Date: 13 Jul 2010

Imaging with radiolabelled anti-membrane type 1 matrix metalloproteinase (MT1-MMP) antibody: potentials for characterizing atherosclerotic plaques

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Abstract

Purpose

Membrane type 1 matrix metalloproteinase (MT1-MMP) activates pro-MMP-2 and pro-MMP-13 to their active forms and plays important roles in the destabilization of atherosclerotic plaques. This study sought to determine the usefulness of 99mTc-labelled monoclonal antibody (mAb), recognizing MT1-MMP, for imaging atherosclerosis in a rabbit model (WHHLMI rabbits).

Methods

Anti-MT1-MMP monoclonal IgG3 and negative control IgG3 were radiolabelled with 99mTc after derivatization with 6-hydrazinonicotinic acid (HYNIC) to yield 99mTc-MT1-MMP mAb and 99mTc-IgG3, respectively. WHHLMI and control rabbits were injected with these radio-probes. The aorta was removed and radioactivity was measured at 24 h after the injection. Autoradiography and histological studies were performed.

Results

99mTc-MT1-MMP mAb accumulation in WHHLMI rabbit aortas was 5.4-fold higher than that of control rabbits. Regional 99mTc-MT1-MMP mAb accumulation was positively correlated with MT1-MMP expression (r = 0.59, p < 0.0001), while 99mTc-IgG3 accumulation was independent of MT1-MMP expression (r = 0.03, p = NS). The highest 99mTc-MT1-MMP mAb accumulation was found in atheromatous lesions (4.8 ± 1.9, %ID×BW/mm2 × 102), followed in decreasing order by fibroatheromatous (1.8 ± 1.3), collagen-rich (1.6 ± 1.0) and neointimal lesions (1.5 ± 1.5). In contrast, 99mTc-IgG3 accumulation was almost independent of the histological grade of lesions.

Conclusion

Higher 99mTc-MT1-MMP mAb accumulation in grade IV atheroma was shown in comparison with neointimal lesions or other more stable lesions. Nuclear imaging with 99mTc-MT1-MMP mAb, in combination with CT and MRI, could provide new diagnostic imaging capabilities for detecting vulnerable plaques, although further investigations to improve target to blood ratios are strongly required.