Epidemiology of bronchopulmonary dysplasia

Phenotypic assessment of pulmonary hypertension using high-resolution echocardiography is feasible in neonatal mice with experimental bronchopulmonary dysplasia and pulmonary hypertension: a step toward preventing chronic obstructive pulmonary disease

Bronchopulmonary dysplasia (BPD) and chronic obstructive pulmonary disease (COPD) are chronic lung diseases of human infants and adults, respectively, that are characterized by alveolar simplification. One-third of the infants with severe BPD develop pulmonary hypertension (PH). More importantly, PH increases morbidity and mortality in BPD patients. Additionally, COPD is a common respiratory morbidity in former BPD patients. The lack of an appropriate small animal model wherein echocardiography (Echo) can demonstrate PH is one of the major barriers to understand the molecular mechanisms of the disease and, thereby, develop rational therapies to prevent and/or treat PH in BPD patients. Thus, the goal of this study was to establish a model of experimental BPD and PH and investigate the feasibility of Echo to diagnose PH in neonatal mice. Since hyperoxia-induced oxidative stress and inflammation contributes to the development of BPD with PH, we tested the hypothesis that exposure of newborn C57BL/6J mice to 70% O2 (hyperoxia) for 14 days leads to lung oxidative stress, inflammation, alveolar and pulmonary vascular simplification, pulmonary vascular remodeling, and Echo evidence of PH. Hyperoxia exposure caused lung oxidative stress and inflammation as evident by increased malondialdehyde adducts and inducible nitric oxide synthase, respectively. Additionally, hyperoxia exposure caused growth restriction, alveolar and pulmonary vascular simplification, and pulmonary vascular remodeling. At 14 days of age, Echo of these mice demonstrated that hyperoxia exposure decreased pulmonary acceleration time (PAT) and PAT/ejection time ratio and increased right ventricular free wall thickness, which are indicators of significant PH. Thus, we have demonstrated the feasibility of Echo to phenotype PH in neonatal mice with experimental BPD with PH, which can aid in discovery of therapies to prevent and/or treat BPD with PH and its sequelae such as COPD in humans.

Reliability of a Noninvasive Measure of V./Q. Mismatch for Bronchopulmonary Dysplasia

RATIONALE

Currently used definitions of bronchopulmonary dysplasia (BPD) lack a continuous measure of disease severity.

OBJECTIVES

To determine if an indirect measure of V./Q. mismatch is reliable when simplified to facilitate more widespread use for grading disease severity in BPD at 36 weeks postmenstrual age.

METHODS

We used prospectively collected data from 32 preterm infants undergoing an oxygen reduction test at 36 weeks postmenstrual age to perform a simplified indirect assessment of V./Q. mismatch for each infant. Independent raters applied the model, and interrater reliability for a quantitative measure of mismatch was measured by intraclass correlation coefficient. A receiver operating characteristic curve evaluated the impact of increasing degrees of V./Q. mismatch on diagnosing BPD as defined by oxygen reduction test failure.

MEASUREMENTS AND MAIN RESULTS

Concordance for the quantitative measure of V./Q. mismatch between independent raters improved from 0.72 (confidence interval [CI], 0.48-0.86) to 0.93 (CI, 0.87-0.96) after refinement of instructions for applying the simplified model. Higher degrees of mismatch were increasingly predictive of oxygen reduction test failure, with a receiver operating characteristic curve analysis area under the curve of 0.83 (CI, 0.68-0.99; P = 0.03).

CONCLUSIONS

A simplified indirect measure of V./Q. mismatch for diagnosing and grading disease severity in BPD has high reliability and can be performed with data obtained during a standard oxygen reduction test. This should facilitate more widespread investigation of this model as a technique for characterizing BPD severity.

Sigh-induced changes of breathing pattern in preterm infants

Sighs are thought to play an important role in control of breathing. It is unclear how sighs are triggered, and whether preterm birth and lung disease influence breathing pattern prior to and after a sigh in infants. To assess whether frequency, morphology, size, and short-term variability in tidal volume (V_T) before, during, and after a sigh are influenced by gestational age at birth and lung disease (bronchopulmonary dysplasia, BPD) in former preterm infants and healthy term controls measured at equivalent postconceptional age (PCA). We performed tidal breathing measurements in 143 infants during quiet natural sleep at a mean (SD) PCA of 44.8 (1.3) weeks. A total of 233 sighs were analyzed using multilevel, multivariable regression. Sigh frequency in preterm infants increased with the degree of prematurity and severity of BPD, but was not different from that of term controls when normalized to respiratory rate. After a sigh, V_T decreased remarkably in all infants (paired t-test: P < 0.001). There was no major effect of prematurity or BPD on various indices of sigh morphology and changes in V_T prior to or after a sigh. Short-term variability in V_T modestly increased with maturity at birth and infants with BPD showed an earlier return to baseline variability in V_T following a sigh. In early infancy, sigh-induced changes in breathing pattern are moderately influenced by prematurity and BPD in preterm infants. The major determinants of sigh-related breathing pattern in these infants remain to be investigated, ideally using a longitudinal study design.

Effect of Hyperoxia on Retinoid Metabolism and Retinoid Receptor Expression in the Lungs of Newborn Mice

BACKGROUND

Preterm newborns that receive oxygen therapy often develop bronchopulmonary dysplasia (BPD), which is abnormal lung development characterized by impaired alveologenesis. Oxygen-mediated injury is thought to disrupt normal lung growth and development. However, the mechanism of hyperoxia-induced BPD has not been extensively investigated. We established a neonatal mouse model to investigate the effects of normobaric hyperoxia on retinoid metabolism and retinoid receptor expression.

METHODS

Newborn mice were exposed to hyperoxic or normoxic conditions for 15 days. The concentration of retinol and retinyl palmitate in the lung was measured by HPLC to gauge retinoid metabolism. Retinoid receptor mRNA levels were assessed by real-time PCR. Proliferation and retinoid receptor expression in A549 cells were assessed in the presence and absence of exogenous vitamin A.

RESULTS

Hyperoxia significantly reduced the body and lung weight of neonatal mice. Hyperoxia also downregulated expression of RARα, RARγ, and RXRγ in the lungs of neonatal mice. In vitro, hyperoxia inhibited proliferation and expression of retinoid receptors in A549 cells.

CONCLUSION

Hyperoxia disrupted retinoid receptor expression in neonatal mice.

Understanding the Short- and Long-Term Respiratory Outcomes of Prematurity and Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease associated with premature birth that primarily affects infants born at less than 28 weeks' gestational age. BPD is the most common serious complication experienced by premature infants, with more than 8,000 newly diagnosed infants annually in the United States alone. In light of the increasing numbers of preterm survivors with BPD, improving the current state of knowledge of long-term respiratory morbidity for infants with BPD is a priority. We undertook a comprehensive review of the published literature to analyze and consolidate current knowledge of the effects of BPD that are recognized at specific stages of life, including infancy, childhood, and adulthood. In this review, we discuss both the short-term and long-term respiratory outcomes of individuals diagnosed as infants with the disease and highlight the gaps in knowledge needed to improve early and lifelong management of these patients.

Omeprazole does not Potentiate Acute Oxygen Toxicity in Fetal Human Pulmonary Microvascular Endothelial Cells Exposed to Hyperoxia

Hyperoxia contributes to the pathogenesis of broncho-pulmonary dysplasia (BPD), which is a developmental lung disease of premature infants that is characterized by an interruption of lung alveolar and pulmonary vascular development. Omeprazole (OM) is a proton pump inhibitor that is used to treat humans with gastric acid related disorders. Earlier we observed that OM-mediated aryl hydrocarbon receptor (AhR) activation attenuates acute hyperoxic lung injury in adult mice and oxygen toxicity in adult human lung cells. However, our later studies in newborn mice demonstrated that OM potentiates hyperoxia-induced developmental lung injury. Whether OM exerts a similar toxicity in primary human fetal lung cells is unknown. Hence, we tested the hypothesis that OM potentiates hyperoxia-induced cytotoxicity and ROS generation in the human fetal lung derived primary human pulmonary microvascular endothelial cells (HPMEC). OM activated AhR as evident by a dose-dependent increase in cytochrome P450 (CYP) 1A1 mRNA levels in OM-treated cells. Furthermore, OM at a concentration of 100 μM (OM 100) increased NADP(H) quinone oxidoreductase 1 (NQO1) expression. Surprisingly, hyperoxia decreased rather than increase the NQO1 protein levels in OM 100-treated cells. Exposure to hyperoxia increased cytotoxicity and hydrogen peroxide (H₂O₂) levels. Interestingly, OM 100-treated cells exposed to air had increased H₂O₂ levels. However, hyperoxia did not further augment H₂O₂ levels in OM 100-treated cells. Additionally, hyperoxia-mediated oxygen toxicity was similar in both vehicle- and OM-treated cells. These findings contradict our hypothesis and support the hypothesis that OM does not potentiate acute hyperoxic injury in HPMEC in vitro.

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

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

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.

Determinants of chronic lung disease severity in the first year of life; A population based study

OBJECTIVES

First, create a clinical severity score for patients with chronic lung disease of infancy (CLDi) following neonatal intensive care unit (NICU) stay. Second, using California wide population-based data, identify factors associated with clinical severity of CLDi at 4-9 months corrected gestational age (CGA).

STUDY DESIGN

Pediatric pulmonologists ranked and weighted eight factors reflecting clinical severity of CLDi. Utilizing these data we scored and assigned these to 4-9 month old CGA moderate/severe bronchopulmonary dysplasia (BPD) infants, born<30 weeks gestational age (GA), within the California High Risk Infant Follow up (HRIF) program. Infants were studied relative to factors from the California Perinatal Quality Care Collaborative (CPQCC).

RESULTS

We received survey responses from 43/88 pediatric pulmonologists from 28/53 North American training centers who are experts in CLDi. Strong agreement between ranking (72-100%) of respiratory system parameters and weighting (out of 100 points weighting was within 20 points) was observed with severity of CLDi. Data from 940 CLDi premature infants <30 weeks GA were obtained. Infants with severe CLDi scores at 4-9 months CGA (relative to a zero score) showed positive associations with being male, odds ratio[OR] = 2.45[confidence interval (CI) 1.26-4.77]), >30 ventilator days, OR = 3.82 (1.30-11.2), postnatal steroids OR = 3.94 (1.94-7.84), and a surprising inverse association with retinopathy of prematurity stage 3-4, OR = 0.24 (0.09-0.67) CONCLUSIONS: The CLDi clinical severity score allowed for standardized assessment of pulmonary morbidity, and evaluation of risk factors in the NICU for CLDi following NICU discharge. These observations point to risk factors associated with CLDi outcomes at 4-9 months CGA.

Beneficial Effect of Etanercept on Hyperoxic Lung Injury Model in Neonatal Rats

PURPOSE

To determine whether prophylaxis with etanercept, an anti-inflammatory drug, would decrease the severity of lung injury in a neonatal rat model of bronchopulmonary dysplasia (BPD);

MATERIALS AND METHODS

Rat pups were divided into three groups: pups exposed to room air (group 1; n = 10), to hyperoxia + placebo (group 2; n = 9), and to hyperoxia + etanercept (group 3; n = 8). Lung morphology was assessed by alveolar surface area percentage, which is a measure of alveolar size. The severities of lung inflammation and antioxidant capacity were assessed by quantifying tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), malondialdehyde (MDA), and superoxide dismutase (SOD) from lung homogenate;

RESULTS

The percentage of alveolar surface areas were significantly higher in group 3 compared to group 2 (p = .004) and similar in both group 1 and group 3 (p = .21). The mean level of lung MDA was significantly higher in group 2 compared to group 1 and group 3 (p < .05 for both). Lung homogenate SOD activities in group 3 was significantly higher than group 2 (p < .001). Furthermore, group 3 pups had lower levels of TNF-α and TGF-β in lung homogenate than that in group 2 (p < .05 for both) but similar in both group 1 and group 3;

CONCLUSION

Etanercept has favorable effects on alveolarization as well as inflammation and oxidative stress markers in a neonatal rat model of BPD.

Aryl hydrocarbon receptor is necessary to protect fetal human pulmonary microvascular endothelial cells against hyperoxic injury: Mechanistic roles of antioxidant enzymes and RelB

Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. Activation of the aryl hydrocarbon receptor (AhR) protects adult and newborn mice against hyperoxic lung injury by mediating increases in the expression of phase I (cytochrome P450 (CYP) 1A) and phase II (NADP(H) quinone oxidoreductase (NQO1)) antioxidant enzymes (AOE). AhR positively regulates the expression of RelB, a component of the nuclear factor-kappaB (NF-κB) protein that contributes to anti-inflammatory processes in adult animals. Whether AhR regulates the expression of AOE and RelB, and protects fetal primary human lung cells against hyperoxic injury is unknown. Therefore, we tested the hypothesis that AhR-deficient fetal human pulmonary microvascular endothelial cells (HPMEC) will have decreased RelB activation and AOE, which will in turn predispose them to increased oxidative stress, inflammation, and cell death compared to AhR-sufficient HPMEC upon exposure to hyperoxia. AhR-deficient HPMEC showed increased hyperoxia-induced reactive oxygen species (ROS) generation, cleavage of poly(ADP-ribose) polymerase (PARP), and cell death compared to AhR-sufficient HPMEC. Additionally, AhR-deficient cell culture supernatants displayed increased macrophage inflammatory protein 1α and 1β, indicating a heightened inflammatory state. Interestingly, loss of AhR was associated with a significantly attenuated CYP1A1, NQO1, superoxide dismutase 1(SOD1), and nuclear RelB protein expression. These findings support the hypothesis that decreased RelB activation and AOE in AhR-deficient cells is associated with increased hyperoxic injury compared to AhR-sufficient cells.

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.

Inhibition of β-catenin signaling improves alveolarization and reduces pulmonary hypertension in experimental bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common and serious chronic lung disease of preterm infants. The development of pulmonary hypertension (PH) significantly increases the mortality and morbidity of this disease. β-Catenin signaling plays an important role in tissue development and remodeling. Aberrant β-catenin signaling is associated with clinical and experiment models of BPD. To test the hypothesis that inhibition of β-catenin signaling is beneficial in promoting alveolar and vascular development and preventing PH in experimental BPD, we examined the effects of ICG001, a newly developed pharmacological inhibitor of β-catenin, in preventing hyperoxia-induced BPD in neonatal rats. Newborn rat pups were randomized at postnatal day (P)2 to room air (RA) + DMSO (placebo), RA + ICG001, 90% FiO2 (O2) + DMSO, or O2 + ICG001. ICG001 (10 mg/kg) or DMSO was given by daily intraperitoneal injection for 14 days during continuous exposure to RA or hyperoxia. Primary human pulmonary arterial smooth muscle cells (PASMCs) were cultured in RA or hyperoxia (95% O2) in the presence of DMSO or ICG001 for 24 to 72 hours. Treatment with ICG001 significantly increased alveolarization and reduced pulmonary vascular remodeling and PH during hyperoxia. Furthermore, administering ICG001 decreased PASMC proliferation and expression of extracellular matrix remodeling molecules in vitro under hyperoxia. Finally, these structural, cellular, and molecular effects of ICG001 were associated with down-regulation of multiple β-catenin target genes. These data indicate that β-catenin signaling mediates hyperoxia-induced alveolar impairment and PH in neonatal animals. Targeting β-catenin may provide a novel strategy to alleviate BPD in preterm infants.

Predicting death or tracheostomy placement in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To estimate the risk of death or tracheostomy placement (D/T) in infants with severe bronchopulmonary dysplasia (sBPD) born < 32 weeks' gestation referred to regional neonatal intensive care units.

STUDY DESIGN

We conducted a retrospective cohort study in infants born < 32 weeks' gestation with sBPD in 2010-2011, using the Children's Hospital Neonatal Database. sBPD was defined as the need for FiO2 ⩾ 0.3, nasal cannula support >2 l min(-1) or positive pressure at 36 weeks' post menstrual age. The primary outcome was D/T before discharge. Predictors associated with D/T in bivariable analyses (P < 0.2) were used to develop a multivariable logistic regression equation using 80% of the cohort. This equation was validated in the remaining 20% of infants.

RESULT

Of 793 eligible patients, the mean gestational age was 26 weeks' and the median age at referral was 6.4 weeks. D/T occurred in 20% of infants. Multivariable analysis showed that later gestational age at birth, later age at referral along with pulmonary management as the primary reason for referral, mechanical ventilation at the time of referral, clinically diagnosed pulmonary hypertension, systemic corticosteroids after referral and occurrence of a bloodstream infection after referral were each associated with D/T. The model performed well with validation (area under curve 0.86, goodness-of-fit χ(2), P = 0.66).

CONCLUSION

Seven clinical variables predicted D/T in this large, contemporary cohort with sBPD. These results can be used to inform clinicians who counsel families of affected infants and to assist in the design of future prospective trials.

Stem cell experiments moves into clinic: new hope for children with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease with long-term complications that affects mainly preterm born children with low birth weights, especially those treated with mechanical ventilation and oxygen therapy. Successful treatment of BPD could reduce the incidence of other diseases of prematurity such as periventricular leukomalacia and retinopathy. The effects of current therapies are unsatisfactory; thus, searching for novel therapeutic is underway. One promising approach seems administration of mesenchymal stem cells (MSC). Preclinical data strongly support the role of progenitor cells in the preservation of lung structure. MSC can be found more often in pre-term than term umbilical cord and its isolation from Wharton's jelly carries a potential in treating diseases of prematurity. Several questions concerning the use of MSC in BPD remain to be answered, including the amount of transferred cells, intervals between infusions, the best route for administration and the timing. MSC can be administered as a treatment or prophylaxis. However, having in mind that not all prematurely born children are at risk of developing bronchopulmonary dysplasia, a search for laboratory markers identifying potential patients should be conducted. This review summarizes the latest achievements in MSC therapy in the context of BPD.

Extracorporeal cardiopulmonary resuscitation outcomes in term and premature neonates*

OBJECTIVE

Extracorporeal cardiopulmonary resuscitation appears to improve survival in patients with acute refractory cardiopulmonary failure. This analysis was performed to determine survival outcomes and predictors of in-hospital mortality for term and preterm neonates who received extracorporeal cardiopulmonary resuscitation.

DESIGN

Retrospective review of data from the Extracorporeal Life Support Organization international registry.

SETTING

Pediatric and neonatal ICUs.

PATIENTS

Infants less than or equal to 30 days.

INTERVENTIONS

Extracorporeal cardiopulmonary resuscitation.

MEASUREMENTS AND MAIN RESULTS

Demographic, clinical, and survival data from patients who received extracorporeal cardiopulmonary resuscitation between 1998 and 2010 were analyzed to determine factors that affect in-hospital mortality. Overall survival to hospital discharge for the 641 neonates who received extracorporeal cardiopulmonary resuscitation was 39%. In univariate analysis, gestational age correlated inversely with stroke (odds ratio, 0.84 [95% CI, 0.75-0.95]; p = 0.006) and death (odds ratio, 0.87 [95% CI, 0.78-0.96]; p = 0.005) as did corrected gestational age (odds ratio, 0.89 [95% CI, 0.81-0.97]; p = 0.006) and birth weight (odds ratio, 0.53 [95% CI, 0.38-0.74]; p < 0.001). Dysrhythmia as the primary diagnosis had significantly lower odds of death than single-ventricle cardiac disease (odds ratio, 0.24 [95% CI, 0.06-0.95]; p = 0.04). Higher pre-extracorporeal cardiopulmonary resuscitation oxygenation decreased the odds of death (odds ratio, 0.996 [95% CI, 0.994-0.999]; p = 0.01), whereas complications occurring on extracorporeal life support increased the odds of death. In the multivariate analysis, lower birth weight and pre-extracorporeal cardiopulmonary resuscitation oxygenation, as well as complications including CNS hemorrhage, pulmonary hemorrhage, acidosis, renal replacement therapy, and mechanical complications, increased the odds of death.

CONCLUSIONS

Overall survival for neonates receiving extracorporeal cardiopulmonary resuscitation is similar to older pediatric patients but decreases with lower gestational age and weight. Despite this, many low-birth weight neonates survive to hospital discharge.

Circulating endothelial progenitor cells decrease in infants with bronchopulmonary dysplasia and increase after inhaled nitric oxide

BACKGROUND

Impairment of endothelial progenitor cells (EPCs) has been shown to contribute to the development of bronchopulmonary dysplasia (BPD). In the current study, the relationship between EPC changes of after birth and the development of BPD was investigated, and the effects of inhaled nitric oxide (iNO) on EPCs were evaluated.

METHODS

Sixty infants with a gestational age of less than 32 weeks and a birth weight of less than 1500 g were studied. NO was administered to infants who were receiving mechanical ventilation or CPAP for at least 2 days between the ages of 7 and 21 days. EPC level was determined by flow cytometry at birth, 7, 21 and 28 days of age and 36 weeks' postmenstrual age (PMA), before and after the iNO treatment. Plasma concentrations of vascular endothelial growth factor (VEGF), stromal cell-derived factor-1 and granulocyte-macrophage colony-stimulating factor were determined via immunochemical assay.

RESULTS

Twenty-five neonates developed BPD, 35 neonates survived and did not develop BPD. EPC level was decreased on day 7 and 21 in infants who later developed BPD compared with infants that did not develop BPD. From birth to 21 days of age, BPD infants had a persistently lower VEGF concentration compared with non-BPD infants. No difference was found between the two groups at day 28 or 36 weeks PMA. In infants that later developed BPD, iNO raised the KDR(+)CD133(+) and CD34(+)KDR(+)CD133(+) EPC numbers along with increasing the level of plasma VEGF.

CONCLUSION

EPC level was reduced at 7 days of age in infants with BPD, and iNO increased the EPC number along with increasing the level of VEGF. Further studies are needed to elucidate the mechanism leading to the decrease of EPCs in infants with BPD and to investigate the role of iNO treatment in the prevention of BPD.

Perinatal risk factors for adverse long-term pulmonary outcome in premature infants: comparison of different definitions of bronchopulmonary dysplasia/chronic lung disease

BACKGROUND

The aim of the study was to determine factors that affect adverse long-term pulmonary outcome in premature infants.

METHODS

This retrospective analysis was done using 306 clinical records of preterm singleton neonates at <32 weeks of gestation. Two definitions of adverse pulmonary outcome were used: chronic lung disease (CLD), defined as a need for supplemental oxygen for at least 28 days after birth; and bronchopulmonary dysplasia (BPD), defined as oxygen dependency for at least 28 days after birth plus at 36 weeks postmenstrual age and/or a need for positive-pressure ventilatory support. Selected perinatal variables were compared between these definitions, and factors related to disease development were identified on multivariate analysis.

RESULTS

The incidence of CLD and of BPD were 42% and 17%, respectively. Regardless of the definitions, the incidence of patent ductus arteriosus and of neonatal infection were significantly higher in the patients who met the disease criteria, but that of chorioamnionitis and of small for gestational age (SGA) were significantly higher in the patients only when the BPD definition was applied. Multivariate analysis identified SGA as an independent risk factor for the development of BPD after controlling for gestational age.

CONCLUSIONS

Among selected perinatal variables, prenatal risk factors, particularly SGA, contributed to prolonged dependency on oxygen and/or positive-pressure ventilatory support, in combination with neonatal risk factors.

Neonatal hyperoxic exposure persistently alters lung secretoglobins and annexin A1

Altered functions of the lung epithelial surface likely contribute to the respiratory morbidities in infants with bronchopulmonary dysplasia (BPD). Infants with BPD exhibit decreased expressions of secretoglobins (SCGBs), including Clara cell secretory protein (CCSP). Expression of lung SCGB and annexin A1 (ANXA1) is persistently altered in CCSP knockout mice suggesting that CCSP indirectly influences innate immune responses. The present studies tested the hypothesis that neonatal hyperoxic exposure induces deficits in CCSP expression that are associated with persistent alterations in lung SCGB and ANXA1 expression. Newborn C3H/HeN mice were exposed to room air (RA) or 85% O2 from birth and were sacrificed at 14 d or returned to RA for 14 d. Neonatal hyperoxia followed by RA recovery was associated with decreased lung CCSP and SCGB3A1 protein but not mRNA expression. Hyperoxia-induced alterations in the charge characteristics of ANXA1 were unchanged by RA recovery and were associated with elevated lung macrophage numbers. These findings support a model in which hyperoxia-induced alterations in Clara cell function influence lung innate immune function through effects on immunomodulatory proteins. Studies to determine the mechanism(s) by which CCSP alterations affect SCGBs, ANXA1, and innate immune responses in BPD are warranted.

[Prevalence, severity, and predictors of bronchopulmonary dysplasia in a cohort of very preterm infants]

OBJECTIVES

The aim of this retrospective cohort study was to determine the prevalence and severity of BPD and its predictors in a regional cohort of very preterm (VP) infants in Reunion Island.

METHODS

All autochthonous VP infants, live-born before the 33rd week of gestation (WG) between 1st January 2008 and 31st December 2009, were eligible for the study. Only VP infants surviving at least 28 days, for whom the parameters were known from birth, were included in the case-control study of predictors of moderate to severe BPD (BPDmo/s).

RESULTS

In VP infants less than 33 WG, the rate of overall BPD (3 grades of severity) was 30.7%. Among those who survived 28 days or more, the rate of BPDmo/s was 13.1% (95%CI: 10.2-15.9%). In VP infants less than 32 WG that survived at 36 WG, the prevalence of BPDmo/s was 18.2% (95% CI: 14.2-22.1%). In a fixed-effect logistic model, adjusted for gestational age, postnatal growth, and the mode of ventilation at 24h, 4 key factors were predictive of BDPmo/s: small for gestational age, surfactant, delayed energy intake, and late-onset neonatal infection. In a mixed-effect logistic model adjusted for these same cofactors, the site was associated with BPDmo/s, in line with a center-effect.

CONCLUSION

The prevalence of BPDmo/s in the mixed-race population of Reunion Island is consistent with those observed in Europe but were site-specific. In our setting, predictors of individual BPDmo/s are similar to those already identified.

Inhibition of LRP5/6-mediated Wnt/β-catenin signaling by Mesd attenuates hyperoxia-induced pulmonary hypertension in neonatal rats

BACKGROUND

Hyperoxia-induced neonatal lung injury is associated with activation of Wnt/β-catenin signaling. Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) are Wnt coreceptors that bind to Wnt ligands and mediate canonical Wnt/β-catenin signaling. We hypothesized that inhibition of LRP5/6 by their universal inhibitor, Mesd, would attenuate hyperoxia-induced lung injury.

METHODS

Newborn rat pups were randomly exposed to normoxia or hyperoxia at 90% FiO2 and injected intraperitoneally with placebo or Mesd every other day for 14 d. On day 15, phosphorylation of LRP5/6 (pLRP5/6), expression of Wnt/β-catenin target genes, cyclin D1 and Wnt-induced signaling protein-1 (WISP-1), right-ventricular systolic pressure (RVSP), right-ventricular hypertrophy (RVH), pulmonary vascular remodeling, alveolarization, and vascularization were measured.

RESULTS

Hyperoxia exposure markedly induced pLRP5/6, cyclin D1, and WISP-1 expression in the lungs of placebo animals, but they were significantly attenuated by the administration of Mesd. Mesd also significantly attenuated hyperoxia-induced pulmonary hypertension (PH) and pulmonary vascular remodeling. However, there was no effect on alveolarization or vascularization after Mesd administration.

CONCLUSION

This study demonstrates that LRP5/6 mediates pulmonary vascular remodeling and PH in hyperoxia-induced neonatal lung injury, thereby suggesting a potential therapeutic target to alleviate PH in neonates with severe bronchopulmonary dysplasia.

Histological chorioamnionitis and bronchopulmonary dysplasia: a retrospective cohort study

OBJECTIVE

To examine the association between histological chorioamnionitis (HC) with or without fetal inflammatory response (FIR) and bronchopulmonary dysplasia (BPD) in preterm infants.

STUDY DESIGN

We conducted a retrospective cohort study of infants born at <29 weeks gestation admitted to the neonatal intensive care unit from 2000 to 2006, who had placental histology. We compared the incidence of BPD among three groups: No HC group, HC without FIR group and HC with FIR group. The multivariable model based on generalized estimating equation was fitted to estimate the adjusted risk ratios (aRR) and 95% confidence intervals (CIs) for BPD and combined outcome of BPD or death.

RESULT

Of 529 infants, 84 (16%) had HC without FIR, 186 (35%) had HC with FIR and 259 (49%) had no HC. Compared with the no HC group, HC with and without FIR group infants were of lower gestational age and singleton births. Multivariable modeling based on generalized estimating equation revealed that HC with FIR is associated with decreased risk of both BPD (aRR 0.88, 95% CI 0.81 to 0.95) and the combined outcome of BPD or death (aRR 0.91, 95% CI 0.86 to 0.97). HC without FIR showed a trend toward reduction in BPD (aRR 0.93, 95% CI 0.86 to 1.00).

CONCLUSIONS

HC with FIR is associated with decreased risk of both BPD and the combined outcome of BPD or death in preterm infants.

Periostin downregulation is an early marker of inhibited neonatal murine lung alveolar septation

BACKGROUND

Extreme preterm birth exposes the saccular lung to multiple teratogens, which ultimately retard alveolar development. Specifically, therapeutic high level oxygen supplementation adversely affects the premature lungs and results in blunted alveolarization. Prolonged hyperoxic lung injury has previously been shown to upregulate the matricellular protein Periostin (Postn) and stimulate ectopic accumulation of alpha smooth muscle actin (αSMA) myofibroblasts. Therapies that promote lung septation are lacking largely due to a lack of reliable early biomarkers of injury. Thus, we determined if Postn expression correlated with the initial appearance of myofibroblasts in the saccular lung and was required for early alveolar development.

METHODS

Lung development in C57BL/6J mice following room-air (RA, 21%-O₂) or continuous hyperoxia (85%-O₂) from birth (P0) through postnatal day P14 was correlated with Postn and αSMA expression. Alveolarization in Postn knockout mice exposed to room-air, 60%-, and 85%-O₂ was also examined.

RESULTS

Postn was widely expressed in distal lung septa through P2 to P4 and peak expression coincided with accumulation of saccular myofibroblasts. Initially, 85%-O₂ prematurely downregulated Postn and αSMA expression and suppressed proliferation before the first evidence of distal lung simplification at P4. By P14, chronic 85%-O₂ resulted in secondary upregulation of Postn and αSMA in blunted septa. Myofibroblast differentiation and alveolar development was unaffected in Postn null mice and acute 85%-O₂ exposure equally inhibited septal formation in Postn null and wild-type littermates.

CONCLUSION

Postn expression is tightly correlated with the presence of αSMA-myofibroblasts and is a novel early biomarker of acutely inhibited alveolar septation during a crucial window of lung development.

Anaesthetic management of the child with co-existing pulmonary disease

Children with co-existing pulmonary disease have a wide range of clinical manifestations with significant implications for anaesthetists. Although there are a number of pulmonary diseases in children, this review focuses on two of the most common pulmonary disorders, asthma and bronchopulmonary dysplasia (BPD). These diseases share the physiology of bronchoconstriction and variably decreased flow in the airways, but also have unique physiological consequences. The anaesthetist can make a difference in outcomes with proper preoperative evaluation and appropriate preparation for surgery in the context of a team approach to perioperative care with implementation of a stepwise approach to disease management. An understanding of the importance of minimizing the risk for bronchoconstriction and having the tools at hand to treat it when necessary is paramount in the care of these patients. Unique challenges exist in the management of pulmonary hypertension in BPD patients. This review covers medical treatment, intraoperative management, and postoperative care for both patient populations.

Arginyl-glutamine dipeptide or docosahexaenoic acid attenuate hyperoxia-induced lung injury in neonatal mice

OBJECTIVES

Supplementation studies of glutamine, arginine, and docosahexaenoic acid (DHA) have established the safety of each of these nutrients in neonates. However, the potential for a more stable and soluble dipeptide, arginyl-glutamine (Arg-Gln) or DHA, a long-chain ω-3 fatty acid with anti-inflammatory properties, to exert benefits on hyperoxia-induced lung injury has not to our knowledge been investigated. The aim of this study was to investigate whether Arg-Gln dipeptide or DHA could attenuate markers of injury and inflammation in neonatal mouse lungs exposed to hyperoxia.

METHODS

Seven-day-old mouse pups were placed with their dams in 75% oxygen for 5 d. After 5 d of hyperoxic exposure (postnatal days 7-12), pups were removed from hyperoxia and allowed to recover in atmospheric conditions for 5 d (postnatal days 12-17). Mouse pups received Arg-Gln (5 g · kg⁻¹ · d⁻¹) or DHA (5 g · kg⁻¹ · d⁻¹) or saline orally from postnatal days 12 through 17. Histologic changes, myeloperoxidase, lactate dehydrogenase, inflammatory cytokines, and nuclear factor-κB inhibitor levels were checked in each group.

RESULTS

The Arg-Gln and DHA prevented the development of key markers of injury, including histologic changes, myeloperoxidase, lactate dehydrogenase, and inflammatory cytokines interleukin-6 and C-X-C motif ligand 1 (CXCL1)/keratinocyte-derived chemokine (KC). The highly beneficial effects of Arg-Gln on the reversal of oxygen-induced lung damage was associated with restoration of levels of nuclear factor-κB inhibitor.

CONCLUSION

The Arg-Gln and DHA, with protective effects on hyperoxic lung injury in neonatal mice, are promising nutritional adjuncts that may prevent lung damage owing to oxygen toxicity in infants.

Effects of intrauterine infection or inflammation on fetal lung development

1. Intrauterine infection or inflammation is common in cases of preterm birth. Preterm infants are at risk of acute respiratory distress as a result of lung immaturity; evidence of exposure to infection and/or inflammation before birth is associated with a reduced risk of neonatal respiratory distress syndrome (RDS). Experimentally induced intrauterine inflammation or infection in sheep causes a precocious increase in pulmonary surfactant in the preterm lungs that improves preterm lung function, consistent with the reduced risk of RDS in human infants exposed to infection and/or inflammation before birth. 2. The effects of intrauterine inflammation on fetal lung development appear to result from direct action of proinflammatory stimuli within the lungs rather than by systemic signals, such as the classical glucocorticoid-mediated lung maturation pathway. However, paracrine and/or autocrine production and/or metabolism of glucocorticoids in fetal lung tissue may occur as a result of inflammation-induced changes in the expression of 11β-hydroxysteroid dehydrogenase (types 1 and 2). 3. Likely candidates that mediate inflammation-induced surfactant production by the preterm lung include prostaglandin E₂ and/or other arachidonic acid metabolites. Intrauterine inflammation induces the expression of enzymes responsible for prostaglandin production in fetal lung tissue. Inhibition of prostaglandin production prevents, at least in part, the effects of inflammation on fetal lungs. 4. Our experiments are identifying mechanisms of surfactant production by the preterm lungs that may be exploited as novel therapies for preventing respiratory distress in preterm infants. Elucidation of the effects of inflammation on the fetal lungs and other organs will allow more refined approaches to the care of preterm infants exposed to inflammation in utero.

Low postnatal serum IGF-I levels are associated with bronchopulmonary dysplasia (BPD)

Aim:

To characterize postnatal changes in serum insulin-like growth factor-1 (IGF-I) in relation to development of bronchopulmonary dysplasia (BPD) in very preterm infants.

Methods:

Longitudinal study of 108 infants with mean (SD) gestational age (GA) 27.2 (2.2) weeks. Weekly serum samples of IGF-I were analysed from birth until postmenstrual age (PMA) 36 weeks. Multivariate models were developed to identify independent predictors of BPD.

Results:

Postnatal mean IGF-I levels at postnatal day (PND) 3–21 were lower in infants with BPD compared with infants with no BPD (16 vs. 26 μg/L, p < 0.001). Longitudinal postnatal change in IGF-I levels (IGF-I regression coefficient (β)), PNDs 3–21, was lower in infants with BPD compared with infants with no BPD (0.28 vs. 0.97, p = 0.002) and mean IGF-I during PMA 30–33 weeks was lower in infants with BPD as compared with infants without BPD (22 vs. 29 μg/L, p < 0.001). In a binomial multiple regression model, lower GA, male gender and lower mean serum IGF-I levels during PND 3–21 were the most predictive risk factors associated with BPD (r² = 0.634, p < 0.001).

Conclusion:

Lower IGF-I concentrations during the first weeks after very preterm birth are associated with later development of BPD.

Increased incidence of bronchopulmonary dysplasia in preterm infants exposed to preeclampsia

OBJECTIVE

The aims of the study were to determine the effect of preeclampsia on bronchopulmonary dysplasia (BPD) development in preterm infants and to investigate the possible association between BPD severity and preeclampsia.

METHODS

The study group involved preterm infants (≤32 gestational week) born to a preeclamptic mother with no co-existing medical condition, whereas the comparison group involved preterm infants born to a normotensive mother. BPD was defined as requirement for supplemental oxygen for the first 28 days of life and classified as mild, moderate and severe.

RESULTS

There were a total of 117 and 215 premature infants that were born to a preeclamptic mother and a normotensive mother, respectively. The incidence of BPD in preterm infants born to preeclamptic mothers (38.5%) was significantly higher than those born to normotensive mothers (19.5%). Frequencies of moderate and severe BPD were significantly higher in the infants born to preeclamptic mothers. Moderate and severe BPD was also significantly higher in infants born to a mother with severe preeclampsia compared with a mother with mild preeclampsia. In logistic regression model, preeclampsia was found to be predictive of BPD.

CONCLUSIONS

Preeclampsia was found to be an important risk factor for BPD development in preterm infants. The incidence of both moderate and severe BPD was significantly higher in infants born to preeclamptic mothers. These findings might be associated with altered angiogenesis in the preeclamptic mother which might be shared by the fetus.

Role of CXC chemokine receptor-2 in a murine model of bronchopulmonary dysplasia

The contribution of neutrophils and CXC chemokines to the pathogenesis of bronchopulmonary dysplasia is not well defined. The transgenic expression of IL-1β in the pulmonary epithelium causes lung inflammation and disrupts alveolar development in infant mice. To study the hypothesis that CXC chemokine receptor-2 (CXCR2) is a mediator of inflammatory lung injury, we compared lung development in IL-1β-expressing mice with wild-type (IL-1β/CXCR2(+/+)) or null (IL-1β/CXCR2(-/-)) CXCR2 loci. CXCR2 deficiency abolished the transmigration of neutrophils into the alveolar lumen in IL-1β-expressing mice, but did not alter the number of neutrophils in the parenchyma. The deletion of CXCR2 increased the alveolar chord length and reduced the survival of mice when IL-1β was expressed from the pseudoglandular to the alveolar stages. The capillary configuration was highly abnormal in both IL-1β/CXCR2(+/+) and IL-1β/CXCR2(-/-) lungs, but in very different ways. The cellular area of the parenchyma and the total capillary area of IL-1β/CXCR2(+/+) and IL-1β/CXCR2(-/-) mice were smaller than those of control/CXCR2(+/+) and control/CXCR2(-/-) mice, but the ratio of capillary area to cellular area was similar in all four genotypes. When IL-1β was expressed during the saccular stage, IL-1β/CXCR2(-/-) mice had smaller alveolar chord lengths and better survival than did IL-1β/CXCR2(+/+) mice. Independent of the timing of IL-1β expression, IL-1β increased alveolar septal thickness in mice with wild-type CXCR2 loci, but not in CXCR2 null mice. Depending on the developmental stage at the time of the inflammatory insult, inhibition of the CXCR2 pathway may exert opposite effects on alveolar septation in the neonatal lung.

Protective Effects of Nigella sativa Oil in Hyperoxia-Induced Lung Injury

BACKGROUND

Oxygen-induced lung injury is believed to lead to the development of bronchopulmonary dysplasia in premature infants. We have evaluated the beneficial effects of Nigella sativa oil (NSO) on rats with hyperoxia-induced lung injury.

METHODS

Thirty newborn Sprague-Dawley rats were randomly divided into 3 groups as hyperoxia (95% O(2)), hyperoxia+NSO and control (21% O(2)). Pups in the hyperoxia+NSO group were administered intraperitoneal NSO at a dose of 4ml/kg daily during the study period. Histopathologic, immunochemical, and biochemical evaluations (superoxide dismutase [SOD], glutathione peroxidase [GSH-Px], malonaldehyde [MDA] and myeloperoxidase [MPO]) were performed.

RESULTS

In the histopathologic and immunochemical evaluation, severity of lung damage was significantly lower in the hyperoxia+NOS group (P<.05). Tissue GSH-Px and SOD levels were significantly preserved, and MDA, MPO levels were significantly lower in the hyperoxia+NSO group (P<.05).

CONCLUSION

NSO significantly reduced the severity of lung damage due to hyperoxia.

Arginyl-glutamine dipeptide or docosahexaenoic acid attenuates hyperoxia-induced small intestinal injury in neonatal mice

BACKGROUND AND OBJECTIVE

Supplementation studies of glutamine, arginine, and docosahexaenoic acid (DHA) have established the safety of each of these nutrients in neonates; however, the potential for a more stable and soluble dipeptide, arginyl-glutamine (Arg-Gln) or DHA with anti-inflammatory properties, to exert benefits on hyperoxia-induced intestinal injury has not been investigated. Arg-Gln dipeptide has been shown to prevent retinal damage in a rodent model of oxygen-induced injury. The objective of the present study was to investigate whether Arg-Gln dipeptide or DHA could also attenuate markers of injury and inflammation to the small intestine in this same model.

METHODS

Seven-day-old mouse pups were placed with their dams in 75% oxygen for 5 days. After 5 days of hyperoxic exposure (P7-P12), pups were removed from hyperoxia and allowed to recover in atmospheric conditions for 5 days (P12-P17). Mouse pups received Arg-Gln (5g·kg·day) or DHA (5g·kg·day) or vehicle orally started on P12 through P17. Distal small intestine (DSI) histologic changes, myeloperoxidase (MPO), lactate dehydrogenase (LDH), inflammatory cytokines, and tissue apoptosis were evaluated.

RESULTS

Hyperoxic mice showed a greater distortion of overall villus structure and with higher injury score (P<0.05). Arg-Gln dipeptide and DHA supplementation groups were more similar to the room air control group. Supplementation of Arg-Gln or DHA reduced hyperoxia-induced MPO activity (P<0.05). Supplementation of Arg-Gln or DHA returned LDH activity to the levels of control. Hyperoxia induced apoptotic cell death in DSIs, and both Arg-Gln and DHA reversed this effect (P<0.05).

CONCLUSIONS

Supplementation with either Arg-Gln or DHA may limit some inflammatory and apoptotic processes involved in hyperoxic-induced intestinal injury in neonatal mice.

Gene expression profiling in fetal rat lung during gestational perfluorooctane sulfonate exposure

Perfluorooctane sulfonate (PFOS) is a persistent environmental contaminant found in the tissues of humans and wildlife. It has been reported that gestational exposure to PFOS causes neonatal death of rats. However, the mechanism is still unclear. In this study, we investigated the effects of gestational PFOS exposure on the gene expression profiling of fetal rat lung at pseudoglandular stage. Adult Sprague Dawley dams were dosed orally from gestational day 12-18 with 0 (control), 5 mg/kg/day or 20 mg/kg/day PFOS. Animals were euthanized on day 18.5, fetal lung samples were collected for histochemical staining and RNA profiling analysis. PFOS did not cause apparent microscopic changes of fetal lungs. Gene expression profiling revealed that PFOS dose-dependently up-regulated the expression of 21 (5 mg/kg) and 43 (20 mg/kg) genes. These genes include five PPARα target genes (Acot1, Hmgcs2, Fabp4, Fabp1 and Myh7), and 4 of them are involved in lipid metabolism. The other genes were primarily included in the categories of cytoskeletal structure (Tpm1, Tnnt2, Actn3, Myoz2, Tmod1, and Mfap5), extracellular matrix (Ckm, Lum, Tnnc1, Art3, Dcn, Col17a1, Aspn, Ctsk, Itm2a, Spock2 and Orm1), transporting (Cox8h, Cox6a2 and Scnn1a) and secreted proteins (Scgb3a1, Nppb and Spp1). Our study demonstrates that in utero PFOS exposure resulted in the alteration of a set of genes which are involved in significant cytoskeletal, extracellular matrix remodeling, lipid metabolism and secreted proteins in the fetal rat lung.

Update on the diagnosis and management of bronchopulmonary dysplasia/chronic lung disease of infancy: what the radiologist should know

Pediatric radiologists are frequently called upon to render interpretations of chest radiographs performed on premature infants with chronic respiratory problems. After the acute phase of surfactant deficiency (respiratory distress syndrome), infants with persistent respiratory problems are loosely categorized by clinicians as evolving toward a broad, rather vague entity called bronchopulmonary dysplasia (BPD) or chronic lung disease (CLD). This review aims to update the radiologist on how the characteristics of the disease have shifted and how management, diagnosis and pathology have changed since the disorder was first described more than 40 years ago. The radiologist armed with this information might be better prepared to provide insightful reporting and address the needs of the neonatologist.

Colchicine protects against hyperoxic lung injury in neonatal rats

BACKGROUND

Bronchopulmonary dysplasia (BPD) is characterized by inflammation, fibrosis and mucosal necrosis, which leads to emphysematous coalescence of alveoli.

OBJECTIVE

We tested whether prophylaxis with colchicine , an anti-inflammatory, antioxidant and antifibrotic drug, would decrease the severity of lung injury in an animal model of BPD.

METHODS

Twenty-five rat pups were divided into three groups: control (n = 8), hyperoxia (n = 7), and hyperoxia + colchicine (n = 10). The hyperoxia groups were exposed to >95% oxygen from day 1 to 10 of life. On day 10, the animals were sacrificed and the lungs were processed for histology and biochemical analysis. Lung morphology was assessed by the mean linear intercept (MLI), a measure of alveolar size. The degree of lung inflammation and antioxidant capacity were assessed by quantifying lung homogenate tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels.

RESULTS

Colchicine significantly decreased lung damage as determined by the MLI in the hyperoxia groups (p < 0.01). The median level of lung MDA was significantly higher in the hyperoxia group compared with the control group (p < 0.05) and the colchicine-treated group (p < 0.05). Lung homogenate SOD and GSH-Px activities in the colchicine-treated group were significantly higher than in the hyperoxia group (p < 0.05). Furthermore, colchicine-treated pups had lower lung homogenate TNF-α and IL-1β levels compared with the hyperoxia group (p < 0.05).

CONCLUSIONS

Colchicine has favorable effects on alveolarization as well as inflammation and oxidative stress markers in an animal model of BPD.

Omeprazole attenuates hyperoxic injury in H441 cells via the aryl hydrocarbon receptor

Hyperoxia contributes to the development of bronchopulmonary dysplasia in premature infants. Earlier we observed that aryl hydrocarbon receptor (AhR)-deficient mice are more susceptible to hyperoxic lung injury than AhR-sufficient mice, and this phenomenon was associated with a lack of expression of cytochrome P450 1A enzymes. Omeprazole, a proton pump inhibitor used in humans with gastric acid-related disorders, activates AhR in hepatocytes in vitro. However, the effects of omeprazole on AhR activation in the lungs and its impact on hyperoxia-induced reactive oxygen species (ROS) generation and inflammation are unknown. In this study, we tested the hypothesis that omeprazole attenuates hyperoxia-induced cytotoxicity, ROS generation, and expression of monocyte chemoattractant protein-1 (MCP-1) in human lung-derived H441 cells via AhR activation. Experimental groups included cells transfected with AhR small interfering RNA (siRNA). Hyperoxia resulted in significant increases in cytotoxicity, ROS generation, and MCP-1 production, which were significantly attenuated with the functional activation of AhR by omeprazole. The protective effects of omeprazole on cytotoxicity, ROS production, and MCP-1 production were lost in H441 cells whose AhR gene was silenced by AhR siRNA. These findings support the hypothesis that omeprazole protects against hyperoxic injury in vitro via AhR activation that is associated with decreased ROS generation and expression of MCP-1.

Secretory phospholipase A2 pathway in various types of lung injury in neonates and infants: a multicentre translational study

BACKGROUND

Secretory phospholipase A2 (sPLA2) is a group of enzymes involved in lung tissue inflammation and surfactant catabolism. sPLA2 plays a role in adults affected by acute lung injury and seems a promising therapeutic target. Preliminary data allow foreseeing the importance of such enzyme in some critical respiratory diseases in neonates and infants, as well. Our study aim is to clarify the role of sPLA2 and its modulators in the pathogenesis and clinical severity of hyaline membrane disease, infection related respiratory failure, meconium aspiration syndrome and acute respiratory distress syndrome. sPLA2 genes will also be sequenced and possible genetic involvement will be analysed.

METHODS/DESIGN

Multicentre, international, translational study, including several paediatric and neonatal intensive care units and one coordinating laboratory. Babies affected by the above mentioned conditions will be enrolled: broncho-alveolar lavage fluid, serum and whole blood will be obtained at definite time-points during the disease course. Several clinical, respiratory and outcome data will be recorded. Laboratory researchers who perform the bench part of the study will be blinded to the clinical data.

DISCUSSION

This study, thanks to its multicenter design, will clarify the role(s) of sPLA2 and its pathway in these diseases: sPLA2 might be the crossroad between inflammation and surfactant dysfunction. This may represent a crucial target for new anti-inflammatory therapies but also a novel approach to protect surfactant or spare it, improving alveolar stability, lung mechanics and gas exchange.

Elastase inhibitory activity of airway α1-antitrypsin is protected by treatment with a catalytic antioxidant in a baboon model of severe bronchopulmonary dysplasia

Recent studies in animal models of bronchopulmonary dysplasia (BPD) suggest that antioxidant treatments may be beneficial for the disease. However, the mechanisms by which these drugs improve the course of BPD are not completely known. Alpha1-antitrypsin (α1-AT) is one of the major serine protease inhibitors in human plasma that has antielastase and antiapoptotic activities. Both activities of α1-AT are dependent on its reactive site loop (RSL), which is highly susceptible to oxidative inactivation. In this study, we investigated the elastase inhibitory activity of α1-AT in two different baboon models of BPD, the "new BPD" and the "severe BPD" models, and determined the effect of treatment with a catalytic antioxidant, Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP), on the elastase inhibitory activity of α1-AT in the severe BPD model. Our results demonstrate the presence of sufficient elastase inhibitory activity of the airway α1-AT in the new but not in the severe BPD model. Treatment of severe BPD group baboons with the catalytic antioxidant MnTE-2-PyP resulted in augmentation of the elastase inhibitory activity of α1-AT. These findings suggest that prevention of the oxidative inactivation of α1-AT may be one of the mechanisms by which antioxidant therapy improves the pulmonary outcomes in animal models of severe BPD.

[Influence of maternal and neonatal factors on bronchopulmonary dysplasia development]

OBJECTIVE

To review epidemiological features of bronchopulmonary dysplasia (BPD) and its relationship with maternal and neonatal conditions in a neonatal unit.

METHODS

Cross-sectional, descriptive and analytical study involving preterm newborns (NBs) with a birth weight lower than 1,500 g and gestational age under 37 weeks. Data was collected through a review of medical records of these newborns admitted to a neonatal unit.

RESULTS

The study included 323 newborns with a mean birth weight of 1,161 g (± 231 g), gestational age between 24 and 36.5 weeks, with a BPD incidence of 17.6%. Among the NBs developing BPD, the mean of days using invasive mechanical ventilation (IMV), non-invasive ventilation (NIMV), and supplemental oxygen was 17.6, 16.2, and 46.1 days, respectively, with a time significantly longer for those NBs developing BPD (p < 0.001). BPD occurred significantly more often in NBs with a patent ductus arteriosus (PDA).

CONCLUSION

BPD incidence in this study was similar to that found in the literature. No BPD association with maternal infection and antenatal corticosteroid use was found. NBs receiving exogenous surfactant had a higher BPD incidence because they had lower BW and GA. Concomitant occurrence of PDA and BPD is associated with staying longer on IMV, NIMV and supplemental oxygen.

Connective tissue growth factor antibody therapy attenuates hyperoxia-induced lung injury in neonatal rats

Despite recent advances in neonatal intensive care and surfactant therapy, bronchopulmonary dysplasia (BPD) continues to be one of the most common long-term pulmonary complications associated with preterm birth. Clinical efforts to prevent and treat BPD have been largely unsuccessful due to its multifactorial nature and poorly understood disease process. Connective tissue growth factor (CTGF) is a matricellular protein that plays an important role in tissue development and remodeling. Previous studies have demonstrated that hyperoxia exposure up-regulates CTGF expression in neonatal rat lungs. Whether CTGF overexpression plays a role in the pathogenesis of BPD, and whether CTGF antagonism has a therapeutic potential for BPD, are unknown. In the present study, we examined CTGF expression in lung autopsy specimens from patients with BPD and control subjects with no BPD. We assessed the effect of a CTGF-neutralizing monoclonal antibody (CTGF Ab) on preventing hyperoxia-induced lung injury in neonatal rats. Our study demonstrates that CTGF expression is increased in BPD lungs. In newborn rats, exposure to 90% oxygen for 14 days resulted in activation of β-catenin signaling, decreased alveolarization and vascular development, and physiological and histological evidence of pulmonary hypertension (PH). However, treatment with CTGF Ab prevented β-catenin signaling activation, improved alveolarization and vascular development, and attenuated PH during hyperoxia. These data indicate that CTGF-β-catenin signaling plays a critical role in the pathogenesis of experimental BPD. CTGF antagonism may offer a novel therapeutic strategy to alleviate BPD and PH in neonates.