Targeted Iron Oxide Particles for In Vivo Magnetic Resonance Detection of Atherosclerotic Lesions With Antibodies Directed to Oxidation-Specific Epitopes

Abstract

Objectives The aim of this study was to determine whether iron oxide particles targeted to oxidation-specific epitopes image atherosclerotic lesions. Background Oxidized low-density lipoprotein plays a major role in atherosclerotic plaque progression and destabilization. Prior studies indicate that gadolinium micelles labeled with oxidation-specific antibodies allow for in vivo detection of vulnerable plaques with magnetic resonance imaging (MRI). However, issues related to biotransformation/retention of gadolinium might limit clinical translation. Iron oxides are recognized as safe and effective contrast agents for MRI. Because the efficacy of passively targeted iron particles remains variable, it was hypothesized that iron particles targeted to oxidation-specific epitopes might increase the utility of this platform. Methods Lipid-coated ultra-small superparamagnetic iron particles (LUSPIOs) (<20 nm) and superparamagnetic iron particles (<40 nm) were conjugated with antibodies targeted to either malondialdehyde-lysine or oxidized phospholipid epitopes. All formulations were characterized, and their in vivo efficacy evaluated in apolipoprotein E deficient mice 24 h after bolus administration of a 3.9-mg Fe/kg dose with MRI. In vivo imaging data were correlated with the presence of oxidation-specific epitopes with immunohistochemistry. Results MRI of atherosclerotic lesions, as manifested by signal loss, was observed after administration of targeted LUSPIOs. Immunohistochemistry confirmed the presence of malondialdehyde-epitopes and iron particles. Limited signal attenuation was observed for untargeted LUSPIOs. Additionally, no significant arterial wall uptake was observed for targeted or untargeted lipid-coated superparamagnetic iron oxide particles, due to their limited ability to penetrate the vessel wall. Conclusions This study demonstrates that LUSPIOs targeted to oxidation-specific epitopes image atherosclerotic lesions and suggests a clinically translatable platform for the detection of atherosclerotic plaque.

Differential expression of oxidation-specific epitopes and apolipoprotein(a) in progressing and ruptured human coronary and carotid atherosclerotic lesions

“…For example, MB47 detects not only the native apoB-100 moiety of unoxidized LDL but also apoB of minimally oxidized LDL and even apoB fragments of extensively oxidized LDL. MDA2 can recognize both MDA-LDL as well as MDA-lysine epitopes on other proteins in the vessel wall, such as apoAI ( 28,29 ), and it has also been utilized for noninvasive imaging of experimental atherosclerotic lesions (3)(4)(5). E06 is a well-characterized murine IgM natural antibody cloned from apoE Ϫ / Ϫ mice ( 20 ) that has previously been used to stain mouse and rabbit atherosclerotic lesions and to image atherosclerotic lesions in apoE Ϫ / Ϫ mice using magnetic resonance techniques (3)(4)(5).…”

“…IK17 is a human Fab fragment derived from a phage display library, and it binds to a unique MDA-like epitope present on both MDA-LDL and copper-oxidized LDL. IK17 has also been used in detecting and imaging atherosclerosis in LDLR Ϫ / Ϫ mice and apoE Ϫ / Ϫ mice (3)(4)(5)22 ).…”

Specific penetration and accumulation of a homing peptide within atherosclerotic plaques of apolipoprotein E-deficient mice

“…However, within the time frame we studied, we found no significant accumulation of nontargeted nanoparticles in plaques. In addition, a report by Briley-Saebo et al (28) indicated that the intraplaque macrophage uptake of ∼35-nm iron oxide particles is limited by the ability of the particles to traverse through the arterial endothelial wall. Our results show that providing the nanoparticles with a LyP-1 coating overcomes this obstacle.…”

Superparamagnetic Iron Oxide Nanoparticles in Biomedicine: Applications and Developments in Diagnostics and Therapy

“…As a result, apoptotic foam cells [133], oxidation-specific epitopes (malondialdehyde-lysine-epitopes of MDA-LDL [134]), oxidized phospholipid epitopes [134], scavenger receptors type A (with sulfated, dextran-coated SPIO) [135], VCAM-1 [136], E-and P-selectin [136], or oxidated LDL [137] in vulnerable and inflammatory plaques were able to be successfully labeled. In molecular myocardial infarction imaging, the use of MION-conjugated antimyosin-F ab (MION-R11D10) against myosin for labeling an infarcted myocardium is described [138].…”