Prolonged cold ischemia in rat cardiac allografts promotes ischemia-reperfusion injury and the development of graft coronary artery disease in a linear fashion

Background: Prolonged cold ischemia is thought to exacerbate ischemia-reperfusion injury and graft coronary artery disease (GCAD). We investigated the effect of varying lengths of cold ischemia on inflammation and apoptosis during ischemia-reperfusion injury and correlated this with the degree of GCAD in rat cardiac allografts. Methods: PVG rat (RT1^c) hearts subjected to 30, 60, 90, 120, or 150 minutes of cold ischemia were heterotopically transplanted into ACI rats (RT1^a). Grafts were procured after 4 hours of reperfusion and analyzed for superoxide generation, myeloperoxidase activity, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1/chemokine (C-C motif) ligand 2 (MCP-1/CCL2) production, cardiomyocyte apoptosis, and caspase-2, -3, -8, -9 activities. Additional transplanted animals received cyclosporine A (7.5 mg/kg/day) for 10 days as chronic rejection models. Indices of GCAD were determined at 90 days. Results: A direct linear correlation was found between cold ischemic time, ischemia-reperfusion injury, and GCAD. Superoxide generation, myeloperoxidase activity, TNF-α, IL-1β, MCP-1/CCL2 production, cardiomyocyte apoptosis, and caspase-2, -3, -8, and -9 activities increased with ischemic time, peaking at 120 minutes and plateauing at 150 minutes. GCAD, assessed by the percentage of luminal narrowing, the intima/media ratio, and the percentage of diseased vessels, worsened with increased ischemic time, peaking at 120 minutes and plateauing at 150 minutes. All tested variables in both the acute and chronic phases were significantly increased with 120-minute ischemia compared with 30-minute ischemia. Conclusions: These data indicate that the degree of cardiomyocyte apoptosis and inflammatory response in cardiac allografts during ischemia-reperfusion injury depends on the duration of cold ischemia. More important, that prolonged cold ischemia correlates with increased GCAD.