Pathology of bronchopulmonary dysplasia

Cumulative effects of neonatal hyperoxia on murine alveolar structure and function

BACKGROUND

Bronchopulmonary dysplasia (BPD) results from alveolar simplification and abnormal development of alveolar and capillary structure. Survivors of BPD display persistent deficits in airflow and membrane and vascular components of alveolar gas diffusion. Despite being the defining feature of BPD, various neonatal hyperoxia models of BPD have not routinely assessed pulmonary gas diffusion.

METHODS

To simulate the most commonly-utilized neonatal hyperoxia models, we exposed neonatal mice to room air or ≥90% hyperoxia during key stages of distal lung development: through the first 4 (saccular), 7 (early alveolar), or 14 (bulk alveolar) postnatal days, followed by a period of recovery in room air until 8 weeks of age when alveolar septation is essentially complete. We systematically assessed and correlated the effects of neonatal hyperoxia on the degree of alveolar-capillary structural and functional impairment. We hypothesized that the degree of alveolar-capillary simplification would correlate strongly with worsening diffusion impairment.

RESULTS

Neonatal hyperoxia exposure, of any duration, resulted in alveolar simplification and impaired pulmonary gas diffusion. Mean Linear Intercept increased in proportion to the length of hyperoxia exposure while alveolar and total lung volume increased markedly only with prolonged exposure. Surprisingly, despite having a similar effect on alveolar surface area, only prolonged hyperoxia for 14 days resulted in reduced pulmonary microvascular volume. Estimates of alveolar and capillary structure, in general, correlated poorly with assessment of gas diffusion.

CONCLUSION

Our results help define the physiological and structural consequences of commonly-employed neonatal hyperoxia models of BPD and inform their clinical utility. Pediatr Pulmonol. 2017;52:616-624. © 2016 Wiley Periodicals, Inc.

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.

Clara Cell Protein Expression in Mechanically Ventilated Term and Preterm Infants with Respiratory Distress Syndrome and at Risk of Bronchopulmonary Dysplasia: A Pilot Study

The aim of this pilot study was to determine Clara cell protein (CC16) concentration in bronchoalveolar lavages (BAL) fluid from full-term and preterm (<37 weeks' gestational age) neonates requiring respiratory support, having symptoms of neonatal respiratory distress syndrome, and at risk of bronchopulmonary dysplasia (BPD). We hypothesized that CC16 may be predictive of BPD diagnosis regardless of gestational age. BAL fluid CC16 was measured by ELISA at birth and at day 7 of life. Both groups that developed BPD showed significantly decreased BAL fluid CC16 levels compared to those infants that did not develop the disease. CC16 positively correlated with diagnosis of BPD and negatively with the severity of the disease. These results suggest that BAL fluid CC16 levels may have a diagnostic value at day 7 for BPD in both term and preterm infants. This study demonstrates the potential utility of BAL fluid CC16 levels as a biomarker for BPD in term infants.

Pulmonary hypertension's variegated landscape: a snapshot

The many types of pulmonary hypertension (PH) are so protean in their biological origin, histological expression, and natural history that it is difficult to create a summary picture of the disease, or to easily compare and contrast characteristics of one type of PH with another. For newcomers to the field, however, such a picture would facilitate a broad understanding of PH. In this paper, we suggest that four characteristics are fundamental to describing the nature of various types of PH, and that taken together they define a number of patterns of PH expression. These characteristics are histopathology, developmental origin, associated clinical conditions, and potential for resolution. The “snapshot” is a way to concisely display the ways that these signal characteristics intersect in select specific types of PH, and is an effort to summarize these patterns in a way that facilitates a “big picture” comprehension of this disease.

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.

Systemic corticosteroid regimens for prevention of bronchopulmonary dysplasia in preterm infants

BACKGROUND

Cochrane systematic reviews show that systemic postnatal corticosteroids reduce the risk of bronchopulmonary dysplasia (BPD) in preterm infants. However, corticosteroids have also been associated with an increased risk of neurodevelopmental impairment. It is unknown whether these beneficial and adverse effects are modulated by differences in corticosteroid treatment regimens.

OBJECTIVES

To assess the effects of different corticosteroid treatment regimens on mortality, pulmonary morbidity, and neurodevelopmental outcome in very low birth weight (VLBW) infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2) in the Cochrane Library (searched 21 March 2016), MEDLINE via PubMed (1966 to 21 March 2016), Embase (1980 to 21 March 2016), and CINAHL (1982 to 21 March 2016). We also searched clinical trials' databases, conference proceedings, and the reference lists of retrieved articles for randomized controlled trials.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing two or more different treatment regimens of systemic postnatal corticosteroids in preterm infants at risk for BPD, as defined by the original trialists. Studies investigating one treatment regimen of systemic corticosteroids to a placebo or studies using inhalation corticosteroids were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility and quality of trials and extracted data on study design, participant characteristics and the relevant outcomes. We asked the original investigators to verify if data extraction was correct and, if possible, to provide any missing data. The primary outcomes to be assessed were: mortality at 36 weeks' postmenstrual age (PMA) or at hospital discharge; BPD defined as oxygen dependency at 36 weeks' PMA; long-term neurodevelopmental sequelae, including cerebral palsy, measured by the Bayley Mental Developmental Index (MDI); and blindness or poor vision. Secondary outcomes were: duration of mechanical ventilation and failure to extubate at day 3 and 7 after initiating therapy; rescue treatment with corticosteroids outside the study period; and the incidence of hypertension, sepsis and hyperglycemia during hospitalizations. Data were analyzed using Review Manager 5 (RevMan 5). We used the GRADE approach to assess the quality of evidence.

MAIN RESULTS

Fourteen studies were included in this review. Only RCTs investigating dexamethasone were identified. Eight studies enrolling a total of 303 participants investigated the cumulative dosage administered; three studies contrasted a high versus a moderate and five studies a moderate versus a low cumulative dexamethasone dose.Analysis of the studies investigating a moderate dexamethasone dose versus a high-dosage regimen showed an increased risk of BPD (typical risk ratio (RR) 1.50, 95% confidence interval (CI) 1.01 to 2.22; typical risk difference (RD) 0.26, 95% CI 0.03 to 0.49; number needed to treat for an additional harmful outcome (NNTH) 4, 95% CI 1.9 to 23.3; I² = 0%, 2 studies, 55 infants) as well as an increased risk of abnormal neurodevelopmental outcome (typical RR 8.33, 95% CI 1.63 to 42.48; RD 0.30, 95% CI 0.14 to 0.46; NNTH 4, 95% CI 2.2 to 7.3; I² = 68%, 2 studies, 74 infants) when using a moderate cumulative-dosage regimen. The composite outcomes of death or BPD and death or abnormal neurodevelopmental outcome showed similar results although the former only reached borderline significance.There were no differences in outcomes between a moderate- and a low-dosage regimen.Four other studies enrolling 762 infants investigated early initiation of dexamethasone therapy versus a moderately early or delayed initiation and showed no significant differences in the primary outcomes. The two RCTs investigating a continuous versus a pulse dexamethasone regimen showed an increased risk of the combined outcome death or BPD when using the pulse therapy. Finally, two trials investigating a standard regimen versus a participant-individualized course of dexamethasone showed no difference in the primary outcome and long-term neurodevelopmental outcomes.The quality of evidence for all comparisons discussed above was assessed as low or very low, because the validity of all comparisons is hampered by small samples of randomized infants, heterogeneity in study population and design, non-protocolized use of 'rescue' corticosteroids and lack of long-term neurodevelopmental data in most studies.

AUTHORS' CONCLUSIONS

Despite the fact that some studies reported a modulating effect of treatment regimens in favor of higher-dosage regimens on the incidence of BPD and neurodevelopmental impairment, recommendations on the optimal type of corticosteroid, the optimal dosage, or the optimal timing of initiation for the prevention of BPD in preterm infants cannot be made based on current level of evidence. A well-designed large RCT is urgently needed to establish the optimal systemic postnatal corticosteroid dosage regimen.

Limiting ventilator-associated lung injury in a preterm porcine neonatal model

PURPOSE

Preterm infants are prone to respiratory distress syndrome (RDS), with severe cases requiring mechanical ventilation for support. However, there are no clear guidelines regarding the optimal ventilation strategy. We hypothesized that airway pressure release ventilation (APRV) would mitigate lung injury in a preterm porcine neonatal model.

METHODS

Preterm piglets were delivered on gestational day 98 (85% of 115day term), instrumented, and randomized to volume guarantee (VG; n=10) with low tidal volumes (5.5cm³kg^-1) and PEEP 4cmH₂O or APRV (n=10) with initial ventilator settings: P_High 18cmH₂O, P_Low 0cmH₂O, T_High 1.30s, T_Low 0.15s. Ventilator setting changes were made in response to clinical parameters in both groups. Animals were monitored continuously for 24hours.

RESULTS

The mortality rates between the two groups were not significantly different (p>0.05). The VG group had relatively increased oxygen requirements (F_iO₂ 50%±9%) compared with the APRV group (F_iO₂ 28%±5%; p>0.05) and a decrease in PaO₂/FiO₂ ratio (VG 162±33mmHg; APRV 251±45mmHg; p<0.05). The compliance of the VG group (0.51±0.07L·cmH₂O^-1) was significantly less than the APRV group (0.90±0.06L·cmH₂O^-1; p<0.05).

CONCLUSION

This study demonstrates that APRV improves oxygenation and compliance as compared with VG. This preliminary work suggests further study into the clinical uses of APRV in the neonate is warranted.

LEVEL OF EVIDENCE

Not Applicable (Basic Science Animal Study).

Bronchopulmonary dysplasia: new becomes old again!

Despite the many advances in neonatology, bronchopulmonary dysplasia (BPD) continues to be a frustrating disease of prematurity. BPD is a disease which is defined oddly by its treatment rather than its pathophysiology, leading to frequently changing nomenclature which has widespread implications on our ability to both understand and follow the progression of BPD. As various treatment modalities for BPD were developed and a larger number of extremely preterm infants survived, the "old" BPD based on lung injury from oxygen therapy and mechanical ventilation transitioned into a "new" BPD focused more on the interruption of normal development. However, the interruption of normal development does not solely apply to lung development. The effects of prematurity on vascular development cannot be overstated and pulmonary vascular disease has become the new frontier of BPD. As we begin to better understand the complex, multifactorial pathophysiology of BPD, it is necessary to again focus on appropriate, pathology-driven nomenclature that can effectively describe the multiple clinical phenotypes of BPD.

Alveolar formation is dysregulated by restricted nutrition but not excess sedation in preterm lambs managed by noninvasive support

BACKGROUND

Preterm birth and respiratory support with invasive mechanical ventilation frequently leads to bronchopulmonary dysplasia (BPD). A hallmark feature of BPD is alveolar simplification. For our preterm lamb model of BPD, invasive mechanical ventilation is associated with postnatal feeding intolerance (reduced nutrition) and sedation. In contrast, preterm lambs managed by noninvasive support (NIS) have normal alveolar formation, appropriate postnatal nutrition, and require little sedation. We used the latter, positive-outcome group to discriminate the contribution of reduced nutrition vs. sedation on alveolar simplification. We hypothesized that, restricted nutrition, but not sedation with pentobarbital, contributes to impaired indices of alveolar formation in preterm lambs managed by NIS.

METHODS

Preterm lambs managed by NIS for 21d were randomized into three groups: NIS control, NIS plus restricted nutrition, and NIS plus excess sedation with pentobarbital. We quantified morphological and biochemical indices of alveolar formation, as well as mesenchymal cell apoptosis and proliferation.

RESULTS

Restricted nutrition impaired morphological and biochemical indices of alveolar formation, and reduced mesenchymal cell apoptosis and proliferation. Excess sedation with pentobarbital did not alter these indices, although mesenchymal cell apoptosis was less.

CONCLUSION

Our results demonstrate that restricted nutrition, but not excess sedation, contributes to impaired alveolar formation during the evolution of BPD in chronically ventilated preterm lambs.

Relationship between birth weight, maternal smoking during pregnancy and childhood and adolescent lung function: A path analysis

BACKGROUND

Low birth weight and gestational maternal smoking have been linked with reduced lung function in children in many cross sectional studies. However, these associations have not yet been assessed with repeated measurements of lung function. Our aim was to investigate the effects of birth weight, gestational age, and gestational maternal smoking on lung function in children at age 10 and 18 years.

METHODS

In the Isle of Wight birth cohort spirometry was performed at age 10 and 18 years. Information on birth weight and gestational age were obtained from hospital records. Mothers were asked about smoking during pregnancy. We employed linear mixed models to estimate the effect of these risk factors on repeated measurements of lung function. We considered maternal asthma, sex, neonatal intensive care unit admission, height, socio-economic status, personal smoking in participants at age 18, body mass index and environmental tobacco smoke exposure as potential confounders. Finally, we used path analysis to determine links between birth weight, gestational age and gestational maternal smoking on lung function at age 10 and 18 years.

RESULTS

Linear mixed models showed that with every 1 kg increase in birth weight, Forced expiratory volume in one second (FEV₁) increased by 42.6 ± 17.2 mL and Forced expiratory flow between 25% and 75% (FEF_25-75) of Forced vital capacity (FVC) increased by 95.5 ± 41.2 mL at age 18 years after adjusting for potential confounders. Path analysis suggested that birth weight had positive direct effects on FEV₁ and FEF_25-75 and positive indirect effect on FVC at 10 years which were carried forward to 18 years. Additionally, results also suggested a positive association between gestational age and FEV₁, FVC and FEF_25-75 at ages 10 and 18 years and an inverse association between gestational smoke exposure and FEV₁/FVC ratio and FEF_25-75 at age 18 years.

CONCLUSIONS

Higher birth weight and gestational age were associated with higher FEV₁, FVC and FEF_25-75 and maternal smoking during pregnancy was associated with reduced FEV₁/FVC ratio and FEF_25-75. The use of path analysis can improve our understanding of underlying "causal" pathways among different prenatal and childhood factors that affect lung function in both pre-adolescent and adolescent periods.

Mid-childhood lung function in a cohort of children with "new bronchopulmonary dysplasia"

OBJECTIVE

Recent advances in perinatal care and neonatal respiratory therapy have led to a new phenotype of bronchopulmonary dysplasia ("new BPD"). The long-term respiratory outcome of this new form of BPD has yet to be adequately described. Aim of this study was to provide longitudinal data on lung function of an unselected cohort of children born extremely premature (EP) with an extremely low birth weight in the post-surfactant era.

STUDY DESIGN

Respiratory function was assessed twice (at 8 and 12 years) in 48 children born at a gestational age <28 weeks with a birth weight <1,000 g. Twenty-eight of them had BPD (oxygen-dependency at 36 weeks postmenstrual age) (EP-BPD), and 20 not (EP non-BPD). Twenty-seven children born at term served as control group.

RESULTS

The EP-BPD group had significantly lower spirometric values (given as z-scores) than controls, especially in parameters indicating airflow obstruction (8 ys: zFEV1:-1.3 ± 1 vs. 0.5 ± 0.8; 12 ys:-1.6 ± 1 vs. 0.5 ± 0.8, P < 0.001). Despite their better spirometric profile, EP-non-BPD children also had significantly lower parameters than controls (8ys: zFEV1:-0.5 ± 0.8; 12 ys:-0.5 ± 0.9, P < 0.001). During the 4-year follow-up, EP-non-BPD and controls had stable mean z-scores, but EP-BPD had a significant decline in mean zFEV1 (from -1.3 ± 1 to -1.6 ± 1, P = 0.03), zFEV1/FVC (from -0.4 ± 1 to -1.1 ± 1, P = 0.008), and zFEF 25-75% (from -1.2 ± 1 to -1.8 ± 1, P = 0.03).

CONCLUSION

EP children born in the post-surfactant era showed a significant airflow limitation, particularly pronounced in BPD subjects who in addition, presented an abnormal airway growth trajectory with a decline in lung function between the ages of 8 and 12 years. Pediatr Pulmonol. 2016;51:1057-1064. © 2016 Wiley Periodicals, Inc.

Lung CT imaging in patients with bronchopulmonary dysplasia: A systematic review

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common respiratory complication of preterm birth and associated with long-term respiratory sequelae. Chest computed tomography (CT) is a sensitive tool to obtain insight in structural lung abnormalities and may be a predictor for later symptoms.

OBJECTIVES

To give an overview of chest CT scoring methods that are used to evaluate chest CT scans of BPD patients. To review which structural lung abnormalities are described in children and adults with BPD and whether these are related to clinical outcomes.

METHODS

An extensive literature search was conducted for relevant studies on chest CT imaging in patients born preterm with BPD.

RESULTS

We retrieved 316 original papers of which 16 articles and three abstracts fulfilled our inclusion criteria. Overall, we identified nine different semi-quantitative scoring methods. Chest CT scans revealed structural abnormalities in >85% of BPD patients. These abnormalities are decreased pulmonary attenuation, opacities, bronchial wall thickening, and consolidations. Some have been found to be negatively correlated with lung function and respiratory symptoms.

CONCLUSIONS

None of the currently described scoring systems are appropriately validated or superior over another. Future studies are needed to generate a validated and universal chest CT quantitative scoring method for patients with BPD. Pediatr Pulmonol. 2016; 51:975-986. © 2016 Wiley Periodicals, Inc.

Oxygen and parenteral nutrition two main oxidants for extremely preterm infants: 'It all adds up'

OBJECTIVES

To assess the effect of early exposure to O2 and parenteral nutrition (PN) on oxidative stress at 36 weeks post-menstrual age (PMA) and on bronchopulmonary dysplasia (BPD) in extremely preterm infants.

STUDY DESIGN

A prospective observational study including 116 infants <29 weeks of gestation. Baseline clinical characteristics, FiO2 on day 7, duration of PN and clinical outcomes data were collected. In 39 infants, whole blood glutathione (GSH) and oxidized glutathione (GSSG) at 36 weeks PMA were measured and the redox potential was calculated using Nernst equation. Student's t-test, Chi-square, Spearman correlation, ANOVA, and logistic regression analyses were used as appropriate. P <  0.05 was considered significant.

RESULTS

FiO2 ≥25% was associated with higher level of GSSG (0.29 ± 0.04 versus 0.18 ± 0.02 nmol/mg of protein), a more oxidized redox potential (-191 ± 2 versus -198 ± 2 mV) and more BPD (90% versus 45%). PN duration >14 days was also associated with higher level of GSSG (0.26 ± 0.03 versus 0.13 ± 0.02 nmol/mg of protein), a more oxidized redox potential (-193 ± 5 versus -203 ± 2 mV) and more BPD (89% versus 24%). In logistic regression model, each 1% increase in FiO2 and each day increase in PN duration resulted in an increase in the OR for BPD by 1.57 (1.09 -2.28) and 1.17 (1.03 -1.33) respectively.

CONCLUSION

Early O2 supplement and PN have additive effects that were associated with prolonged oxidative stress and increased risk of BPD. Strategies targeting judicious use of O2 and decreasing the duration or developing a safer formulation of PN can be targeted to decrease BPD.

A Comparison of 3 Vitamin D Dosing Regimens in Extremely Preterm Infants: A Randomized Controlled Trial

OBJECTIVE

To determine the optimal dose of vitamin D supplementation to achieve biochemical vitamin D sufficiency in extremely low gestational age newborns in a masked randomized controlled trial.

STUDY DESIGN

100 infants 23 0/7-27 6/7 weeks gestation were randomized to vitamin D intakes of placebo (n = 36), 200 IU (n = 34), and 800 IU/d (n = 30) (approximating 200, 400, or 1000 IU/d, respectively, when vitamin D routinely included in parenteral or enteral nutrition is included). The primary outcomes were serum 25-hydroxy vitamin D concentrations on postnatal day 28 and the number of days alive and off respiratory support in the first 28 days.

RESULTS

At birth, 67% of infants had 25-hydroxy vitamin D <20 ng/mL suggesting biochemical vitamin D deficiency. Vitamin D concentrations on day 28 were (median [25th-75th percentiles], ng/mL): placebo: 22 (13-47), 200 IU: 39 (26-57), 800 IU: 84.5 (52-99); P < .001. There were no differences in days alive and off respiratory support (median [25th-75th percentiles], days): placebo: 1 (0-11), 200 IU: 0 (0-8), and 800 IU: 0.5 (0-22); P = .63, or other respiratory outcomes among groups.

CONCLUSIONS

At birth, most extremely preterm infants have biochemical vitamin D deficiency. This biochemical deficiency is reduced on day 28 by supplementation with 200 IU/d and prevented by 800 IU/d. Larger trials are required to determine if resolution of biochemical vitamin D deficiency improves clinical outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01600430.

Sphingolipids in Congenital Diaphragmatic Hernia; Results from an International Multicenter Study

BACKGROUND

Congenital diaphragmatic hernia is a severe congenital anomaly with significant mortality and morbidity, for instance chronic lung disease. Sphingolipids have shown to be involved in lung injury, but their role in the pathophysiology of chronic lung disease has not been explored. We hypothesized that sphingolipid profiles in tracheal aspirates could play a role in predicting the mortality/ development of chronic lung disease in congenital diaphragmatic hernia patients. Furthermore, we hypothesized that sphingolipid profiles differ between ventilation modes; conventional mechanical ventilation versus high-frequency oscillation.

METHODS

Sphingolipid levels in tracheal aspirates were determined at days 1, 3, 7 and 14 in 72 neonates with congenital diaphragmatic hernia, born after > 34 weeks gestation at four high-volume congenital diaphragmatic hernia centers. Data were collected within a multicenter trial of initial ventilation strategy (NTR 1310).

RESULTS

36 patients (50.0%) died or developed chronic lung disease, 34 patients (47.2%) by stratification were initially ventilated by conventional mechanical ventilation and 38 patients (52.8%) by high-frequency oscillation. Multivariable logistic regression analysis with correction for side of the defect, liver position and observed-to-expected lung-to-head ratio, showed that none of the changes in sphingolipid levels were significantly associated with mortality /development of chronic lung disease. At day 14, long-chain ceramides 18:1 and 24:0 were significantly elevated in patients initially ventilated by conventional mechanical ventilation compared to high-frequency oscillation.

CONCLUSIONS

We could not detect significant differences in temporal sphingolipid levels in congenital diaphragmatic hernia infants with mortality/development of chronic lung disease versus survivors without development of CLD. Elevated levels of ceramides 18:1 and 24:0 in the conventional mechanical ventilation group when compared to high-frequency oscillation could probably be explained by high peak inspiratory pressures and remodeling of the alveolar membrane.

Dose-dependent effects of glucocorticoids on pulmonary vascular development in a murine model of hyperoxic lung injury

BACKGROUND

Exposure of neonatal mice to hyperoxia results in pulmonary vascular remodeling and aberrant phosphodiesterase type 5 (PDE5) signaling. Although glucocorticoids are frequently utilized in the NICU, little is known about their effects on the developing pulmonary vasculature and on PDE5. We sought to determine the effects of hydrocortisone (HC) on pulmonary vascular development and on PDE5 in a neonatal mouse model of hyperoxic lung injury.

METHODS

C57BL/6 mice were placed in 21% O2 or 75% O2 within 24 h of birth and received HC (1, 5, or 10 mg/kg subcutaneously every other day) or vehicle. At 14 d, right ventricular hypertrophy (RVH), medial wall thickness (MWT), lung morphometry, and pulmonary artery (PA) PDE5 activity were assessed. PDE5 activity was measured in isolated pulmonary artery smooth muscle cells exposed to 21 or 95% O2 ± 100 nmol/l HC for 24 h.

RESULTS

Hyperoxia resulted in alveolar simplification, RVH, increased MWT, and increased PA PDE5 activity. HC decreased hyperoxia-induced RVH and attenuated MWT. HC had dose-dependent effects on alveolar simplification. HC decreased hyperoxia-induced PDE5 activity both in vivo and in vitro.

CONCLUSIONS

HC decreases hyperoxia-induced pulmonary vascular remodeling and attenuates PDE5 activity. These findings suggest that HC may protect against hyperoxic injury in the developing pulmonary vasculature.

Biomarkers for Bronchopulmonary Dysplasia in the Preterm Infant

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease of very-low-birth-weight (VLBW) preterm infants, associated with arrested lung development and a need for supplemental oxygen. Over the past few decades, the incidence of BPD has significantly raised as a result of improved survival of VLBW infants requiring mechanical ventilation. While early disease detection is critical to prevent chronic lung remodeling and complications later in life, BPD is often difficult to diagnose and prevent due to the lack of good biomarkers for identification of infants at risk, and overlapping symptoms with other diseases, such as pulmonary hypertension (PH). Due to the current lack of effective treatment available for BPD and PH, research is currently focused on primary prevention strategies, and identification of biomarkers for early diagnosis, that could also represent potential therapeutic targets. In addition, novel histopathological, biochemical, and molecular factors have been identified in the lung tissue and in biological fluids of BPD and PH patients that could associate with the disease phenotype. In this review, we provide an overview of biomarkers for pediatric BPD and PH that have been identified in clinical studies using various biological fluids. We also present a brief summary of the information available on current strategies and guidelines to prevent and diagnose BPD and PH, as well as their pathophysiology, risk factors, and experimental therapies currently available.

Children Born Preterm at the Turn of the Millennium Had Better Lung Function Than Children Born Similarly Preterm in the Early 1990s

Objective

Compare respiratory health in children born extremely preterm (EP) or with extremely low birthweight (ELBW) nearly one decade apart, hypothesizing that better perinatal management has led to better outcome.

Design

Fifty-seven (93%) of 61 eligible 11-year old children born in Western Norway in 1999–2000 with gestational age (GA) <28 weeks or birthweight <1000 gram (EP_1999–2000) and matched term-controls were assessed with comprehensive lung function tests and standardized questionnaires. Outcome was compared with data obtained at 10 years of age from all (n = 35) subjects born at GA <29 weeks or birthweight <1001 gram within a part of the same region in 1991–92 (EP_1991–1992) and their matched term-controls.

Results

EP_1999–2000 had significantly reduced forced expiratory flow in 1 second (FEV₁), FEV₁ to forced vital capacity (FEV₁/FVC) and forced expiratory flow between 25–75% of FVC (FEF_25–75), with z-scores respectively -0.34, -0.50 and -0.61 below those of the term-control group, and more bronchial hyperresponsiveness to methacholine (dose-response-slope 13.2 vs. 3.5; p<0.001), whereas other outcomes did not differ. Low birthweight z-scores, but not neonatal bronchopulmonary dysplasia (BPD) or low GA, predicted poor outcome. For children with neonatal BPD, important lung-function variables were better in EP_1999–2000 compared to EP_1991–1992. In regression models, improvements were related to more use of antenatal corticosteroids and surfactant treatment in the EP_1999–2000.

Conclusions

Small airway obstruction and bronchial hyperresponsiveness were still present in children born preterm in 1999–2000, but outcome was better than for children born similarly preterm in 1991–92, particularly after neonatal BPD. The findings suggest that better neonatal management not only improves survival, but also long-term pulmonary outcome.

Adult respiratory outcomes of extreme preterm birth. A regional cohort study

RATIONALE

Lifetime respiratory function after extremely preterm birth (gestational age≤28 wk or birth weight≤1,000 g) is unknown.

OBJECTIVES

To compare changes from 18-25 years of age in respiratory health, lung function, and airway responsiveness in young adults born extremely prematurely to that of term-born control subjects.

METHODS

Comprehensive lung function investigations and interviews were conducted in a population-based sample of 25-year-old subjects born extremely prematurely in western Norway in 1982-1985, and in matched term-born control subjects. Comparison was made to similar data collected at 18 years of age.

MEASUREMENTS AND MAIN RESULTS

At 25 years of age, 46/51 (90%) eligible subjects born extremely prematurely and 39/46 (85%) control subjects participated. z-Scores for FEV1, forced expiratory flow at 25-75% of vital capacity, and FEV1/FVC were significantly reduced in subjects born extremely prematurely by 1.02, 1.26, and 0.88, respectively, and airway resistance (kPa/L/s) was increased (0.23 versus 0.18). Residual volume to total lung capacity increased with severity of neonatal bronchopulmonary dysplasia. Responsiveness to methacholine (dose-response slope; 3.16 versus 0.85) and bronchial lability index (7.5 versus 4.8%) were increased in subjects born extremely prematurely. Lung function changes from 18 to 25 years and respiratory symptoms were similar in the prematurely born and term-born groups.

CONCLUSIONS

Lung function in early adult life was in the normal range in the majority of subjects born extremely prematurely, but methacholine responsiveness was more pronounced than in term-born young adults, suggesting a need for ongoing pulmonary monitoring in this population.

Gene expression profile in newborn rat lungs after two days of recovery of mechanical ventilation

BACKGROUND

Preterm infants having immature lungs often require respiratory support, potentially leading to bronchopulmonary dysplasia (BPD). Conventional BPD rodent models based on mechanical ventilation (MV) present outcome measured at the end of the ventilation period. A reversible intubation and ventilation model in newborn rats recently allowed discovering that different sets of genes modified their expression related to time after MV. In a newborn rat model, the expression profile 48 h after MV was analyzed with gene arrays to detect potentially interesting candidates with an impact on BPD development.

METHODS

Rat pups were injected P4-5 with 2 mg/kg lipopolysaccharide (LPS). One day later, MV with 21 or 60% oxygen was applied during 6 h. Animals were sacrified 48 h after end of ventilation. Affymetrix gene arrays assessed the total gene expression profile in lung tissue.

RESULTS

In fully treated animals (LPS + MV + 60% O(2)) vs. controls, 271 genes changed expression significantly. All modified genes could be classified in six pathways: tissue remodeling/wound repair, immune system and inflammatory response, hematopoiesis, vasodilatation, and oxidative stress. Major alterations were found in the MMP and complement system.

CONCLUSION

MMPs and complement factors play a central role in several of the pathways identified and may represent interesting targets for BPD treatment/prevention.Bronchopulmonary dysplasia (BPD) is a chronic lung disease occurring in ~30% of preterm infants born less than 30 wk of gestation (1). Its main risk factors include lung immaturity due to preterm delivery, mechanical ventilation (MV), oxygen toxicity, chorioamnionitis, and sepsis. The main feature is an arrest of alveolar and capillary formation (2). Models trying to decipher genes involved in the pathophysiology of BPD are mainly based on MV and oxygen application to young mammals with immature lungs of different species (3). In newborn rodent models, analyses of lung structure and gene and protein expression are performed for practical reasons directly at the end of MV (4,5,6). However, later appearing changes of gene expression might also have an impact on lung development and the evolution towards BPD and cannot be discovered by such models. Recently, we developed a newborn rat model of MV using an atraumatic (orotracheal) intubation technique that allows the weaning of the newborn animal off anesthesia and MV, the extubation to spontaneous breathing, and therefore allows the evaluation of effects of MV after a ventilation-free period of recovery (7). Indeed, applying this concept of atraumatic intubation by direct laryngoscopy, we recently were able to show significant differences between gene expression changes appearing directly after MV compared to those measured after a ventilation-free interval of 48 h. Immediately after MV, inflammation-related genes showed a transitory modified expression, while another set of more structurally related genes changed their expression only after a delay of 2 d (7). Lung structure, analyzed by conventional 2D histology and also by 3D reconstruction using synchrotron x-ray tomographic microscopy revealed, 48 h after end of MV, a reduced complexity of lung architecture compared to the nonventilated rat lungs, similar to the typical findings in BPD. To extend these observations about late gene expression modifications, we performed with a similar model a full gene expression profile of lung tissue 48 h after the end of MV with either room air or 60% oxygen. Essentially, we measured changes in the expression of genes related to the MMPs and complement system which played a role in many of the six identified mostly affected pathways.

Genetic predisposition to bronchopulmonary dysplasia

The objective of this study is to review the candidate gene and genome-wide association studies relevant to bronchopulmonary dysplasia, and to discuss the emerging understanding of the complexities involved in genetic predisposition to bronchopulmonary dysplasia and its outcomes. Genetic factors contribute much of the variance in risk for BPD. Studies to date evaluating single or a few candidate genes have not been successful in yielding results that are replicated in GWAS, perhaps due to more stringent p-value thresholds. GWAS studies have identified only a single gene (SPOCK2) at genome-wide significance in a European White and African cohort, which was not replicated in two North American studies. Pathway gene-set analysis in a North American cohort confirmed involvement of known pathways of lung development and repair (e.g., CD44 and phosphorus oxygen lyase activity) and indicated novel molecules and pathways (e.g., adenosine deaminase and targets of miR-219) involved in genetic predisposition to BPD. The genetic basis of severe BPD is different from that of mild/moderate BPD, and the variants/pathways associated with BPD vary by race/ethnicity. A pilot study of whole exome sequencing identified hundreds of genes of interest, and indicated the overall feasibility as well as complexity of this approach. Better phenotyping of BPD by severity and pathophysiology, and careful analysis of race/ethnicity is required to gain a better understanding of the genetic basis of BPD. Future translational studies are required for the identification of potential genetic predispositions (rare variants and dysregulated pathways) by next-generation sequencing methods in individual infants (personalized genomics).

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.

Exome Sequencing of Neonatal Blood Spots and the Identification of Genes Implicated in Bronchopulmonary Dysplasia

RATIONALE

Bronchopulmonary dysplasia (BPD), a prevalent severe lung disease of premature infants, has a strong genetic component. Large-scale genome-wide association studies for common variants have not revealed its genetic basis.

OBJECTIVES

Given the historical high mortality rate of extremely preterm infants who now survive and develop BPD, we hypothesized that risk loci underlying this disease are under severe purifying selection during evolution; thus, rare variants likely explain greater risk of the disease.

METHODS

We performed exome sequencing on 50 BPD-affected and unaffected twin pairs using DNA isolated from neonatal blood spots and identified genes affected by extremely rare nonsynonymous mutations. Functional genomic approaches were then used to systematically compare these affected genes.

MEASUREMENTS AND MAIN RESULTS

We identified 258 genes with rare nonsynonymous mutations in patients with BPD. These genes were highly enriched for processes involved in pulmonary structure and function including collagen fibril organization, morphogenesis of embryonic epithelium, and regulation of Wnt signaling pathway; displayed significantly elevated expression in fetal and adult lungs; and were substantially up-regulated in a murine model of BPD. Analyses of mouse mutants revealed their phenotypic enrichment for embryonic development and the cyanosis phenotype, a clinical manifestation of BPD.

CONCLUSIONS

Our study supports the role of rare variants in BPD, in contrast with the role of common variants targeted by genome-wide association studies. Overall, our study is the first to sequence BPD exomes from newborn blood spot samples and identify with high confidence genes implicated in BPD, thereby providing important insights into its biology and molecular etiology.

New BPD predicts lung function at school age: Follow-up study and meta-analysis

New treatment practices have improved survival of preterm infants and decreased airway pathology in bronchopulmonary dysplasia (BPD). Our aim was to investigate whether preterm birth, BPD, and the severity of BPD predict lung function in school children that are born in surfactant era. We studied pulmonary function of 88 school-aged children born very preterm (gestational age <32 weeks) and paired them with 88 age- and sex-matched controls born at term. Spirometry and diffusion capacity were recorded. We also performed a meta-analysis covering the era of antenatal corticosteroid and surfactant treatment. BPD was defined as oxygen dependence for ≥ 28 days and it was severity-graded by oxygen requirement at 36 weeks postmenstrual age (mild, none; moderate, FiO2 = 0.22-0.29; severe, FiO2 ≥ 0.30). Preterm children had lower forced expiratory volume in 1 sec (FEV1 ) 86.4 ± 11.8 versus 94.9 ± 10.1 (mean % predicted ± SD; P < 0.001), and lower diffusion capacity (DLCO) 87.6 ± 13.9 versus 93.7 ± 12.0 (P = 0.005) compared with term controls. BPD group differed in both FEV1 (P = 0.037) and DLCO (P = 0.018) from those without BPD. For meta-analysis, search identified 210 articles. Together with present results, six articles met the inclusion criteria. FEV1 of no BPD, all BPD, and moderate to severe BPD groups differed from that in term controls by -7.4, -10.5, and -17.8%, respectively. According to meta-analysis and follow-up study, the adverse effects of prematurity on pulmonary function are still detectable in school-age. BPD was associated with reductions in both diffusion capacity and spirometry. New interventions are required to document a further decrease in the life-long consequences of prematurity.

Automated High-Performance Analysis of Lung Morphometry

Automation of lung morphometric analysis is an asset in the study of lung pathophysiology because it is an assurance of robustness, reproducibility, and rapidity. The novel automated morphometric approach presented here meets these criteria. This new method collects multiple parameters, allowing quantitative elucidation of the pathophysiology of the developing and mature lungs. The automated morphometric analysis is reliable and allows the analysis of a greater proportion of each lung together with a higher number of samples and superior reproducibility than manual analysis. The use of this method revealed that treatment with 80% oxygen and lung development presented an opposite effect on most of the analyzed parameters. In conclusion, this novel approach allowed the collection of new fundamental morphometric data on lung development and a deeper comprehension of the effect of hyperoxia.

Maternal/neonatal vitamin D deficiency: a risk factor for bronchopulmonary dysplasia in preterms?

OBJECTIVE

The objective of this study was to investigate the possible association between maternal/neonatal 25-hydroxy vitamin D (25-OHD) levels and development of bronchopulmonary dysplasia.

STUDY DESIGN

One hundred and thirty-two preterm infants ⩽32 weeks of gestation who were diagnosed with respiratory distress syndrome were enrolled. 25-OHD levels were determined in maternal/neonatal blood samples that were obtained at the time of admission to the neonatal intensive care unit.

RESULT

A total of 100 infants were included and 31 (31%) developed bronchopulmonary dysplasia (BPD). Both maternal and neonatal 25-OHD levels in the BPD group were significantly lower compared with those in the no-BPD group (P=0.0001). A positive correlation was detected between maternal and neonatal 25-OHD levels. All of the infants with BPD had a 25-OHD level <10 ng ml(-1), which represented severe deficiency. Univariate logistic regression analysis revealed that maternal/neonatal vitamin D levels were a significant predictor of BPD (odds ratio (OR): 0.76 and 0.61, respectively, P<0.001).

CONCLUSION

We demonstrated for the first time that lower maternal and neonatal vitamin 25-OHD levels were associated with BPD development in preterm infants. However, further studies with larger sample sizes are needed to delineate the possible link between vitamin D deficiency and BPD.

Correlation of radiographic thoracic area and oxygenation impairment in bronchopulmonary dysplasia

We hypothesized that radiographically-assessed hyperinflation in bronchopulmonary dysplasia (BPD) is related to the degree of oxygenation impairment. Our objective was to explore the relation of chest radiographic thoracic area (CRTA) with right-to-left shunt, right shift of the oxyhemoglobin dissociation curve and ventilation/perfusion ratio (VA/Q) in infants with BPD. Twenty-two infants born at median (IQR) gestation of 26 (24-28) weeks with BPD were prospectively studied at 39 (30-69) days. Inspired oxygen (FiO2) was varied to obtain transcutaneous oxygen saturation (SpO2) values between 85 and 96%. Shunt, shift and VA/Q were derived by plotting and analysing pairs of SpO2 and FiO2. CRTA was measured by free hand-tracing the perimeter of the thoracic area in anterio-posterior chest radiographs. Median (IQR) shunt was 8 (1-14)%, shift was 13 (11-19)kPa and VA/Q 0.42 (0.30-0.48). Median (IQR) CRTA/kg was 2495 (1962-2838)mm(2) and was significantly related to shift (r=0.674, p<0.001), VA/Q (r=-0.633, p<0.001), weight at study (r=-0.457, p=0.003) and day of life (r=-0.406, p=0.009), but not to shunt. CRTA in BPD is significantly related to oxygenation impairment as quantified by shift and VA/Q. CRTA can be used as a simple radiographic test to quantify BPD severity.

Alterations in gene expression and DNA methylation during murine and human lung alveolar septation

DNA methylation, a major epigenetic mechanism, may regulate coordinated expression of multiple genes at specific time points during alveolar septation in lung development. The objective of this study was to identify genes regulated by methylation during normal septation in mice and during disordered septation in bronchopulmonary dysplasia. In mice, newborn lungs (preseptation) and adult lungs (postseptation) were evaluated by microarray analysis of gene expression and immunoprecipitation of methylated DNA followed by sequencing (MeDIP-Seq). In humans, microarray gene expression data were integrated with genome-wide DNA methylation data from bronchopulmonary dysplasia versus preterm and term lung. Genes with reciprocal changes in expression and methylation, suggesting regulation by DNA methylation, were identified. In mice, 95 genes with inverse correlation between expression and methylation during normal septation were identified. In addition to genes known to be important in lung development (Wnt signaling, Angpt2, Sox9, etc.) and its extracellular matrix (Tnc, Eln, etc.), genes involved with immune and antioxidant defense (Stat4, Sod3, Prdx6, etc.) were also observed. In humans, 23 genes were differentially methylated with reciprocal changes in expression in bronchopulmonary dysplasia compared with preterm or term lung. Genes of interest included those involved with detoxifying enzymes (Gstm3) and transforming growth factor-β signaling (bone morphogenetic protein 7 [Bmp7]). In terms of overlap, 20 genes and three pathways methylated during mouse lung development also demonstrated changes in methylation between preterm and term human lung. Changes in methylation correspond to altered expression of a number of genes associated with lung development, suggesting that DNA methylation of these genes may regulate normal and abnormal alveolar septation.

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.

Stem Cells and Their Mediators - Next Generation Therapy for Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) remains a major complication of premature birth. Despite great achievements in perinatal medicine over the past decades, there is no treatment for BPD. Recent insights into the biology of stem/progenitor cells have ignited the hope of regenerating damaged organs. Animal experiments revealed promising lung protection/regeneration with stem/progenitor cells in experimental models of BPD and led to first clinical studies in infants. However, these therapies are still experimental and knowledge on the exact mechanisms of action of these cells is limited. Furthermore, heterogeneity of the therapeutic cell populations and missing potency assays currently limit our ability to predict a cell product’s efficacy. Here, we review the therapeutic potential of mesenchymal stromal, endothelial progenitor, and amniotic epithelial cells for BPD. Current knowledge on the mechanisms behind the beneficial effects of stem cells is briefly summarized. Finally, we discuss the obstacles constraining their transition from bench-to-bedside and present potential approaches to overcome them.

Choriodecidual Group B Streptococcal Infection Induces miR-155-5p in the Fetal Lung in Macaca nemestrina

The mechanisms underlying fetal lung injury remain poorly defined. MicroRNAs (miRNAs) are small noncoding, endogenous RNAs that regulate gene expression and have been implicated in the pathogenesis of lung disease. Using a nonhuman primate model of choriodecidual infection, we sought to determine if differentially expressed miRNAs were associated with acute fetal lung injury. After inoculating 10 chronically catheterized pregnant monkeys (Macaca nemestrina) with either group B streptococcus (GBS) at 1 × 10(6) CFU (n = 5) or saline (n = 5) in the choriodecidual space, we extracted fetal lung mRNA and miRNA and profiled the changes in expression by microarray analysis. We identified 9 differentially expressed miRNAs in GBS-exposed fetal lungs, but of these, only miR-155-5p was validated by quantitative reverse transcription-PCR (P = 0.02). Significantly elevated miR-155-5p expression was also observed when immortalized human fetal airway epithelial (FeAE) cells were exposed to proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha [TNF-α]). Overexpression of miR-155-5p in FeAE cells in turn increased the production of IL-6 and CXCL10/gamma interferon-induced protein 10, which are implicated in leukocyte recruitment but also in protection from lung injury. Interestingly, while miR-155-5p decreased fibroblast growth factor 9 (FGF9) expression in a luciferase reporter assay, FGF9 levels were actually increased in GBS-exposed fetal lungs in vivo. FGF9 overexpression is associated with abnormal lung development. Thus, upregulation of miR-155-5p may serve as a compensatory mechanism to lessen the increase in FGF9 and prevent aberrant lung development. Understanding the complicated networks regulating lung development in the setting of infection is a key step in identifying how to prevent fetal lung injury leading to bronchopulmonary dysplasia.

Neonatal exposure to mild hyperoxia causes persistent increases in oxidative stress and immune cells in the lungs of mice without altering lung structure

Preterm infants often require supplemental oxygen due to lung immaturity, but hyperoxia can contribute to an increased risk of respiratory illness later in life. Our aim was to compare the effects of mild and moderate levels of neonatal hyperoxia on markers of pulmonary oxidative stress and inflammation and on lung architecture; both immediate and persistent effects were assessed. Neonatal mice (C57BL6/J) were raised in either room air (21% O2), mild (40% O2), or moderate (65% O2) hyperoxia from birth until postnatal day 7 (P7d). The mice were killed at either P7d (immediate effects) or lived in air until adulthood (P56d, persistent effects). We enumerated macrophages in lung tissue at P7d and immune cells in bronchoalveolar lavage fluid (BALF) at P56d. At P7d and P56d, we assessed pulmonary oxidative stress [heme oxygenase-1 (HO-1) and nitrotyrosine staining] and lung architecture. The data were interrogated for sex differences. At P7d, HO-1 gene expression was greater in the 65% O2 group than in the 21% O2 group. At P56d, the area of nitrotyrosine staining and number of immune cells were greater in the 40% O2 and 65% O2 groups relative to the 21% O2 group. Exposure to 65% O2, but not 40% O2, led to larger alveoli and lower tissue fraction in the short term and to persistently fewer bronchiolar-alveolar attachments. Exposure to 40% O2 or 65% O2 causes persistent increases in pulmonary oxidative stress and immune cells, suggesting chronic inflammation within the adult lung. Unlike 65% O2, 40% O2 does not affect lung architecture.

rIL-10 enhances IL-10 signalling proteins in foetal alveolar type II cells exposed to hyperoxia

Although the mechanisms by which hyperoxia promotes bronchopulmonary dysplasia are not fully defined, the inability to maintain optimal interleukin (IL)-10 levels in response to injury secondary to hyperoxia seems to play an important role. We previously defined that hyperoxia decreased IL-10 production and pre-treatment with recombinant IL-10 (rIL-10) protected these cells from injury. The objectives of these studies were to investigate the responses of IL-10 receptors (IL-10Rs) and IL-10 signalling proteins (IL-10SPs) in hyperoxic foetal alveolar type II cells (FATIICs) with and without rIL-10. FATIICs were isolated on embryonic day 19 and exposed to 65%-oxygen for 24 hrs. Cells in room air were used as controls. IL-10Rs protein and mRNA were analysed by ELISA and qRT-PCR, respectively. IL-10SPs were assessed by Western blot using phospho-specific antibodies. IL-10Rs protein and mRNA increased significantly in FATIICs during hyperoxia, but JAK1 and TYK2 phosphorylation showed the opposite pattern. To evaluate the impact of IL-8 (shown previously to be increased) and the role of IL-10Rs, IL-10SPs were reanalysed in IL-8-added normoxic cells and in the IL-10Rs' siRNA-treated hyperoxic cells. The IL-10Rs' siRNA-treated hyperoxic cells and IL-8-added normoxic cells showed the same pattern in IL10SPs with the hyproxic cells. And pre-treatment with rIL-10 prior to hyperoxia exposure increased phosphorylated IL-10SPs, compared to the rIL-10-untreated hyperoxic cells. These studies suggest that JAK1 and TYK2 were significantly suppressed during hyperoxia, where IL-8 may play a role, and rIL-10 may have an effect on reverting the suppressed JAK1 and TYK2 in FATIICs exposed to hyperoxia.

Utility of large-animal models of BPD: chronically ventilated preterm lambs

This paper is focused on unique insights provided by the preterm lamb physiological model of bronchopulmonary dysplasia (BPD). Connections are also made to insights provided by the former preterm baboon model of BPD, as well as to rodent models of lung injury to the immature, postnatal lung. The preterm lamb and baboon models recapitulate the clinical setting of preterm birth and respiratory failure that require prolonged ventilation support for days or weeks with oxygen-rich gas. An advantage of the preterm lamb model is the large size of preterm lambs, which facilitates physiological studies for days or weeks during the evolution of neonatal chronic lung disease (CLD). To this advantage is linked an integrated array of morphological, biochemical, and molecular analyses that are identifying the role of individual genes in the pathogenesis of neonatal CLD. Results indicate that the mode of ventilation, invasive mechanical ventilation vs. less invasive high-frequency nasal ventilation, is related to outcomes. Our approach also includes pharmacological interventions that test causality of specific molecular players, such as vitamin A supplementation in the pathogenesis of neonatal CLD. The new insights that are being gained from our preterm lamb model may have important translational implications about the pathogenesis and treatment of BPD in preterm human infants.

Pigment epithelium-derived factor mediates impaired lung vascular development in neonatal hyperoxia

Bronchopulmonary dysplasia is a chronic lung disease of preterm infants characterized by arrested microvascularization and alveolarization. Studies show the importance of proangiogenic factors for alveolarization, but the importance of antiangiogenic factors is unknown. We proposed that hyperoxia increases the potent angiostatin, pigment epithelium-derived factor (PEDF), in neonatal lungs, inhibiting alveolarization and microvascularization. Wild-type (WT) and PEDF(-/-) mice were exposed to room air (RA) or 0.9 fraction of inspired oxygen from Postnatal Day 5 to 13. PEDF protein was increased in hyperoxic lungs compared with RA-exposed lungs (P < 0.05). In situ hybridization and immunofluorescence identified PEDF production primarily in alveolar epithelium. Hyperoxia reduced alveolarization in WT mice (P < 0.05) but not in PEDF(-/-) mice. WT hyperoxic mice had fewer platelet endothelial cell adhesion molecule (PECAM)-positive cells per alveolus (1.4 ± 0.4) than RA-exposed mice (4.3 ± 0.3; P < 0.05); this reduction was absent in hyperoxic PEDF(-/-) mice. The interactive regulation of lung microvascularization by vascular endothelial growth factor and PEDF was studied in vitro using MFLM-91U cells, a fetal mouse lung endothelial cell line. Vascular endothelial growth factor stimulation of proliferation, migration, and capillary tube formation was inhibited by PEDF. MFLM-91U cells exposed to conditioned medium (CM) from E17 fetal mouse lung type II (T2) cells cultured in 0.9 fraction of inspired oxygen formed fewer capillary tubes than CM from T2 cells cultured in RA (hyperoxia CM, 51 ± 10% of RA CM, P < 0.05), an effect abolished by PEDF antibody. We conclude that PEDF mediates reduced vasculogenesis and alveolarization in neonatal hyperoxia. Bronchopulmonary dysplasia likely results from an altered balance between pro- and antiangiogenic factors.

Two cases of bronchopulmonary dysplasia of similar appearance in adult monozygotic twin: pathology and computed tomographic findings

Bronchopulmonary dysplasia (BPD) is related to decreased lung function throughout life. However, the pathology and radiology pattern of BPD of adults are not documented well yet. In this case report, we present BPD case of an adult monozygotic twin showing nearly identical lesions on chest computed tomography (CT). CT images showed mixed areas of ground-glass and reticular opacities in both lungs. They had common histories of pneumonias requiring mechanical ventilations in period of infants. Pulmonary function test of one patient showed a pulmonary insufficiency with airway obstruction. Pathologic findings showed bronchiolar hyperplasia and peribronchiolar fibrosis which was similar to classic BPD patients. Our twin case report might help provide distinguishing pathology and radiology pattern of an adult pulmonary sequelaes of BPD. It might be reasonable to make close follow-up for BPD patients to evaluate the long-term outcomes of BPD survivors.

Polymorphisms of the gene encoding Kit ligand are associated with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease that affects infants born preterm. Family studies indicate that BPD has a significant genetic component.

RATIONALE

We assessed the gene encoding Kit ligand (KITLG) as a candidate for genetic predisposition to moderate-to-severe BPD (controls were infants with no or mild BPD).

STUDY DESIGN

Eight KITLG-tagging single nucleotide polymorphisms (SNPs) were analyzed in cohorts of very preterm infants originating from northern Finland (56 cases and 197 controls), southern Finland (n = 59 + 52), and Canada (n = 58 + 68). Additional replication populations included infants born in Finland (n = 41 + 241) and Hungary (n = 29 + 40). All infants were of European origin. Results were controlled for risk factors of BPD. Kit ligand concentration in umbilical cord blood, collected from very preterm infants (n = 120), was studied.

RESULTS

Six SNPs of KITLG and a haplotype including all eight genotyped SNPs were associated with moderate-to-severe BPD in the northern Finnish population. When all the populations were combined, SNP rs11104948 was significantly associated with BPD. Kit ligand concentration in umbilical cord blood of infants born very preterm was an independent risk factor of BPD.

CONCLUSIONS

We show that KITLG polymorphisms are associated with susceptibility to moderate-to-severe BPD. In addition, higher Kit ligand concentrations were observed in infants that subsequently developed BPD. These results support the possibility that KITLG gene is involved in predisposition to BPD. Pediatr Pulmonol. 2015; 50:260-270. © 2014 Wiley Periodicals, Inc.

C21-steroids inactivation and glucocorticoid synthesis in the developing lung

Glucocorticoids (GCs) are important regulators of lung development. The genes normally involved in GC synthesis in adrenals are co-expressed with 20α-hydroxysteroid dehydrogenase (20α-HSD) in the developing lung. In this study, C21-steroid metabolism was investigated in fetal and postnatal mouse lungs. Incubation of [(3)H]-progesterone with lung explant cultures of different perinatal developmental time points revealed two different (antenatal vs. postnatal) complex metabolization patterns. Progesterone inactivation was predominant. 20αOH-derivatives were more abundant after birth and some metabolites were 5α-reduced. Using [(3)H]-progesterone as substrate, corticosterone synthesis was only observed in a fraction of lung explants from gestation day (GD) 15.5. Neither aldosterone synthase nor P450c17 activity was observed. With epithelial-enriched primary cell cultures, deoxycorticosterone synthesis from [(3)H]-progesterone was observed. With lung explants incubated with [(3)H]-corticosterone as substrate, [(3)H]-4-pregnen-21-ol-3,11,20-trione (11-dehydrocorticosterone), the product of 11β-HSD2, accumulated in higher proportion on GD 15.5 than at later developmental time points. The temporal correlation observed between levels of progesterone inactivation by 20α-HSD (higher after birth) and the sensitivity of lung development to GCs suggests a role for 20α-HSD in the modulation of GR occupancy through the control of 21-hydroxylase substrate and product levels. In conclusion, the developing lung is characterized by effective inactivation of c21-steroids by 20α-HSD. The formation of active GCs from the "adrenal"-like pathway was observed with some lung explants and primary epithelial cell cultures. Coexistence of this GC synthesis pathway with 20α-HSD activity strongly suggests local regulation of GC action and is compatible with intracrine/paracrine actions of GC.

Bronchopulmonary dysplasia - an overview about pathophysiologic concepts

Neonatal chronic lung disease in the preterm infant, i.e. bronchopulmonary dysplasia (BPD) is characterized by impaired pulmonary development with its effects persisting into adulthood. Triggered in the immature lung by infectious complications, oxygen toxicity and the impact of mechanical ventilation, a sustained inflammatory response, extensive remodeling of the extracellular matrix, increased apoptosis as well as altered growth factor signaling characterize the disease. The current review focuses on selected pathophysiologic processes and their interplay in disease development. Furthermore, the potential of both, acute and long-term changes to the pulmonary scaffold and the cellular interface in concert with dysregulated growth factor signaling to affect aging and repair processes in the adult lung is discussed.

Association between oxidative DNA damage and the expression of 8-oxoguanine DNA glycosylase 1 in lung epithelial cells of neonatal rats exposed to hyperoxia

Previous studies have demonstrated that oxidative stress‑induced lung injury is involved in the occurrence and developmental process of bronchopulmonary dysplasia (BPD). The present study assessed whether oxidative DNA damage occurs in the early stages of hyperoxia‑induced BPD in neonatal rats and evaluated the expression and localization of the DNA repair gene, 8‑oxoguanine DNA glycosylase 1 (OGG1), upon exposure to hyperoxia. Neonatal rats and primary cultured neonatal rat alveolar epithelial type II (AECII) cells were exposed to hyperoxia (90% O2) or normoxia (21% O2) and the expression levels of 8‑hydroxy‑2'‑deoxyguanosine (8‑OHdG) in the lung tissues and AECII cells were determined using a competitive enzyme‑linked immunosorbent assay. DNA strand breaks in the AECII cells were detected using a comet assay. The expression and localization of the OGG1 protein in the lung tissues and AECII cells were determined by immunofluorescence confocal microscopy and western blotting. The mRNA expression levels of OGG1 in the lung tissues and AECII cells were determined by reverse transcription polymerase chain reaction. The expression of 8‑OHdG was elevated in the hyperoxia‑exposed neonatal rat lung tissue and the AECII cells compared with the normoxic controls. The occurrence of DNA strand breaks in the AECII cells increased with increasing duration of hyperoxia exposure. The protein expression of OGG1 was significantly increased in the hyperoxia‑exposed lung tissues and AECII cells, with OGG1 preferentially localized to the cytoplasm. No concomitant increase in the mRNA expression of OGG1 was detected. These results revealed that oxidative DNA damage occurred in lung epithelial cells during early‑stage BPD, as confirmed by in vitro and in vivo hyperoxia exposure experiments, and the increased expression of OGG1 was associated with this process.

Neonatal hyperoxic lung injury favorably alters adult right ventricular remodeling response to chronic hypoxia exposure

The development of pulmonary hypertension (PH) requires multiple pulmonary vascular insults, yet the role of early oxygen therapy as an initial pulmonary vascular insult remains poorly defined. Here, we employ a two-hit model of PH, utilizing postnatal hyperoxia followed by adult hypoxia exposure, to evaluate the role of early hyperoxic lung injury in the development of later PH. Sprague-Dawley pups were exposed to 90% oxygen during postnatal days 0-4 or 0-10 or to room air. All pups were then allowed to mature in room air. At 10 wk of age, a subset of rats from each group was exposed to 2 wk of hypoxia (Patm = 362 mmHg). Physiological, structural, and biochemical endpoints were assessed at 12 wk. Prolonged (10 days) postnatal hyperoxia was independently associated with elevated right ventricular (RV) systolic pressure, which worsened after hypoxia exposure later in life. These findings were only partially explained by decreases in lung microvascular density. Surprisingly, postnatal hyperoxia resulted in robust RV hypertrophy and more preserved RV function and exercise capacity following adult hypoxia compared with nonhyperoxic rats. Biochemically, RVs from animals exposed to postnatal hyperoxia and adult hypoxia demonstrated increased capillarization and a switch to a fetal gene pattern, suggesting an RV more adept to handle adult hypoxia following postnatal hyperoxia exposure. We concluded that, despite negative impacts on pulmonary artery pressures, postnatal hyperoxia exposure may render a more adaptive RV phenotype to tolerate late pulmonary vascular insults.

Advances in paediatric pulmonary vascular disease associated with bronchopulmonary dysplasia

Pulmonary hypertension (PH) is a common finding in infants with bronchopulmonary dysplasia (BPD). The aim of this review is to describe recent advances in the diagnosis and treatment of PH and discuss whether they will benefit infants and children with BPD related PH. Echocardiography remains the mainstay of diagnosis but has limitations, further developments in diagnostic techniques and identification of biomarkers are required. There are many potential therapies for PH associated with BPD. Inhaled nitric oxide has been shown to improve short term outcomes only. Sidenafil in resource limited settings was shown in three randomized trials to significantly reduce mortality. The efficacy of other therapies including prostacyclin, PDE3 inhibitors and endothelin receptor blockers has only been reported in case reports or case series. Randomized controlled trials with long term follow up are required to appropriately assess the efficacy of therapies aimed at improving the outcome of children with PH.

Pulmonary vascular development goes awry in congenital lung abnormalities

Pulmonary vascular diseases of the newborn comprise a wide range of pathological conditions with developmental abnormalities in the pulmonary vasculature. Clinically, pulmonary arterial hypertension (PH) is characterized by persistent increased resistance of the vasculature and abnormal vascular response. The classification of PH is primarily based on clinical parameters instead of morphology and distinguishes five groups of PH. Congenital lung anomalies, such as alveolar capillary dysplasia (ACD) and PH associated with congenital diaphragmatic hernia (CDH), but also bronchopulmonary dysplasia (BPD), are classified in group three. Clearly, tight and correct regulation of pulmonary vascular development is crucial for normal lung development. Human and animal model systems have increased our knowledge and make it possible to identify and characterize affected pathways and study pivotal genes. Understanding of the normal development of the pulmonary vasculature will give new insights in the origin of the spectrum of rare diseases, such as CDH, ACD, and BPD, which render a significant clinical problem in neonatal intensive care units around the world. In this review, we describe normal pulmonary vascular development, and focus on four diseases of the newborn in which abnormal pulmonary vascular development play a critical role in morbidity and mortality. In the future perspective, we indicate the lines of research that seem to be very promising for elucidating the molecular pathways involved in the origin of congenital pulmonary vascular disease.

Hyperoxia-induced changes in estradiol metabolism in postnatal airway smooth muscle

Supplemental oxygen, used to treat hypoxia in preterm and term neonates, increases the risk of neonatal lung diseases, such as bronchopulmonary dysplasia (BPD) and asthma. There is a known sex predilection for BPD, but the underlying mechanisms are not clear. We tested the hypothesis that altered, local estradiol following hyperoxia contributes to pathophysiological changes observed in immature lung. In human fetal airway smooth muscle (fASM) cells exposed to normoxia or hyperoxia, we measured the expression of proteins involved in estrogen metabolism and cell proliferation responses to estradiol. In fASM cells, CYP1a1 expression was increased by hyperoxia, whereas hyperoxia-induced enhancement of cell proliferation was blunted by estradiol. Pharmacological studies indicated that these effects were attributable to upregulation of CYP1a1 and subsequent increased metabolism of estradiol to a downstream intermediate 2-methoxyestradiol. Microarray analysis of mouse lung exposed to 14 days of hyperoxia showed the most significant alteration in CYP1a1 expression, with minimal changes in expression of five other genes related to estrogen receptors, synthesis, and metabolism. Our novel results on estradiol metabolism in fetal and early postnatal lung in the context of hyperoxia indicate CYP1a1 as a potential mechanism for the protective effect of estradiol in hyperoxia-exposed immature lung, which may help explain the sex difference in neonatal lung diseases.