Introduction: Transportable machine perfusion devices contribute to expanding the chance of organ donation such as the use of marginal donors. Several transportable kidney machine perfusion devices are widely used in Europe and the United States, these devices are not compact and not portable. These devices are difficult to transport on a train or airplane in Japan. Additionally, injection-molded products increase costs, and complex circuits make maintenance difficult. It is necessary to develop a compact and transportable device adapted to Japan and the Asian region countries. This study develops a compact and transportable hypothermic machine perfusion system for kidney transplantation and evaluates its feasibility through porcine kidney preservation experiments.
Method: The developed system was sufficiently compact (200 mm L × 150 mm W × 170 mm H). The weight of the system, including the perfusion solution, is less than 2 kg (The perfusion solution volume was 450 ml.). The system is situated inside a transportable cooling chamber or preservation box. The developed system consisted of a small tubing pump, a pressure gauge, a thermometer and a flowmeter. The perfusion pressure was precisely regulated by a feedback control system.  In this experiment, porcine kidneys, controlled for warm ischemic time (WIT 0 and 60 minutes), were preserved for 240 minutes under hypothermic conditions (8-10°C) using UW(MPS) solution. The kidneys were evaluated for vascular resistance during the preservation process. The target perfusion pressure was 30 mmHg. The temperature was controlled by an integrated Peltier element of the transportable cooling chamber.
Results: The perfusion pressure was maintained at a stable setpoint throughout the preservation process. The flow rate increased in response to the condition of the organs. The vascular resistance at the start of perfusion was 2.5 mmHg/ml/min (WIT 0) and 6.7 mmHg/ml/min (WIT 60). These results suggest that the device can be used to assess organ viability based on initial vascular resistance.  The tissue of WIT 0min retained tubular epithelium and there was no damage to the arterial epithelium. the well-preserved state of the tissue indicated that the perfusion process itself did not induce organ damage. Future studies are needed to extend the preservation time, transplantation experiments, and reperfusion experiments. Further miniaturization of the device could facilitate its use within conventional preservation box for kidney transplantation.
Conclusion: This study evaluated the availability of the compact and transportable kidney hypothermic machine perfusion system with porcine preservation experiments.