Mitochondrial injury during normothermic regional perfusion (NRP) and hypothermic oxygenated perfusion (HOPE) in a rodent model of DCD liver transplantation.

BACKGROUND: Normothermic regional perfusion (NRP) and hypothermic-oxygenated-perfusion (HOPE), were both shown to improve outcomes after liver transplantation from donors after circulatory death (DCD). Comparative clinical and mechanistical studies are however lacking. METHODS: A rodent model of NRP and HOPE, both in the donor, was developed. Following asystolic donor warm ischemia time (DWIT), the abdominal compartment was perfused either with a donor-blood-based-perfusate at 37 °C (NRP) or with oxygenated Belzer-MPS at 10 °C (donor-HOPE) for 2 h. Livers were then procured and underwent 5 h static cold storage (CS), followed by transplantation. Un-perfused and HOPE-treated DCD-livers (after CS) and healthy livers (DBD) with direct implantation after NRP served as controls. Endpoints included the entire spectrum of ischemia-reperfusion-injury. FINDINGS: Healthy control livers (DBD) showed minimal signs of inflammation during 2 h NRP and achieved 100% posttransplant recipient survival. In contrast, DCD livers with 30 and 60 min DWIT suffered from greater mitochondrial injury and inflammation as measured by increased perfusate Lactate, FMN- and HMGB-1-levels with subsequent Toll-like-receptor activation during NRP. In contrast, donor-HOPE (instead of NRP) led to significantly less mitochondrial-complex-I-injury and inflammation. Results after donor-HOPE were comparable to ex-situ HOPE after CS. Most DCD-liver recipients survived when treated with one HOPE-technique (86%), compared to only 40% after NRP (p = 0.0053). Following a reduction of DWIT (15 min), DCD liver recipients achieved comparable survivals with NRP (80%). INTERPRETATION: High-risk DCD livers benefit more from HOPE-treatment, either immediately in the donor or after cold storage. Comparative prospective clinical studies are required to translate the results. FUNDING: Funding was provided by the Swiss National Science Foundation (grant no: 32003B-140776/1, 3200B-153012/1, 320030-189055/1, and 31IC30-166909) and supported by University Careggi (grant no 32003B-140776/1) and the OTT (grant No.: DRGT641/2019, cod.prog. 19CT03) and the Max Planck Society. Work in the A.G. laboratory was partially supported by the NIH R01NS112381 and R21NS125466 grants.

Observations and findings during the development of a subnormothermic/normothermic long-term ex vivo liver perfusion machine.

BACKGROUND: Ex situliver machine perfusion at subnormothermic/normothermic temperature isincreasingly applied in the field of transplantation to store and evaluateorgans on the machine prior transplantation. Currently, various perfusionconcepts are in clinical and preclinical applications. Over the last 6 years ina multidisciplinary team, a novel blood based perfusion technology wasdeveloped to keep a liver alive and metabolically active outside of the bodyfor at least one week. METHODS: Within thismanuscript, we present and compare three scenarios (Group 1, 2 and 3) we werefacing during our research and development (R&D) process, mainly linked tothe measurement of free hemoglobin and lactate in the blood based perfusate. Apartfrom their proven value in liver viability assessment (ex situ), these twoparameters are also helpful in R&D of a long-term liver perfusion machine and moreover supportive in the biomedical engineering process. RESULTS: Group 1 ("good" liver on the perfusion machine) represents the best liver clearance capacity for lactate and free hemoglobin wehave observed. In contrast to Group 2 ("poor" liver on the perfusion machine), that has shown the worst clearance capacity for free hemoglobin. Astonishingly,also for Group 2, lactate is cleared till the first day of perfusion andafterwards, rising lactate values are detected due to the poor quality of theliver. These two perfusate parametersclearly highlight the impact of the organ quality/viability on the perfusion process. Whereas Group 3 is a perfusion utilizing a blood loop only (without a liver). CONCLUSION: Knowing the feasible ranges (upper- and lower bound) and the courseover time of free hemoglobin and lactate is helpful to evaluate the quality ofthe organ perfusion itself and the maturity of the developed perfusion device. Freehemoglobin in the perfusate is linked to the rate of hemolysis that indicates how optimizing (gentle blood handling, minimizing hemolysis) the perfusion machine actually is. Generally, a reduced lactate clearancecapacity can be an indication for technical problems linked to the blood supplyof the liver and therefore helps to monitor the perfusion experiments.Moreover, the possibility is given to compare, evaluate and optimize developed liverperfusion systems based on the given ranges for these two parameters. Otherresearch groups can compare/quantify their perfusate (blood) parameters withthe ones in this manuscript. The presented data, findings and recommendations willfinally support other researchers in developing their own perfusion machine ormodifying commercially availableperfusion devices according to their needs.