Ephrin-B1, -B2, and -B4 Expression is Decreased in Developing Diaphragms and Lungs of Fetal Rats with Nitrofen-Induced Congenital Diaphragmatic Hernia.

INTRODUCTION

Congenital diaphragmatic hernia (CDH) is assumed to originate from a malformation of the amuscular mesenchymal component of the primordial diaphragm. Mutations in ephrin-B1, a membrane protein that is expressed by mesenchymal cells, have been found in newborn infants with CDH and associated pulmonary hypoplasia (PH), highlighting its important role during diaphragmatic and airway development. Ephrin-B1, -B2, and -B4 are expressed in fetal rat lungs and have been identified as key players during lung branching morphogenesis. We hypothesized that diaphragmatic and pulmonary expression of ephrin-B1, -B2, and -B4 is decreased in the nitrofen-induced CDH model.

MATERIALS AND

METHODS

Time-mated rats received nitrofen or vehicle on day 9 (D9). Fetal diaphragms (n = 72) and lungs (n = 72) were harvested on D13, D15, and D18, and divided into control and nitrofen-exposed specimens. Ephrin-B1, -B2, and -B4 gene expression was analyzed by quantitative real-time polymerase chain reaction. Immunofluorescence double staining for ephrin-B1, -B2, and -B4 was combined with mesenchymal and epithelial markers (Gata-4/Fgf-10 and calcitonin gene-related peptide) to evaluate protein expression/localization.

RESULTS

Ephrin-B1, -B2, and -B4 gene expression was significantly reduced in pleuroperitoneal folds/primordial lungs (D13), developing diaphragms/lungs (D15), and fully muscularized diaphragms/differentiated lungs (D18) of nitrofen-exposed fetuses compared with controls. Confocal laser scanning microscopy demonstrated markedly diminished ephrin-B1 immunofluorescence in diaphragmatic and pulmonary mesenchyme of nitrofen-exposed fetuses on D13, D15, and D18 compared with controls, whereas ephrin-B2 and -B4 expression was mainly decreased in distal airway epithelium.

CONCLUSION

Decreased ephrin-B1, -B2, and -B4 expression may disrupt diaphragmatic development and lung branching morphogenesis by interfering with epithelial-mesenchymal interactions, thus causing diaphragmatic defects and PH.