Vascular endothelial growth factor (VEGF) is a hypoxia-inducible endothelial cell mitogen and survival factor. Its receptor VEGFR-2 (KDR/Flk-1) mediates these effects. We studied the expression of VEGF and VEGFR-2 in ischemic human and rabbit skeletal muscle by immunohistochemistry and in situ hybridization. Human samples were obtained from eight lower limb amputations because of acute or chronic critical ischemia. In chronically ischemic human skeletal muscle VEGF and VEGFR-2 expression was restricted to atrophic and regenerating skeletal myocytes, whereas in acutely ischemic limbs VEGF and VEGFR-2 were expressed diffusely in the affected muscle. Hypoxia-inducible factor-1alpha was associated with VEGF and VEGFR-2 expression both in acute and chronic ischemia but not in regeneration. Hindlimb ischemia was induced in 20 New Zealand White rabbits by excising the femoral artery. Magnetic resonance imaging and histological sections revealed extensive ischemic damage in the thigh and leg muscles of ischemic rabbit hindlimbs with VEGF expression similar to acute human lower limb ischemia. After 1 and 3 weeks of ischemia VEGF expression was restricted to regenerating myotubes and by 6 weeks regeneration and expression of VEGF was diminished. VEGFR-2 expression was co-localized with VEGF expression in regenerating myotubes. Macrophages and an increased number of capillaries were associated with areas of ischemic muscle expressing VEGF and VEGFR-2. In conclusion, two patterns of VEGF and VEGFR-2 expression in human and rabbit ischemic skeletal muscle are demonstrated. In acute skeletal muscle ischemia VEGF and VEGFR-2 are expressed diffusely in the affected muscle. In chronic skeletal muscle ischemia and in skeletal muscle recovering from ischemia VEGF and VEGFR-2 expression are restricted to atrophic and regenerating muscle cells suggesting the operation of an autocrine pathway that may promote survival and regeneration of myocytes.

Background-18 F-Galacto-RGD is a positron emission tomography (PET) tracer binding to ␣ v ␤ 3 integrin that is expressed by macrophages and endothelial cells in atherosclerotic lesions. Therefore, we evaluated 18 F-galacto-RGD for imaging vascular inflammation by studying its uptake into atherosclerotic lesions of hypercholesterolemic mice in comparison to deoxyglucose. Methods and results-Hypercholesterolemic LDLRϪ/Ϫ ApoB 100/100 mice on a Western diet and normally fed adult C57BL/6 control mice were injected with 18 F-galacto-RGD and 3 H-deoxyglucose followed by imaging with a small animal PET/CT scanner. The aorta was dissected 2 hours after tracer injection for biodistribution studies, autoradiography, and histology. Biodistribution of 18 F-galacto-RGD was higher in the atherosclerotic than in the normal aorta. Autoradiography demonstrated focal 18 F-galacto-RGD uptake in the atherosclerotic plaques when compared with the adjacent normal vessel wall or adventitia. Plaque-to-normal vessel wall ratios were comparable to those of deoxyglucose. Although angiogenesis was not detected, 18 F-galacto-RGD uptake was associated with macrophage density and deoxyglucose accumulation in the plaques. Binding to atherosclerotic lesions was efficiently blocked in competition experiments. In vivo imaging visualized 18 F-galacto-RGD uptake colocalizing with calcified lesions of the aortic arch as seen in CT angiography. Conclusions-18 F-Galacto-RGD demonstrates specific uptake in atherosclerotic lesions of mouse aorta. In this model, its uptake was associated with macrophage density.18 F-Galacto-RGD is a potential tracer for noninvasive imaging of inflammation in atherosclerotic lesions. (Circ Cardiovasc Imaging. 2009;2:331-338.)

Background— The role of vascular endothelial growth factors (VEGFs) in large arteries has been proposed to be either vasculoprotective or proatherogenic. Because VEGF family members are used for human therapy, it is important to know whether they could enhance atherogenesis. We tested the effects of the members of the VEGF gene family on atherogenesis in LDL-receptor/apolipoprotein (apo) B48 double-knockout (LDLR/apoB48) mice using systemic adenoviral gene transfer. Methods and Results— Six groups of LDLR/apoB48-deficient mice (n=110) were kept 3 months on a Western-type diet. After 6 weeks of diet, mice were injected via tail vein with recombinant adenoviruses expressing VEGF-A, -B, -C, or -D or LacZ (1×10 9 PFU) or rhVEGF-A protein (2 μg/kg) and euthanized 6 weeks later. Also, older mice (n=36) were injected after 4 months on the diet and euthanized 6 weeks later (total time on the diet, 22 weeks) to evaluate the effects of gene transfers on the development of more mature lesions. Aortas were analyzed for the presence of macroscopic lesions, cross-sectional lesion areas, neovascularization, and cellular composition of the lesions. All groups had equivalent plasma cholesterol and triglyceride levels. Gene transfers with recombinant adenoviruses or administration of rhVEGF-A protein had no statistically significant effects on en face atherosclerotic lesions in the aorta, cross-sectional lesion area, neovascularization, or cellular composition of the lesions. Conclusions— This study shows no proatherogenic effects of adenovirus-mediated gene transfers of VEGF-A, -B, -C, or -D in the LDLR/apoB48-deficient hypercholesterolemic mice, in which lipoprotein profile and atherosclerosis closely resemble those in human disease.

Our results suggest that silencing of either SR-A or CD36 alone reduces atherogenesis in mice. However, due to reciprocal upregulation, silencing of both SR-A and CD36 is not effective.

Abstract-No mouse model is currently available where the induction of type 2 diabetes on an atherosclerotic background could be achieved without significant concomitant changes in plasma lipid levels. We crossbred 2 genetically modified mouse strains to achieve a model expressing both atherosclerosis and characteristics of type 2 diabetes. For atherosclerotic background we used low-density lipoprotein receptor-deficient mice synthetizing only apolipoprotein B100 (LDLR Ϫ/Ϫ

DOTA-RGD peptide was successfully labelled with the generator-produced 68Ga. The tracer had reasonably good specific radioactivity (8.7 ± 1.1 GBq/μmol) and was quite stable in vivo. According to ex vivo biodistribution results, 68Ga-DOTA-RGD was cleared rapidly from the blood circulation and excreted through the kidneys to the urine with high radioactivity in the intestine, lungs, spleen and liver. Autoradiography results showed significantly higher uptake of 68Ga-DOTA-RGD peptide in the atherosclerotic plaques compared to healthy vessel wall (mean ratio ± SD 1.4 ± 0.1, p = 0.0004). Conclusion We observed that 68Ga-DOTA-RGD is accumulated into the plaques of atherosclerotic mice. However, this data only shows the feasibility of the approach, while the clinical significance still remains to be proven. Further studies are warranted to assess the uptake of this tracer into human atherosclerotic plaques.

Our results suggest that in large arteries VEGF-D is mainly expressed in smooth muscle cells and that it may have a role in the maintenance of vascular homeostasis. However, in complicated lesions it was also expressed in macrophages and may contribute to plaque neovascularization. The constitutive expression of VEGFR-2 in arteries suggests that it may be one of the principal mediators of the VEGF-D effects in large arteries.

Our results indicate that the uptake of [(11)C]PK11195 is higher in inflamed atherosclerotic plaques containing a large number of inflammatory cells than in the non-inflamed plaques. However, the tracer uptake to other structures of the artery wall was also prominent and may limit the use of [(11)C]PK11195 in clinical imaging of atherosclerotic plaques.