Gene expression of insulin-like growth factor-1 and epidermal growth factor is downregulated in the heart of rats with nitrofen-induced diaphragmatichernia

Newborns with congenital diaphragmatic hernia (CDH) still have high mortali ty. Recently, a possible role of cardiac maldevelopment has been suggested. Human and experimental studies have demonstrated that heart weight is sign ificantly reduced in the presence of CDH. Recent studies have suggested an important role for insulin-like growth factor-I (IGF-I) in the regulation o f cardiac growth, structure, and function. Administration of IGF-I to norma l rats has been shown to cause cardiac hypertrophy. Epidermal growth factor (EGF) plays an important role in cardiac differentiation and development. The aim of this study was to determine the gene-level expression of IGF-I a nd EGF in the hearts of rats with nitrofen-induced CDH using the reverse-tr anscription polymerase chain reaction technique (RT-PCR). CDH was induced i n pregnant rats following administration of 100 mg nitrofen on day 9.5 of g estation (tt:rm 22 days). In control animals, the same dose of olive oil wa s given without nitrofen. Cesarean section was performed on day 21 of gesta tion. The fetuses were divided into three groups: normal controls (n = 8), nitrofen without CDH (n = 8), and nitrofen-induced CDH (n = 8). Total RNA w as extracted from the hearts in each group and measured. mRNA was extracted from total RNA. RT-PCR was performed to evaluate mRNA expressions of IGF-I and EGF. Levels of mRNA were expressed as a ratio of band density divided by that of beta-actin, a housekeeping gene known to be expressed at a const ant level. IGF-I mRNA expression was significantly decreased in CDH hearts (0.177 +/- 0.109) compared to controls (0.393 +/- 0.138) (P < 0.01) and nit rofen hearts without CDH (0.321 +/- 0.088) (P < 0.05). EGF mRNA expression was significantly decreased in CDH hearts (0.218 +/- 0.118) compared to con trols (0.534 +/- 0.196) (P < 0.01) and nitrofen hearts without CDH (0.383 /- 0.136) (P < 0.05). Decreased cardiac gene expression of IGF-I and EGF il l the hypoplastic heart suggests that cardiac hypoplasia in nitrofen-induce d rat CDH may be due to reduced synthesis of IGF-I and EGF by myocytes in t he developing heart.