Novel Matrix Metalloproteinase 12 selective radiotracers for vascular molecular imaging.

Matrix metalloproteinase-12 (MMP-12) is highly upregulated in several inflammatory diseases, including abdominal aortic aneurysm (AAA). Here we report four novel Tc-99m-labeled radiotracers derived from a highly selective competitive MMP-12 inhibitor. These tracers in their Tc-99g version were assessed in vitro on a set of human metalloproteases and displayed high affinity and selectivity toward MMP-12. Their radiolabeling with Tc-99m was shown to be efficient and stable in both buffer and mouse blood. The tracers showed major differences in their biodistribution and blood clearance. On the basis of its in vivo performance, [Tc-99m]-1 was selected for evaluation in murine AAA, where MMP-12 gene expression is upregulated. Autoradiography of aortae at 2 h postinjection revealed high uptake of [Tc-99m]-1 in AAA relative to adjacent aorta. Tracer uptake specificity was demonstrated through in vivo competition. This study paves the way for further evaluation of [Tc-99m]-1 for imaging AAA and other MMP-12-associated diseases.