Rationale:: Endothelial cells have the ability to undergo endothelial–mesenchymal transitions (EndMTs), by which they acquire a mesenchymal phenotype and stem cell–like characteristics. We previously found that EndMTs occurred in the endothelium deficient in matrix γ-carboxyglutamic acid protein enabling endothelial cells to contribute cells to vascular calcification. However, the mechanism responsible for initiating EndMTs is not fully understood. Objective:: To determine the role of specific serine proteases and sex determining region Y-box 2 (Sox2) in the initiation of EndMTs. Methods and Results:: In this study, we used in vivo and in vitro models of vascular calcification to demonstrate that serine proteases and Sox2 are essential for the initiation of EndMTs in matrix γ-carboxyglutamic acid protein–deficient endothelium. We showed that expression of a group of specific serine proteases was highly induced in endothelial cells at sites of vascular calcification in Mgp null aortas. Treatment with serine protease inhibitors decreased both stem cell marker expression and vascular calcification. In human aortic endothelial cells, this group of serine proteases also induced EndMTs, and the activation of proteases was mediated by Sox2. Knockdown of the serine proteases or Sox2 diminished EndMTs and calcification. Endothelial-specific deletion of Sox2 decreased expression of stem cell markers and aortic calcification in matrix γ-carboxyglutamic acid protein–deficient mice. Conclusions:: Our results suggest that Sox2-mediated activation of specific serine proteases is essential for initiating EndMTs, and thus, may provide new therapeutic targets for treating vascular calcification.

Endoglin is involved in the regulation of endothelial function, but there are no studies concerning its relation with hypertension- and diabetes-associated pathologies. Thus, we studied the relationship between plasma levels of soluble endoglin and cardiovascular alterations associated with hypertension and diabetes.

Cerebral arteriovenous malformations (AVMs) are common vascular malformations, which may result in hemorrhagic strokes and neurological deficits. Bone morphogenetic protein (BMP) and Notch signaling are both involved in the development of cerebral AVMs, but the cross-talk between the two signaling pathways is poorly understood. Here, we show that deficiency of matrix Gla protein (MGP), a BMP inhibitor, causes induction of Notch ligands, dysregulation of endothelial differentiation, and the development of cerebral AVMs in MGP null (Mgp^−/−) mice. Increased BMP activity due to the lack of MGP induces expression of the activin receptor-like kinase 1, a BMP type I receptor, in cerebrovascular endothelium. Subsequent activation of activin receptor-like kinase 1 enhances expression of Notch ligands Jagged 1 and 2, which increases Notch activity and alters the expression of Ephrin B2 and Ephrin receptor B4, arterial and venous endothelial markers, respectively. Reducing the expression of Jagged 1 and 2 in the Mgp^−/− mice by crossing them with Jagged 1 or 2 deficient mice reduces Notch activity, normalizes endothelial differentiation, and prevents cerebral AVMs, but not pulmonary or renal AVMs. Our results suggest that Notch signaling mediates and can modulate changes in BMP signaling that lead to cerebral AVMs. Significance Cerebral arteriovenous malformations (AVMs) are common vascular abnormalities that may lead to strokes. Signaling by bone morphogenetic proteins (BMPs) and Notch play important roles in the formation of cerebral AVMs, but the cross-talk between the pathways is poorly understood. We report that gene deletion of matrix Gla protein (MGP), a BMP inhibitor, causes cerebral AVMs in mice by activating activin receptor-like kinase 1, a BMP receptor. This activation enhances Notch activity and disrupts endothelial cell differentiation by inducing the Notch ligands Jagged 1 and 2. Reducing Jagged 1 and 2 expression prevents the disruption in differentiation and AVM formation. The findings suggest that MGP maintains the balance between BMP and Notch signaling and promotes a normal brain vasculature.

Oxidative stress is associated with cardiac and vascular defects leading to hypertension and atherosclerosis, being superoxide dismutase (SOD) one of the main intracellular antioxidant defence mechanisms. Although several parameters of vascular function and structure have a predictive value for cardiovascular morbidity‐mortality in hypertensive patients, there are no studies on the involvement of SOD serum levels with these vascular parameters. Thus, we assessed if SOD serum levels are correlated with parameters of vascular function and structure and with cardiovascular risk in hypertensive and type 2 diabetic patients. We enrolled 255 consecutive hypertensive and diabetic patients and 52 nondiabetic and nonhypertensive controls. SOD levels were measured with an enzyme‐linked immunosorbent assay kit. Vascular function and structure were evaluated by pulse wave velocity, augmentation index, ambulatory arterial stiffness index, and carotid intima‐media thickness. We detected negative correlations between SOD and pressure wave velocity, peripheral and central augmentation index and ambulatory arterial stiffness index, pulse pressure, and plasma HDL‐cholesterol, as well as positive correlations between SOD and plasma uric acid and triglycerides. Our study shows that SOD is a marker of cardiovascular alterations in hypertensive and diabetic patients, since changes in its serum levels are correlated with alterations in vascular structure and function.