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Objective-Angiogenic expansion of the vasa vasorum is a well-known feature of progressive atherosclerosis, suggesting that antiangiogenic therapies may stabilize or regress plaques. ␣ ␤ 3 Integrin-targeted paramagnetic nanoparticles were prepared for noninvasive assessment of angiogenesis in early atherosclerosis, for site-specific delivery of antiangiogenic drug, and for quantitative follow-up of response. Methods and Results-Expression of ␣ ␤ 3 integrin by vasa vasorum was imaged at 1.5 T in cholesterol-fed rabbit aortas using integrin-targeted paramagnetic nanoparticles that incorporated fumagillin at 0 g/kg or 30 g/kg. Both formulations produced similar MRI signal enhancement (16.7%Ϯ1.1%) when integrated across all aortic slices from the renal arteries to the diaphragm. Seven days after this single treatment, integrin-targeted paramagnetic nanoparticles were readministered and showed decreased MRI enhancement among fumagillin-treated rabbits (2.9%Ϯ1.6%) but not in untreated rabbits (18.1%Ϯ2.1%). In a third group of rabbits, nontargeted fumagillin nanoparticles did not alter vascular ␣ ␤ 3 -integrin expression (12.4%Ϯ0.9%; PϾ0.05) versus the no-drug control. In a second study focused on microscopic changes, fewer microvessels in the fumagillin-treated rabbit aorta were counted compared with control rabbits. Conclusions-This study illustrates the potential of combined molecular imaging and drug delivery with targeted nanoparticles to noninvasively define atherosclerotic burden, to deliver effective targeted drug at a fraction of previous levels, and to quantify local response to treatment. Key Words: magnetic resonance imaging Ⅲ atherosclerosis Ⅲ molecular imaging Ⅲ angiogenesis Ⅲ nanoparticles Ⅲ fumagillin A key feature of the atherosclerotic process is the angiogenic expansion of the vasa vasorum in the adventitia, which extends into the thickening intimal layer of the atheroma in concert with other neovessels originating from the primary arterial lumen. 1 Extensive neovascular proliferation within atherosclerotic plaques is prominent within "culprit" lesions clinically associated with unstable angina, myocardial infarction, and stroke. [2][3][4] Plaque angiogenesis has been suggested to promote plaque growth, intraplaque hemorrhage, 5 and lesion instability.Magnetic resonance (MR) molecular imaging of focal angiogenesis in vivo with integrin-targeted paramagnetic contrast agents was reported with perfluorocarbon nanoparticles 6 -8 and liposomes. 9 Subsequently, we have developed MRI and postprocessing techniques to permit molecular imaging of the diffuse proliferating neovasculature associated with atherosclerotic plaque development. 10,11 The widespread expression of ␣ ␤ 3 integrins observed by MR agreed with the diffuse nature of angiogenesis microscopically observed in the early atherosclerotic aortas of cholesterol-fed rabbits.The importance of angiogenesis in the progression of atherosclerotic plaque combined with the antiangiogenic impact of 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase ...

Neovascularization is a critical component in the progression of malignant melanoma. The objective of this study was to determine whether ␣ ␤ 3 -targeted paramagnetic nanoparticles can detect and characterize sparse ␣ ␤ integrin expression on neovasculature induced by nascent melanoma xenografts (ϳ30 mm

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.

The goal of this research is the development of tumor imaging and radiotherapeutic agents based on targeting of the integrin alpha(v)beta(3) (vitronectin receptor). Macrocyclic chelator DOTA has been conjugated to peptidomimetic vitronectin receptor antagonist SH066 to give TA138. TA138 and (89)Y-TA138 retain antagonist properties and high affinity for integrin alpha(v)beta(3) (IC(50) = 12 and 18 nM, respectively), and good selectivity versus integrin alpha(IIb)beta(3) (IC(50) > 10,000 nM). TA138 forms stable complexes with (111)In and (90)Y in > 95% RCP. (111)In-TA138 demonstrates high tumor uptake in the c-neu Oncomouse (Charles River Laboratories [Charles River, Canada]) mammary adenocarcinoma model (9.39% ID/g at 2 hours PI) and low background activity. Blood clearance is rapid and excretion is renal. Tumors are visible as early as 0.5 hours PI. Radiotherapy studies in the c-neu Oncomouse model demonstrated a slowing of tumor growth at a dose of 15 mCi/m(2), and a regression of tumors at a dose of 90 mCi/m(2).