EFFICIENT AND SELECTIVE ADENOVIRUS-MEDIATED GENE-TRANSFER INTO VASCULAR NEOINTIMA

Background. Previous attempts to target arterial smooth muscle cells ( SMCs) for gene delivery using liposomal or retroviral methods were lim ited by low transfection efficiency. We therefore evaluated the effici ency of adenovirus-mediated gene delivery in cultured vascular SMCs an d in an in vivo model of balloon injury-induced SMC cell proliferation , Methods and Results. We used a recombinant adenovirus, Ad.RSV beta g al, which contained the beta-galactosidase (beta-gal) histochemical ma rker gene. For in vitro studies, rat aortic SMCs were incubated in med ia containing Ad.RSV beta gal for 5 to 120 minutes. The proportion of SMCs expressing the beta-gal gene product increased from 25% (5-minute exposure) to 80% (120-minute exposure). For in vivo studies, uninjure d and injured rat carotid segments were incubated with 0.5 to 1.0x10(9 ) pfu Ad.RSV beta gal for 45 minutes. Uninjured arteries showed adenov irus-mediated gene transfer limited to the endothelium. Injured arteri es were exposed to adenovirus 0, 3, 7, or 12 days after injury. In the se segments, beta-gal expression was minimal with infection at 0 or 3 days after injury but marked when infection was delayed until 7 or 12 days after injury. Neointimal cells constituted the dominant target of adenovirus gene transfer, with efficiency of gene transfer ranging fr om 10% to >75%. Medial SMCs, whether covered or uncovered by neointima l cells, were minimally infected, Infection with a control adenovirus vector showed no beta-gal staining. Conclusions. Recombinant adenoviru s selectively targets neointimal cells with high-efficiency gene trans fer. This suggests that adenovirus vectors should be useful in targeti ng cells for the delivery of genes whose products may be relevant to t he treatment of restenosis.