Pressure Assisted Liposome Mediated Exvivo Transfection of Canine Saphenous Vein Grafts with Endothelial Nitric Oxide Synthase Gene Reduces Intimal Hyperplasia

Objectives: Virus mediated gene transfer to vein grafts limits intimal hyperplasia, but is associated with cytotoxicity and host immune response. Liposome mediated gene transfer is free of these effects but results in less efficient gene transfer. This study was designed (1) to evaluate the effect of pressure on liposome mediated ecNOS (endothelial constitutive nitric oxide synthase) gene transfection in vein grafts and (2) to assess it's functional effects.
Methods: Male mongrel dogs (n=12) underwent femoral artery bypass grafting with saphenous vein transfected with the ecNOS gene, and a contralateral control bypass. Transfection was performed through the adventitia with 100 µg/ml ecNOS DNA along with liposome ((Lipofectamine Plus). In Group I (n=6) transfection was at 37oC in an atmosphere of 95% O2 and 5% CO2 for one hour; in Group II (n=6) at room temperature and pressurized to 300 mmHg for 20 minutes. Grafts were harvested at 4 weeks and calcium dependent nitric oxide synthase activity (NOS activity) was measured. Intimal hyperplasia was quantified by computerized planimetry of histological sections and intimal/medial (I/M) ratio was calculated.
Results: NOS activity was significantly higher in all transfected grafts compared to controls (p<0.05): the increase was greater in Group II compared to Group I (mean, 212% vs 146%, p=0.04). Significant reduction in intimal hyperplasia was seen in Group II (mean I/M ratio, 0.41 vs 0.49, p=0.01).
Conclusion: Liposome mediated adventitial transfection of canine saphenous vein grafts with the ecNOS gene is enhanced by pressure and results in reduction of intimal hyperplasia in the short-term.