In vivo suppression of vein graft disease by nonviral, electroporation-mediated, gene transfer of tissue inhibitor of metalloproteinase-1 linked to the amino terminal fragment of urokinase (TIMP-1.ATF), a cell-surface directed matrix metalloproteinase inhibitor

Abstract

Background: Smooth muscle cell (SMC) migration and proliferation are important in the development of intimal hyperplasia, the major cause of vein graft failure. Proteases of the plasminogen activator (PA) system and of the matrix metalloproteinase (MMP) system are pivotal in extracellular matrix degradation and, by that, SMC migration. Previously, we demonstrated that inhibition of both protease systems simultaneously with viral gene delivery of the hybrid protein TIMP-1.ATF, consisting of the tissue inhibitor of metalloproteinase-1 (TIMP-1) and the receptor-binding amino terminal fragment (ATF) of urokinase, reduces SMC migration and neointima formation in an in vitro restenosis model using human saphenous vein cultures more efficiently than both protease systems separately. Because use of viral gene delivery is difficult in clinical application, this study used nonviral delivery of TIMP-1.ATF plasmid to reduce vein graft disease in a murine bypass model. Nonviral gene transfer by electroporation was used to avert major disadvantages of viral gene delivery, such as immune responses and short-term expression.

Methods: Plasmids encoding ATF, TIMP-1, TIMP-1.ATF, or luciferase, as a control, were injected and electroporated in both calf muscles of hypercholesterolemic apolipoprotein E3-Leiden (APOE*3Leiden) mice (n = 8). One day after electroporation, a venous interposition of a donor mouse was placed into the carotid artery of a recipient mouse. In this model, vein graft thickening develops with features of accelerated atherosclerosis. Vein grafts were harvested 4 weeks after electroporation and surgery, and histologic analysis of the vessel wall was performed.

Results: Electroporation-mediated overexpression of the plasmid vectors resulted in a prolonged expression of the transgenes and resulted in a significant reduction of vein graft thickening (ATF: 36% +/- 9%, TIMP-1: 49% +/- 5%, TIMP-1.ATF: 58% +/- 5%; P < .025). Although all constructs reduced vein graft thickening compared with the controls, the luminal area was best preserved in the TIMP-1.ATF-treated mice.

Conclusion: Intramuscular electroporation of TIMP-1.ATF inhibits vein graft thickening in vein grafts in carotid arteries of hypercholesterolemic mice. Binding of TIMP-1.ATF hybrid protein to the u-PA receptor at the cell surface enhances the inhibitory effect of TIMP-1 on vein graft remodeling in vitro as well as in vivo and may be an effective strategy to prevent vein graft disease.