Inhibition of vascular and epithelial differentiation in murine nitrofen-induced diaphragmatic hernia

Neonates with congenital diaphragmatic hernia (DH) die of pulmonary hypoplasia and persistent pulmonary hypertension. We used immunohistochemical localization of alpha-smooth muscle actin (alpha-SMA), platelet endothelial cell adhesion molecule (PECAM)-1, thyroid transcription factor (TTF)-1, surfactant protein (SP) A, SP-C, and competitive RT-PCR quantitation of TTF-1, SP-A, SP-C, and alpha-SMA mRNA expression to characterize the epithelial and vascular phenotype of lungs from ICR fetal mice with a nitrofen-induced DH. Nitrofen (25 mg) was gavage fed to pregnant mice on day 8 of gestation. Fetal mice were delivered on day 17. The diaphragm was examined for a defect, and the lungs were either fixed, sectioned, and immunostained or processed for mRNA isolation. In comparison with control lungs, DH lungs showed increased expression of alpha-SMA mRNA, fewer and more muscular arterioles (alpha-SMA), less well-developed capillary networks (PECAM-1), delayed epithelial development marked by a persistence of TTF-1 in the periphery, and decreased SP-A mRNA and SP-A expression. These data suggest that in the murine nitrofen-induced DH, as in human congenital DH, pulmonary insufficiency is due to an inhibition of peripheral pulmonary development including terminal airway and vascular morphogenesis.