Expression patterns of heat shock proteins in lungs of neonates with congenital diaphragmatic hernia.

BACKGROUND

Congenital diaphragmatic hernia (CDH) is associated in many cases with pulmonary hypertension. Currently, extracorporeal membrane oxygenation (ECMO) is one of the possible modalities of treatment of pulmonary hypertension and prevention of parenchymal lung injury in neonates with CDH.

HYPOTHESIS

Molecular stress is present in the lungs of neonates with CDH. To test this hypothesis, we investigate the expression pattern of stress genes (heat shock proteins [HSPs] 27 and 70) in lungs of patients with CDH who have pulmonary hypertension, and evaluate the influence of ECMO on the expression levels of these genes to understand the underlying molecular mechanisms.

DESIGN

Paraffin-embedded lung autopsy specimens from patients with CDH and lung hypoplasia who either did or did not receive ECMO treatment and age-matched controls were immunostained by means of monoclonal antihuman antibodies against HSP 70 and HSP 27, with the streptavidin-biotin complex method.

SETTING

Level III academic children's hospital.

MAIN OUTCOME MEASURES

Expression levels of both HSP 27 and HSP 70 were semiquantitatively evaluated in bronchial epithelium, as well as in medial smooth muscle cells (SMCs) and endothelium of large and small pulmonary arteries, by means of a score ranging from 0 to 4. Statistical analysis of the data was performed with the nonparametric Mann-Whitney test, with significant probability value at P < or = .05.

RESULTS

For HSP 70, the most pronounced immunoreactivity was observed in the bronchial epithelium, followed by the medial SMCs of small arteries (of external diameter < 200 microm). The overall expression was significantly higher in patients with CDH than controls in bronchi as well as in pulmonary arteries. For HSP 27, intense expression was found in medial SMCs, followed by the bronchial epithelium in controls, with significantly increased expression in medial SMCs of large and small arteries in patients with CDH. Treatment with ECMO was associated with significantly reduced expression levels of HSP 70 in medial SMCs of both large and small arteries, whereas HSP 27 expression levels were decreased only in small arteries. In addition, the expression levels of both HSPs were significantly lower in endothelium of small arteries.

CONCLUSIONS

Increased expression of HSPs in CDH points to a condition of pulmonary stress. This pulmonary stress appears to be partially ameliorated by ECMO treatment. This may point to one of the mechanisms by which ECMO alleviates pulmonary hypertension associated with CDH.