Glucocorticoid receptor gene expression in the hypoplastic lung of newborns with congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: In experimentally produced congenital diaphragmatic hernia (CDH), antenatal glucocorticoids have been shown to improve morphologic and biochemical lung immaturity and normalize the thickened pulmonary vascular wall. The action of glucocorticoids on a target tissue is mediated by glucocorticoid receptors (GRs), which have 2 isoforms; GRalpha binds glucocorticoids and acts as a ligand-dependent transcription factor, and GRbeta does not bind glucocorticoids and acts as an inhibitor of GRalpha. The aim of this study was to examine the expression of GR gene and its isoforms in the CDH lung.

METHODS: RNA was extracted from archival lung tissue of 11 patients (mean age, 3.5 days) with CDH. Five age-matched newborns (mean age, 13.5 days) with sudden death syndrome served as control. Reverse transcription (RT) and polymerase chain reaction (PCR) was performed using primers specific to the common region of GR, GRalpha, and GRbeta. Soluble enzyme immunohistochemistry was carried out using polyclonal antibodies to GRalpha.

RESULTS: Relative mRNA levels of GR, GRalpha, and GRbeta as detected by RT-PCR were increased significantly in CDH lung compared with controls. GRalpha immunoreactivity confined only to the cytoplasm of the cells was markedly increased in the epithelium and interstitial cells in the CDH lung compared with controls.

CONCLUSION: The findings of increased mRNA expression of GR and particularly of its isoform GRalpha in the CDH lung suggests that GR may play an important role in regulating target cell responsiveness to glucocorticoids in the hypoplastic lung.