Pulmonary arterioles from rats with congenital diaphragmatic hernias are hypoplastic but not hyperresponsive

Single-cell transcriptomic profiling of microvascular endothelial cell heterogeneity in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a neonatal anomaly that includes pulmonary hypoplasia and hypertension. We hypothesized that microvascular endothelial cell (EC) heterogeneity is different in CDH lungs and related to lung underdevelopment and remodeling. To test this, we evaluated rat fetuses at E21.5 in a nitrofen model of CDH to compare lung transcriptomes among healthy controls (2HC), nitrofen-exposed controls (NC) and nitrofen-exposed subjects with CDH. Single-cell RNA sequencing with unbiased clustering revealed 3 distinct microvascular EC clusters: a general population (mvEC), a proliferative population and a population high in hemoglobin. Only the CDH mvEC cluster had a distinct inflammatory transcriptomic signature as compared to the 2HC and NC endothelial cells, e.g. greater activation and adhesion of inflammatory cells and production of reactive oxygen species. Furthermore, CDH mvECs had downregulated Ca4, Apln and Ednrb gene expression. Those genes are markers for ECs important to lung development, gas exchange and alveolar repair (mvCa4+). mvCa4+ ECs were reduced in CDH (2HC [22.6%], NC [13.1%] and CDH [5.3%], p < 0.0001). Overall, these findings identify transcriptionally distinct microvascular endothelial cell clusters in CDH, including the distinctly inflammatory mvEC cluster and the depleted group of mvCa4+ ECs, which together may contribute to pathogenesis.

Congenital diaphragmatic hernia: searching for answers

BACKGROUND

Pulmonary hypoplasia and hypertension are the primary causes of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). At present, the origin of CDH and the causes of pulmonary hypoplasia and hypertension are unknown.

DATA SOURCES

This article reviews the available published data regarding the origin of CDH and the pathogenesis of the associated pulmonary hypertension and hypoplasia. These investigations have employed human tissues as well as two types of CDH animal models.

CONCLUSIONS

Investigations performed to date have not yet provided definitive answers regarding the pathogenesis of CDH. However, they have yielded many new and exciting discoveries and several opportunities for intervention. Ongoing research should open new possibilities to improve the outcome for these unfortunate babies with CDH.

Airway smooth muscle changes in the nitrofen-induced congenital diaphragmatic hernia rat model

In the fetal rat, nitrofen induces congenital diaphragmatic hernia (CDH) and pulmonary vascular remodeling similar to what is observed in the human condition. Airway hyperactivity is common in infants with CDH and attributed to the ventilator-induced airway damage. The purpose of this study was to test the hypothesis that airway smooth muscle mechanical properties are altered in the nitrofen-induced CDH rat model. Lungs from nitrofen-exposed fetuses with hernias (CDH) or intact diaphragm (nitrofen) and untreated fetuses (control) were studied on gestation d 21. The left intrapulmonary artery and bronchi were removed and mounted on a wire myograph, and lung expression, content, and immunolocalization of cyclooxygenases COX-1 and COX-2 were evaluated. Pulmonary artery muscle in the CDH group had significantly (p < 0.01) lower force generation compared with control and nitrofen groups. In contrast, the same generation bronchial smooth muscle of the CDH and nitrofen groups developed higher force compared with control. Whereas no differences were found in endothelium-dependent pulmonary vascular muscle tone, the epithelium-dependent airway muscle relaxation was significantly decreased (p < 0.01) in the CDH and nitrofen groups. The lung mRNA levels of COX-1 and COX-2 were increased in the CDH and nitrofen groups. COX-1 vascular and airway immunostaining, as well as COX-1 and COX-2 lung protein content, were increased in the CDH group. This is the first report of airway smooth muscle abnormalities in the nitrofen-induced fetal rat model of CDH. We speculate that congenital airway muscle changes may be present in the human form of this disease.

Oxygen-induced vasodilation is blunted in pulmonary arterioles from fetal rats with nitrofen-induced congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Persistent pulmonary hypertension contributes to the high mortality rate associated with congenital diaphragmatic hernia (CDH). Oxygen is an important stimulus for pulmonary vasodilation in the perinatal period. The authors have investigated the responses of isolated pulmonary arterioles from fetal rats with and without CDH to an increase in oxygen tension.

METHODS

CDHs were induced in fetal rats by feeding nitrofen to timed-pregnant rats at midgestation. A third-generation pulmonary arteriole was isolated from the right lung at term. Isolated arterioles were pressurized at their "optimal distending pressure." Diameter changes in response to an increase in oxygen tension from 25 to 40 mm Hg ("hypoxic" conditions) to 90 to 150 mm Hg ("normoxic" conditions) were recorded for K(+) preconstricted arterioles from control rats, from rats with nitrofen-induced CDH, and from rats that were nitrofen exposed but did not have a CDH.

RESULTS

"Normoxic" exposure reversed the K(+) preconstriction in control arterioles by 124 +/- 26%. In contrast, arterioles from rats with nitrofen-induced CDH dilated significantly less than controls (20 +/- 15% of the K(+) preconstriction). The responses of arterioles from rats that were nitrofen exposed but did not get a CDH were not different (P >.05) from controls.

CONCLUSIONS

Oxygen-induced vasodilation is blunted in pulmonary arterioles from rats with nitrofen-induced CDH. Blunted oxygen-induced vasodilation may contribute to persistent pulmonary hypertension in CDH. J Pediatr Surg 36:593-597.