Altered expression of angiotensin II receptor subtypes and transforming growth factor-beta in the heart of nitrofen-induced diaphragmatic hernia in rats

Beyond the diaphragm and the lung: a multisystem approach to understanding congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a birth defect characterized by the incomplete closure of the diaphragm and herniation of abdominal organs into the chest during gestation. This invariably leads to an impairment in fetal lung development (pulmonary hypoplasia) that involves the pulmonary vessels (vascular remodeling) leading to postnatal pulmonary hypertension. Moreover, approximately 60% of CDH survivors have long-term comorbidities, including critical cardiac anomalies, neurodevelopmental impairment, gastroesophageal reflux, and musculoskeletal malformations. While the pathophysiology of the diaphragmatic defect and pulmonary hypoplasia have been studied in detail over the decades, less is known about the other organs affected in CDH. In this review, we searched the literature for reports on other organs beyond the lung and diaphragm in human and experimental models of CDH. We found studies reporting gross morphometric changes and alterations to biological pathways in the heart, brain, liver, kidney, gastrointestinal tract, and musculoskeletal system. Given the paucity of literature and the importance that these comorbidities play in the life of patients with CDH, further studies are needed to comprehensively uncover the pathophysiology of the changes observed in these other organs.

Opposing Effects of TGFβ and BMP in the Pulmonary Vasculature in Congenital Diaphragmatic Hernia

Background: Pulmonary hypertension is the major cause of morbidity and mortality in congenital diaphragmatic hernia (CDH). Mutations in several genes that encode signaling molecules of the transforming growth factor β (TGFβ) and bone morphogenetic protein (BMP) pathways have previously been associated with CDH. Since studies on the activation of these pathways in CDH are scarce, and have yielded inconsistent conclusions, the downstream activity of both pathways was assessed in the nitrofen-CDH rat model.

Methods and Results: Pregnant Sprague-Dawley rats were treated with nitrofen at embryonic day (E) 9.5 to induce CDH in offspring. At E21, lungs were screened for the expression of key factors of both signaling pathways, at both the mRNA transcript and protein levels. Subsequently, paying particular attention to the pulmonary vasculature, increased phosphorylation of SMAD2, and decreased phosphorylation of Smad5 was noted in the muscular walls of small pulmonary vessels, by immunohistochemistry. This was accompanied by increased proliferation of constituent cells of the smooth muscle layer of these vessels.

Conclusions: Increased activation of the TGFβ pathway and decreased activation of the BMP pathway in the pulmonary vasculature of rats with experimentally-induced CDH, suggesting that the deregulated of these important signaling pathways may underlie the development of pulmonary hypertension in CDH.

Perinatal profile of ventricular overload markers in congenital diaphragmatic hernia

BACKGROUND

In congenital diaphragmatic hernia (CDH), pulmonary hypertension increases right ventricle (RV) afterload, which could impair heart function and contribute to poor outcome for most affected infants. Nevertheless, the real significance of vascular pulmonary alterations in perinatal hemodynamics is largely unknown. It is defined that ventricular pressure overload induces increased myocardium gene expression of B-type natriuretic peptide (BNP) and components of the renin-angiotensinogen and endothelin (ET)-1 systems. Our aim was to evaluate perinatal myocardium expression of these genes associated with ventricular pressure overload in a nitrofen-induced CDH rat model.

METHODS

In the nitrofen-induced CDH rat model, fetuses from dated pregnant Sprague-Dawley rats at 15.5, 17.5, 19.5 and 21.5 days postcoitum as well as newborn pups were assigned to 3 experimental groups: control, nitrofen (exposed to nitrofen, without CDH), and CDH (exposed to nitrofen, with CDH). Myocardial samples collected from the RV and left ventricle (LV) were processed for quantification of messenger RNA (mRNA) of BNP, angiotensinogen, and ET-1.

RESULTS

The perinatal expression of BNP, angiotensinogen, and ET-1 mRNA in the RV and LV of the control group revealed daily changes. During gestation, the expression of BNP and angiotensinogen mRNA underwent significant oscillation compared with control in both nitrofen-exposed fetuses, although we cannot identify significant differences between the nitrofen and CDH groups. After birth, we found a significant increasing expression of all studied genes only in the RV of CDH pups.

CONCLUSIONS

Perinatal myocardial quantification of BNP, angiotensinogen, and ET-1 mRNA levels suggests that both nitrofen-exposed and control pups revealed prenatal variations of expression of the studied genes. Moreover, CDH is associated with significant molecular alterations only in the RV after birth.

Downregulation of GATA4 and GATA6 in the heart of rats with nitrofen-induced diaphragmatic hernia

PURPOSE

The high incidence of cardiac malformations in humans and animal models with congenital diaphragmatic hernia (CDH) is well known. The precise molecular mechanisms underlying cardiac maldevelopment in CDH are still unclear. It has been reported that GATA4 and GATA6, members of the GATA transcription factor family, act cooperatively to regulate cardiovascular development, and the levels of cardiac GATA4 and GATA6 are important regulators of cardiomyocyte proliferation, cardiac morphogenesis, and embryo survival. In addition, the GATA4/GATA6 double heterozygous mutant embryo model displayed a spectrum of cardiovascular malformations similar to those seen in human CDH and nitrofen-induced animal models, including ventricular and aortopulmonary septal defects and thin ventricular myocardium. To test the hypothesis that expression of GATA4 and GATA6 is reduced in early stages of gestation in a CDH hypoplastic heart, we investigated the expression of GATA4 and GATA6 in the hearts of nitrofen-treated rats in early gestation. Wnt2, bone morphogenetic protein 4 (BMP4), and myocyte enhancer factor 2C (MEF2C) were also investigated as GATA4/6 target genes involved in cardiogenesis.

MATERIALS AND METHODS

Fetal rat hearts of normal (n = 7) and nitrofen-treated (n = 7) dams were harvested on embryonic day 13. The expression of GATA4, GATA6, Wnt2, BMP4, and MEF2C was analyzed in each heart by real-time reverse transcription-polymerase reaction.

RESULTS

The gene expression of GATA4, GATA6, Wnt2, BMP4, and MEF2C on embryonic day 13 were significantly reduced (P < .05) in the hearts of nitrofen-treated animals compared with normal hearts of equivalent age.

CONCLUSION

Decreased expression of GATA4 and GATA6 and their target genes in the developing fetal heart may perturb the delicate regulation of cardiovascular development, resulting in cardiovascular malformations in the nitrofen rat model.