Inhibition of vascular smooth muscle cell proliferation and neointimal accumulation by adenovirus-mediated gene transfer of cytosine deaminase

Background: Restenosis remains a significant problem after balloon angioplasty. Previous studies have demonstrated that recombinant adenoviruses are efficient vectors for gene transfer to the arterial wall and can be used to inhibit the proliferative aspect of restenosis. We sought to extend these observations using AdCMV.CD, an adenovirus that encodes cytosine deaminase (CD) and is capable of metabolizing 5-fluorocytosine (5-FC) to 5- fluorouracil. Methods and Results: Infection of vascular smooth muscle cells (VSMC) with AdCMV.CD increases by two to three orders of magnitude the growth-inhibitory effects of 5-FC. The degree of VSMC inhibition in vitro was a function of 5-FC concentration and the level of CD expression. Cells infected with AdCMV.CD exhibited a profound bystander effect on the growth of neighboring cells, which did not require direct cell-to-cell contact. The predominant effect of AdCMV.CD on growth of VSMC appeared to be cytostatic, not cytotoxic. Assessment of this strategy in a rabbit femoral artery model of balloon-induced injury demonstrated that compared with animals in either of two control groups, animals treated with the active combination of infection with AdCMV.CD and 1-week treatment with parenteral 5-FC had a significant reduction at 30 days in the neointimal-to-medial ratio. Conclusions: Our results suggest that adenovirus-mediated gene transfer of CD along with 5-FC administration may be a useful strategy to treat the proliferative aspects of restenosis.