Sustained Reduction of Vein Graft Neointima Formation by Ex Vivo TIMP-3 Gene Therapy

Background- Coronary artery vein graft failure, resulting from thrombosis, intimal thickening, and atherosclerosis, is a significant clinical problem, with approximately 50% of vein grafts failing within 10 years. Intimal thickening is caused by migration of vascular smooth muscle cells from the media to the intima, where they proliferate. Interventions using gene transfer to inhibit vascular smooth muscle cells proliferation and migration are attractive because ex vivo access to the graft is possible. The involvement of matrix-degrading metalloproteinases in intimal thickening is well established, and we previously showed that adenoviral-delivered overexpression of an endogenous inhibitor, the tissue inhibitor of metalloproteinases-3 (TIMP-3), significantly retarded intimal thickening in short-term autologous porcine arteriovenous interposition grafts (28 days). However, it is essential to determine whether this approach will provide longer-term benefits. Methods and Results- We assessed whether a recombinant adenovirus that overexpresses TIMP-3 (RAdTIMP-3) affects vein graft intimal thickening in the longer term (at 3 months). Porcine saphenous veins were subjected to luminal infection with 2.5×10(10) pfu/mL RAdTIMP-3 or RAd60 (control virus) or vehicle control, for 30 minutes before implantation into the carotid artery. Analysis of grafts harvested 3 months after delivery revealed that RAdTIMP-3-infected grafts had significantly reduced intimal areas compared with both controls (3.2±0.4 mm(2) versus 5.6±0.7 mm(2) and 5.9±0.5 mm(2), RAdTIMP-3, RAd60, and vehicle, respectively). Medial areas were also significantly decreased by TIMP-3 (3.8±0.3 mm(2) versus 6.7±1.0 mm(2) and 5.2±0.4 mm(2), RAdTIMP-3, RAd60, and vehicle, respectively). Conclusions- Overexpression of TIMP-3 provides a sustained retardation of vein graft intimal thickening and highlights the translational potential for ex vivo TIMP-3 gene therapy.