Adenovirus-mediated gene transfer of human inducible nitric oxide synthasein porcine vein grafts inhibits intimal hyperplasia

Objective: The aim of this study is to determine whether adenoviral inducib le nitric oxide synthase (iNOS) gene transfer could inhibit intimal hyperpl asia (IH) in porcine internal jugular veins interposed into the carotid art ery circulation. Methods: Porcine internal jugular veins were transduced passively with 1 x 10(11) particles of an adenoviral vector carrying either the human iNOS (Ad iNOS) or P-galactosidase (AdlacZ) cDNA for 30 minutes and then interposed i nto the carotid artery circulation. Segments of each vein graft were mainta ined in an ex vivo organ culture to measure nitrite accumulation, a marker of nitric oxide synthesis. The grafts were analyzed immunohistochemically f or the presence of neutrophils, macrophages, and leukocytes by staining for myeloperoxidase, ED1, and CD45, respectively, at 3 (n = 4) and 7 (n = 4) d ays. Morphometric analyses and cellular proliferation (Ki67 staining) were assessed at 3 (n = 4), 7 (n = 4), and 21 days (n = 8). Results: AdlacZ-treated vein grafts demonstrated high levels of beta -galac tosidase expression at 3 days with a gradual decline thereafter. Nitrite pr oduction from AdiNOS-treated vein grafts was approximately fivefold greater than AdlacZ-treated grafts (P =.00001). AdiNOS or AdlacZ treatment was ass ociated with minimal graft inflammation. Cellular proliferation rates were significantly reduced in AdiNOS-treated grafts as compared with controls at both 3 (41%, P =.000004) and 7 days (32%, P =.0001) after bypass. This ear ly antiproliferative effect was most pronounced at the distal anastomosis ( 65%, P =.0005). The iNOS gene transfer reduced the intimal/medial area rati o in vein grafts at 7 (36%, P =.009) and 21 days (30%, P =.007) versus cont rols. This inhibition of IH was again more prominent in the distal segments of the grafts (P =.01). Conclusion: Adenovirus-mediated iNOS gene transfer to porcine interval jugu lar vein grafts effectively reduced cellular proliferation and IH. Although iNOS gene transfer reduced IH throughout the entire vein graft, the most p ronounced effect was measured at the distal anastomosis. These results sugg est potential for iNOS-based genetic modification of vein grafts to prolong graft patency.