Tracheal ligation and corticosteroids in congenital diaphragmatic hernia: for better for worse?

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Current therapy of infants with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a life-threatening anomaly with a significant mortality rate. Despite widespread prenatal diagnosis, few parameters have been well defined to aid in prediction of outcome of these infants. Antenatal maternal steroid administration and foetal surgery are not proven interventions. Postnatal treatment has changed over the last 10 years, with avoidance of hyperventilation and ventilator-induced lung injury resulting in improved survival. Therapies such as inhaled nitric oxide, exogenous surfactant administration and extracorporeal membrane oxygenation (ECMO) have undergone limited study, but show no clear benefit in this population. With improved outcome, principally due to avoidance of barotrauma, greater opportunity exists for long-term evaluation of survivors. To date, continuing problems with pulmonary function, nutrition and growth, effects of right ventricular hypertension and developmental issues have been identified. Through co-ordinated, multidisciplinary evaluation of CDH survivors, improved long-term outcome for these challenging patients can be attained.

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a lethal human birth defect. Hypoplastic lung development is the leading contributor to its 30-50% mortality rate. Efforts to improve survival have focused on fetal surgery, advances in intensive care and elective delivery at specialist centres following in utero diagnosis. The impact of abnormal lung development on affected infants has stimulated research into the developmental biology of CDH. Traditionally lung hypoplasia has been viewed as a secondary consequence of in utero compression of the fetal lung. Experimental evidence is emerging for a primary defect in lung development in CDH. Culture systems are providing research tools for the study of lung hypoplasia and the investigation of the role of growth factors and signalling pathways. Similarities between the lungs of premature newborns and infants with CDH may indicate a role for antenatal corticosteroids. Further advances in postnatal therapy including permissive hypercapnia and liquid ventilation hold promise. Improvements in our basic scientific understanding of lung development may hold the key to future developments in CDH care.

Thyroid transcription factor-1 expression during normal human lung development and in patients with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Thyroid transcription factor-1 (TTF-1) was detected in human respiratory epithelial cells from 11 weeks of gestation. TTF-1 is involved in both lung morphogenesis and in the regulation of surfactant proteins. Recently, low expression of TTF-1 in the nitrofen rat model of congenital diaphragmatic hernia (CDH) was shown and restoration of this downregulation by antenatal glucocorticolds (CS) was reported. The aim of this study was to investigate the expression of TTF-1 as a marker of lung morphogenesis in normal human lung development and in age-matched controls of human lung specimen in hypoplastic lungs of human CDH and other forms of lung hypoplasia.

METHODS

Immunohistochemistry by a monoclonal TTF-1 antibody was performed on paraffin sections of human fetal and neonatal lung tissues. The so-called developmental group (12 weeks' gestation to full term) included 47 lung specimens. The congenital hypoplasia group included 8 full-term CDH patients who died within 12 hours after birth, 3 full-term CDH patients who had antenatal CS therapy, and 4 full-term CDH patients after extracorporeal membrane oxygenation (ECMO) therapy. For comparison, 6 full-term born patients, who died of other forms of pulmonary hypoplasia, were used as comparative specimen. Immunohistochemical localization of TTF-1 was evaluated by light microscopy for 3 different areas of the airways including intrapulmonary bronchi, intermediate airways so-called terminal bronchioles, distal airways, and later sacculi and alveoli.

RESULTS

Nuclear TTF-1 staining was observed in the progenitor cells of the developing bronchiolar cells early in the human lung developmental series. At full term, TTF-1 was expressed in both type II epithelial cells and in subsets of respiratory nonciliated bronchiolar epithelial cells in a pattern similar in all studied groups. No TTF-1 expression was detected at the level of the intrapulmonary bronchi.

CONCLUSIONS

No difference in TTF-1 expression was observed in the developing early fetal and full-term neither in hypoplastic human lungs. This expression did not change with antenatal CS and postnatal ECMO treatment. Although TTF-1 appears to play an important role in lung morphogenesis, a pivotal role in human lung development is not likely.

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia occurs in approximately 1 in every 2500 live births and is associated with a reported mortality of almost 35% in live-born patients and a higher mortality when in utero deaths are counted. Ventilator-induced lung injury, pulmonary hypoplasia, and other associated anomalies account for the high death rate. Numerous adjunctive measures have been used to treat these patients. Inhaled vasodilators (nitric oxide), intravenous vasodilators, and fetal therapy have no proven benefit. While animal models of congenital diaphragmatic hernia are surfactant deficient, controversy remains over the use of surfactant in infants. There has been no clinical trial showing any clear benefit with the use of exogenous surfactant in these patients. Similarly, prenatal corticosteroids show some improvements in animal models, but again, there is a complete absence of supportive data to show benefit in humans. Mechanical ventilator strategies that limit ventilator-induced lung injury by avoiding hyperventilation and lung over inflation are the strategies currently in use that have been associated with improved survival. Long-term follow-up of these patients is quite important since gastroesophageal reflux, developmental delay, chronic lung disease, and chest wall deformity are all seen with increased frequency in these children.

The history of congenital diaphragmatic hernia from 1850s to the present

Congenital diaphragmatic hernia (CDH) is believed to result from incomplete fusion of the pleuroperitoneal membrane, and passage of the abdominal contents into the chest. A historical review of the literature on this subject shows a wide divergence of opinion on the etiology of the various types of CDH, and on the recommended treatment. A variety of theories regarding its causes and the optimal way of approaching it have been published from the mid 19th century through the 20th century, and are reviewed in this article.