Noninvasive vascular cell adhesion molecule-1 imaging identifies inflammatory activation of cells in atherosclerosis

Background-Noninvasive imaging of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) may identify early stages of inflammation in atherosclerosis. We hypothesized that a novel, second-generation VCAM-1 targeted agent with enhanced affinity had sufficient sensitivity to enable real-time detection of VCAM-1 expression in experimental atherosclerosis in vivo, to quantify pharmacotherapy-induced reductions in VCAM-1 expression, and to identify activated cells in human plaques. Methods and Results-In vivo phage display in apolipoprotein E-deficient mice identified a linear peptide affinity ligand, VHPKQHR, homologous to very late antigen-4, a known ligand for VCAM-1. This peptide was developed into a multivalent agent detectable by MRI and optical imaging (denoted VINP- 28 for VCAM-1 internalizing nanoparticle 28, with 20 times higher affinity than previously reported for VNP). In vitro, VINP- 28 targeted all cell types expressing VCAM-1. In vivo, MRI and optical imaging in apolipoprotein E-deficient mice (n=28) after injection with VINP- 28 or saline revealed signal enhancement in the aortic root of mice receiving VINP-28 (P < 0.05). VINP-28 colocalized with endothelial cells and other VCAM-1-expressing cells, eg, macrophages, and was spatially distinct compared with untargeted control nanoparticles. Atheromata of atorvastatin-treated mice showed reduced VINP- 28 deposition and VCAM-1 expression. VINP- 28 enhanced early lesions in juvenile mice and resected human carotid artery plaques. Conclusions-VINP-28 allows noninvasive imaging of VCAM-1-expressing endothelial cells and macrophages in atherosclerosis and spatial monitoring of anti-VCAM-1 pharmacotherapy in vivo and identifies inflammatory cells in human atheromata. This clinically translatable agent could noninvasively detect inflammation in early, subclinical atherosclerosis.