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Rationale: There are conflicting data on the effects of vascular endothelial growth factor (VEGF) in vascular remodeling. Furthermore, there are species-specific differences in leukocyte and vascular cell biology and little is known about the role of VEGF in remodeling of human arteries., Objective: We sought to address the role of VEGF blockade on remodeling of human arteries in vivo., Methods and Results: We used an anti-VEGF antibody, bevacizumab, to study the effect of VEGF blockade on remodeling of human coronary artery transplants in severe combined immunodeficient mice. Bevacizumab ameliorated peripheral blood mononuclear cell-induced but not interferon-gamma-induced neointimal formation. This inhibitory effect was associated with a reduction in graft T-cell accumulation without affecting T-cell activation. VEGF enhanced T-cell capture by activated endothelium under flow conditions. The VEGF effect could be recapitulated when a combination of recombinant intercellular adhesion molecule 1 and vascular cell adhesion molecule-1 rather than endothelial cells was used to capture T cells. A subpopulation of CD3+ T cells expressed VEGF receptor (VEGFR)-1 by immunostaining and FACS analysis. VEGFR-1 mRNA was also detectable in purified CD4+ T cells and Jurkat and HSB-2 T-cell lines. Stimulation of HSB-2 and T cells with VEGF triggered downstream ERK phosphorylation, demonstrating the functionality of VEGFR-1 in human T cells., Conclusions: VEGF contributes to vascular remodeling in human arteries through a direct effect on human T cells that enhances their recruitment to the vessel. These findings raise the possibility of novel therapeutic approaches to vascular remodeling based on inhibition of VEGF signaling.

Vascular remodeling is a common feature of many vasculopathies, including graft arteriosclerosis (GA). We investigated whether endothelial and smooth muscle cell-derived neuropilin-like protein (ESDN) is a marker of vascular remodeling in GA. Immunostaining of human coronary arteries demonstrated high levels of ESDN in GA, but not in normal arteries. In a model of GA, where a segment of human coronary is transplanted into a severe combined immunodeficient mouse, followed by allogeneic human peripheral blood mononuclear cell (PBMC) reconstitution, ESDN was minimally expressed in transplanted human arteries in the absence of reconstitution. By 2 weeks following PBMC reconstitution, at a time corresponding to maximal vascular cell proliferation, high levels of ESDN were detected in the transplanted arteries. Similarly, injury-induced vascular remodeling in apoE(-/-) mice was associated with early and transient ESDN upregulation, in parallel with cell proliferation. In vascular smooth muscle cell (VSMC) cultures, ESDN expression was significantly higher in proliferating, as compared to growth-arrested cells. ESDN overexpression in VSMC led to a decline in growth curves, while ESDN knock down had the opposite effect. We conclude that ESDN is a marker of vascular remodeling and regulator of VSMC proliferation. ESDN may serve as a therapeutic or diagnostic target for GA.

Graft arteriopathy (GA), characterized by diffuse concentric narrowing of coronary arteries, is the major cause of late graft failure in cardiac transplantation. alphavbeta3 Integrin is up-regulated in proliferating vascular cells and may constitute an appropriate target for imaging GA. We used a human/mouse chimeric model of GA, in which segments of human coronary artery were transplanted to severe combined immunodeficiency mice, followed by reconstitution with allogeneic human peripheral blood mononuclear cells (PBMC). This led to vascular remodeling characterized by neointima formation over a period of 4 wk. alphavbeta3 expression in the graft was minimal in animals without PBMC, considerably increased by 2 wk, and decreased toward baseline by 4 wk after PBMC reconstitution. Cell proliferation was maximal at 2 wk, correlating with peak alphavbeta3 expression. RP748, an 111In-labeled alphavbeta3 (active conformation)-targeted radiotracer was injected into groups of 5 recipients at 0, 2, and 4 wk after PBMC reconstitution. Relative uptakes, defined as autoradiographic intensity in the graft/native aortas closely tracked the proliferative process. Specificity of uptake was demonstrated using excess nonlabeled tracer. In conclusion, alphavbeta3 integrin is transiently up-regulated (and activated) in GA and may be targeted by RP748 for detection of the proliferative process in early GA.

Noninvasive imaging strategies will be critical for defining the temporal characteristics of angiogenesis and assessing efficacy of angiogenic therapies. The alphavbeta3 integrin is expressed in angiogenic vessels and represents a potential novel target for imaging myocardial angiogenesis. We demonstrated the localization of an indium-111-labeled ((111)In-labeled) alphavbeta3-targeted agent in the region of injury-induced angiogenesis in a chronic rat model of infarction. The specificity of the targeted alphavbeta3-imaging agent for angiogenesis was established using a nonspecific control agent. The potential of this radiolabeled alphavbeta3-targeted agent for in vivo imaging was then confirmed in a canine model of postinfarction angiogenesis. Serial in vivo dual-isotope single-photon emission-computed tomographic (SPECT) imaging with the (111)In-labeled alphavbeta3-targeted agent demonstrated focal radiotracer uptake in hypoperfused regions where angiogenesis was stimulated. There was a fourfold increase in myocardial radiotracer uptake in the infarct region associated with histological evidence of angiogenesis and increased expression of the alphavbeta3 integrin. Thus, angiogenesis in the heart can be imaged noninvasively with an (111)In-labeled alphavbeta3-targeted agent. The noninvasive evaluation of angiogenesis may have important implications for risk stratification of patients following myocardial infarction. This approach may also have significant clinical utility for noninvasively tracking therapeutic myocardial angiogenesis.