Abstract 1454: Targeted Molecular Imaging Probes For In Vivo MR Detection Of Atherosclerotic Lesions Using Antibodies Against Oxidized Low Density Lipoprotein

Abstract

Background: Oxidized low-density lipoprotein (OxLDL) plays a key role in the initiation, progression and destabilization of atherosclerotic plaque. Molecular imaging probes that target OxLDL may allow in vivo detection of vulnerable plaques. In this study, magnetic resonance imaging (MRI) was used to detect atherosclerotic lesions in apolipoprotein deficient mice (ApoE−/−) using micelles comprised of gadolinium lipids, fluorescent rhodamine, PEG-lipids, and MDA2, a murine monoclonal antibody that binds malondialdehyde (MDA) lysine epitopes present in OxLDL. Materials and Results: Untargeted micelles, MDA2-labeled micelles and nonspecific polyclonal IgG micelles were prepared and characterized with respect to OxLDL binding capacity, pharmacokinetics, and biodistribution in wild type (WT) and ApoE−/− mice. MR imaging was performed at 9.4T over a 3-week interval after administration of 0.075 mmol Gd/kg micelles. MDA2 increased the micelle size, blood half-life, and MR efficacy relative to untargeted and IgG-micelles. Maximal plaque enhancement (>125%) was observed 72 hours post MDA2-micelle injection (Figure ). Untargeted and IgG-micelles did not exhibit significant wall enhancement at any of the time points studied. Confocal microscopy revealed that MDA2-micelles accumulate within foam cells associated with atherosclerotic plaque. WT mice showed no significant MR wall enhancement for any of the micelles studied. Conclusions: MR imaging using MDA2-micelles demonstrates specific targeting of OxLDL and foam cells and provides excellent MR image quality. This study suggests that it may be feasible to image similar atherosclerotic lesions in humans with MRI.