In vivo uptake of radiolabeled antibody to proliferating smooth muscle cells in a swine model of coronary stent restenosis

Z2D3 is a monoclonal chimeric antibody fragment that is directed against a protein expressed on the surface of proliferating smooth muscle cells. The purpose of this study was to investigate the uptake of In-111-labeled Z2D3 F(ab')(2) in a swine model of coronary neointimal proliferation after overe xpansion coronary stenting. Methods: Twenty-two domestic swine underwent ov erexpansion coronary stenting of 2 vessels. Fifteen swine survived 2-4 wk, at which time they received an injection of In-111 Z2D3 F(ab')(2) and under went planar imaging. After the swine were killed, the hearts were excised a nd imaged on the detector. The cross-sectional area of each stented vessel was measured with digital morphometry. Results: Pathology could be correlat ed with imaging for 24 vessels. The cross-sectional area of stenosis compri sing neointimal proliferation ranged from 8% to 95%, with a mean +/- SD of 41% +/- 21%. The maximal stenosis ranged from 13% to 95%, with a mean of 51 % +/- 20%. Seventeen of 24 vessels (71%) showed focal uptake on in vivo ima ging, and 7 of 24 (29%) did not. Twenty of 24 (83%) showed uptake on ex viv o imaging. Of 11 stented vessels with maximal vessel stenosis less than 50% , 7 (64%) showed uptake both in vivo and ex vivo, and of 13 stented vessels with maximal vessel stenosis greater than 50%, 10 (77%) showed uptake both in vivo and ex vivo. Conclusion: Uptake of a radiolabeled antibody directe d against a component of proliferating neointimal tissue can be visualized in the coronary arteries on in vivo imaging using a scintillation gamma cam era.