Naked Small Interfering RNA of Caspase-3 in Preservation Solution and Autologous Blood Perfusate Protects Isolated Ischemic Porcine Kidneys

Background. Ischemia-reperfusion injury (IRI) plays key roles in graft viability and posttransplantation function. Caspase-3 associated with apoptosis and inflammation is up-regulated by IRI. We propose that naked small interfering RNA (siRNA) targeting caspase-3 may prevent IRI and improve kidney preservation. Methods. Porcine kidneys were retrieved after 10-min warm ischemia and flushed with 500 mL hyperosmolar citrate. Caspase-3 siRNA was administered directly into the renal artery in hyperosmolar citrate solution (3 mu g/ml) with the renal vein clamped and into autologous blood (0.15 mu g/ml), both of which were stored for 24 hr on ice. The kidneys were reperfused with oxygenated autologous blood for 3 hr on an isolated organ perfusion system to assess renal function. Results. In the siRNA-treated group, the expression of 32-kDa caspase-3 precursor and 17-kDa active subunit was down-regulated by 30% and 56%, respectively, with 40% reduction in active caspase-3+ cells. Consequently, apoptotic cells in the renal cortex were significantly decreased by 47%, whereas inflammatory cells were only marginally reduced by 26%. Caspase-3 siRNA also doubled oxygen consumption and significantly neutralized perfusate pH. Renal blood flow was gradually increased from 5 min to 3 hr by caspase-3 siRNA and marginally improved at the end of 3-hr reperfusion by 45%. Conclusions. The administration of caspase-3 siRNA directly into the kidney and hemoperfusate during cold preservation improved IRI with reduced caspase-3 and apoptosis, and better renal oxygenation and acid-base homeostasis. This proof of principle experiment using a novel siRNA therapy in large animal organs provides valuable data for human kidney transplantation.