No abstract

Aortic aneurysm is a vascular disease whereby the ECM (extracellular matrix) of a blood vessel degenerates, leading to dilation and eventually vessel wall rupture. Recently, it was shown that calcification of the vessel wall is involved in both the initiation and progression of aneurysms. Changes in aortic wall structure that lead to aneurysm formation and vascular calcification are actively mediated by vascular smooth muscle cells. Vascular smooth muscle cells in a healthy vessel wall are termed contractile as they maintain vascular tone and remain quiescent. However, in pathological conditions they can dedifferentiate into a synthetic phenotype, whereby they secrete extracellular vesicles, proliferate, and migrate to repair injury. This process is called phenotypic switching and is often the first step in vascular pathology. Additionally, healthy vascular smooth muscle cells synthesize VKDPs (vitamin K-dependent proteins), which are involved in inhibition of vascular calcification. The metabolism of these proteins is known to be disrupted in vascular pathologies. In this review, we summarize the current literature on vascular smooth muscle cell phenotypic switching and vascular calcification in relation to aneurysm. Moreover, we address the role of vitamin K and VKDPs that are involved in vascular calcification and aneurysm. Visual Overview— An online visual overview is available for this article.

We hypothesized that diabetes-induced oxidative stress may affect postischemic neovascularization. The response to unilateral femoral artery ligation was studied in wild-type or gp91 phox -deficient control or type 1 diabetic mice or in animals treated with the anti-oxidant N-acetyl-L-cysteine (NAC) or with in vivo electrotransfer of a plasmid encoding dominant-negative Rac1 (50 g) for 21 days. Postischemic neovascularization was reduced in diabetic mice in association with down-regulated vascular endothelial growth factor-A protein levels. In diabetic animals vascular endothelial growth factor levels and postischemic neovascularization were restored to nondiabetic levels by the scavenging of reactive oxygen species (ROS) by NAC administration or the inhibition of ROS generation by gp91 phox deficiency or by administration of dominant-negative Rac1. Finally, diabetes reduced the ability of adherent bone marrow-derived mononuclear cells (BM-MNCs) to differentiate into endothelial progenitor cells. Treatment with NAC (3 mmol/L), apocynin (200 mol/L), or the p38MAPK inhibitor LY333351 (10 mol/L) up-regulated the number of endothelial progenitor cell colonies derived from diabetic BM-MNCs by 1.5-, 1.6-, and 1.5-fold, respectively (P < 0.05). In the ischemic hindlimb model, injection of diabetic BM-MNCs isolated from NACtreated or gp91 phox -deficient diabetic mice increased neovascularization by ϳ1.5-fold greater than untreated diabetic BM-MNCs (P < 0.05). Thus, inhibition of NADPH oxidase-derived ROS overproduction improves the angiogenic and vasculogenic processes and restores postischemic neovascularization in type 1 diabetic mice.

Background-We hypothesized that microparticles (MPs) released after ischemia are endogenous signals leading to postischemic vasculogenesis. Methods and Results-MPs from mice ischemic hind-limb muscle were detected by electron microscopy 48 hours after unilateral femoral artery ligation as vesicles of 0.1-to 1-m diameter. After isolation by sequential centrifugation, flow cytometry analyses showed that the annexin V ϩ MP concentration was 3.5-fold higher in ischemic calves than control muscles (1392Ϯ406 versus 394Ϯ180 annexin V ϩ MPs per 1 mg; PϽ0.001) and came mainly from endothelial cells (71% of MPs are CD 144ϩ ). MPs isolated from ischemic muscles induced more potent in vitro bone marrow-mononuclear cell (BM-MNC) differentiation into cells with endothelial phenotype than those isolated from control muscles. MPs isolated from atherosclerotic plaques were ineffective, whereas those isolated from apoptotic or interleukin-1␤-activated endothelial cells also promoted BM-MNC differentiation. Interestingly, MPs from ischemic muscles produced more reactive oxygen species and expressed significantly higher levels of NADPH oxidase p47 (6-fold; PϽ0.05) and p67 subunits (16-fold; PϽ0.001) than controls, whereas gp91 subunit expression was unchanged. BM-MNC differentiation was reduced by 2-fold with MPs isolated from gp91-deficient animals compared with wild-type mice (PϽ0.05). MP effects on postischemic revascularization were then examined in an ischemic hind-limb model. MPs isolated from ischemic muscles were injected into ischemic legs in parallel with venous injection of BM-MNCs. MPs increased the proangiogenic effect of BM-MNC transplantation, and this effect was blunted by gp91 deficiency. In parallel, BM-MNC proangiogenic potential also was reduced in ABCA1 knockout mice with impaired vesiculation. Conclusion-MPs