory distress syndrome (RDS). Our aim was to evaluate lung inflammation in preterm infants undergoing synchronized intermittent positive-pressure ventilation (SIPPV) with two different tidal volumes Vt during the acute phase of RDS. Thirty preterm infants (gestational age, 25-32 weeks) with acute RDS were randomly assigned to be ventilated with Vt = 5 ml/kg (n = 15) or Vt = 3 ml/kg (n = 15). Proinflammatory cytokines (interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor (TNF)-alpha) were determined in the tracheal aspirate on days 1, 3, and 7 of life. IL-8 and TNF-alpha levels collected on day 7 were significantly higher (P < 0.05), and mechanical ventilation lasted longer in the group with Vt = 3 ml/kg (16.8 +/- 4 vs. 9.2 +/- 4 days; P = 0.05). In conclusion, our data show significantly higher lung inflammation in preterm infants ventilated with Vt = 3 ml/kg, suggesting a role for Vt = 5 ml/kg in reducing both inflammatory response during the acute phase of RDS and the length of ventilation. Whether the use of this starting Vt prevents bronchopulmonary dysplasia requires further study.