Elevation of fibronectin levels in lung secretions of infants with respiratory distress syndrome and development of bronchopulmonary dysplasia

Unique Patterns of Circulating Extracellular Vesicles in Preterm Infants During Adaptation to Extra-Uterine Life

There is growing interest in the role of extracellular vesicles (EVs) in neonatal pathology. This study aimed to characterise circulating EVs following preterm birth. This single-centre prospective observational study included cord and postnatal plasma from preterm (n = 101) and full-term infants (n = 66). EVs were analysed using nanoparticle tracking analysis, flow cytometry, proteomics and procoagulant activity assay. We found changes in the concentration, size, cellular origin and proteomic content of circulating EVs in preterm infants during perinatal adaptation. To understand if these changes were related to prematurity or normal adaptation to extrauterine life, they were also investigated in term infants. There was a dramatic increase in the concentration of small and large EVs on Day 3 in the preterm group; specific subsets of platelet (CD42b+ and CD62P+), endothelial (VEGFR2) and tissue factor EVs were elevated. Differentially expressed proteins relating to haemostasis, pulmonary physiology and immunity were identified between Day 1 and 3 in preterm infants. These changes have never previously been described in a large cohort of preterm infants and differ from healthy term infants. These findings have major implications for future neonatal EV studies, particularly the timing of sample collection. Further work is required to understand the clinical implications of this unique EV profile following preterm birth.

Role of oxidative stress in neonatal respiratory distress syndrome

Respiratory distress syndrome is the commonest respiratory disorder in preterm infants. Although it is well known that preterm birth has a key role, the mechanisms of lung injury have not been fully elucidated. The pathogenesis of this neonatal condition is based on the rapid formation of the oxygen reactive species, which surpasses the detoxification capacity of anti-oxidative defense system. The high reactivity of free radical leads to damage to a variety of molecules and may induce respiratory cell death. There is evidence that the oxidative stress involved in the physiopathology of this disease, is particularly related to oxygen supplementation, mechanical ventilation, inflammation/infection and diabetes. This narrative review summarizes what is known regarding the connection between oxidative stress and respiratory distress syndrome.

Inhaled versus systemic corticosteroids for preventing bronchopulmonary dysplasia in ventilated very low birth weight preterm neonates

BACKGROUND

Bronchopulmonary dysplasia (BPD) remains an important cause of mortality and morbidity in preterm infants and inflammation plays a significant role in its pathogenesis. The use of inhaled corticosteroids may modulate the inflammatory process without concomitant high systemic steroid concentrations and less risk of adverse effects. This is an update of a review published in 2012 (Shah 2012). We recently updated the related review on "Inhaled versus systemic corticosteroids for treating bronchopulmonary dysplasia in ventilated very low birth weight preterm neonates".

OBJECTIVES

To determine the effect of inhaled versus systemic corticosteroids started within the first 7 days of life on preventing death or BPD in ventilated very low birth weight infants.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2017, Issue 1), MEDLINE via PubMed (1966 to 23 February 2017), Embase (1980 to 23 February 2017), and CINAHL (1982 to 23 February 2017). We searched clinical trials registers, conference proceedings and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing inhaled versus systemic corticosteroid therapy (irrespective of dose and duration) starting in the first seven days of life in very low birth weight preterm infants receiving assisted ventilation.

DATA COLLECTION AND ANALYSIS

Clinical outcomes data were extracted and analysed using Review Manager. When appropriate, meta-analysis was performed using typical relative risk (RR), typical risk difference (RD) and weighted mean difference (WMD). Meta-analyses were performed using typical relative risk, typical risk difference (RD), and weighted mean difference with their 95% confidence intervals (CI). If RD was statistically significant, the number needed to benefit or the number needed to harm was calculated. We assessed the quality of evidence was evaluated using GRADE principles.

MAIN RESULTS

We included two trials that involved 294 infants. No new studies were included for the 2017 update. The incidence of death or BPD at 36 weeks' postmenstrual age was not statistically significantly different between infants who received inhaled or systemic steroids (RR 1.09, 95% CI 0.88 to 1.35; RD 0.05, 95% CI -0.07 to 0.16; 1 trial, N = 278). The incidence of BPD at 36 weeks' postmenstrual age among survivors was not statistically significant between groups (RR 1.34, 95% CI 0.94 to 1.90; RD 0.11, 95% CI -0.02 to 0.24; 1 trial, N = 206). There was no statistically significant difference in the outcomes of BPD at 28 days, death at 28 days or 36 weeks' postmenstrual age and the combined outcome of death or BPD by 28 days between groups (2 trials, N = 294). The duration of mechanical ventilation was significantly longer in the inhaled steroid group compared with the systemic steroid group (typical MD 4 days, 95% CI 0.2 to 8; 2 trials, N = 294; I² = 0%) as was the duration of supplemental oxygen (typical MD 11 days, 95% CI 2 to 20; 2 trials, N = 294; I² = 33%).The incidence of hyperglycaemia was significantly lower with inhaled steroids (RR 0.52, 95% CI 0.39 to 0.71; RD -0.25, 95% CI -0.37 to -0.14; 1 trial, N = 278; NNTB 4, 95% CI 3 to 7 to avoid 1 infant experiencing hyperglycaemia). The rate of patent ductus arteriosus increased in the group receiving inhaled steroids (RR 1.64, 95% CI 1.23 to 2.17; RD 0.21, 95% CI 0.10 to 0.33; 1 trial, N = 278; NNTH 5, 95% CI 3 to 10). In a subset of surviving infants in the United Kingdom and Ireland there were no significant differences in developmental outcomes at 7 years of age. However, there was a reduced risk of having ever been diagnosed as asthmatic by 7 years of age in the inhaled steroid group compared with the systemic steroid group (N = 48) (RR 0.42, 95% CI 0.19 to 0.94; RD -0.31, 95% CI -0.58 to -0.05; NNTB 3, 95% CI 2 to 20).According to GRADE the quality of the evidence was moderate to low. Evidence was downgraded on the basis of design (risk of bias), consistency (heterogeneity) and precision of the estimates.Both studies received grant support and the industry provided aero chambers and metered dose inhalers of budesonide and placebo for the larger study. No conflict of interest was identified.

AUTHORS' CONCLUSIONS

We found no evidence that early inhaled steroids confer important advantages over systemic steroids in the management of ventilator-dependent preterm infants. Based on this review inhaled steroids cannot be recommended over systemic steroids as a part of standard practice for ventilated preterm infants. Because they might have fewer adverse effects than systemic steroids, further randomised controlled trials of inhaled steroids are needed that address risk/benefit ratio of different delivery techniques, dosing schedules and long-term effects, with particular attention to neurodevelopmental outcome.

Hyperoxia-Induced Proliferative Retinopathy: Early Interruption of Retinal Vascular Development with Severe and Irreversible Neurovascular Disruption

Bronchopulmonary dysplasia (BPD) is a major cause of neonatal morbidity in premature infants, occurring as a result of arrested lung development combined with multiple postnatal insults. Infants with BPD exposed to supplemental oxygen are at risk of retinopathy of prematurity as well. Thus, we studied the effects of hyperoxia on the retinal vasculature in a murine model of BPD. The retinal phenotype of this model, which we termed hyperoxia-induced proliferative retinopathy (HIPR), shows severe disruption of retinal vasculature and loss of vascular patterning, disorganized intra-retinal angiogenesis, inflammation and retinal detachment. Neonatal mice were subjected to 75% oxygen exposure from postnatal day (P)0 to P14 to model BPD, then allowed to recover in room air for 1 (P15), 7 (P21), or 14 days (P28). We quantified retinal thickness, protein levels of HIF-1α, NOX2, and VEGF, and examined the cellular locations of these proteins by immunohistochemistry. We examined the retinal blood vessel integrity and inflammatory markers, including macrophages (F4/80) and lymphocytes (CD45R). Compared to controls, normal retinal vascular development was severely disrupted and replaced by a disorganized sheet of intra-retinal angiogenesis in the HIPR mice. At all time-points, HIPR showed persistent hyaloidal vasculature and a significantly thinner central retina compared to controls. HIF-1α protein levels were increased at P15, while VEGF levels continued to increase until P21. Intra-retinal fibrinogen was observed at P21 followed by sub-retinal deposition in at P28. Inflammatory lymphocytes and macrophages were observed at P21 and P28, respectively. This model presents a severe phenotype of disrupted retinal vascular development, intra-retinal angiogenesis inflammation and retinal detachment.

The Extracellular Matrix in Bronchopulmonary Dysplasia: Target and Source

Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth that contributes significantly to morbidity and mortality in neonatal intensive care units. BPD results from life-saving interventions, such as mechanical ventilation and oxygen supplementation used to manage preterm infants with acute respiratory failure, which may be complicated by pulmonary infection. The pathogenic pathways driving BPD are not well-delineated but include disturbances to the coordinated action of gene expression, cell-cell communication, physical forces, and cell interactions with the extracellular matrix (ECM), which together guide normal lung development. Efforts to further delineate these pathways have been assisted by the use of animal models of BPD, which rely on infection, injurious mechanical ventilation, or oxygen supplementation, where histopathological features of BPD can be mimicked. Notable among these are perturbations to ECM structures, namely, the organization of the elastin and collagen networks in the developing lung. Dysregulated collagen deposition and disturbed elastin fiber organization are pathological hallmarks of clinical and experimental BPD. Strides have been made in understanding the disturbances to ECM production in the developing lung, but much still remains to be discovered about how ECM maturation and turnover are dysregulated in aberrantly developing lungs. This review aims to inform the reader about the state-of-the-art concerning the ECM in BPD, to highlight the gaps in our knowledge and current controversies, and to suggest directions for future work in this exciting and complex area of lung development (patho)biology.

Altered pulmonary lymphatic development in infants with chronic lung disease

Pulmonary lymphatic development in chronic lung disease (CLD) has not been investigated, and anatomy of lymphatics in human infant lungs is not well defined. Hypothesis. Pulmonary lymphatic hypoplasia is present in CLD. Method. Autopsy lung tissues of eighteen subjects gestational ages 22 to 40 weeks with and without history of respiratory morbidity were stained with monoclonal antipodoplanin and reviewed under light microscopy. Percentage of parenchyma podoplanin stained at the acinar level was determined using computerized image analysis; 9 CLD and 4 control subjects gestational ages 27 to 36 weeks were suitable for the analysis. Results. Distinct, lymphatic-specific staining with respect to other vascular structures was appreciated in all gestations. Infants with and without respiratory morbidity had comparable lymphatic distribution which extended to the alveolar ductal level. Podoplanin staining per parenchyma was increased and statistically significant in the CLD group versus controls at the alveolar ductal level (0.06% ± 0.02% versus 0.04% ± 0.01%, 95% CI −0.04% to −0.002%, P < 0.03). Conclusion. Contrary to our hypothesis, the findings show that there is an increase in alveolar lymphatics in CLD. It is suggested that the findings, by expanding current knowledge of CLD pathology, may offer insight into the development of more effective therapies to tackle CLD.

Inhaled versus systemic corticosteroids for preventing chronic lung disease in ventilated very low birth weight preterm neonates

BACKGROUND

Chronic lung disease (CLD) remains an important cause of mortality and morbidity in preterm infants and inflammation plays an important role in its pathogenesis. The use of inhaled corticosteroids may modulate the inflammatory process without concomitant high systemic steroid concentrations and less risk of adverse effects.

OBJECTIVES

To determine the effect of inhaled versus systemic corticosteroids started within the first two weeks of life on preventing CLD in ventilated very low birth weight (VLBW) infants.

SEARCH METHODS

Randomised and quasi-randomised trials were identified by searching The Cochrane Library, MEDLINE , EMBASE , CINAHL, reference lists of published trials and abstracts published in Pediatric Research or electronically on the Pediatric Academic Societies web site in June 2007.This search was updated in June 2011 and included additional searches of Clinicaltrials.gov, Controlled-trials.com and Web of Science.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing inhaled versus systemic corticosteroid therapy (regardless of the dose and duration of therapy) started in the first two weeks of life in VLBW infants receiving assisted ventilation.

DATA COLLECTION AND ANALYSIS

Outcomes including CLD at 28 days or 36 weeks postmenstrual age (PMA), mortality, the combined outcome of death or CLD at 28 days or 36 weeks PMA, other pulmonary outcomes and adverse effects were evaluated. All data were analysed using RevMan 5.1. Meta-analyses were performed using relative risk (RR), risk difference (RD), and mean difference (MD) with their 95% confidence intervals (CI). If RD was significant, the numbers needed to benefit (NNTB) or to harm (NNTH) were calculated.

MAIN RESULTS

No new trials were identified in this update. Two trials qualified for inclusion in this review. The incidence of CLD at 36 weeks PMA was increased (of borderline statistical significance) in the inhaled steroid group [RR 1.45 (95% CI 0.99 to 2.11); RD 0.11 (95% CI 0.00 to 0.21), p = 0.05, one trial, n = 278]. The incidence of CLD at 36 weeks PMA among all survivors [RR 1.34 (95% CI 0.94 to 1.90); RD 0.11 (95% CI -0.02 to 0.24), one trial, n = 206], oxygen dependency at 28 days (two trials, n = 294), death by 28 days (two trials, n = 294) or 36 weeks PMA (two trials, n = 294) and the combined outcome of death or CLD by 28 days (two trials, n = 294) or 36 weeks PMA (one trial, n = 278) did not differ significantly between the groups. The duration of mechanical ventilation was significantly longer in the inhaled steroid group as compared to the systemic steroid group [typical MD 4 days (95% CI 0.2 to 8); two trials, n = 294] as was the duration of supplemental oxygen [typical MD 11 days (95% CI 2 to 20); two trials, n = 294]. The incidence of hyperglycaemia was significantly lower in the group receiving inhaled steroids [RR 0.52 (95% CI 0.39 to 0.71); RD -0.25 (95% CI -0.37 to -0.14); one trial, n = 278; NNTB 4 (95% CI 3 to 7) to avoid one infant experiencing hyperglycaemia]. The rate of patent ductus arteriosus was increased in the group receiving inhaled steroids [RR 1.64 (95% CI 1.23 to 2.17); RD 0.21 (95% CI 0.10 to 0.33); one trial, n = 278; NNTH 5 (95% CI 3 to 10)]. No information was available on long-term neurodevelopmental outcomes.

AUTHORS' CONCLUSIONS

This review found no evidence that early inhaled steroids confer important advantages over systemic steroids in the management of ventilator dependent preterm infants. Neither inhaled steroids nor systemic steroids can be recommended as a part of standard practice for ventilated preterm infants. Because they might have fewer adverse effects than systemic steroids, further randomised controlled trials of inhaled steroids are needed that address risk/benefit ratio of different delivery techniques, dosing schedules and long-term effects, with particular attention to neurodevelopmental outcome.

Choriodecidual group B streptococcal inoculation induces fetal lung injury without intra-amniotic infection and preterm labor in Macaca nemestrina

BACKGROUND

Early events leading to intrauterine infection and fetal lung injury remain poorly defined, but may hold the key to preventing neonatal and adult chronic lung disease. Our objective was to establish a nonhuman primate model of an early stage of chorioamnionitis in order to determine the time course and mechanisms of fetal lung injury in utero.

METHODOLOGY/PRINCIPAL FINDINGS

Ten chronically catheterized pregnant monkeys (Macaca nemestrina) at 118-125 days gestation (term=172 days) received one of two treatments: 1) choriodecidual and intra-amniotic saline (n=5), or 2) choriodecidual inoculation of Group B Streptococcus (GBS) 1×10(6) colony forming units (n=5). Cesarean section was performed regardless of labor 4 days after GBS or 7 days after saline infusion to collect fetal and placental tissues. Only two GBS animals developed early labor with no cervical change in the remaining animals. Despite uterine quiescence in most cases, blinded review found histopathological evidence of fetal lung injury in four GBS animals characterized by intra-alveolar neutrophils and interstitial thickening, which was absent in controls. Significant elevations of cytokines in amniotic fluid (TNF-α, IL-8, IL-1β, IL-6) and fetal plasma (IL-8) were detected in GBS animals and correlated with lung injury (p<0.05). Lung injury was not directly caused by GBS, because GBS was undetectable in amniotic fluid (~10 samples tested/animal), maternal and fetal blood by culture and polymerase chain reaction. In only two cases was GBS cultured from the inoculation site in low numbers. Chorioamnionitis occurred in two GBS animals with lung injury, but two others with lung injury had normal placental histology.

CONCLUSIONS/SIGNIFICANCE

A transient choriodecidual infection can induce cytokine production, which is associated with fetal lung injury without overt infection of amniotic fluid, chorioamnionitis or preterm labor. Fetal lung injury may, thus, occur silently without symptoms and before the onset of the fetal systemic inflammatory response syndrome.

Ureia como marcador de diluição em amostras de lavado traqueobrônquico de potros com rodococose

No estudo das infecções e dos mecanismos inflamatórios do trato respiratório posterior, a diluição desconhecida de amostras de lavados traqueobrônquicos leva a um grave problema na interpretação das concentrações de várias substâncias. Foi investigada a amplitude da diluição em uma situação clínica verdadeira, com o objetivo de determinar a validez do uso da dosagem da ureia em lavados traqueobrônquicos para correção da diluição. As amostras do estudo consistiram em lavados traqueobrônquicos obtidos de sete potros com infecção por Rhodococcus equi. Foi realizada a contagem celular total e diferencial e comprado com o quadro clínico e a recuperação bacteriana de todas as amostras. Os fatores de diluição dos lavados variaram entre 14,3 e 130 (média 59,7). O uso da ureia como marcador de diluição melhorou a exatidão na determinação da concentração total de células nos lavados. Estes resultados sugerem que a prática de mensurar substâncias em lavado traqueobrônquico sem correção da diluição possa induzir a falsas conclusões.

Inflammatory mediators in the immunobiology of bronchopulmonary dysplasia

Inflammation is important in the development of bronchopulmonary dysplasia (BPD). Polymorphonuclear cells and macrophages and proinflammatory cytokines/chemokines denote early inflammation in clinical scenarios such as in utero inflammation with chorioamnionitis or initial lung injury associated with respiratory distress syndrome or ventilator-induced lung injury. The persistence and non-resolution of lung inflammation contributes greatly to BPD, including altering the lung's ability to repair, contributing to fibrosis, and inhibiting secondary septation, alveolarization, and normal vascular development. Further understanding of the role of inflammation in the pathogenesis of BPD, in particular, during the chronic inflammatory period, offers us the opportunity to develop inflammation-related prevention and treatment strategies of this disease that has long-standing consequences for very premature infants.

Placental growth factor and vascular endothelial growth factor receptor-2 in human lung development

OBJECTIVE

We examined the pulmonary expression of 2 proangiogenic factors, namely, placental growth factor and vascular endothelial growth factor receptor-2, during lung development and acute and chronic lung injury in newborn infants.

METHODS

Six groups were included in an immunohistochemical study of placental growth factor and vascular endothelial growth factor receptor-2, that is, 9 fetuses, 4 preterm and 8 term infants without lung injury who died soon after birth, 5 preterm infants with respiratory distress syndrome of <2 days and 7 with respiratory distress syndrome of >10 days, and 6 with bronchopulmonary dysplasia. Placental growth factor concentrations in tracheal aspirate fluid were measured in 70 samples from 20 preterm infants during the first postnatal week.

RESULTS

In immunohistochemical analyses, placental growth factor staining was seen in bronchial epithelium and macrophages in all groups. Distal airway epithelium positivity was observed mostly in fetuses and in preterm infants who died soon after birth. Vascular endothelial growth factor receptor-2 staining was seen in vascular endothelium in all groups and also in lymphatic endothelium in fetuses. Vascular endothelial growth factor receptor-2 staining in arterial endothelium was associated with higher and staining in venous endothelium with lower gestational age. In capillaries, less vascular endothelial growth factor receptor-2 staining was seen in bronchopulmonary dysplasia. The mean placental growth factor protein concentration in tracheal aspirate fluid during the first postnatal week was 0.64 +/- 0.42 pg/mL per IgA-secretory component unit. Concentrations during the first postnatal week were stable. Lower placental growth factor concentrations correlated with chorioamnionitis and lactosyl ceramide positivity.

CONCLUSIONS

The vascular endothelial growth factor receptor-2 staining pattern seems to reflect ongoing differentiation and activity of different endothelia. Lower vascular endothelial growth factor receptor-2 expression in capillary endothelium in bronchopulmonary dysplasia might be a reflection of the dysregulation of vascular development that is characteristic of bronchopulmonary dysplasia.

Pulmonary Biomarkers of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia, or BPD, is a chronic pulmonary disorder of premature infants, commonly defined as having an oxygen requirement at 36 weeks postmenstrual age. It is an important source of morbidity and mortality in premature neonates. Its' etiology appears to be multifactorial with the most common associations being prematurity, need for mechanical ventilation, and oxygen exposure. Implied in the pathogenesis of BPD is the role of cytokines which are immune mediators produced by most cell types. This is evidenced by studies in which there exist alterations in the levels of "pro-inflammatory" and "anti-inflammatory" cytokines. The imbalance of these cytokines have either heralded the onset or predicted the presence of BPD, or indicated a decreased propensity to developing this chronic respiratory disorder of preterm infants. Many other pulmonary markers have been shown to be altered in patients with BPD. These include markers indicative of altered lung repair processes, decreased endothelial integrity, oxidative damage and abnormal fibrinolytic activity, all of which are thought to be mechanisms contributing to the development of BPD.In this review, we will discuss the physiologic role of specific biomarkers in the pulmonary tract of the human premature neonate, the perturbations that enable them to be deranged, and their proposed association with BPD.

Angiopoietin 2 concentrations in infants developing bronchopulmonary dysplasia: attenuation by dexamethasone

OBJECTIVES

To study the association between angiopoietin 2 (Ang2) concentrations in tracheal aspirates (TAs) and adverse outcome (bronchopulmonary dysplasia (BPD)/death) in ventilated premature infants (VPIs) and modulation of Ang2 concentrations with dexamethasone (Dex) use.

STUDY DESIGN

Serial TA samples were collected on days 1, 3, 5 and 7, and Ang2 concentrations were measured. Ang2 TA concentrations were compared prior to and after 48 to 72 h of using Dex.

RESULT

A total of 151 TA samples were collected from 60 VPIs. BPD was defined as the oxygen requirement at 36 weeks postmenstrual age (PMA). Twelve infants (mean+/-s.d.) (gestational age (GA) 26.5+/-2.1 weeks, birth weight (BW) 913+/-230 g) had no BPD, 32 infants (GA 25.8+/-1.4 weeks, BW 768+/-157 g) developed BPD and 16 infants (GA 24.5+/-1.1 weeks, BW 710+/-143 g) died before 36 weeks PMA. Ang2 concentrations were significantly lower in infants with no BPD (median, 25th and 75th percentile) (157, 16 and 218 pg mg(-1)) compared with those who developed BPD (234, 138 and 338 pg mg(-1), P=0.03) or BPD and/or death (234, 157 and 347 pg mg(-1), P=0.017), in the first week of life. Twenty-six VPIs (BW 719+/-136 g, GA 25.1+/-1.3 weeks) received 27 courses of Dex. Ang2 concentrations before starting Dex were 202, 137 and 278 pg mg(-1) and significantly decreased to 144, 0 and 224 pg mg(-1) after therapy (P=0.007).

CONCLUSIONS

Higher Ang2 concentrations in TAs are associated with the development of BPD or death in VPIs. Dex use suppressed Ang2 concentrations.

Pepsin, a marker of gastric contents, is increased in tracheal aspirates from preterm infants who develop bronchopulmonary dysplasia

OBJECTIVE

The objective of this study was to study the association between pepsin in tracheal aspirate samples and the development of bronchopulmonary dysplasia in preterm infants.

METHODS

Serial tracheal aspirate samples were collected during the first 28 days from mechanically ventilated preterm neonates. Bronchopulmonary dysplasia was defined as the need for supplemental oxygen at 36 weeks' postmenstrual age. An enzymatic assay with a fluorescent substrate was used to detect pepsin. Total protein was measured by the Bradford assay to correct for the dilution during lavage. Immunohistochemistry using antibody against human pepsinogen was performed in 10 lung tissue samples from preterm infants.

RESULTS

A total of 256 tracheal aspirate samples were collected from 59 preterm neonates. Pepsin was detected in 234 (91.4%) of 256 of the tracheal aspirate samples. Twelve infants had no bronchopulmonary dysplasia, 31 infants developed bronchopulmonary dysplasia, and 16 infants died before 36 weeks' postmenstrual age. The mean pepsin concentration was significantly lower in infants with no bronchopulmonary dysplasia compared with those who developed bronchopulmonary dysplasia or developed bronchopulmonary dysplasia/died before 36 weeks' postmenstrual age. Moreover, the mean pepsin level was significantly higher in infants with severe bronchopulmonary dysplasia compared with moderate bronchopulmonary dysplasia. The mean pepsin level in tracheal aspirate samples from the first 7 days was also lower in infants with no bronchopulmonary dysplasia compared with those who developed bronchopulmonary dysplasia or developed bronchopulmonary dysplasia/died before 36 weeks' postmenstrual age. Pepsinogen was not localized in the lung tissues by immunohistochemistry.

CONCLUSION

The concentration of pepsin was increased in the tracheal aspirate of preterm infants who developed bronchopulmonary dysplasia or died before 36 weeks' postmenstrual age. Recovery of pepsin in tracheal aspirate samples is secondary to gastric aspiration, not by hematogenous spread or local synthesis in the lungs. Chronic aspiration of gastric contents may contribute in the pathogenesis of bronchopulmonary dysplasia.

Pulmonary endostatin perinatally and in lung injury of the newborn infant

OBJECTIVE

Endostatin is a potent angiogenesis inhibitor. Angiogenesis is central for the development of the human lung. The role of endostatin in the development of the human lung and its connection to chronic lung disease remain unclear. We set out to study the role of endostatin in the developing human lung and in acute and chronic lung injury in the preterm infant.

METHODS

Nine fetuses, 14 control neonates without primary lung disease, 14 preterm infants with respiratory distress syndrome, and 8 infants with bronchopulmonary dysplasia were included in the immunohistochemistry study. Tracheal aspirate-fluid samples of intubated very low birth weight infants during postnatal weeks 1 through 5 were analyzed with enzyme-linked immunosorbent assay.

RESULTS

Endothelial cell staining was positive for endostatin in all 45 samples. Staining of epithelial cells (cuboidal, bronchiolar, and alveolar) was seen mostly in fetuses, as well as in infants with late respiratory distress syndrome and bronchopulmonary dysplasia. Staining in alveolar macrophages was most abundant in infants with late respiratory distress syndrome and bronchopulmonary dysplasia. Endostatin was expressed consistently in tracheal aspirate fluid, being highest during the first postnatal day. Higher endostatin concentrations correlated with parameters reflecting lower lung maturity.

CONCLUSIONS

The pattern of pulmonary endostatin protein expression in immunohistochemistry and consistent endostatin protein appearance in tracheal aspirate fluid in human preterm infants indicate a role in the physiologic development of the lung. Preterm birth influences pulmonary endostatin protein expression, which may alter normal lung development and response to lung injury.

Pulmonary Vascular Endothelial Growth Factor-C in Development and Lung Injury in Preterm Infants

RATIONALE

In mice, vascular endothelial growth factor-C (VEGF-C) plays an important role in development of the lymphatic system and in pathogenesis of pulmonary inflammation. Its role in development of the lymphatic system in human lung and in lung injury in newborns remains unclear.

OBJECTIVES

We studied the role of VEGF-C in developing human lung, and in acute and chronic lung injury in preterm infants.

METHODS

Included in the immunohistochemistry study were 10 fetuses, 15 control neonates without primary lung disease, 15 preterm infants with respiratory distress syndrome, and 8 infants with bronchopulmonary dysplasia. Tracheal aspirate fluid samples of intubated very-low-birth-weight infants during Postnatal Weeks 1-5 were analyzed with ELISA.

RESULTS

Bronchiolar staining for VEGF-C was observed in all 48 samples. Alveolar epithelial staining was seen in most fetuses (8/10). In addition, staining was observed in alveolar macrophages in bronchopulmonary dysplasia (4/8), and late respiratory distress syndrome (2/7). VEGF receptor-3 (VEGFR-3) staining was observed in lymphatic endothelium adjacent to vascular endothelium. VEGF-C was expressed consistently in tracheal aspirate fluid, being highest during the first 2 postnatal days. Antenatal administration of glucocorticoids was associated with higher VEGF-C in tracheal aspirate fluid.

CONCLUSIONS

The pattern of pulmonary VEGF-C and VEGFR-3 protein expression and consistent VEGF-C protein appearance in tracheal aspirate fluid in human preterm infants indicate a role for VEGF-C in the physiologic development of the lymphatic system of the lung.

Low levels of tissue inhibitors of metalloproteinases with a high matrix metalloproteinase-9/tissue inhibitor of metalloproteinase-1 ratio are present in tracheal aspirate fluids of infants who develop chronic lung disease

OBJECTIVE

The pathogenesis of chronic lung disease (CLD) involves inflammation with proteolytic damage to lung extracellular matrix. Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that, acting in concert with their tissue inhibitors, tightly orchestrate extracellular matrix morphogenesis and repair after injury. Imbalances in their levels relative to that of their inhibitors have been implicated in diseases characterized by matrix disruption and remodeling. We investigated the possibility that imbalances in MMP-9 and MMP-2 relative to their tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2, respectively, in tracheal aspirates of preterm infants may be involved in the development of CLD.

METHODS

Serial tracheal aspirates collected from birth until extubation in 49 ventilated preterm infants (24-32 weeks' gestations) were analyzed for MMP-2, MMP-9, TIMP-1, and TIMP-2. Data normalized by TA values of free secretory component of immunoglobulin A were compared for CLD (n = 22) versus no CLD (n = 27). Also, known clinical predictors of CLD (gestational age, birth weight, and sex) were assessed for both groups. Association of predictors with the outcome CLD was assessed by logistic regression.

RESULTS

Mean gestational age was lower in CLD infants, but birth weight and gender were comparable for both groups. CLD infants had significantly lower TIMP-1 level with higher MMP-9/TIMP-1 ratio during the first 2 weeks of life and low TIMP-2 and MMP-2 levels during the first 3 days of life compared with no-CLD infants. Logistic regression analysis indicated that the findings are predictive of CLD.

CONCLUSIONS

We conclude that low tracheal aspirate levels of TIMPs, with a high MMP-9/TIMP-1 ratio early in life, are associated with subsequent development of CLD.

Thrombin contributes to bronchoalveolar lavage fluid mitogenicity in lung disease of the premature infant

Chronic lung disease of prematurity (CLD) is a common consequence of neonatal respiratory distress syndrome (RDS) and is characterized by pulmonary fibrosis. Increased thrombin activity in the alveolar compartment is associated with pulmonary fibrosis in adults and animals, and contributes to bronchoalveolar lavage (BAL) fluid mitogenicity for fibroblasts. We hypothesized that BAL fluid from infants who develop CLD contains increased mitogenic activity for lung fibroblasts compared to BAL fluid from resolving RDS, and that increased thrombin levels contribute to this activity. Sequential BAL (postnatal days 2-14) was obtained from 37 premature infants who were ventilated for RDS. Twenty-six infants developed CLD, whereas 11 resolved. BAL fluid mitogenic activity was determined in a proliferation assay, using human fetal lung fibroblasts. The contribution of thrombin to mitogenic activity was determined using the thrombin inhibitor PPACK. Furthermore, thrombin levels in BAL fluid were measured using a specific substrate to detect thrombin activity and by measuring thrombin-antithrombin III complex (TATIII). BAL fluid mitogenic activity was comparable between CLD and RDS (CLD, 33% proliferation on day 2 to 41% on day 14; RDS, 21% on day 2 to 54% on day 7). Thrombin inactivation by PPACK completely inhibited mitogenic activity in BAL samples obtained on days 2 and 4 (CLD, P < 0.001 on days 2 and 4; RDS, P < 0.05 on day 4). From day 7 onwards, inhibition of thrombin only partly reduced (P < 0.05) CLD BAL fluid mitogenic activity, indicating that other mitogenic factors contribute as well. Surprisingly, thrombin activity and TATIII were decreased in BAL fluid from CLD compared with RDS patients on days 2 and 4. In conclusion, our study shows that BAL fluid from infants with and without CLD development is equally mitogenic for lung fibroblasts, and that thrombin is a major mitogen in these samples. This suggests that fibroproliferation may occur early in the lungs from infants with both CLD and RDS, and that thrombin contributes to this.

Inhaled versus systemic corticosteroids for preventing chronic lung disease in ventilated very low birth weight preterm neonates

BACKGROUND

Chronic lung disease (CLD) remains an important cause of mortality and morbidity in preterm infants despite the administration of antenatal corticosteroids, surfactant replacement therapy and other advances in neonatal intensive care. There is increasing evidence from cellular and biochemical research that inflammation plays an important role in the pathogenesis of CLD. Thus, interventions aimed at reducing or modulating the inflammatory process may reduce the incidence or severity of CLD. Theoretically, the use of inhaled corticosteroids may allow for beneficial effects on the pulmonary system without concomitant high systemic concentrations and less risk of adverse effects.

OBJECTIVES

To compare the effectiveness of inhaled versus systemic corticosteroids, started within the first two weeks of life, in preventing CLD in ventilated very low birth weight infants.

SEARCH STRATEGY

Randomized and quasi-randomized trials were identified by searching the Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2002), MEDLINE (1966 - September 2002), EMBASE (1980 - September 2002), CINAHL (1982 - September 2002), reference lists of published trials and abstracts published in Pediatric Research (1990 - April 2002) from the Society of Pediatric Research/ Pediatric Academic Society's annual meetings.

SELECTION CRITERIA

Randomized or quasi-randomized clinical trials comparing inhaled versus systemic corticosteroid therapy (regardless of the dose and duration of therapy), started in first two weeks of life in very low birth weight preterm infants receiving assisted ventilation.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including CLD at 28 days or 36 weeks corrected gestational age (CGA), mortality, combined outcome of death or CLD at 28 days or 36 weeks CGA, other pulmonary outcomes and adverse effects were evaluated. All data were analyzed using RevMan 4.1. When appropriate, meta-analysis was performed using relative risk (RR), risk difference (RD), and weighted mean difference (WMD) along with their 95% confidence intervals (CI). If RD was significant, number needed to treat (NNT) or number needed to harm (NNH) was calculated.

MAIN RESULTS

Two trials qualified for inclusion in this review. There was an increase in the incidence of CLD at 36 weeks CGA in the inhaled steroid group amongst all randomized infants, which was of borderline statistical significance: [RR 1.45 (95% CI 0.99, 2.11); RD 0.11 (95% CI 0.00, 0.21), p = 0.05, 1 trial and n = 278]. There was no statistically significant difference in the incidence of CLD at 36 weeks amongst all survivors [RR 1.34 (95% CI 0.94, 1.90); RD 0.11(95% CI -0.02, 0.24), 1 trial and n = 206]. There were no statistically significant differences for oxygen dependency at 28 days (2 trials and n = 294), death by 28 days (2 trials and n = 294) or 36 weeks (2 trials and n = 294) and the combined outcome of death or CLD by 28 days (2 trials and n = 294) or 36 weeks CGA (1 trial and n = 278). The duration of mechanical ventilation was statistically significantly longer in the inhaled as compared to the systemic steroid group (WMD 3.89 days, 95% CI 0.24, 7.55; 2 trials and n = 294). The duration of supplemental oxygen was statistically significantly longer in the inhaled as compared to the systemic steroid group (WMD 11.10 days, 95% CI 1.97, 20.22; 2 trials and n = 294). There was a significantly lower incidence of hyperglycemia in the group receiving inhaled steroids (RR 0.52, 95% CI 0.39,0.71; RD -0.25, 95% CI -0.37, -0.14; 1 trial and n = 278). The NNT was 4.0 (95% CI 2.7, 7.14) to avoid one infant experiencing hyperglycemia. There was a statistically significant increase in the rate of patent ductus arteriosus (RR 1.64, 95% CI 1.23, 2.17; RD 0.21, 95% CI 0.10, 0.33; 1 trial and n = 278) in the group receiving inhaled steroids. The NNH was 4.8, 95% CI 3, 10. There were decreases of borderline statistical significance in the incidences of gastrointestinal hemorrhage and gastrointestinal perforation in the inhaled as compared to systemic steroid group: for gastrointestinal hemorrhage, RR 0.40, 95% CI 0.16, 1.02; RD -0.06, 95% CI -0.12, 0.00, p = 0.05 (1 trial and n = 278); for gastrointestinal perforation, RR 0.16, 95% CI 0.02, 1.29; RD -0.04, 95% CI -0.07, 0.00, p = 0.05 (1 trial and n = 278). The incidence of other side effects was not statistically significantly different in the two groups. No information was available on long term neurodevelopmental outcomes.

REVIEWER'S CONCLUSIONS

This review found no evidence that early inhaled steroids confer important advantages over systemic steroids in the management of ventilator dependent preterm infants. Neither inhaled steroids, nor systemic steroids, can be recommended as a part of standard practice for ventilated preterm infants. Because they might have fewer adverse effects than systemic steroids, further randomized controlled trials of inhaled steroids are needed which address risk/benefit ratio of different delivery techniques, dosing schedules and long term effects, with particular attention to neurodevelopmental outcome.

Repeatability of cellular constituents and cytokine concentration in fluid obtained by non-bronchoscopic bronchoalveolar lavage of infants receiving extracorporeal oxygenation

BACKGROUND

Since few studies have assessed the repeatability of non-bronchoscopic bronchoalveolar lavage (NB-BAL), we compared cellular counts and cytokine concentrations in fluid obtained by standardised NB-BAL from each side of 20 intubated infants receiving extracorporeal membrane oxygenation (ECMO).

METHODS

Total cell counts were obtained from 95 paired lavages and 77 pairs were suitable for differential counts and measurement of cytokine concentrations.

RESULTS

Moderate correlation was noted between the two sides for most cell types including total cell counts and percentages of neutrophils and macrophages (R=0.70-0.84) and for cytokine concentrations (IL-8 R=0.78, IL-6 R=0.75, TNF-alpha R=0.64, all p< or =0.001). Using Bland-Altman analysis the mean difference between the two sides approached zero for cellular constituents (total cell counts mean difference 1.7, limits of agreement -187.5 to +190.9 x 10(4)/ml; percentage neutrophils -3.9%, -41.5% to +33.6%; percentage macrophages 3.9%, -33.8% to +41.6%) but tended to be greater on the right for logarithmically transformed cytokine measurements (IL-8: left/right ratio 0.74, limits of agreement 0.12 to 5.45, IL-6: 0.93, 0.09 to 5.87, and TNF-alpha: 0.93, 0.27 to 3.16). Using linear regression with random effects to assess the variability, only the infant's age appeared to influence the cellular results but, for cytokines, only the volume retrieved affected the variability. The magnitude of the measurements, the underlying disease, the operator's experience, days on ECMO, or survival did not affect the variability.

CONCLUSION

Measurements obtained by NB-BAL need to be interpreted with caution and strongly suggest that normalisation for the dilutional effects of saline is essential.

Pulmonary vascular endothelial growth factor and Flt-1 in fetuses, in acute and chronic lung disease, and in persistent pulmonary hypertension of the newborn

Respiratory distress syndrome (RDS) and development of bronchopulmonary dysplasia (BPD) are characterized by endothelial cell damage. Persistent pulmonary hypertension of the newborn (PPHN) is a disorder that alters the pulmonary microvasculature. Immunohistochemistry for VEGFA(165), an endothelial cell mitogen, and its receptor Flt-1, was performed on lung tissues from autopsies from four fetuses, three preterm infants, four term infants without primary lung disease, four infants with BPD, and four infants with PPHN. VEGF was measured in tracheal aspirates from 31 preterm infants, 5 intubated term infants without primary lung injury, and 12 infants with PPHN during the first 10 postnatal days, and from 8 infants with BPD. Immunohistochemistry for VEGF and Flt-1 was similar in fetuses, preterm infants, and term infants: for VEGF mostly in bronchial epithelium and alveolar macrophages, and for Flt-1 mostly in vascular endothelial cells and bronchial epithelial cells. In patients with BPD, and PPHN, staining for VEGF and Flt-1 appeared also in Type II pneumocytes. Preterm infants with more severe RDS had lower VEGF than those who recovered. The persistent expression of VEGF and Flt-1 during the fetal and neonatal period supports a physiological role for VEGF in human lung development. The lower pulmonary VEGF in preterm infants with more severe RDS may contribute to the pathophysiology of the acute lung injury. In BPD, the expression of VEGF in alveolar epithelium may represent a compensatory increase after the acute phase of the lung disease. In PPHN, that more cell types express VEGF and Flt-1, and the tendency toward a higher concentration of pulmonary VEGF may represent enhanced production of VEGF in response to impaired endothelial function.

Rationale for the development of recombinant human CC10 as a therapeutic for inflammatory and fibrotic disease

CC10/uteroglobin is a remarkable protein whose physiological roles have only recently been explored in vivo. Both transgenic mice that have been rendered deficient and humans that have been characterized as deficient in this protein exhibit tendencies toward inflammatory, fibrotic, and oncologic disease, demonstrating the potential of the protein as a therapeutic agent. The protein itself is an excellent candidate for clinical development because of its inherent physical properties. It is relatively small, resistant to proteases, stable to extremes of heat and pH, and can be produced by recombinant methods. The physiological roles of this multifunctional protein continue to be uncovered as research progresses in vitro, in animals, and eventually in humans. The pathways through which CC10 mediates its effects, its receptors, and other family members will be a rich source of exciting research, as well as potential diagnostic and therapeutic agents. This paper is an introductory, noncomprehensive review of some of the scientific and medical rationale in support of CC10-based therapies in selected clinical applications.

Inhaled glucocorticoid therapy in infants at risk for neonatal chronic lung disease

The primary impetus for the study of inhaled glucocorticoid therapy in the treatment and prevention of neonatal chronic lung disease (CLD) was to achieve effective anti-inflammatory therapy with few adverse effects. Initial reports of inhaled glucocorticoid therapy in infants with established CLD suggest modest improvement in neonatal respiratory outcomes. Recent randomized trials also indicate that inhaled glucocorticoid therapy may provide some benefit, but have not demonstrated a reduction in CLD. Some studies suggest that the pulmonary response to systemic glucocorticoid may be greater and faster than response to inhaled glucocorticoid therapy. Few adverse effects have been noted with inhaled glucocorticoid therapy. One limitation of studies of inhaled glucocorticoid therapy is the uncertainty of the dose delivered and deposited in peripheral airways and regions of the lungs. Experience with and systematic study of inhaled glucocorticoid therapy is still in its early stages. The role of inhaled glucocorticoid therapy in the treatment and prevention of CLD is evolving. Advances in delivery devices and new developments of drug formulations should improve aerosol delivery and deposition in infants. Given the clinical dilemma of systemic glucocorticoid therapy and potential benefits demonstrated by recent trials of inhaled glucocorticoid therapy, further study of inhaled glucocorticoid therapy for CLD is warranted.

Pediatric bronchoscopy

Diagnostic flexible endoscopy for pediatric respiratory diseases is performed in many centers. Technical advances have resulted in performance of interventional bronchoscopies, and new diagnostic indications are being explored. Indications with documented clinical benefit include congenital or acquired progressive or unexplained airway obstruction. Pulmonary infections in immunodeficient children who do not respond to empirical antibiotic treatment may be diagnosed by bronchoscopy and bronchoalveolar lavage (BAL). The potential usefulness of bronchoscopy and BAL for managing chronic cough, wheeze, or selected cases with asthma or cystic fibrosis requires further study. The use of transbronchial biopsies (TBB) is established in pediatric lung transplantation. The role of TBB in the diagnosis of chronic interstitial lung disease in children remains to be determined. For a number of interventional applications, rigid endoscopy is required, and pediatric bronchoscopists should be trained in its use. Complications in pediatric bronchoscopy are rare, but severe nosocomial infection or overdosing with local anesthetics has occurred. The issues of quality control, video documentation, interobserver variability of findings, and educational standards will have to be addressed in the future as bronchoscopy use becomes less restricted to only large pediatric pulmonary units.

Transport of bifunctional proteins across respiratory epithelial cells via the polymeric immunoglobulin receptor

Neutrophil elastase (NE) contributes to progression of the lung disease characteristic of cystic fibrosis (CF). We developed a strategy that permits the delivery of alpha(1)-antitrypsin (alpha(1)-AT) to inaccessible CF airways by targeting the respiratory epithelium via the polymeric immunoglobulin receptor (pIgR). A fusion protein consisting of a single-chain Fv directed against human secretory component (SC) and linked to human alpha(1)-AT was effectively transported in a basolateral-to-apical direction across in vitro model systems of polarized respiratory epithelium consisting of 16HBEo cells transfected with human pIgR complementary DNA, which overexpress the receptor, and human respiratory epithelial cells grown in primary culture at an air-liquid interface. When applied to the basolateral surface, the anti-SC Fv/alpha(1)-AT fusion protein penetrated the respiratory epithelia, with transcytosis of the fusion protein being related to the amount of SC detected at the apical surface. Significantly less fusion protein crossed the cells in the opposite direction. In addition, because the antihuman SC Fv/alpha(1)-AT fusion protein was transported vectorially and deposited into the small volume of apical surface fluid, the antiprotease component of this protein was concentrated atop the epithelium. Thus, in cell models, this system is capable of concentrating the antiprotease of the fusion protein, in the thin film of epithelial surface fluid to a level expected to be therapeutic in the airways of many patients with CF.

Postnatal glucocorticosteroid therapy for treatment and prevention of neonatal chronic lung disease

Neonatal chronic lung disease (CLD) is a persistent complication, primarily of premature infants. Postnatal glucocorticoid therapy is widely used in the treatment and prevention of CLD. Most studies reveal acute improvement in the pulmonary status of infants treated with postnatal glucocorticoid therapy. Recent studies of 'earlier' intervention (< 14 days of age) demonstrated a reduction in mortality and in the occurrence of CLD between 28 days of age and 36 weeks postmenstrual age. Great concern remains, however, regarding the potential adverse outcomes, including growth inhibition, infection, catastrophic GI complications and CNS injury. Therefore, the use of postnatal glucocorticoid therapy remains controversial with respect to the clinical indications for initiating therapy, the dose, duration, onset and route of administration, as well as potential benefits and risks. Inhaled glucocorticoid therapy is increasingly used to treat and prevent CLD in order to avoid adverse effects of high dose systemic glucocorticoid therapy. Recent studies with inhaled glucocorticoid therapy show promise. Further work, however, for improving aerosol delivery and deposition, will be needed to refine their role in the prevention and treatment of CLD. Future studies enabling early, accurate identification of infants at greatest risk for CLD, coupled with a more comprehensive understanding of the different pathogeneses, will provide information regarding appropriate timing of onset, dosing, route of therapy and duration of intervention.

Validity of markers of dilution in small volume lung lavage

Definitive analysis of solute concentrations in lung lavage fluid involves the use of a marker of dilution to correct for variable recovery of epithelial lining fluid (ELF), but the question of the most appropriate dilutional marker remains unresolved. In lavage fluid collected from infants with lung disease and healthy control subjects, we examined ELF concentration of protein, albumin, sphingomyelin (SM), and IgA secretory component (SC), and critically appraised the relative validity of SC and urea as dilutional markers in the context of lung infection and lung injury. Protein, albumin, and SM were found not to be valid dilutional markers, as their ELF concentration varied significantly between the diseased, recovering, and normal lung. Differences in concentration were noted in both tracheal aspirate samples (TA, 4 x 0.5 ml) and nonbronchoscopic bronchoalveolar lavage fluid (NB-BAL, 3 x 1 ml/kg), but were not uniform (e.g., TA-disease versus control: albumin 2.8 versus 0.68 mg/ml, SM 45 versus 16 microgram/ml, both p < 0.05; NB-BAL-disease versus recovery: protein 8.1 versus 4.8 mg/ml, albumin 2.9 versus 1. 4 mg/ml, both p < 0.05). Overall, SC concentrations in ELF were not different between the diseased and normal lung, but in the NB-BAL samples, significantly higher SC concentration was noted in viral bronchiolitis and pneumonia than in noninfective lung diseases. No clear evidence of additional influx of urea into lavage fluid in association with epithelial disruption was found in the diseased lung. Comparative analysis of SC and urea revealed no difference in TA samples, but in NB-BAL specimens, urea best standardized the lavage concentration of surfactant indices to correspond to the degree of lung dysfunction as indicated by oxygenation index. We conclude that SC and urea, but not protein, albumin, or SM, are valid dilutional markers with which to estimate ELF recovery during small volume lung lavage. Urea appears a more appropriate choice in return fluid derived from the distal tracheobronchial tree, and SC should not be used in the context of lung infection.

A three-day course of dexamethasone therapy to prevent chronic lung disease in ventilated neonates: a randomized trial

BACKGROUND

Although several trials of early dexamethasone therapy have been completed to determine if such therapy would reduce mortality and chronic lung disease (CLD) in infants with respiratory distress, optimal duration and side effects of such therapy remain unknown.

PURPOSE

The purpose of this study was: 1) to determine if a 3-day course of early dexamethasone therapy would reduce CLD and increase survival without CLD in neonates who received surfactant therapy for respiratory distress syndrome and 2) to determine adverse effects associated with such therapy.

DESIGN

This was a prospective multicenter randomized trial comparing a 3-day course of dexamethasone therapy beginning at 24 to 48 hours of life to placebo therapy. Two hundred forty-one neonates (dexamethasone n = 118, placebo n = 123), who weighed between 500 g and 1500 g, received surfactant therapy, and were at significant risk for CLD or death using a model to predict CLD or death at 24 hours of life, were enrolled in the trial. Infants randomized to receive early dexamethasone were given 6 doses of dexamethasone at 12-hour intervals beginning at 24 to 48 hours of life. The primary outcomes compared were survival without CLD and CLD. CLD was defined by the need for supplemental oxygen at the gestational age of 36 weeks. Complication rates and adverse effects of study drug therapy were also compared.

RESULTS

Neonates randomized to early dexamethasone treatment were more likely to survive without CLD (RR: 1.3; 95% CI: 1.03, 1.7) and were less likely to develop CLD (RR: 0.6; CI: 0.3, 0. 98). Mortality rates were not significantly different. Subsequent dexamethasone therapy use was less in early dexamethasone-treated neonates (RR: 0.8; CI: 0.7, 0.96). Very early (</=7 days of life) intestinal perforations were more common among dexamethasone-treated neonates (8% vs 1%).

CONCLUSION

We conclude that an early 3-day course of dexamethasone therapy increases survival without CLD, reduces CLD, and reduces late dexamethasone therapy in high-risk, low birth weight infants who receive surfactant therapy for respiratory distress syndrome. Potential benefits of early dexamethasone therapy at the dosing schedule used in this trial need to be weighed against the risk for early intestinal perforation.

Early prediction of neonatal chronic lung disease: a comparison of three scoring methods

A variety of postnatal therapies have been and will be evaluated for prevention or treatment of neonatal chronic lung disease (CLD). A simple method for early selection of the highest risk infants would optimize intervention trials. Our study compared a clinical scoring system for predicting neonatal CLD (defined at 36 weeks postconceptional age) with previous regression models developed by Sinkin et al. (Sinkin model) [Pediatrics 1990;86:728-736] and Ryan et al. (Ryan model) [Eur J Pediatr 1996;668-671] in two distinct populations. A respiratory failure score (RFS) was prospectively developed for infants at <32 weeks of gestation admitted to the Wilford Hall Medical Center from January 1990-December 1992. Logistic regression modeling identified three independent predictors of CLD: gestation, birth weight, and RFS. Applying a modified RFS score (to include gestation and birth weight), the RFS, Sinkin, and Ryan models were compared among high-risk infants admitted to Wilford Hall from January 1993-December 1995, and to Crawford Long Hospital (Atlanta, GA) from January 1993-December 1994. Predictive values, sensitivity, specificity, and receiver operating characteristic (ROC) curves were determined for the primary outcome variable: CLD at 36 weeks of corrected gestation. Of 248 infants at <32 weeks admitted to Wilford Hall, 220 survived >7 days. Thirty of 31 (97%) infants diagnosed with CLD were <29 weeks or < or =1,000 g at birth. Despite important demographic and treatment differences between the study populations, similar ROC curves were found for each scoring method when individually evaluated among the three study groups. The RFS method at 72 h demonstrated the greatest area under the ROC curve for prediction of neonatal CLD in the groups as a whole. Application of the RFS method for early prediction of neonatal CLD at age 72 h should improve patient selection for early prevention trials.

Vascular endothelial growth factor in human preterm lung

Endothelial cell damage is characteristic for respiratory distress syndrome and development of chronic lung disease. Vascular endothelial growth factor (VEGF) is an endothelial mitogen that takes part in the growth and repair of vascular endothelial cells. We measured VEGF in 189 tracheal aspirate samples (TAF), and in 24 plasma samples from 44 intubated preterm infants (gestational age, 27.3 +/- 2.0 wk; birth weight, 962 +/- 319 g) during their first postnatal week. VEGF in TAF increased from 25 +/- 12 pg/ml (mean +/- SEM) on Day 1 to 526 +/- 120 pg/ml on Day 7 (mean concentrations, 106 +/- 25 pg/ml on Days 1 to 3 and 342 +/- 36 pg/ml on Days 4 to 7). In plasma, mean concentration of VEGF during the first week was 48 +/- 6 pg/ml, with no increase observed. In TAF, higher VEGF was found in patients born to mothers with premature rupture of the membranes, or chorionamnionitis, whereas preeclampsia of the mother was associated with lower VEGF (all p < 0.05). In TAF, no correlations existed between VEGF and gestational age or birth weight, but a correlation existed between lecithin/sphengomyelin ratio and VEGF (p < 0.05). During Days 4 to 7 patients developing bronchopulmonary dysplasia (BPD) had lower VEGF in TAF than did those surviving without BPD (235 +/- 31 versus 383 +/- 50; p < 0.05). VEGF increased rapidly in the lungs of the preterm infant during the first days of life. VEGF may be indicative of pulmonary maturity and may participate in pulmonary repair after acute lung injury.

Fibronectin expression in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic fibrotic lung disease of neonates. Fibronectin (FN), a component of the extracellular matrix, is increased in the tracheobronchial effluent of neonates destined to develop BPD. Pulmonary FN is derived from plasma and local cellular synthesis. In order to identify which pulmonary cells synthesize FN and to test the hypothesis that FN is more abundant in lungs with BPD, we examined the distribution of pulmonary FN by in situ hybridization (for mRNA) and immunohistochemistry (for protein) in neonatal autopsy lung specimens, comparing lungs with BPD to those without. We used a staging system in which BPD is characterized by disruption of alveolar architecture, severe vascular changes, airway epithelial necrosis, smooth muscle hypertrophy, and peribronchial fibrosis. FN mRNA and protein were found in vascular endothelium, macrophages, fibroblasts, vascular and airway smooth muscle, and chondrocytes as well as in the pulmonary parenchyma in neonates with and without BPD. Hyaline membranes, when present, immunostained intensely for FN protein. FN mRNA was not seen in airway epithelial cells of either group. FN mRNA and protein were first increased in early acute BPD with their levels appearing greatest during the chronic reparative stage of BPD. In long-standing "healed" BPD, lower levels of FN mRNA and protein were seen. These findings are consistent with the association of increased FN with adult fibrotic lung disease and the previously reported increase in FN tracheal effluent levels in infants with BPD. Our results suggest an important role for pulmonary cell-derived FN in the early inflammatory and later proliferative stages of BPD.

Mechanisms initiating lung injury in the preterm

Bronchopulmonary dysplasia (BPD)/chronic lung disease occurs primarily in very low birth weight infants (VLBW) often without antecedent severe respiratory distress syndrome. The BPD in these VLBW infants results in less fibrosis than the traditional BPD but the normal process of alveolarization seems to be disrupted. This review develops the thesis that BPD in VLBW infants results from inflammatory mediators interfering with the signaling required for normal late gestational lung development. Proinflammatory mediators may be elevated because of fetal exposure, postnatal infection or by release from preterm lungs ventilated at either low or high lung volumes. The preterm lung is highly susceptible to injury during resuscitation or more chronic mechanical ventilation because the gas volumes/kg body weight of the lungs are small. An understanding of what causes cytokine release and how cytokines influence lung development is necessary to develop targeted therapies to minimize BPD. However, care strategies that minimize inflammation and ventilator-induced lung injury should help decrease BPD.

Comparison of pulmonary inflammatory mediators in preterm infants treated with intermittent positive pressure ventilation or high frequency oscillatory ventilation

Ventilated preterm infants prone to the development of bronchopulmonary dysplasia have been shown to have increased inflammatory mediators in their tracheal aspirates. High frequency oscillatory ventilation (HFOV) is thought to be less traumatic than intermittent positive pressure ventilation (IPPV) in premature infants with surfactant deficiency, and therefore may reduce the inflammatory response in tracheobronchial aspirates. We randomized 76 premature infants requiring mechanical ventilation (birth weight 420-1830 g, median 840 g, gestational age 23 3/7 to 29 2/7 wk, median 26 4/7 to receive either an IPPV with a high rate (60-80/min) and low peak pressures, or an HFOV aiming at an optimization of lung volume, within 1 h of intubation. Tracheal aspirates were systematically collected during the first 10 d of life and analyzed for albumin, IL-8, leukotriene B4 (LTB4), and the secretory component (SC) for IgA as a reference protein. Bacterially colonized samples were excluded. On the treatment d 1, 3, 5, 7, and 10, the resulting median values of albumin (milligrams/mg of SC) were 28, 23, 24, 18, and 10, in IPPV-ventilated infants, and 33, 28, 18, 25, and 39 in HFOV-ventilated infants, respectively. Median IL-8 values (nanograms/mg of SC) were 671, 736, 705, 1362, and 1879 (IPPV) and 874, 1713, 1029, 1426, and 1823 (HFOV), respectively, and median LTB4 values (nanograms/mg of SC) were 26, 13, 27, 22, and 11 (IPPV) and 15, 12, 7, 12, and 16 (HFOV), respectively. Values were similar in IPPV- and HFOV-ventilated infants, and no significant differences were noted. We conclude that HFOV, when compared with a high rate low pressure IPPV, does not reduce concentrations of albumin, IL-8, and LTB4 in tracheal aspirates of preterm infants requiring mechanical ventilation.

Inhibitors of elastase in airway lavage samples from ventilated preterm human neonates

Surplus elastase released from neutrophils during lung injury is balanced mainly by alpha1-protease inhibitor (alpha1-PI) and by two acid-resistant inhibitors. The latter include mucus protease inhibitor (MPI, also named SLPI, BSI, ALP) and elastase-specific inhibitor (ESI or Elafin), but their functional role during the neonatal period has not yet been characterized precisely. The saline airway lavage samples from neonates intubated for respiratory distress were separated by centrifugation into a cellular and a soluble, supernatant fraction and then analyzed. During the first 36 h of life (42 neonates, gestational age 24-40 wk), elastase activity was confined to the cellular fraction. Thirty percent of the acid-resistant inhibitors but almost no alpha1-PI, was cell-associated. In the soluble fraction, about 20-30% of the acid-resistant inhibitors was functionally active, but only about 10% of alpha1-PI was. In seven infants with a nosocomial infection and deterioration during mechanical ventilation, only a very modest increase in elastase activity was observed. However, the functional activity of the acid-resistant inhibitors was reduced in the soluble fraction, whereas total mass remained unchanged. A full assessment of protease and protease inhibitors should include the cellular and the soluble lavage compartments.

Elevated interleukin-8 concentrations in amniotic fluid of mothers whose neonates subsequently develop bronchopulmonary dysplasia

OBJECTIVE

To determine if an intrauterine sub-clinical inflammatory process is a risk factor for the development of bronchopulmonary dysplasia.

METHODS

A cohort study was conducted in patients who met the following criteria: (1) Singleton gestation; (2) preterm labor or preterm premature rupture of the membranes; (3) amniocentesis for microbiologic studies of the amniotic fluid and (4) delivery between 24 and 28 weeks of gestation. Bronchopulmonary dysplasia was defined as the need for supplemental oxygen for 28 days or longer after birth, associated with compatible chest radiographic findings. Amniotic fluid interleukin-8, was measured using a specific immunoassay. Logistic regression analysis and bootstrap procedure were used for statistical purposes.

RESULTS

Forty-seven patients met the inclusion criteria for this study. Among these patients, the prevalence of bronchopulmonary dysplasia was 23.4% (11/47). Amniotic fluid culture was positive in 21 out of 47 (44.7%) patients. Median (range) amniotic fluid interleukin-8 concentration was higher in patients whose neonates subsequently developed bronchopulmonary dysplasia than in those who did not (17 [9.8-583.7] ng ml(-1) versus 9.6 [0.91-744] ng ml(-1), P=0.057). An amniotic fluid IL-8 level greater than 11.5 ng ml(-1) was far more common in mothers whose fetuses went on to develop bronchopulmonary dysplasia than in those who did not (10/11 [90.9%] versus 17/36 [47%]; P=0.01). This relationship remained significant even after correcting for the effect of gestational age and birthweight (Odds ratio: 11.9; P<0.05).

CONCLUSION

Sub-clinical intrauterine inflammation is a risk factor for the subsequent development of bronchopulmonary dysplasia. We propose that in utero aspiration of fluid with high concentration of pro-inflammatory mediators may contribute to the lung injury responsible for the development of bronchopulmonary dysplasia.

Ureaplasma urealyticum respiratory tract colonization is associated with an increase in interleukin 1-beta and tumor necrosis factor alpha relative to interleukin 6 in tracheal aspirates of preterm infants

OBJECTIVE

To determine whether Ureaplasma urealyticum respiratory tract colonization in very low birth weight infants during the first week of life is associated with changes in tracheal aspirate concentrations of the cytokines interleukin 1-beta (IL-1-beta), tumor necrosis factor alpha (TNF-alpha) and IL-6.

METHODS

Infants with birth weights < or =1250 g were prospectively enrolled. Samples were obtained from the endotracheal tube or nasopharynx on Day 1 and again between Days 7 and 10 for U. urealyticum culture. The concentrations of IL-1-beta, TNF-alpha and IL-6 were measured in tracheal aspirate samples by enzyme-linked immunosorbent assay.

RESULTS

There were 18 positive cultures for U. urealyticum from 15 of 96 infants (15.6%). IL-1-beta in tracheal aspirates expressed as concentration per volume or as a ratio of IL-1-beta to IL-6 were 7- and 14.9-fold higher, respectively, in Ureaplasma-positive infants than in Ureaplasma-negative infants (P < 0.05). The TNF-alpha/IL-6 ratio was 18.9 and 15.5 times higher in the Ureaplasma-positive aspirates than in the Ure aplasma-negative aspirates on Day 1 and Days 7 to 10 (P < 0.05). Concentrations of IL-1-beta and TNF-alpha were significantly correlated on Day 1 and Days 7 to 10. Although there was no clinical association demonstrated between U. urealyticum colonization and the development of bronchopulmonary dysplasia (BPD) in this study, infants who developed BPD had significantly higher IL-1-beta concentrations and ratios of IL-1-beta to IL-6 in Day 1 aspirates than infants who did not develop BPD. Conclusions. Isolation of U. urealyticum from the respiratory tract is associated with increased IL-1-beta concentrations and IL-1-beta-IL-6 ratios on Day 1 and increased TNF-alpha-IL-6 ratios on Days 1 and 7 to 10 in tracheal aspirates of colonized infants. Infants who developed BPD had higher IL-1-beta concentrations and IL-1-beta-IL-6 ratios, suggesting that these may be early markers of lung inflammation.

Early increase of TNF alpha and IL-6 in tracheobronchial aspirate fluid indicator of subsequent chronic lung disease in preterm infants

AIM

To investigate if early changes in concentrations of proinflammatory cytokines in tracheobronchial aspirate fluid (TAF) from preterm infants could be used to detect infants at risk of chronic lung disease (CLD) and help in the selection of patients for early steroid treatment.

METHODS

Twenty eight preterm infants less than 34 weeks of gestation (median 26 weeks) were intubated and daily measurements of TAF concentrations of tumour necrosis factor alpha (TNF alpha) and the interleukins IL-1 beta, IL-6, and IL-8 were made, using enzyme immunoassay techniques.

RESULTS

Seventeen of the infants developed CLD. The infants who developed CLD had significantly increased concentrations of TNF alpha, IL-1 beta, IL-6 on days 2 and 3. TNF alpha, IL-6, and IL-8 concentrations were significantly related to gestational age and duration of supplemental oxygen; TNF alpha, IL-6, and IL-8 concentrations also correlated with length of time on the ventilator.

CONCLUSION

These data indicate that tracheobronchial aspirate fluid cytokine concentrations may be used as a predictor of subsequent CLD and may help select a group of preterm infants at high risk of developing CLD for early treatment.

Cromolyn sodium prophylaxis inhibits pulmonary proinflammatory cytokines in infants at high risk for bronchopulmonary dysplasia

An imbalance of proinflammatory cytokines such as TNF-alpha, IL-1 beta, and the neutrophil chemotactic factor IL-8 and inhibitors (e.g., soluble TNF receptors and IL-1ra) in the lung during the first week of life may contribute to prolonged pulmonary inflammation and fibrosis in bronchopulmonary dysplasia (BPD). Disodium cromoglycate (DSCG) has anti-inflammatory effects in asthma, a disease with many similarities with BPD. In a prospective, randomized, blinded study, we examined whether early DSCG therapy inhibits proinflammatory cytokines in infants at risk for BPD. Twenty-six infants who were identified as high risk (> or = 75% probability) for oxygen-dependency at 28 d by a 12-h predictive score and survived 48 h were randomized to nebulized DSCG 20 mg (n = 13) or 2 cc NS (control, n = 13) every 6 h from Day 3 to Day 28. Lung lavage was collected on Day 3 (pre-study) and Day 7 and analyzed for cell count and differential and TNF-alpha, sTNFR1, sTNFR2, IL-1 beta, IL-1ra, and IL-8 concentrations. The groups' pre-study lavage cytokine concentrations were similar, but TNF-alpha and IL-8 concentrations were 3.6- and 4.9-fold lower in the DSCG group on Day 7 compared with levels in the control group. Soluble TNF receptors were unaffected by DSCG. There was a trend towards lower IL-1 beta levels in DSCG-treated infants on Day 7, but IL-1ra levels were unaffected by DSCG therapy. Three control subjects, but no DSCG-treated infants, died during the study period (p = 0.07). There were no significant differences between survivors of the two groups for oxygen-dependency at 28 d (100% control subjects; 85% DSCG). These results suggest that nebulized DSCG may exert an anti-inflammatory effect in the lungs of infants < or = 1,000 g at risk for BPD.

Elevated laminin concentrations in lung secretions of preterm infants supported by mechanical ventilation are correlated with radiographic abnormalities

OBJECTIVE

The objective of this study was to test the hypothesis that the presence of laminin in neonatal tracheal aspirates would be indicative of damage to the structural integrity of the basal laminae of the lung caused by barotrauma and hyperoxia. We predicted that disruption of the basal laminae would be a critical determinant of lung injury and fibrotic repair in the preterm infant whose lungs were ventilated with supplemental oxygen.

STUDY DESIGN

The study group consisted of 23 premature infants in the neonatal intensive care unit whose lungs were ventilated by supplemental oxygen. We quantitated concentrations of laminin and fibronectin from sequential tracheal aspirates by enzyme-linked immunosorbent assays. A two-way analysis of variance was used to compare laminin and fibronectin concentrations in infants with and without radiographic evidence of coarse pulmonary markings indicative of fibrotic repair of lung injury.

RESULTS

The concentrations of laminin, but not fibronectin, were significantly higher throughout the first 5 weeks of life in infants with abnormal chest radiographs at 36 weeks after conception. The concentrations of laminin in infant serum were approximately 1/30 that of tracheal aspirate laminin concentrations, suggesting that little if any of the laminin detected in the tracheal aspirates was derived from the serum.

CONCLUSIONS

Increased concentrations of laminin in tracheal aspirates may be an indication of lung injury and fibrotic repair in the preterm infant.

Different role of serum components and cytokines on alveolar macrophage activation by soluble fungal (1-->3)-beta-D-glucan

In this study, we investigated the mechanism of alveolar macrophage activation by systemic administration of SSG, a soluble highly branched (1-->3)-beta-D-glucan obtained from a fungus Sclerotinia sclerotiorum IFO 9395. Multiple i.v. administration (10 mg/kg; once daily for 10 consecutive days) of SSG enhanced some functions of alveolar macrophages, such as lysosomal enzyme activity and nitric oxide secretion, on day 1 after the last administration, and it also elevated the concentrations of serum protein, interferon gamma and SSG in bronchoalveolar lavage fluid on the same day. On the in vitro assay system, stimulation by SSG alone (500 microg/ml) slightly augmented the lysosomal enzyme activity of alveolar macrophages, but it had no effect on nitric oxide production of cells. Stimulation by serum (1 or 10% mouse serum) or serum components, such as fibronectin (25 microg/ml) and albumin (500 microg/ml), alone strongly augmented only the lysosomal enzyme activity of alveolar macrophages, but it had no effect on nitric oxide secretion from cells, and no synergism or additive-like effect was observed between serum components and SSG. In contrast, stimulation by crude lymphokine (5%) or recombinant murine interferon gamma (100 U/ml) alone did not induce augmentation of lysosomal enzyme activity and nitric oxide production of alveolar macrophages in vitro, but when cells were incubated together with crude lymphokine or recombinant murine interferon gamma and SSG (500 microg/ml), a significant combined effect was observed on both functions of alveolar macrophages. In addition, pretreatment of crude lymphokine or recombinant murine interferon gamma enhanced the expression of beta-D-glucan specific binding sites on the alveolar macrophage surface in vitro though pretreatment by serum components had no effect. Based on these findings, the enhancement of alveolar macrophage functions by systemic administration of SSG appears to be mediated, at least in part, by both the simple effect of serum components including fibronectin and albumin leaked from pulmonary peripheral blood into the alveoli and the synergistic effect between lymphokines released from activated pulmonary T cells and SSG itself entering the alveoli after SSG injection via the priming effect of lymphokines which enhances the expression of beta-D-glucan specific binding sites on the alveolar macrophage surface.

Amniotic fluid tumor necrosis factor-alpha and the risk of respiratory distress syndrome among preterm infants

OBJECTIVE

We examined the effect of exposure to amniotic fluid infection and cytokines on the pulmonary outcome of preterm infants.

STUDY DESIGN

A cohort of 136 preterm infants born to women in preterm labor had amniotic fluid cultures and tumor necrosis factor-alpha assays performed. Amniotic fluid was collected by transabdominal amniocentesis. Outcome measures included respiratory distress syndrome and length of oxygen and ventilator support. Logistic regression and Cox proportional hazards regression adjusted for birth weight and other confounders.

RESULTS

Respiratory distress syndrome developed in 67 (49%) of 136 infants. Elevated amniotic fluid tumor necrosis factor-alpha levels and amniotic fluid infection were significantly associated with respiratory distress syndrome. This association persisted after adjustment for birth weight. Infants exposed to tumor necrosis factor-alpha remained on supplemental oxygen and assisted ventilation longer and had longer hospital stays compared with nonexposed infants.

CONCLUSION

Prenatal exposure to tumor necrosis factor-alpha may be a risk factor for respiratory distress syndrome and its complications.

Uric acid and ascorbic acid redox ratios in plasma and tracheal aspirate of preterm babies with acute and chronic lung disease

This study compared plasma redox ratios of uric acid and ascorbic acid in well preterm babies with those with respiratory distress syndrome (RDS) and chronic lung disease (CLD), and investigated the relationship between these ratios and their respective measurements in tracheal aspirate. On day 1 after birth, plasma allantoin and allantoin/uric acid ratio were elevated in CLD (p < .05), and both markers of oxidative stress enabled early prediction of development of CLD (sensitivity and specificity: 54 and 83%, respectively). The relation between allantoin production and oxidative stress is supported by the correlation between the allantoin level and oxygen therapy in both RDS and CLD (p < .05). Reduced and oxidize ascorbic acid in plasma decreased postnatally in all groups and their redox ratio remained stable. Uric acid and ascorbic acid redox ratios were significantly elevated in tracheal aspirates compared to plasma samples (p < .05), and there was a strong positive correlation between both ratios (p < .005). These markers may be useful in monitoring babies with respiratory distress.

Mucosal tumor necrosis factor-alpha production and extensive disruption of sulfated glycosaminoglycans begin within hours of birth in neonatal respiratory distress syndrome

Many of the clinicopathologic features of neonatal respiratory distress syndrome (RDS) may be related to the inflammatory response mounted by the affected infant, although little is known about the interstitial component of this response. We have thus studied the local inflammatory response in this condition by immunohistochemical analysis of whole lung lobes, obtained at postmortem from 40 infants who died from acute RDS in the first week of life. All had demonstrated classical clinical history and histologic features. An archival subgroup from the early 1970s had never received ventilatory support. Immunohistochemical analysis demonstrated rapid temporal increase from birth in the mucosal density of CD68+ macrophages, MAC-387+ monocytes/macrophages, polymorphonuclear neutrophils, and tumor necrosis factor-alpha-immunoreactive cells, maximal in those dying at or after 72 h. Using a cationic probe specific for sulfated glycosaminoglycans (GAGs), the inflammatory infiltration was seen to be associated with striking loss of endothelial, basement membrane, and interstitial GAGs, which was almost complete by 48-72 h. GAG degradation products were found within hyaline membranes in all infants dying after 48 h. This study confirms that neonatal RDS is characterized by intense interstitial inflammation, significantly underestimated on routine staining. This begins within hours of birth and is maximal by 72 h of age. Breakdown of sulfated GAGs within the extracellular matrix follows the same time course and may explain much of the physiologic derangement characteristic of this condition.

Cytokines in chronic lung disease of prematurity

Chronic lung disease of prematurity (CLD) is a common respiratory disorder of preterm infants. At autopsy, fibroblast proliferation, and components of the extracellular matrix, including collagen and fibronectin, are markedly increased in the lungs of infants who die from CLD. Examination of broncho-alveolar fluid suggests that the persistence of neutrophils is associated with the development of CLD. In our studies, the pro-inflammatory cytokines, interleukin-1 beta (IL-1 beta) and interleukin-6, (IL-6) and mediators which reflect neutrophil recruitment and activation, including soluble intercellular adhesion molecule, interleukin-8 (IL-8) and neutrophil elastase, were increased in lavage fluid obtained from infants who developed CLD when compared to infants who did not. Furthermore, semiquantitative reverse transcriptase-polymerase chain reaction of mRNA extracted from lavage cells suggested that luminal cells may be the source of IL-6 detected in lavage fluid but non-luminal cells may be the sources of IL-1 beta and IL-8. Fibrosis is thought to be mediated by the pro-fibrotic cytokines including transforming growth factor-beta1 (TGF-beta 1). Both active and total TGF-beta 1 were increased in lavage fluid from infants who developed CLD. Furthermore, both type I procollagen and TGF-beta were increased qualitatively in lung tissue obtained at autopsy from infants who died from respiratory failure. The increase in inflammatory mediators was maximal at 10 days of age. By contrast, the increase in TGF-beta 1 was maximal at 4 days of age. This suggests that the interaction between inflammation and fibrosis in CLD is complex, and that prenatal factors may be important in the pathogenesis of CLD.

Potential role of interleukin-1 in the development of bronchopulmonary dysplasia

Increased activities of inflammatory mediators unopposed by their inhibitors contribute to chronic lung injury and impaired healing in BPD. The deleterious effects of IL-1 beta, a cytokine involved in inflammation and host defense, are blocked by IL-1 receptor antagonist (IL-1Ra). We proposed that an imbalance of IL-1 beta and its inhibitors may contribute to the development of BPD. To determine the relative antigen concentrations of IL-1 beta and IL-1Ra and functional IL-1 activity in lung lavage of infants at risk for BPD, lung lavage was serially obtained from 1 to 28 days from 17 infants with evolving BPD, 13 infants with self-limited RDS, and 6 controls ventilated for nonpulmonary reasons. Overall, there was a high correlation between IL-1 beta antigen concentration and IL-1 activity (r = 0.82, p = 0.0001). There were no significant differences among the groups for lung lavage variables on day 1. However, in infants who developed BPD, IL-1 beta antigen concentration and IL-1 activity increased 16- and 61-fold, respectively, during the first week. IL-1Ra remained relatively unchanged during the first month. IL-1 beta/IL-1Ra antigen ratio was significantly higher on days 5 (median 0.024) and 7 (median 0.025) compared with day 1 (median 0.004), p < 0.05. These results suggest that a relative imbalance of IL-1 beta and IL-1Ra may contribute to prolonged inflammation in BPD.

Increase in the concentration of transforming growth factor beta-1 in bronchoalveolar lavage fluid before development of chronic lung disease of prematurity

OBJECTIVE

Pulmonary fibrosis is a prominent feature of chronic lung disease of prematurity (CLD). We sought to determine the influence of the potent profibrotic cytokine transforming growth factor beta-1 (TGF-Beta 1) on the development of CLD.

METHODS

We determined the concentration of active and total TGF-Beta 1 in bronchoalveolar lavage fluid obtained from 18 infants who subsequently had CLD (mean gestation, 25.7 weeks; birth weight, 816 gm) 15 (29.8 weeks, 1493 gm) who recovered from the respiratory distress syndrome, and 7 (35.1 weeks, 2441 gm) control infants.

RESULTS

The concentration of both active and total TGF-Beta 1 was increased in the infants with CLD when compared with the respiratory distress syndrome and control groups. The increase in active and total TGF-Beta 1 was greatest on day 4 of age, when infants who eventually had CLD were compared with those who did not progress to CLD (active TGF-Beta 1, 39.5 vs 4.6 ng/ml; total TGF-Beta 1, 43.8 vs 13.8 ng/ml). In addition, immunocytochemistry studies localized pan-TGF-Beta to alveolar macrophages obtained by bronchoalveolar lavage.

CONCLUSIONS

These observations indicate that TGF-Beta 1 may contribute to the fibrotic response that is observed in the lungs of infants who have CLD.

Inflammatory bronchopulmonary response of preterm infants with microbial colonisation of the airways at birth

The inflammatory indicators in the tracheobronchial aspirate (TA) of 81 ventilated preterm infants with microbial colonisation of the airways and in non-colonised neonates were analysed on the first day of life. TA was assessed for chemotactic activity, neutrophil cell count, and concentrations of leukotriene B4, C5a, interleukin-1, interleukin-8, elastase-alpha 1-proteinase inhibitor, free elastase and albumin. Concentrations of mediators were related to concentrations of the secretory component of IgA. The infants' gestational age was mean (SD) 27.9 (2.0) weeks, birthweight 945 (179) g. In 12 infants (15%) microbial colonisation of the airways was present (Ureaplasma urealyticum n = 7; bacteria n = 5). Compared with non-colonised neonates (n = 69), chemotactic activity, neutrophil count, and concentrations of interleukin-1, leukotriene B4 and elastase-alpha 1-proteinase inhibitor were significantly higher in the colonised group. The difference was most pronounced for IL-1 concentrations, both with and without correction for secretory component. There was also a trend towards increased concentrations of interleukin-8 in the latter group. There were no differences for concentrations of C5a and albumin in the TA of both groups. It is concluded that airway colonisation with U urealyticum or bacteria at birth is associated with a clinically relevant bronchopulmonary inflammatory response. Increased concentrations of interleukin-1 in TA on the first day of life may be a marker of perinatal colonisation of the airways.