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This study investigated simple in situ perfusion of a kidney to reduce its susceptibility to warm ischemia in rodent and porcine ischemic kidney models. Organ temperature was managed via simple continuous perfusion using newly developed thermal barrier sheet (TBS).ATP retention following cold perfusion with extracellular-trehalose-Kyoto (ETK) solution was investigated in a rat model.Kidneys from adult male genetically modified luciferase transgenic (Luc Tg) rats were removed. The renal artery/vein underwent simple cold preservation at 4°C for 5 to 18 hours using ETK solution. After cold storage, the kidney was transplanted into a dummy living body that was heated to 37°C and perfused with ETK solution using a drip. The surface temperature (Ts) was measured with an infrared camera and ATP luminescence in organs was observed for 60 minutes.In porcine, the renal artery and vein were clamped within the abdominal cavity and the left kidney was prepared as a donor organ after 25 minutes of exposure to warm ischemia. The kidney was perfused via the renal artery at 4°C using ETK solution and subsequently underwent cold preservation (Fig1.a). We continued the surgery, while the kidney continued to undergo cold perfusion (Fig2.b) using a TBS. Continuous suturing was performed and the cannula was removed immediately after reflux. Blood flow then resumed. Control kidneys were sutured without undergoing perfusion. The time required for anastomosis was 1 hour, during which time the Ts of the kidney was measured. After resuming blood flow, the right kidney was removed. Following transplantation, blood and tissue were collected.Using a TBS and cold reflux in the dummy body, the rodent kidney Ts was maintained at 15°C or less for more than 30 minutes. During perfusion with the conventional method, the kidney Ts was at least 28°C immediately following removal. In the case of cold perfusion and TBS, the ATP level was elevated by approximately 4-fold that of pre-removal levels during preservation. Meanwhile, while using the conventional method, the ATP level was 0.9-fold of the pre-removal level during cold preservation. The porcine kidney Ts in the control group increased to 32°C during transplantation. Whereas, in the cold perfusion group, transplantation was performed while the kidney Ts was maintained at 24°C. The primary non-function rate after transplantation was 60% in the control group and 25% in the cold perfusion group.The cold perfusion method using a TBS can maintain the temperature and ischemic time in all organs obtained after cardiac death. In addition, the preclinical porcine model is a useful renal transplantation graft model that does not exhibit rejection and can be used to identify appropriate constant temperature perfusion solutions.By developing this perfusion system, we believe that we can promote research toward practical application of machine perfusion.