The relative effects of leukocyte depletion and nitric oxide modulation in an ex-vivo porcine normothermic perfusion model of donation after cardiac death in the kidney

Introduction: The shortage of donors necessitates the use of organs from donation after cardiac death (DCD) donors. These organs demonstrate a high rate of delayed graft function (DGF) and primary non-function (PNF) when compared to those from non-DCD donors. DGF and PNF are associated with shorter graft survival times. Reperfusion injury (RI) is important in the aetiology of DGF and PNF. The roles of leukocytes and nitric oxide (NO) are pivotal in the generation of RI. The aim of this study was to assess the effect on RI of modulating leukocyte and NO levels at the time of reperfusion. Methods: This study utilised a porcine extra-corporeal normothermic perfusion model of RI. Kidneys were perfused with whole (WB) or leukocyte depleted blood (LDB) alone, or with an inducible nitric oxide (iNOS) inhibitor or NO donor. This model allows the collection of haemodynamic and functional data, as well as plasma and urine for biochemical analysis. Results: Kidneys reperfused with LDB demonstrated improved blood flow and function compared to those reperfused with WB. Initial blood flow and function in the iNOS supplemented groups was worse than in the WB/LDB perfused groups, but improved in the NO donor groups. Late blood flow plateaued in the NO donor groups but improved in the iNOS supplemented WB group. LDB and iNOS supplementation together gave poor blood flow and function throughout reperfusion. Conclusion: Depletion of leukocytes abrogates the no-reflow phenomenon and reduces the oxidative stress caused by white cell infiltration, thereby improving blood flow and function. The effects of nitric oxide and its inhibition on the endothelium, glomerulus and renal tubule during initial reperfusion are dependent upon the phase of reperfusion. Early benefits to blood flow by NO supplementation are offset by the generation of NO free radicals later after reperfusion.