JAGGED1/NOTCH3 activation promotes aortic hypermuscularization and stenosis in elastin deficiency.

Obstructive arterial diseases, including supravalvular aortic stenosis (SVAS), atherosclerosis, and restenosis, share 2 important features: an abnormal or disrupted elastic lamellae structure and excessive smooth muscle cells (SMCs). However, the relationship between these pathological features is poorly delineated. SVAS is caused by heterozygous loss-of-function, hypomorphic, or deletion mutations in the elastin gene (ELN), and SVAS patients and elastin-mutant mice display increased arterial wall cellularity and luminal obstructions. Pharmacological treatments for SVAS are lacking, as the underlying pathobiology is inadequately defined. Herein, using human aortic vascular cells, mouse models, and aortic samples and SMCs derived from induced pluripotent stem cells of ELN-deficient patients, we demonstrated that elastin insufficiency induced epigenetic changes, upregulating the NOTCH pathway in SMCs. Specifically, reduced elastin increased levels of γ-secretase, activated NOTCH3 intracellular domain, and downstream genes. Notch3 deletion or pharmacological inhibition of γ-secretase attenuated aortic hypermuscularization and stenosis in Eln-/- mutants. Eln-/- mice expressed higher levels of NOTCH ligand JAGGED1 (JAG1) in aortic SMCs and endothelial cells (ECs). Finally, Jag1 deletion in SMCs, but not ECs, mitigated the hypermuscular and stenotic phenotype in the aorta of Eln-/- mice. Our findings reveal that NOTCH3 pathway upregulation induced pathological aortic SMC accumulation during elastin insufficiency and provide potential therapeutic targets for SVAS.

Effect of Inhaled Nitric Oxide on Hemodynamics in Lambs with 1½ Ventricle Circulation.

Inhaled nitric oxide (NO) is widely used to treat postoperative pulmonary hypertension in congenital heart disease. It is believed that NO increases cardiac output (CO) by decreasing pulmonary vascular resistance (PVR), leading to increased left ventricular preload. However, the effect of NO on CO in patients with 1½ ventricle circulation remains unclear. To evaluate this, a superior cavopulmonary (SCP) shunt was constructed in 10 juvenile sheep. A PTFE graft was inserted between the superior vena cava (SVC) and the main pulmonary artery (PA). The SVC was clamped at the right atrial junction to establish a 1½ ventricle circulation. Flows, pressures, and arterial blood gases were recorded before and during inhalation of NO. Mean arterial pressure (46.6 ± 5.4 to 44.6 ± 5.9 mm Hg; p = 0.06) and left atrial pressure (4.0 ± 2.5 to 4.0 ± 2.3 mm Hg; p = 1.0) did not change. Mean PA pressure (13.6 ± 2.4 to 11.7 ± 2.9 mm Hg; p = 0.006) and PVR (5.47 ± 2.99 to 4.54 ± 2.61 Wood Units; p = 0.037) decreased significantly. SVC flow (24.8 ± 11.3 to 22.0 ± 9.7 ml/min/kg; p = 0.09) did not change, and CO decreased (140.2 ± 37.2 to 132.1 ± 39.2 ml/min/kg; p = 0.033). Arterial PO2 improved (103.72 ± 29.30 to 132.43 ± 47.02 mm Hg; p = 0.007). In this 1½ ventricle model, NO surprisingly decreased cardiac output (CO) and did not increase left ventricular preload.

Identification and characterization of cells with high angiogenic potential and transitional phenotype in calcific aortic valve.

Recent data suggest that angiogenesis plays an important role in the pathogenesis of valvular disease. However, the cellular mechanisms underlying this process remain unknown. This study aimed at identifying and characterizing the cellular components responsible for pathological neovascularization in calcific aortic valves (CAV). Immunohistochemical analysis of uncultured CAV tissues revealed that smooth muscle alpha-actin (alpha-SMA)-positive cells, which coexpressed Tie-2 and vascular endothelial growth factor receptor-2 (VEGFR-2), can be identified prior to the initiation of capillary-like tube formation. In a second step, leaflets of CAV and non-calcific aortic valves (NCAV) were cultured and the cells involved in capillary-like tube formation were isolated. The majority of these cells displayed the same phenotype as non-cultured cells identified in CAV tissues, i.e., expression of alpha-SMA, Tie-2, and VEGFR-2. In comparison to cells isolated from cultures of NCAV leaflets, these cells showed enhanced angiogenic activity as demonstrated by migration and tube assays. The coexpression of VEGFR-2 and Tie-2 together with alpha-SMA suggests both endothelial and mesenchymal properties of the angiogenically activated cells involved in valvular neovascularization. Hence, our findings might provide new insights into the process of pathological angiogenesis in cardiac valves.