Imaging RAGE expression in atherosclerotic plaques in hyperlipidemic pigs.

Lynne L Johnson,Maria Kollaros,Dhanansayan Shanmuganayagam,George Eng,Ketan Bhatia,Yared Tekabe,Christian G Krueger,Ann Marie Schmidt,Chong Li

doi:10.1186/s13550-014-0026-6

Abstract

BackgroundReceptor for advanced glycated end product (RAGE) expression is a prominent feature of atherosclerosis. We have previously shown in apoE null mice uptake of a radiolabeled anti-RAGE antibody in atherosclerotic plaque and now evaluate RAGE-directed imaging to identify advanced plaques in a large animal model.MethodsNine hyperlipidemic (HL) pigs were injected with 603.1 ± 129.5 MBq of 99mTc-anti-RAGE F(ab′)2, and after 6 h (blood pool clearance), they underwent single-photon emission computed tomography/computed tomography (SPECT/CT) imaging of the neck, thorax, and hind limbs. Two HL pigs received 99mTc non-immune IgG F(ab′)2, and three farm pigs were injected with 99mTc-anti-RAGE F(ab′)2. After imaging, the pigs were euthanized. The aorta from the root to bifurcation was dissected, and the innominates, proximal carotids, and coronaries were dissected and counted, stained for H&E and RAGE, and AHA-classified.ResultsOn pathology, 24% of the arterial segments showed AHA class III or IV lesions, and these lesions were confined almost exclusively to coronaries and carotids with % stenosis from 15% to 65%. Scatter plots of %ID/g for class III/IV vs. I/II lesions showed almost complete separation. Focal vascular uptake of tracer visualized on SPECT scans corresponded to class III/IV lesions in the coronary and carotid vessels. In addition, uptake in the hind limbs was noted in the HL pigs and corresponded to RAGE staining of small arteries in the muscle sections. Correlations for the vascular lesions were r = 0.747, P = 0.001 for %ID vs. %ID/g and r = 0.83, P = 0.002 for %ID/g vs. % RAGE staining.ConclusionsUptake of radiolabeled anti-RAGE antibody in coronary and carotid fibroatheroma and in the small arteries of the hind limbs in a relevant large animal model of atherosclerosis supports the important role of RAGE in atherosclerosis and peripheral artery disease as a target for imaging and treatment.

Highlights

Receptor for advanced glycated end product (RAGE) expression is a prominent feature of atherosclerosis
We developed a radiolabeled monoclonal antibody fragment targeting a unique peptide sequence on the extracellular domain of the RAGE receptor and have shown in mouse models of atherosclerosis uptake on in vivo nuclear scans located in the sites of the atheroma in the aortic root and proximal aorta [6,7]
Animals This study was designed as a single group of hyperlipidemic (HL) pigs for two purposes: to evaluate the extent and severity of atherosclerosis and RAGE expression in this large animal model and to see whether the signal from a radiolabeled antibody coming from this receptor can be visualized on in vivo imaging and correlated with quantitative histomorphometry

Summary

Introduction

Receptor for advanced glycated end product (RAGE) expression is a prominent feature of atherosclerosis. Receptor for advanced glycation end products (RAGE) is a multi-ligand receptor that plays an important role in the initiation and progression of atherosclerotic plaque and in mediating vascular inflammation in a variety of conditions [1,2]. Molecular imaging can show the distribution and intensity of the probe signal over the entire animal to identify the location and extent as well as the semi-quantitative expression of the target in an intact animal This imaging approach is well suited to describe the expression of a receptor such as RAGE in atherosclerosis, a disease involving the entire arterial vascular tree

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