Passivation of Metallic Stents After Arterial Gene Transfer of phVEGF165 Inhibits Thrombus Formation and Intimal Thickening

Objectives. This study sought to test the hypothesis that direct gene transfer of an endothelial cell mitogen could passivate metallic stents by accelerating endothelialization of the prosthesis. Background. Thrombosis and restenosis comprise the principal clinical manifestations of compromised biocompatibility of endovascular stents. Previous studies have demonstrated that endothelial recovery at sites of balloon injury is critical determinant of consequent intimal thickening and mural thrombus. We therefore investigated the potential for an endothelial cell mitogen delivered as plasmid DN to optimize stent biocompatibility. Methods. Naked plasmid DN encoding vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF) (phVEGF165) was delivered locally using hydrogel-coated balloon angioplasty catheter to 16 rabbit iliac arteries in which metallic stents had been placed at the site of balloon injury; the contralateral iliac artery of each rabbit was balloon injured and stented but not transfected. Results. Stent endothelialization was accelerated by phVEGF165 gene transfer (87.38 ± 5.06% vs. 33.13 ± 9.73% [mean ± SEM] of the planimetered stent surface in the treated vs. contralateral limb, p = 0.005). This was associated with significant reduction in mural thrombus (3.7 ± 2.4% vs. 32.7 ± 9.7%, p = 0.01) at day 7 and intimal thickening (maximal intimal are 0.61 ± 0.09 vs. 1.44 ± 0.12 mm2, p < 0.0001) at day 28. No benefit was observed from pCMV-luciferase in 14 similarly instrumented control rabbits. Conclusions. These findings indicate that arterial gene transfer of naked plasmid DN encoding for an endothelial cell mitogen may successfully passivate endovascular stents by accelerating stent endothelialization, thereby reducing in-stent thombus and obstruction due to intimal thickening.