Adventitial versus intimal liposome-mediated ex vivo transfection of canine saphenous vein grafts with endothelial nitric oxide synthase gene

Purpose: Experiments were designed (1) to evaluate liposome-mediated endothelial constitutive nitric oxide synthase (ecNOS) transfection in vein grafts and (2) to compare intimal and adventitial routes of transfection. Methods: Male mongrel dogs (N = 36) underwent bilateral femoral artery bypass grog with the lateral saphenous vein. In each animal one vein was transfected with plasmid (pVR1012) containing the ecNOS gene, and another vein was transfected with plasmid alone (control). Gene transfer was performed from either the intimal surface (Group I, n = 18) or the adventitial surface (Group II, n = 18). In each group there were three transfection subgroups (n = 6 each): (a) 10 μg/mL naked plasmid DNA, (b) 10 μg/mL plasmid DNA + liposome (LipofectAMINE PLUS), and (c) 100 μg/mL plasmid DNA + LipofectAMINE PLUS. Grafts were harvested on the third postoperative day, and the transfection was assessed with molecular techniques and enzyme assay for activity of NOS by conversion of tritiated L-arginine to tritiated L-citrulline. Proliferating cells were quantified with a digital analysis of histologic sections after nuclear antigen Ki-67 (MIB1) immunohistochemistry. Results: Transgene was identified with polymerase chain reaction in all ecNOS-transfected grafts, regardless of transfection modality. However, significant transcription of the ecNOS transgene was observed only in Group IIc (mean ecNOS messenger RNA, 8.7 ± 1.7 vs 3.1 ± 0.7 x 10^-2 attomole/μL, in transfected compared with control grafts, respectively, P = .01). NOS activity, increased approximately twofold in this group (11.58 ± 2.1 and 6.3 ± 1.0 pmol tritiated b-citrulline per milligram protein per hour in transfected and control grafts, respectively, P = .05). Numbers of proliferating cells did not differ among ecNOS-transfected and control grafts in any transfection group. Conclusion: These results suggest that ecNOS transfection of veto grafts is feasible through intimal and adventitial routes with naked DNA or a liposomal vector. However, efficient transcription of the transgene is evident at postoperative day 3 only after adventitial transfection of 100 μg/mL of the gene.