Near-infrared fluorescence imaging of murine atherosclerosis using an oxidized low density lipoprotein-targeted fluorochrome

Abstract

The aim of this study was to explore the feasibility of detecting plaques using an NIR797 fluorochrome-labeled, anti-oxLDL antibody (anti-oxLDL-NIR797) and near-infrared fluorescence (NIRF) imaging in a murine model of atherosclerosis. Anti-mouse oxLDL polyclonal antibodies were conjugated to NIR797 dyes to synthesis oxLDL-targeted NIRF probe. In situ and ex vivo NIRF imaging of the high-cholesterol diet-induced atherosclerotic lesions of apoE-/- mice (baseline) as well as ex vivo NIRF imaging in the progression and regression group (without or with atorvastatin treatment for another 8 weeks) were performed 24 h after an intravenous injection of 1 mg/kg of anti-oxLDL-NIR797, while phosphate-buffered saline (PBS) was used for the controls. The plaque areas were investigated using Oil Red O (ORO) staining. Aortas isolated from the apoE-/- mice 24 h post-injection exhibited a selective, strong, heterogeneous NIRF signal enhancement in the aortic root, arch, and bifurcation, whereas the PBS and competitive inhibition groups had limited NIRF signal changes (p < 0.05). There was a significant correlation between ORO staining and NIRF in the atherosclerotic aortas that received anti-oxLDL-NIR797. Immunofluorescence studies confirmed the colocalization of the oxLDL/macrophages and NIR797 fluorochromes. Furthermore, the atherosclerotic lesions of atorvastatin-treated mice showed reduced anti-oxLDL-NIR797 uptake and oxLDL expression. These results indicate that NIRF plaque imaging is feasible with an oxLDL-targeted NIRF probe. Thus, oxLDL-based molecular imaging of atherosclerotic plaques is feasible and may provide important methods for characterizing vulnerable plaques and monitoring the response to therapeutic interventions for atherosclerosis.