Intraoperative adenoviral gene transfer of NOS in venous bypass grafts: Reduction of early inflammation and intimal hyperplasia

Nitric oxide (NO), produced by nitric oxide synthase (NOS), plays key roles in the cardiovascular system, including anti-inflammatory actions. Loss of NOS/NO activity may be important in inflammation and vascular injury in early vein grafts (VG). We used a recombinant adenoviral vector (Ad.nNOS), to augment NOS activity in VG. Methods: Male New Zealand White rabbits (n=16) underwent interposition venous bypass grafting to the carotid artery using the jugular vein. Ad.nNOS (5 × 10 9pfu/ml) was instilled into the VG for 20 minutes during surgery. Experimental vessels and controls were harvested at 3 or 7 days (n=4 all groups). Vessel wet weight /length ratio was measured, and frozen sections analysed for: (1) presence of NOS by NADPH diaphorase (NADPH/d) staining; (2) expression of adhesion molecules (VCAM, ICAM) and (3) inflammatory cell markers (CD18, RAM11) by immunohistochemistry, using computer-aided image analysis; (4) intimal thickness on histology. Results: Adhesion molecule expression, inflammatory cell infiltration and intimal hyperplasia were all significantly reduced after Ad.nNOS gene transfer, as illustrated in the table (*p<0.05, **p<0.01): 3 days 7 days Control Ad.nNOS Control Ad.nNOS Weight/length (mg/mm) 2.9±0.2 2.2±0.3 * 4.7±0.5 3.2±0.2 ** Intimal thickness (μm) N/A N/A 8.3±0.8 2.2±0.2 ** VCAM (μm 2/HPF) 54±7.5 20±3.8* 61±6.2 29±5.1 * ICAM (μm 2/HPF) 100±10 37±6.6** 80±9.3 42±6.1 ** CD18 (cells/HPF) 3.4±0.7 1.4±0.4* 2.1±0.4 0.7±0.2* RAM 11 (cells/HPF) 5.1±0.7 2.2±0.4** 9.6±1.6 3.3±1.2** NADPH/d (μm 2/HPF) 62±4.8 118±5.6 ** 34±4.8 62±6.4* Conclusions: Intraoperative gene transfer of Ad.nNOS significantly reduces early vascular inflammation and subsequent intimal hyperplasia in VG. These findings suggest an important role for NO in early VG pathobiology, and highlight NOS as a potential gene therapy target.