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

Abstract

Newborns with congenital diaphragmatic hernia (CDH) still have high mortality. Recently, a possible role of cardiac maldevelopment has been suggested. Human and experimental studies have demonstrated that heart weight is significantly reduced in the presence of CDH. Recent studies have suggested an important role for insulin-like growth factor-I (IGF-I) in the regulation of cardiac growth, structure, and function. Administration of IGF-I to normal 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 and EGF in the hearts of rats with nitrofen-induced CDH using the reverse-transcription polymerase chain reaction technique (RT-PCR). CDH was induced in pregnant rats following administration of 100 mg nitrofen on day 9.5 of gestation (term 22 days). In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The fetuses were divided into three groups: normal controls (n = 8), nitrofen without CDH (n = 8), and nitrofen-induced CDH (n = 8). Total RNA was 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 constant 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 nitrofen 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 controls (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 in the hypoplastic heart suggests that cardiac hypoplasia in nitrofen-induced rat CDH may be due to reduced synthesis of IGF-I and EGF by myocytes in the developing heart.