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Evaluation of [99mTc]Radiolabeled Macrophage Mannose Receptor-Specific Nanobodies for Targeting of Atherosclerotic Lesions in Mice.

Abstract：

PURPOSE:Macrophage accumulation characterizes the development of atherosclerotic plaques, and the presence of certain macrophage subsets might be an indicator of plaque phenotype and (in)stability. The macrophage mannose receptor (MMR) is expressed on alternatively activated macrophages and found at sites of intraplaque hemorrhage and neovascularization. It has been proposed as target to identify vulnerable plaques. Therefore, we aimed to assess the feasibility of using anti-MMR nanobodies (Nbs) as molecular tracers for nuclear imaging in an animal model of atherosclerosis. PROCEDURE:Anti-MMR and control Nb, radiolabeled with Tc-99m, were injected in ApoE-/- and/or C57Bl/6 mice (n = 6). In vivo competition studies involving pre-injection of excess of unlabeled anti-MMR Nb (n = 3) and injection of anti-MMR Nb in MMR-/- mice (n = 3) were performed to demonstrate specificity. At 3 h p.i. radioactive uptake in organs, tissues and aorta segments were evaluated. Autoradiography and immunofluorescence were performed on aortic sections. RESULTS:Significantly higher uptake was observed in all aortic segments of ApoE-/- mice injected with anti-MMR Nb compared to control Nb (1.36 ± 0.67 vs 0.38 ± 0.13 percent of injected dose per gram (%ID/g), p ≤ 0.001). Surprisingly, high aortic uptake was also observed in C57Bl/6 mice (1.50 ± 0.43%ID/g, p ≥ 0.05 compared to ApoE-/-), while aortic uptake was reduced to background levels in the case of competition and in MMR-/- mice (0.46 ± 0.10 and 0.22 ± 0.06%ID/g, respectively; p ≤ 0.001). Therefore, expression of MMR along healthy aortas was suggested. Autoradiography showed no specific radioactive signal within atherosclerotic plaques, but rather localization of the signal along the aorta, correlating with MMR expression in perivascular tissue as demonstrated by immunofluorescence. CONCLUSIONS:No significant uptake of MMR-specific Nb could be observed in atherosclerotic lesions of ApoE-/- mice in this study. A specific perivascular signal causing a non-negligible background level was demonstrated. This observation should be considered when using MMR as a target in molecular imaging of atherosclerosis, as well as use of translational animal models with vulnerable plaques.

journal_name

Mol Imaging Biol

journal_title

Molecular imaging and biology

authors

Bala G,Baudhuin H,Remory I,Gillis K,Debie P,Krasniqi A,Lahoutte T,Raes G,Devoogdt N,Cosyns B,Hernot S

doi

10.1007/s11307-017-1117-3

subject

Has Abstract

pub_date

2018-04-01 00:00:00

pages

260-267

issue

eissn

1536-1632

issn

1860-2002

pii

10.1007/s11307-017-1117-3

journal_volume

pub_type

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Evaluation of [99mTc]Radiolabeled Macrophage Mannose Receptor-Specific Nanobodies for Targeting of Atherosclerotic Lesions in Mice.