Extremely thickened media of small pulmonary arteries in fatal pulmonary hypertension with congenital heart disease--a morphometric and clinicopathological study

Insufficient development of vessels and alveoli in lungs of infants with trisomy 18-Features of pulmonary histopathological findings from lung biopsy

The aim of this study was to evaluate the features of pulmonary histopathological changes in cases of trisomy 18 complicated with congenital heart disease and pulmonary arterial hypertension. Twenty-eight patients with trisomy 18 underwent open lung biopsy at the time of primary operation in our hospital between 2008 and 2019. We compared these histopathological findings with those from previously described groups without trisomy 18. Mean age at primary cardiac surgery was 37 days (range, 9-69 days). According to the Heath-Edwards (HE) classification, 1, 8, 12, and 5 patients were graded as 0, 1, 2, and 3, respectively, whereas 2 patients were not classifiable due to medial defects in the small pulmonary arteries (MD). Four (14.3%) and 13 (46.4%) patients presented with MD and hypoplasia of the small pulmonary arteries (HS). Fifteen (53.6%) and 21 (75.0%) patients presented with alveolar hypoplasia (AH) and alveolar wall thickening (AT). MD, HS, and AH in trisomy 18 were present frequently, differing significantly from previous reports. These findings might be associated with congenital inadequate development of vessels and alveoli in the lung, contributing to a high risk of PAH in trisomy 18.

A reliable rabbit model for hyperkinetic pulmonary hypertension

OBJECTIVE

To study the mechanisms of vascular remodeling and increased vascular reactivity, a reliable, economic, easy, and stable animal model of hyperkinetic pulmonary hypertension is needed. The purpose of this study was to construct an animal model of hyperkinetic pulmonary arterial hypertension by chronic systemic-pulmonary shunt in young rabbits.

METHODS

Thoracotomy was performed through a midsternal incision in 1-month-old rabbits, and anastomosis between the left carotid artery and pulmonary artery trunk created a chronic left-to-right shunt. After 3 months, the shunted artery was checked by echocardiography. Systolic, diastolic, and mean pulmonary arterial pressures were measured by microcatheterization. The pathologic changes of small pulmonary arteries were observed after staining with hematoxylin and eosin. Thickness and area indices were calculated.

RESULTS

High-flow pulmonary hypertension was successfully established in 24 rabbits 3 months after operation. Relative to a sham operation group, the systolic, diastolic, and mean pulmonary arterial pressures were obviously increased in the experimental group (P < .05). Histologic examination showed that the thickness of arterial wall increased, the lumen became narrowed, and thickness and area indices increased in small pulmonary arteries (P < .05).

CONCLUSIONS

We constructed a model mimicking the aberrant hemodynamic state in children with congenital heart disease with increased pulmonary blood flow to produce early characteristic morphology of hyperkinetic pulmonary hypertension. This method may provide an economic, easy, and stable animal model to study the mechanisms of pulmonary vascular remodeling in hyperkinetic pulmonary hypertension.

Advances in diagnosis and treatment of pulmonary arterial hypertension in neonates and children with congenital heart disease

BACKGROUND

This article aims to review recent advances in the diagnosis and treatment of pulmonary arterial hypertension in neonates and children with congenital heart disease.

DATA SOURCES

Articles on pulmonary arterial hypertension in congenital heart disease were retrieved from PubMed and MEDLINE published after 1958.

RESULTS

A diagnosis of primary (or idiopathic) pulmonary arterial hypertension is made when no known risk factor is identified. Pulmonary arterial hypertension associated with congenital heart disease constitutes a heterogenous group of conditions and has been characterized by congenital systemic-to-pulmonary shunts. Despite the similarities in histologic appearance of pulmonary vascular disease, there are differences between pulmonary arterial hypertension secondary to congenital systemic-to-pulmonary shunts and those with other conditions with respect to pathophysiology, therapeutic strategies, and prognosis. Revision and subclassification within the category of secondary pulmonary arterial hypertension based on pathophysiology were conducted to improve specific treatments. The timing of surgical repair is crucial to prevent and minimize risk of postoperative pulmonary arterial hypertension. Drug therapies including prostacyclin, endothelin-receptor antagonist, phosphodiesterase inhibitor, and nitric oxide have been evolved with promising results in neonates and children.

CONCLUSIONS

Among the different forms of congenital heart diseases, an early correction generally prevents subsequent development of pulmonary arterial hypertension. Emerging therapies for treatment of patients with idiopathic pulmonary arterial hypertension also improve quality of life and survival in neonates and children with congenital heart disease associated with pulmonary arterial hypertension. Heart and lung transplantation or lung transplantation in combination with repair of the underlying cardiac defect is a therapeutic option in a minority of patients. Partial repair options are also beneficial in some selected cases. Randomized controlled trials are needed to evaluate the safety and efficacy of these therapies including survival and long-term outcome.

Regulation of fibroblast growth factor-2 expression in pulmonary arterial smooth muscle cells involves increased reactive oxygen species generation

We have previously demonstrated increased fibroblast growth factor-2 (FGF-2) expression in a lamb model of increased pulmonary blood flow secondary to congenital heart disease, which may contribute to the associated increases in pulmonary arterial muscularization. However, the mechanisms underlying these increases in FGF-2 expression remain to be identified. Initially, we found that exogenous FGF-2 increased endogenous FGF-2 promoter activity and protein levels in ovine pulmonary arterial smooth muscle cells (PASMC). Furthermore, we found that these increases in FGF-2 expression were mediated by increases in superoxide levels via NADPH oxidase activation. In addition, FGF-2-mediated increases in FGF-2 expression and PASMC proliferation were attenuated by inhibition of phosphatidylinositol 3-kinase, Akt, and NADPH oxidase. Increases in FGF-2 expression could be stimulated by other factors known to increase reactive oxygen species (ROS) signaling in PASMC (endothelin-1 and transforming growth factor-beta1), whereas antioxidants attenuated these increases. Deletion constructs localized the growth factor- and ROS-sensitive region within the proximal 103 bp of the FGF-2 promoter, and sequence analysis identified a putative hypoxia response element (HRE), a DNA binding site for the ROS-sensitive transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha). Stabilization of HIF-1alpha increased FGF-2 promoter activity, whereas mutation of the putative HRE attenuated FGF-2-induced FGF-2 promoter activity. Furthermore, FGF-2 increased HIF-1alpha protein levels and consensus HRE promoter activity in PASMC via antioxidant-sensitive mechanisms. Thus we conclude that FGF-2 can stimulate its own expression in PASMC via NADPH oxidase-mediated activation of ROS-sensitive transcription factors, including HIF-1alpha. This positive feedback mechanism may contribute to pulmonary vascular remodeling associated with increased pulmonary blood flow.

Fibroblast growth factor-2 expression is altered in lambs with increased pulmonary blood flow and pulmonary hypertension

A lamb model of pulmonary hypertension, developed by inserting an aortopulmonary vascular graft (shunt), displays vascular remodeling and increased pulmonary blood flow characteristic of children with congenital heart disease. The purpose of this study was to determine whether expression of fibroblast growth factor-2 (FGF-2), a smooth muscle cell mitogen, is altered in shunt lambs. FGF-2 mRNA and protein levels were increased in lung tissue extracts from shunt lambs at 4 wk of age relative to age-matched controls (p < 0.05). FGF-2 protein levels were also increased in the pulmonary arteries and serum of shunt lambs (p < 0.05). Pulmonary arterial smooth muscle cells (PASMC) and endothelial cells (PAEC) were isolated from 4 wk-old lambs and subjected to cyclic stretch and laminar shear stress to mimic increased pulmonary blood flow. Stretch and shear increased FGF-2 promoter activity, and intracellular and extracellular FGF-2 protein levels in both cell types (p < 0.05). Exogenous FGF-2 stimulated PASMC proliferation at levels detected in the extracellular medium of sheared cells (p < 0.05). Elevated FGF-2 signaling by PASMC and PAEC exposed to increased pulmonary blood flow may play a role in the pulmonary vascular remodeling associated with the shunt model of pulmonary hypertension secondary to congenital heart disease.

Two-Stage Procedure for Pulmonary Vascular Obstructive Disease in Down Syndrome With Congenital Heart Disease

BACKGROUND

Down syndrome patients are characterized by early progression of pulmonary vascular obstructive disease because of insufficient thickness of the pulmonary arterial media. For those with congenital heart disease (CHD) associated with pulmonary hypertension (PH), a 2-stage procedure of pulmonary artery banding (PAB) and then intracardiac repair (ICR) in early infancy is performed to prevent such pulmonary vascular diseases in early infancy.

METHODS AND RESULTS

The subjects were 16 patients with Down syndrome who underwent lung biopsy during PAB and ICR. PAB was planned to be performed in early infancy and ICR approximately 1 year later. Efficacy of the 2-stage procedure was retrospectively examined with reference to pulmonary vascular disease and pulmonary diseases. The index of pulmonary vascular disease at PAB fulfilled the indication for ICR, and it was significantly lower at ICR than at PAB (p=0.0469); furthermore, PAB prevented progression of pulmonary diseases.

CONCLUSIONS

The results of the lung biopsies support the safety of the 2-stage procedure and show that it is effective for Down syndrome patients with CHD and PH.

Alterations in TGF-beta1 expression in lambs with increased pulmonary blood flow and pulmonary hypertension

The mechanisms responsible for pulmonary vascular remodeling in congenital heart disease with increased pulmonary blood flow remain unclear. We developed a lamb model of congenital heart disease and increased pulmonary blood flow utilizing an in utero placed aortopulmonary vascular graft (shunted lambs). Morphometric analysis of barium-injected pulmonary arteries indicated that by 4 wk of age, shunts had twice the pulmonary arterial density of controls (P < 0.05), and their pulmonary vessels showed increased muscularization and medial thickness at both 4 and 8 wk of age (P < 0.05). To determine the potential role of TGF-beta1 in this vascular remodeling, we investigated vascular changes in expression and localization of TGF-beta1 and its receptors TbetaRI, ALK-1, and TbetaRII in lungs of shunted and control lambs at 1 day and 1, 4, and 8 wk of life. Western blots demonstrated that TGF-beta1 and ALK-1 expression was elevated in shunts compared with control at 1 and 4 wk of age (P < 0.05). In contrast, the antiangiogenic signaling receptor TbetaRI was decreased at 4 wk of age (P < 0.05). Immunohistochemistry demonstrated shunts had increased TGF-beta1 and TbetaRI expression in smooth muscle layer and increased TGF-beta1 and ALK-1 in endothelium of small pulmonary arteries at 1 and 4 wk of age. Moreover, TbetaRI expression was significantly reduced in endothelium of pulmonary arteries in the shunt at 1 and 4 wk. Our data suggest that increased pulmonary blood flow dysregulates TGF-beta1 signaling, producing imbalance between pro- and antiangiogenic signaling that may be important in vascular remodeling in shunted lambs.