Aneurysm-type plexiform lesions form in supernumerary arteries in pulmonary arterial hypertension: potential therapeutic implications

Dysregulated VEGF/VEGFR-2 Signaling and Plexogenic Lesions in the Embryonic Lungs of Chickens Predisposed to Pulmonary Arterial Hypertension

Plexiform lesions are a hallmark of pulmonary arterial hypertension (PAH) in humans and are proposed to stem from dysfunctional angioblasts. Broiler chickens (Gallus gallus) are highly susceptible to PAH, with plexiform-like lesions observed in newly hatched individuals. Here, we reported the emergence of plexiform-like lesions in the embryonic lungs of broiler chickens. Lung samples were collected from broiler chickens at embryonic day 20 (E20), hatch, and one-day-old, with PAH-resistant layer chickens as controls. Plexiform lesions consisting of CD133+/vascular endothelial growth factor receptor type-2 (VEGFR-2)+ angioblasts were exclusively observed in broiler embryos and sporadically in layer embryos. Distinct gene profiles of angiogenic factors were observed between the two strains, with impaired VEGF-A/VEGFR-2 signaling correlating with lesion development and reduced arteriogenesis. Pharmaceutical inhibition of VEGFR-2 resulted in enhanced lesion development in layer embryos. Moreover, broiler embryonic lungs displayed increased activation of HIF-1α and nuclear factor erythroid 2-related factor 2 (Nrf2), indicating a hypoxic state. Remarkably, we found a negative correlation between lung Nrf2 activation and VEGF-A and VEGFR-2 expression. In vitro studies indicated that Nrf2 overactivation restricted VEGF signaling in endothelial progenitor cells. The findings from broiler embryos suggest an association between plexiform lesion development and impaired VEGF system due to aberrant activation of Nrf2.

Chest computed tomography findings of ground-glass nodules with enhancing central vessel/nodule in pediatric patients with BMPR2 mutations and plexogenic arteriopathy

BACKGROUND

Germline mutation in bone morphogenetic protein type II (BMPR2) is the most common cause of idiopathic/heritable pulmonary hypertension in pediatric patients. Despite the discovery of this gene there are no known descriptions of the CT or CT angiography findings in these children.

OBJECTIVE

To correlate the clinical presentation, pathology and chest CT findings in pediatric patients with pulmonary hypertension caused by mutations in the BMPR2 gene.

MATERIALS AND METHODS

We performed a search to identify pediatric patients with a BMPR2 mutation and CT or CT angiography with the clinical history of pulmonary hypertension. Three pediatric radiologists reviewed the children's CT imaging findings and ranked the dominant findings in order of prevalence via consensus.

RESULTS

We identified three children with pulmonary hypertension and confirmed germline BMPR2 mutations, two of whom had undergone lung biopsy. We then correlated the imaging findings with histopathology and clinical course.

CONCLUSION

All of our patients with BMPR2 mutations demonstrated a distinct CT pattern of ground-glass nodules with a prominent central enhancing vessel/nodule. These findings correlated well with the pathological findings of plexogenic arteriopathy.

Shunt-type plexiform lesions identified in the Sugen5416/Hypoxia rat model of pulmonary arterial hypertension using SPµCT

We recently described four distinct types of plexiform lesions in human idiopathic and familial pulmonary arterial hypertension (PAH) [1], visualising the three-dimensional lesion structure using synchrotron-based phase-contrast micro-computed tomography (SPµCT). Two types, 1 and 2, are shunt-type lesions that connect pulmonary arteries to the bronchial circulation: type 1 to the vasa vasorum, and type 2 to peribronchial vessels. Type 3 lesions are found peripherally in the lung as spherical structures abruptly terminating the distal pulmonary artery/arteriole, and type 4 lesions are characterised by recanalisation of an occluded artery/arteriole. Our observation of type 1 and type 2 lesions in PAH supports previous work that demonstrated intrapulmonary bronchopulmonary anastomoses (IBAs) connected to plexiform lesions in human PAH, suggesting that shunting of blood can occur within lesions in the setting of supra-systemic pulmonary arterial pressure [2]. Further haemodynamic studies of distinct subtypes of plexiform lesions have been hampered by the lack of available animal models with plexiform lesions representative of the full range of lesion types found in human disease. Plexiform lesions have previously been described in the Sugen5416/hypoxia rat model of pulmonary hypertension when time until sacrifice following hypoxia is extended to 13–14 weeks. Initially plexiform lesions were identified within the pulmonary artery, as well as in the form of aneurysm-like lesions projecting outside the vessel lumen [3], and recently the latter type was shown to form in supernumerary arteries [4]. However, neither study observed plexiform lesions communicating with the bronchial circulation, possibly because of methodological limitations of the histological analysis.

Human like plexiform lesions identified in the prolonged Sugen5416/hypoxia rat model, visualised by synchrotron tomography imaging https://bit.ly/3KQvDHg

Distinct types of plexiform lesions identified by synchrotron-based phase-contrast micro-CT

In pulmonary arterial hypertension, plexiform lesions are associated with severe arterial obstruction and right ventricular failure. Exploring their structure and position is crucial for understanding the interplay between hemodynamics and vascular remodeling. The aim of this research was to use synchrotron-based phase-contrast micro-CT to study the three-dimensional structure of plexiform lesions. Archived paraffin-embedded tissue samples from 14 patients with pulmonary arterial hypertension (13 idiopathic, 1 with known BMPR2-mutation) were imaged. Clinical data showed high-median PVR (12.5 WU) and mPAP (68 mmHg). Vascular lesions with more than 1 lumen were defined as plexiform. Prior radiopaque dye injection in some samples facilitated 3-D rendering. Four distinct types of plexiform lesions were identified: 1) localized within or derived from monopodial branches (supernumerary arteries), often with a connection to the vasa vasorum; 2) localized between pulmonary arteries and larger airways as a tortuous transformation of intrapulmonary bronchopulmonary anastomoses; 3) as spherical structures at unexpected abrupt ends of distal pulmonary arteries; and 4) as occluded pulmonary arteries with recanalization. By appearance and localization, types 1-2 potentially relieve pressure via the bronchial circulation, as pulmonary arteries in these patients were almost invariably occluded distally. In addition, types 1-3 were often surrounded by dilated thin-walled vessels, often connected to pulmonary veins, peribronchial vessels, or the vasa vasorum. Collaterals, bypassing completely occluded pulmonary arteries, were also observed to originate within plexiform lesions. In conclusion, synchrotron-based imaging revealed significant plexiform lesion heterogeneity, resulting in a novel classification. The four types likely have different effects on hemodynamics and disease progression.

Development of an endothelial cell-restricted transgenic reporter rat: a resource for physiological studies of vascular biology

Here, we report the generation of a Cre-recombinase (iCre) transgenic rat, where iCre is driven using a vascular endothelial-cadherin (CDH5) promoter. The CDH5 promoter was cloned from rat pulmonary microvascular endothelial cells and demonstrated ~60% similarity to the murine counterpart. The cloned rat promoter was 2,508 bp, it extended 79 bp beyond the transcription start site, and it was 22,923 bp upstream of the translation start site. The novel promoter was cloned upstream of codon-optimized iCre and subcloned into a Sleeping Beauty transposon vector for transpositional transgenesis in Sprague-Dawley rats. Transgenic founders were generated and selected for iCre expression. Crossing the CDH5-iCre rat with a tdTomato reporter rat resulted in progeny displaying endothelium-restricted fluorescence. tdTomato fluorescence was prominent in major arteries and veins, and it was similar in males and females. Quantitative analysis of the carotid artery and the jugular vein revealed that, on average, more than 50% of the vascular surface area exhibited strong fluorescence. tdTomato fluorescence was observed in the circulations of every tissue tested. The microcirculation in all tissues tested displayed homogenous fluorescence. Fluorescence was examined across young (6-7.5 mo), middle (14-16.5 mo), and old age (17-19.5 mo) groups. Although tdTomato fluorescence was seen in middle- and old-age animals, the intensity of the fluorescence was significantly reduced compared with that seen in the young rats. Thus, this endothelium-restricted transgenic rat offers a novel platform to test endothelial microheterogeneity within all vascular segments, and it provides exceptional resolution of endothelium within-organ microcirculation for application to translational disease models.NEW & NOTEWORTHY The use of transgenic mice has been instrumental in advancing molecular insight of physiological processes, yet these models oftentimes do not faithfully recapitulate human physiology and pathophysiology. Rat models better replicate some human conditions, like Group 1 pulmonary arterial hypertension. Here, we report the development of an endothelial cell-restricted transgenic reporter rat that has broad application to vascular biology. This first-in-kind model offers exceptional endothelium-restricted tdTomato expression, in both conduit vessels and the microcirculations of organs.

Newer approaches and novel drugs for inhalational therapy for pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of small pulmonary arteries leading to increased pulmonary arterial pressure. Existing treatments acts to normalize vascular tone via three signaling pathways: the prostacyclin, the endothelin-1, and the nitric oxide. Although over the past 20 years, there has been considerable progress in terms of treatments for PAH, the disease still remains incurable with a disappointing prognosis.Areas covered: This review summarizes the pathophysiology of PAH, the advantages and disadvantages of the inhalation route, and assess the relative advantages various inhaled therapies for PAH. The recent studies concerning the development of controlled-release drug delivery systems loaded with available anti-PAH drugs have also been summarized.Expert opinion: The main obstacles of current pharmacotherapies of PAH are their short half-life, stability, and formulations, resulting in reducing the efficacy and increasing systemic side effects and unknown pathogenesis of PAH. The pulmonary route has been proposed for delivering anti-PAH drugs to overcome the shortcomings. However, the application of approved inhaled anti-PAH drugs is limited. Inhalational delivery of controlled-release nanoformulations can overcome these restrictions. Extensive studies are required to develop safe and effective drug delivery systems for PAH patients.