Abstract-Vascular development and maturation are dependent on the interactions of endothelial cell integrins with surrounding extracellular matrix. Previous investigations of the primacy of certain integrins in vascular development have not addressed whether this could also be a secondary effect due to poor embryonic nutrition. Here, we show that the ␣ 5 integrin subunit and fibronectin have critical roles in blood vessel development in mouse embryos and in embryoid bodies (EBs) differentiated from embryonic stem cells (a situation in which there is no nutritional deficit caused by the mutations). In contrast, vascular development in vivo and in vitro is not strongly dependent on ␣ v or ␤ 3 integrin subunits. In mouse embryos lacking ␣ 5 integrin, greatly distended blood vessels are seen in the vitelline yolk sac and in the embryo itself. Additionally, overall blood vessel pattern complexity is reduced in ␣ 5 -null tissues. This defective vascular phenotype is correlated with a decrease in the ligand for ␣ 5 integrin, fibronectin (FN), in the endothelial basement membranes. A striking and significant reduction in early capillary plexus formation and maturation was apparent in EBs formed from embryonic stem cells lacking ␣ 5 integrin or FN compared with wild-type EBs or EBs lacking ␣ v or ␤ 3 integrin subunits. Vessel phenotype could be partially restored to FN-null EBs by the addition of whole FN to the culture system. These findings confirm a clear role for ␣ 5 and FN in early blood vessel development not dependent on embryo nutrition or ␣ v or ␤ 3 integrin subunits. Thus, successful early vasculogenesis and angiogenesis require Key Words: ␣ 5 ␤ 1 integrins Ⅲ fibronectin Ⅲ vascular development Ⅲ angiogenesis B lood vessels in vertebrate embryos can develop through either of 2 processes, vasculogenesis or angiogenesis. 1,2 In vasculogenesis, blood vessels are generated from mesodermally derived angioblasts, whereas in angiogenesis, vessels arise as sprouts from preexisting vessels by bridging or by intussusception. 2 In the mouse, vessels are formed by the migration of angioblasts in the embryo and in the blood islands in the extraembryonic tissues. During vessel development, the endothelial precursors and differentiated cells are regulated by a number of environmental cues, including growth factors (such as fibroblast growth factors and vascular endothelial growth factors), cytokines, proteoglycans, extracellular adhesive glycoproteins, and interactions with the extracellular matrix. [3][4][5][6] See coverEndothelial cell interactions with the extracellular matrix are mediated in large part by the integrin family of adhesion receptors, heterodimeric transmembrane glycoproteins, consisting of ␣ and ␤ subunits. At the cell surface, integrins can play adhesive as well as signaling functions. 7,8 Ligand specificity and signaling ability of specific integrins are determined by their heterodimeric composition. Endothelial cells have been shown to express a variety of integrins, including the following: ␣ 1 ␤ 1 , ␣...

Despite decades of research, our understanding of the processes controlling late-stage atherosclerotic plaque stability remains poor. A prevailing hypothesis is that reducing inflammation may improve advanced plaque stability, as recently tested in the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial, in which post-myocardial infarction subjects were treated with an IL-1β antibody. Here, we performed intervention studies in which smooth muscle cell (SMC) lineage-tracing Apoe mice with advanced atherosclerosis were treated with anti-IL-1β or IgG control antibodies. Surprisingly, we found that IL-1β antibody treatment between 18 and 26 weeks of Western diet feeding induced a marked reduction in SMC and collagen content, but increased macrophage numbers in the fibrous cap. Moreover, although IL-1β antibody treatment had no effect on lesion size, it completely inhibited beneficial outward remodeling. We also found that SMC-specific knockout of Il1r1 (encoding IL-1 receptor type 1) resulted in smaller lesions nearly devoid of SMCs and lacking a fibrous cap, whereas macrophage-selective loss of IL-1R1 had no effect on lesion size or composition. Taken together, these results show that IL-1β has multiple beneficial effects in late-stage murine atherosclerosis, including promotion of outward remodeling and formation and maintenance of an SMC- and collagen-rich fibrous cap.

Progress in cardiovascular gene therapy has been hampered by concerns over the safety and practicality of viral vectors and the inefficiency of current nonviral transfection techniques. We have previously reported that ultrasound exposure (USE) enhances transgene expression in vascular cells by up to 10-fold after naked DNA transfection, and enhances lipofection by up to three-fold. We report here that performing USE in the presence of microbubble echocontrast agents enhances acoustic cavitation and is associated with approximately 300-fold increments in transgene