In vivo suppression of restenosis in balloon-injured rat carotid artery byadenovirus-mediated gene transfer of the cell surface-directed plasmin inhibitor ATF.BPTI

Injury-induced neointimal development results from migration and proliferat ion of vascular smooth muscle cells (SMC). Cell migration requires controll ed proteolytic degradation of extracellular matrix surrounding the cell. Pl asmin is a major contributor to this process by degrading Various matrix pr oteins directly, or indirectly by activating matrix metalloproteinases. Thi s makes it an attractive target for inhibition by gene transfer. An adenovi ral vector. Ad.ATF.BPTI. was constructed encoding a hybrid protein, which c onsists of the aminoterminal fragment (ATF) of urokinase-type plasminogen a ctivator (u-PA) linked to bovine pancreas trypsin inhibitor (BPTI), a poten t inhibitor of plasmin. This hybrid protein binds to the u-PA receptor, the reby inhibiting plasmin activity at the cell surface. and was found to be a potent inhibitor of cell migration in vitro. Local infection with Ad.ATF.B PTI of balloon-injured rat carotid artery resulted in detectable expression of A TF. BPTI mRNA and protein in the vessel wall. Morphometric analysis o f arterial cross-sections revealed that delivery of Ad.ATF.BPTI to the caro tid artery wail at the time of balloon injury inhibited neointima formation by 53% (P < 0.01) at 14 days and 19% (P = NS) at 28 days after injury when compared with control vector-infected arteries. Intima/media ratios were d ecreased by 60% (P < 0.01) and 35% (P < 0.05) at 14 and 28 days, respective ly, when compared with control vector-infected arteries. Furthermore, a sma ll but significant increase in medial area was found in the Ad.ATF.BPTI-tre ated arteries at 28 days (P < 0.05). These results show that local infectio n of the vessel wall with Ad.ATF.BPTI reduces neointima formation, presumab ly by inhibiting SMC migration, thereby offering a novel therapeutic approa ch to inhibiting neointima development.