Abstract 050: Loss of Argininosuccinate Lyase Leads to Nitric Oxide Deficiency, Endothelial Dysfunction, Impaired Angiogenesis, and Hypertension

Nitric oxide (NO) is an important mediator of vascular homeostasis and its deficiency in murine models results in hypertension. However, there are few monogenic causes of NO deficiency in humans and the effects of such genetic forms of NO deficiency on vasculature are not well-studied. We have recently shown that argininosuccinate lyase (ASL), a urea cycle enzyme, is necessary for synthesis of NO. ASL deficiency results in decreased production of NO and hypertension in humans and mice. To investigate whether loss of Asl-mediated NO synthesis in the vascular endothelium alone can cause hypertension, we generated a mouse model with endothelial-specific deletion of Asl (VE-Cadherin Cre(tg/+); Asl(flox/flox), or cKO). Asl cKO mice developed hypertension and had higher mean arterial pressure compared to control littermates (102.2± 2.9 vs. 89.8±3.6 mmHg, pu003c0.05). This hypertension was secondary to endothelial-specific NO deficiency as demonstrated by abnormal relaxation of aortic rings and correction with treatment with an NOS-independent NO supplement (MAP in sodium nitrite treated Asl cKO 97.7±3.8 vs. 97.6±7.3 mmHg in untreated control mice). To evaluate the human relevance of these findings, we developed human cell-based models from patients with ASL deficiency. Human induced pluripotent stem cells (hiPSCs) were generated and differentiated into endothelial cells. Interestingly, ASL-deficient hiPSCs differentiated less efficiently into endothelial cells as compared to control hiPSCs (9.7±4.0 vs. 20.8±3.7 % of CD144+; CD31+ cells, pu003c0.01). Furthermore, ASL-deficient hiPSCs-derived endothelial cells had a significantly reduced capacity to form capillary-like structures on Matrigel. Our study using a novel mouse model and hiPSCs-derived endothelial cells from patients with a rare Mendelian form of hypertension supports the hypothesis that structural and functional abnormalities in endothelial cells contribute to pathogenesis of hypertension. Our study is the first to use hiPSC-derived endothelial cells as a model system to study hypertension and highlights the utility of this technology in exploring the pathogenesis of other vascular diseases.