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Background: Gradual warming up of cold stored organ grafts using a controlled machine perfusion protocol facilitates restitution of cellular homeostasis and mitigates rewarming injury by adapted increase of temperature and metabolism. The aim of the present study was to compare intra‐ and extracellular type perfusion media for the use in machine perfusion‐assisted rewarming from hypo‐ to normothermia. Methods: Rat livers were retrieved 20 min after cardiac arrest. After 18 h of cold storage (CS) with or without additional 2 h of rewarming machine perfusion from 8°C up to 35°C with either diluted Steen solution or with Belzer MPS, liver functional parameters were evaluated by an established ex vivo reperfusion system. Results: Rewarming machine perfusion with either solution significantly improved graft performance upon reperfusion in terms of increased bile production, less enzyme release, and reduced lipid peroxidation compared to CS alone. Cellular apoptosis (release of caspase‐cleaved keratin 18) and release of tumor necrosis factor were only reduced significantly after machine perfusion with Belzer MPS. Histological evaluation did not disclose any major morphological damage in any of the groups. Conclusion: Within the limitation of our model, the use of Belzer MPS seems to be an at least adequate alternative to a normothermic medium like Steen solution for rewarming machine perfusion of cold liver grafts. [ABSTRACT FROM AUTHOR]

Background: Sudden restoration of normothermic conditions upon reperfusion of cold‐stored grafts has been suggested to entail a massive energy demand not yet met by the cells that still suffer from hypothermic torpor. An adapted and gentle rise of graft temperature by ex‐vivo machine perfusion has, therefore, been proposed. This should now be tested in the clinical setting. Methods: In a first clinical series, six ECD‐kidneys were subjected to controlled oxygenated rewarming (COR) during short term pre‐implantation machine perfusion. Matched kidneys that were conventionally kept on ice served as controls. Results: Early allograft function after transplantation was significantly improved by COR. On post‐operative day 7, clearance of creatinine was more than twofold higher after COR and fractional excretion of sodium in the normal range, while significantly elevated in control kidneys. Good correlations were seen between ulterior graft function and real‐time parameters obtained during pre‐transplant machine perfusion (Lactate: r2 =.9; TIMP2: r2 =.74). Conventional denominators of graft viability like kidney donor risk index KDRI were far less predictive (r2 =.26). Conclusion: It is concluded that COR can be safely applied to renal grafts and appears to be a valuable tool to predict and improve early renal function after transplantation. [ABSTRACT FROM AUTHOR]

Background: Machine perfusion was found an effective tool to recover organ grafts from ischemic insults during preservation. It could be observed that organ integrity is significantly affected by abrupt temperature shifts during hypothermic storage and implantation periods. Studies showed that a gentle and controlled rise of the temperature during oxygenated machine perfusion prior to implantation can protect the tissue from reperfusion injury. Now, the possible role of temperature kinetics upon retrieval of the graft and prior to later cold storage should be investigated. Methods: Rat livers were retrieved after cardiac arrest and subjected to a brief ex situ machine perfusion with either hypothermic resuscitation (HR) at 8°C, near‐normothermic resuscitation (NR) at 30°C or progressive resuscitation with lowering the temperature in a controlled fashion from 30°C to 8°C (PR). After cold storage (CS), liver functional parameters were evaluated by an established ex vivo reperfusion system. Results: NR and PR resulted in significantly lower release of hepatic enzymes and less production of tumor necrosis factor upon reperfusion compared to CS while HR had a far less protective effect. An increase in bile production was only observed in the PR group, which also significantly increased the recovery of tissue adenosine triphosphate, the amount of which was, however, nearly paralleled by the NR protocol. Conclusion: Within the limitations of this model, it seems that normothermic recirculation appears to be a superior approach for the restitution of warm‐ischemically injured liver grafts than immediate hypothermic machine perfusion. [ABSTRACT FROM AUTHOR]

Organ shortage and the increasing use of extended criteria donor grafts for transplantation drives efforts for more efficient organ preservation strategies from simple cold storage toward dynamic organ reconditioning. The choice of a suitable preservation solution is of high relevance in different organ preservation or reconditioning situations. Custodiol‐MP is a new machine perfusion solution giving the opportunity to add colloids according to organ requirements. The present study aimed to compare new Custodiol‐MP with clinically established Belzer MPS solution. Porcine kidneys were ischemically predamaged and cold stored for 20 hours. Ex vivo machine reconditioning was performed either with Custodiol‐MP (n = 6) or with Belzer MPS solution (n = 6) for 90 minutes with controlled oxygenated rewarming up to 20°C. Kidney function was evaluated using an established ex vivo reperfusion model. In this experimental setting, differences between both types of perfusion solutions could not be observed. Machine perfusion with Custodiol‐MP resulted in higher creatinine clearance (7.4 ± 8.6 mL/min vs. 2.8 ± 2.5 mL/min) and less TNC perfusate levels (0.22 ± 0.25 ng/mL vs. 0.09 ± 0.08 ng/mL), although differences did not reach significance. For short‐term kidney perfusion Custodiol‐MP is safe and applicable. Particularly, the unique feature of flexible colloid supplementation makes the solution attractive in specific experimental and clinical settings. [ABSTRACT FROM AUTHOR]

Objectives: The benefit of machine perfusion during storage of liver grafts retrieved after cardiac death should be investigated as applied either at the beginning or near the end of the preservation period., Methods: Rat livers were explanted 20 min after cardiac arrest of the donor and cold-stored (CS) for 18 h. Other grafts were additionally subjected to 2 h of normothermic machine perfusion (MP) either 3 h after retrieval (early MP) or 3 h before reperfusion (late MP), thus extending total ischemic time to 20 h. The 3 h period should represent a short transport period between a resident regional pumping center and the explant or implant hospital, respectively. Viability of all livers was assessed thereafter by warm reperfusion in vitro., Results: In comparison to the controls, both regimens significantly improved hepatic recovery upon post-preservation reperfusion as evaluated by enzyme release, bile production, and energetic recovery. Molecular upregulation of pro-inflammatory signals was also significantly mitigated. No functional differences between early and late machine perfusion could be disclosed., Conclusion: Our data suggest that it might not be necessary to hurry with the attempt to connect the graft to a machine early after retrieval., Competing Interests: None., (AJTR Copyright © 2023.)

The possible reno-protective effect of a controlled brief heat-shock treatment during isolated ex vivo machine perfusion of donor grafts prior to reperfusion should be investigated in a primary in vitro study. Porcine kidneys (n = 14) were retrieved after 20 minutes of cardiac standstill of the donor and subjected to 20 hours of static cold storage in University of Wisconsin solution. Prior to reperfusion, kidneys were subjected to 2 hours of reconditioning machine perfusion with gradual increase in perfusion temperature up to 35°C. In half of the kidneys (n = 7), a brief hyperthermic impulse (10 minutes perfusion at 42°C) was implemented in the machine perfusion period. Functional recovery of the grafts was observed upon normothermic reperfusion in vitro. Hyperthermic treatment resulted in a 50% increase of heat shock protein (HSP) 70 and HSP 27 mRNA and was accompanied by ~ 50% improvement of tubular re-absorption of sodium and glucose upon reperfusion, compared with the controls. Furthermore, renal loss of aspartate aminotransferase was significantly reduced to one-third of the controls as was urinary protein loss, evaluated by the albumin to creatinine ratio. It is concluded that ex vivo heat-shock treatment seems to be an easily implementable and promising option to enhance renal self-defense machinery against reperfusion injury after preservation that merits further investigation in preclinical models., (© 2020 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of the American Society for Clinical Pharmacology and Therapeutics.)

Pretransplant machine perfusion of donor grafts has gained clinical appreciation to improve graft function and survival after transplantation. This study was aimed as pilot investigation to evaluate the additive potential of a transient ex vivo heat shock treatment of the isolated organ during machine perfusion to further protect the graft from subsequent reperfusion injury. Rat livers were retrieved after 20 min of cardiac arrest and preserved for 18 h by cold storage in HTK solution. Prior to reperfusion, livers were subjected to 2 h of reconditioning machine perfusion with gradual increase in perfusion temperature up to 35 °C. In half of the livers (n = 7), a brief hyperthermic impulse (10 min perfusion at 42 °C) was implemented in the machine perfusion period. Functional recovery of the grafts was observed upon normothermic reperfusion in vitro. Induction of heat shock protein 70 was followed on the mRNA and protein level. Chaperone induction by transient hyperthermia was associated with a significant improvement of bile production upon reperfusion and significantly reduced enzyme loss of mitochondrial GLDH. Heat shock treatment further affected pro-inflammatory upregulation in the graft in significantly reducing gene expression as wells as protein release of TNF-alpha. It is concluded, that graft conditioning by controlled hyperthermia ex vivo may represent a feasible and useful tool to improve liver recovery after preservation., (© 2019 The Authors. Transplant International published by John Wiley & Sons Ltd on behalf of Steunstichting ESOT.)

Ex vivo machine perfusion of the liver after cold storage has found to be most effective if combined with controlled oxygenated rewarming up to (sub)-normothermia. On disconnection of the warm graft from the machine, most surgeons usually perform a cold flush of the organ as protection against the second warm ischemia incurred upon implantation. Experimental evidence, however, is lacking and protective effect of deep hypothermia has been challenged for limited periods of liver ischemia in other models. A first systematic test was carried out on porcine livers, excised 30 min after cardiac arrest, subjected to 18 h of cold storage in UW and then machine perfused for 90 min with Aqix-RSI solution. During machine perfusion, livers were gradually rewarmed up to 20 °C. One group (n = 6) was then reflushed with 4 °C cold Belzer UW solution whereas the second group (n = 6) remained without cold flush. All livers were exposed to 45 min warm ischemia at room temperature to simulate the surgical implantation period. Organ function was evaluated in an established reperfusion model using diluted autologous blood. Cold reflush after disconnection from the machine resulted in a significant increase in bile production upon blood reperfusion, along with a significant reduction in transaminases release alanine aminotransferase and of the intramitochondrial enzyme glutamate dehydrogenase. Interestingly, free radical-mediated lipid peroxidation was also found significantly lower after cold reflush. No differences between the groups could be evidenced concerning histological injury and recovery of hepatic energy metabolism (tissue content of adenosine triphosphate). Post-machine preservation cold reflush seems to be beneficial in this particular setting, even if the organs are warmed up only to 20 °C, without notion of adverse effects, and should therefore be implemented in the protocol., (© 2018 The Authors. Transplant International published by John Wiley & Sons Ltd on behalf of Steunstichting ESOT.)

Normothermic machine perfusion can decrease reperfusion injury in renal transplantation. Clinical procurement logistics include retrieval and initial transport of the graft using static cold storage. Therefore, use and benefits of brief normothermic reconditioning by machine perfusion should be investigated in the initially cold preserved graft. Porcine kidneys (6 per group) were retrieved 20 min after cardiac standstill. After 20 h of static cold preservation some grafts were put on a machine perfusion circuit and normothermically perfused for 2 h at 35°C (NMP). Another group was subjected to controlled oxygenated rewarming (COR), starting perfusion at 8°C and elevating temperature and pressure slowly up to 35°C and 75 mmHg during the first 90 min of 2 h perfusion. Control kidneys were only cold stored (CS). Post implant graft function was evaluated afterwards in an established in vitro reperfusion model. During graft reconditioning, COR reduced oxygen free radical production and formation of 4-hydroxy-2-nonenal (HNE), an activator of mitochondrial uncoupling proteins, in comparison to NMP. Upon reperfusion, NMP only led to a slight improvement of renal function (clearance of creatinine, fractional excretion of Na and glucose) compared to controls. But 2-3 fold improvements of renal function were seen after COR, which also significantly improved aerobic efficiency (total Na absorption/VO 2 ) upon reperfusion. A slow and controlled increase in temperature up to normothermia improves mitochondrial recovery and oxygen utilization efficiency, resulting in better functional recovery, possibly through a more mild and adapted increase of cellular metabolism., Competing Interests: None.

Controlled oxygenated rewarming (COR) up to 20°C during ex vivo machine perfusion limits reperfusion-induced tissue injury upon graft implantation. Rewarming up to normothermia might add further benefits and provide better prediction of post-transplantation organ function. The effect of 90 minutes of oxygenated machine perfusion with Aqix RS-I after cold storage combined with gentle rewarming up to 20°C (COR20) or 35°C (COR35) was studied in rat livers and compared with cold storage alone (CS, n = 6, resp). Postpreservation recovery was evaluated upon warm reperfusion using an established in vitro system. COR generally resulted in significantly improved energetic recovery, increased bile flow, less activities alanine aminotransferase (ALT) release, and improved histopathology upon reperfusion as compared to only cold-stored livers, without significant differences between COR20 and COR35. Parameters obtained during COR, especially during COR35, also allowed for prediction of hepatic recovery upon reperfusion. For instance, ulterior bile production upon reperfusion was found closely correlated to bile flow observed already during COR35 (R 2  = 0.91). COR significantly improved liver quality after static cold storage. Elevation of machine perfusion temperature up to 35°C may prove promising to refine ex vivo evaluation of the graft prior to transplantation., (© 2017 The Authors. Clinical Transplantation published by John Wiley & Sons Ltd.)