Bruno Piedboeuf

Deleterious Effect of Tracheal Obstruction on Type II Pneumocytes in Fetal Sheep

It was previously shown that tracheal obstruction accelerated fetal lung growth and eventually reversed the pulmonary hypoplasia in experimental diaphragmatic hernia. We have successfully developed a reversible tracheal obstruction technique in fetal sheep using balloon occlusion and showed that 3 wk of obstruction induced significant lung growth of the same magnitude as the tracheal ligation. The purpose of this study was to examine the effects of 1 and 3 wk of tracheal occlusion on the alveolar cell population with specific attention to the type II pneumocytes. We first showed that 1 wk of occlusion induced a significant increase in lung weight and in alveolar surface area. We then used the surfactant protein C (SP-C) mRNA as a specific marker of differentiated type II pneumocytes. Total RNA was isolated from fetal sheep lung with or without tracheal occlusion, and Northern blots were hybridized with a cDNA probe specific for the sheep SP-C. The results show a dramatic decrease in SP-C mRNA expression (8.8-fold, p < 0.01). In situ hybridization showed a marked decrease in the density of cells expressing SP-C, as well as the amount of SP-C mRNA expressed by the cells. The effect was present as early as 1 wk of occlusion. The sparseness of type II pneumocytes was further confirmed by electron microscopy. We thus conclude that tracheal obstruction causes a profound decrease in the number of type II pneumocytes in the lungs. Given the crucial role of type II pneumocytes in surfactant production, we could speculate that, if tracheal occlusion is able to accelerate lung growth, the final product is probably surfactant-deficient.

An international trial of antioxidants in the prevention of preeclampsia (INTAPP).

OBJECTIVE We sought to investigate whether prenatal vitamin C and E supplementation reduces the incidence of gestational hypertension (GH) and its adverse conditions among high- and low-risk women. STUDY DESIGN In a multicenter randomized controlled trial, women were stratified by the risk status and assigned to daily treatment (1 g vitamin C and 400 IU vitamin E) or placebo. The primary outcome was GH and its adverse conditions. RESULTS Of the 2647 women randomized, 2363 were included in the analysis. There was no difference in the risk of GH and its adverse conditions between groups (relative risk, 0.99; 95% confidence interval, 0.78-1.26). However, vitamins C and E increased the risk of fetal loss or perinatal death (nonprespecified) as well as preterm prelabor rupture of membranes. CONCLUSION Vitamin C and E supplementation did not reduce the rate of preeclampsia or GH, but increased the risk of fetal loss or perinatal death and preterm prelabor rupture of membranes.

Differences in correlation of mRNA gene expression in mice sensitive and resistant to radiation-induced pulmonary fibrosis.

Fibrosis, characterized by the accumulation of collagen, is a late result of thoracic irradiation. The purpose of this study was to determine if extracellular matrix protein and transforming growth factor beta mRNA expression are altered late in the course of pulmonary fibrosis after irradiation, and then to determine if these changes differ between two strains of mice which vary in their sensitivity to radiation. Radiation-sensitive (C57BL/6) and radiation-resistant (C3H/HeJ) mice were irradiated with a single dose of 5 or 12.5 Gy to the thorax. Total lung RNA was prepared and immobilized by Northern and slot blotting and hybridized with radiolabeled cDNA probes for collagens I, III and IV, fibronectin, and transforming growth factor beta 1 and beta 3. Autoradiographic data were quantified by video densitometry and results normalized to a control probe encoding for glyceraldehyde-3-phosphate dehydrogenase. Alterations in mRNA abundance were observed in the sensitive mice at all times, while levels in the resistant mice were unaffected until 26 weeks after irradiation. The relationship between extracellular matrix protein per se and increased mRNA abundance suggests that late matrix protein accumulation may be a function of gene expression. Differences in levels of transforming growth factor beta mRNA may lead to strain-dependent variation in fibrotic response and may also contribute to the radiation-induced component of pulmonary fibrosis.

Outcomes of preterm infants <29 weeks gestation over 10-year period in Canada: a cause for concern?

Objective:To compare risk-adjusted changes in outcomes of preterm infants <29 weeks gestation born in 1996 to 1997 with those born in 2006 to 2007.Study Design:Observational retrospective comparison of data from 15 units that participated in the Canadian Neonatal Network during 1996 to 1997 and 2006 to 2007 was performed. Rates of mortality and common neonatal morbidities were compared after adjustment for confounders.Result:Data on 1897 infants in 1996 to 1997 and 1866 infants in 2006 to 2007 were analyzed. A higher proportion of patients in the later cohort received antenatal steroids and had lower acuity of illness on admission. Unadjusted analyses revealed reduction in mortality (unadjusted odds ratio (UAOR): 0.83, 95% confidence interval (CI): 0.63, 0.98), severe retinopathy (UAOR: 0.68, 95% CI: 0.50 to 0.92), but increase in bronchopulmonary dysplasia (UAOR: 1.61, 95% CI: 1.39 to 1.86) and patent ductus arteriosus (UAOR: 1.22, 95% CI: 1.07 to 1.39). Adjusted analyses revealed increases in the later cohort for bronchopulmonary dysplasia (adjusted odds ratio (AOR): 1.88, 95% CI: 1.60 to 2.20) and severe neurological injury (AOR: 1.49, 95% CI: 1.22 to 1.80). However, the ascertainment methods for neurological findings and ductus arteriosus differed between the two time periods.Conclusion:Improvements in prenatal care has resulted in improvement in the quality of care, as reflected by reduced severity of illness and mortality. However, after adjustment of prenatal factors, no improvement in any of the outcomes was observed and on the contrary bronchopulmonary dysplasia increased. There is need for identification and application of postnatal strategies to improve outcomes of extreme preterm infants.

Prolonged Survival in Hereditary Surfactant Protein B (SP-B) Deficiency Associated with a Novel Splicing Mutation

Hereditary surfactant protein B (SP-B) deficiency has been lethal in the first year of life without lung transplantation. We tested the hypothesis that SP-B gene mutations may result in milder phenotypes by investigating the mechanisms for lung disease in two children with less severe symptoms than have been previously observed in SP-B deficiency. Immunostaining patterns for pulmonary surfactant proteins were consistent with SP-B deficiency in both children. DNA sequence analysis indicated that both children were homozygous for a mutation in exon 5 that created an alternative splice site. Reverse transcriptase PCR and sequence analysis confirmed use of this splice site, which resulted in a frameshift and a premature termination codon in exon 7. The predominant reverse transcriptase PCR product, however, lacked exon 7, which restored the reading frame but would not allow translation of the exons that encode mature SP-B. Western blot analysis detected reduced amounts of mature SP-B as well as an aberrant SP-B proprotein that corresponded to the size expected from translation of the abnormal transcript. We conclude that a novel splicing mutation was the cause of lung disease in these children and that hereditary SP-B deficiency can be the cause of lung disease in older children.

Tracheal occlusion: A review of obstructing fetal lungs to make them grow and mature†

Fetal lung growth and functional differentiation are affected strongly by the extent that pulmonary tissue is distended (expanded) by liquid that naturally fills developing future airspaces. Methods that prevent normal egress of this lung fluid through the trachea magnify mechanical stretching of lung parenchymal cells, thereby promoting lung development. Indeed, experimental observations demonstrate that in utero tracheal occlusion (TO) performed on fetuses during the late canalicular‐early saccular stage potently stimulates pulmonary growth and maturation. In this review, we present the four principle non‐human animal models of TO/obstruction and discuss them in relation to their utility in elucidating lung development, in remedying congenital diaphragmatic hernia (CDH) as well as in investigating the stretching effects on growth and remodeling of the fine vasculature.

Unscheduled apoptosis during acute inflammatory lung injury.

Apoptosis is a mode of cell death currently thought to occur in the absence of inflammation. In contrast, inflammation follows unscheduled events such as acute tissue injury which results in necrosis, not apoptosis. We examined the relevance of this paradigm in three distinct models of acute lung injury; hyperoxia, oleic acid, and bacterial pneumonia. In every case, it was found that apoptosis is actually a prominent component of the acute and inflammatory phase of injury. Moreover, using strains of mice that are differentially sensitive to hyperoxic lung injury we observed that the percent of apoptotic cells was well correlated with the severity of lung injury. These observations suggest that apoptosis may be one of the biological consequences during acute injury and the failure to remove these apoptotic cells may also contribute to the inflammatory response.

Sex hormone metabolism in lung development and maturation

Sex hormones are increasingly recognized as regulators of lung development. Respiratory distress syndrome (RDS) is the leading cause of morbidity in preterm neonates and occurs with a higher incidence in males. The mechanisms underlying the effects of androgens on lung development and the occurrence of RDS are only partially deciphered, and positive roles of estrogens on surfactant production and alveologenesis are relevant to our understanding of pulmonary diseases. This manuscript reviews current knowledge on androgen and estrogen metabolism and on relevant hormone targets in the fetal lung. Further investigations are needed to elucidate mechanisms orchestrating sex hormone effects on lung development. These studies aim to decrease mortality and morbidity associated with RDS and other pathologies related to lung immaturity at birth.

Role of gender in morbidity and mortality of extremely premature neonates.

We investigated the effect of gender on survival and short-term outcomes of extremely premature infants (≤27 weeks) born in Canada. The records of infants admitted between 2000 and 2005 to a neonatal intensive care unit participating in the Canadian Neonatal Network were reviewed for infant gender, birth weight, gestational age, outborn status, Score for Neonatal Acute Physiology II, and antenatal corticosteroid exposure. The following outcomes were recorded: survival at final discharge, necrotizing enterocolitis, bronchopulmonary dysplasia (BPD), intraventricular hemorrhage grade ≥3, retinopathy grade ≥3, days on ventilation, and length of hospital stay. Among 2744 extremely premature infants, 1480 (54%) were male and 1264 (46%) were female. Mean birth weight of female neonates was significantly lower at each week of gestational age. Although no significant difference in survival at discharge was found between genders overall, the prevalence of BPD, combined adverse outcomes, and mortality for infants born between 24 and 26 weeks were significantly higher in males. This study suggests that, in the postsurfactant era, males remain at higher risk of respiratory complications and may have higher mortality when born between 24 and 26 weeks of gestation.

Fluticasone Inhalation in Moderate Cases of Bronchopulmonary Dysplasia

Objective.This randomized, controlled trial was designed to determine the efficacy of inhaled fluticasone propionate on oxygen therapy weaning in a population of preterm infants who were born at <32 weeks of gestation and experienced moderate bronchopulmonary dysplasia (BPD). Methods.Thirty-two infants who were ≤32 weeks of gestation, had moderate BPD that required supplemental oxygen (fraction of inspired oxygen ≥0.25), and were aged between 28 and 60 days were randomized. Fluticasone propionate 125 μg twice daily for 3 weeks and once daily for a fourth week was delivered to infants who weighed between 500 and 1200 g. The dosage was doubled for infants who weighed ≥1200 g. Results.Compared with placebo, treatment had no effect on either duration of supplemental O2 therapy or ventilatory support as assessed by survival analysis. At 28 days, a trend toward a lower cortisol/creatinine ratio in the treatment group was noted compared with placebo (25.1 ± 18.9 vs 43 ± 14.4). In the fluticasone group at 28 days, the systolic arterial pressure (78 ± 3 vs 68 ± 3 mm Hg) and diastolic arterial pressure (43 ± 3.4 mm Hg vs 38 ± 2.0 mm Hg) were higher compared with baseline fluticasone values. The chest radiograph score was lower than baseline (2.8 ± 1.4 vs 3.7 ± 2.2) in the fluticasone group at 28 days. This study has a statistical power of 1.0 to detect a significant difference in the duration of oxygen supplementation of >21 days between the study groups. Conclusion.We conclude that fluticasone propionate reduces neither supplemental O2 use nor the need for ventilatory support in this patient population. However, fluticasone does have a positive radiologic effect in lowering chest radiograph scores. In addition, our data point to a possible association among inhaled fluticasone treatment and higher arterial blood pressure. Thus, the results of this investigation do not support the use of inhaled corticosteroids in the treatment of oxygen-dependent infants who have established moderate BPD.