Background-Angiogenesis is a critical feature of plaque development in atherosclerosis and might play a key role in both the initiation and later rupture of plaques that lead to myocardial infarction and stroke. The precursory molecular or cellular events that initiate plaque growth and that ultimately contribute to plaque instability, however, cannot be detected directly with any current diagnostic modality. Methods and Results-Atherosclerosis was induced in New Zealand White rabbits fed 1% cholesterol for Ϸ80 days.␣ v ␤ 3 -Integrin-targeted, paramagnetic nanoparticles were injected intravenously and provided specific detection of the neovasculature within 2 hours by routine magnetic resonance imaging (MRI) at a clinically relevant field strength (1.5 T). Increased angiogenesis was detected as a 47Ϯ5% enhancement in MRI signal averaged throughout the abdominal aortic wall among rabbits that received ␣ v ␤ 3 -targeted, paramagnetic nanoparticles. Pretreatment of atherosclerotic rabbits with ␣ v ␤ 3 -targeted, nonparamagnetic nanoparticles competitively blocked specific contrast enhancement of the ␣ v ␤ 3 -targeted paramagnetic agent. MRI revealed a pattern of increased ␣ v ␤ 3 -integrin distribution within the atherosclerotic wall that was spatially heterogeneous along both transverse and longitudinal planes of the abdominal aorta. Histology and immunohistochemistry confirmed marked proliferation of angiogenic vessels within the aortic adventitia, coincident with prominent, neointimal proliferation among cholesterol-fed, atherosclerotic rabbits in comparison with sparse incidence of neovasculature in the control animals. Conclusions-This molecular imaging approach might provide a method for defining the burden and evolution of atherosclerosis in susceptible individuals as well as responsiveness of individual patients to antiatherosclerotic therapies.

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 ...

BackgroundCommunity acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA) increasingly causes disease worldwide. USA300 has emerged as the predominant clone causing superficial and invasive infections in children and adults in the USA. Epidemiological studies suggest that USA300 is more virulent than other CA-MRSA. The genetic determinants that render virulence and dominance to USA300 remain unclear.ResultsWe sequenced the genomes of two pediatric USA300 isolates: one CA-MRSA and one CA-methicillin susceptible (MSSA), isolated at Texas Children's Hospital in Houston. DNA sequencing was performed by Sanger dideoxy whole genome shotgun (WGS) and 454 Life Sciences pyrosequencing strategies. The sequence of the USA300 MRSA strain was rigorously annotated. In USA300-MRSA 2658 chromosomal open reading frames were predicted and 3.1 and 27 kilobase (kb) plasmids were identified. USA300-MSSA contained a 20 kb plasmid with some homology to the 27 kb plasmid found in USA300-MRSA. Two regions found in US300-MRSA were absent in USA300-MSSA. One of these carried the arginine deiminase operon that appears to have been acquired from S. epidermidis. The USA300 sequence was aligned with other sequenced S. aureus genomes and regions unique to USA300 MRSA were identified.ConclusionUSA300-MRSA is highly similar to other MRSA strains based on whole genome alignments and gene content, indicating that the differences in pathogenesis are due to subtle changes rather than to large-scale acquisition of virulence factor genes. The USA300 Houston isolate differs from another sequenced USA300 strain isolate, derived from a patient in San Francisco, in plasmid content and a number of sequence polymorphisms. Such differences will provide new insights into the evolution of pathogens.