Effect of insulin-like growth factors on lung development in a nitrofen-induced CDH rat model

Purpose: Both the mortality and morbidity associated with congenital diaphragmatic hernia (CDH) are mainly caused by pulmonary hypoplasia and persistent pulmonary hypertension. A previous study revealed that insulin-like growth factors (IGFs) play important roles in fetal lung development. The aim of this study was to investigate the effect of IGF-1 and IGF-2 on tissue cultures of fetal hypoplastic lungs obtained from nitrofen-induced CDH model rats. Methods: Pregnant rats were exposed to nitrofen on day 9 of gestation (D9). Fetuses were harvested on D18 by caesarian section. Lung specimens of the CDH (+) fetus were divided into three groups; control, IGF-1, and IGF-2. The specimens from the control group were cultured in culture medium without IGFs. The IGF-1 group specimens were cultured with IGF-1 (500 ng/ml), and those in the IGF-2 group were cultured with IGF-2 (500 ng/ml). The mRNA expression of TTF-1, T1α and α-SMA were analyzed in each group using real-time RT-PCR after 24 and 48 h of incubation. Immunohistochemical staining of these markers was also assessed for each of the cultured specimens. Results: There was a significant increase in the expression of both TTF-1 and T1α mRNA in the IGF-2 group, in comparison to the control group after 48 h of culture. Immunohistochemical staining revealed that the cell morphology was changed from cuboidal to squamous type in the IGF-2 group. Conclusions: An increased mRNA expression of the markers related to type 1 and 2 alveolar epithelial cells, and morphological changes in the epithelial cells were observed in the IGF-2 group. The administration of IGF-2 to nitrofen-induced hypoplastic lungs might lead to alveolar maturation, which thus results in their improved development.