Evaluation Using an Isolated Reperfusion Model for Porcine Liver Donated After Cardiac Death Preserved with Oxygenated Hypothermic Machine Perfusion

Combined Use of Subnormothermic Extracorporeal Support and Hypothermic Oxygenated Machine Perfusion for Liver Graft After Cardiac Death in Pigs

BACKGROUND

The use of grafts from donors after cardiac death (DCD) would greatly contribute to the expansion of the donor organ pool. This study aims to determine the benefits of extracorporeal membrane oxygenation (ECMO) and hypothermic oxygenated machine perfusion (HOPE) in a large animal model of DCD liver.

METHODS

After cardiac arrest, the abdominal aorta and the inferior vena cava were cannulated and connected to an ECMO circuit. Porcine livers were perfused in situ with ECMO at 22°C for 60 minutes after 45 minutes of cardiac death. Then, the livers were perfused for 4 hours by cold storage (CS) or HOPE. In group 1, non-in situ ECMO and grafts were preserved by HOPE. In group 2, in situ ECMO and grafts were preserved by HOPE. In group 3, in situ ECMO and grafts were preserved by CS. After preservation, all grafts were evaluated using an isolated reperfusion model (IRM) with autologous blood for 2 hours.

RESULTS

During HOPE, aspartate aminotransferase (AST) levels and hepatic arterial pressure in group 2 tended to be lower than in group 1. Hematoxylin-eosin staining findings after HOPE showed more massive sinusoidal congestion and hepatocyte cytoplasmic vacuolization in group 1 than in group 2. The AST and LDH levels in group 2 at the start-up of IRM tended to be lower than in group 1.

CONCLUSIONS

The combined use of in situ subnormothermic ECMO and HOPE is essential for the functional recovery of DCD liver grafts.

Beneficial effects of end-ischemic oxygenated machine perfusion preservation for split-liver transplantation in recovering graft function and reducing ischemia-reperfusion injury

This study examined the efficacy of end-ischemic hypothermic oxygenated machine perfusion preservation (HOPE) using an originally developed machine perfusion system for split-liver transplantation. Porcine split-liver grafts were created via 75% liver resection after 10 min of warm ischemia. In Group 1, grafts were preserved by simple cold storage (CS) for 8 h (CS group; n = 4). In Group 2, grafts were preserved by simple CS for 6 h and end-ischemic HOPE for 2 h (HOPE group; n = 5). All grafts were evaluated using an isolated ex vivo reperfusion model with autologous blood for 2 h. Biochemical markers (aspartate aminotransferase and lactate dehydrogenase levels) were significantly better immediately after reperfusion in the HOPE group than in the CS group. Furthermore, the HOPE group had a better histological score. The levels of inflammatory cytokines (tumor necrosis factor-α, interferon-γ, interleukin-1β, and interleukin-10) were significantly lower after reperfusion in the HOPE group. Therefore, we concluded that end-ischemic HOPE for split-liver transplantation can aid in recovering the graft function and reducing ischemia-reperfusion injury. HOPE, using our originally developed machine perfusion system, is safe and can improve graft function while attenuating liver injury due to preservation.

Current review of machine perfusion in liver transplantation from the Japanese perspective

In light of the present evidence, machine perfusion is opening up new horizons in the field of liver transplantation. Although many advances have been made in liver transplantation, organ preservation methods have so far changed very little. Static cold storage is universally used for graft preservation in liver transplantation; however, there is a need for better preservation methods, such as ex vivo machine perfusion, to improve the outcomes by decreasing warm ischemic damage. Based on the findings of basic and clinical trials, hypothermic and normothermic machine perfusion techniques are now commercially available and include the OrganOx metra, Liver Assist, Cleveland NMP device, Organ Care System, and LifePort Liver. Recent clinical trials have provided further evidence for the potential role of normothermic machine perfusion to resuscitate and subsequently improve utilization of marginal or currently discarded livers. Further studies are required to explore the longer-term outcomes, late biliary complications, outcomes in specific high-risk groups, viability biomarkers, optimum and maximum perfusion duration, perfusate composition, and liver-directed therapeutic interventions during normothermic machine perfusion. The use of organs from marginal donors after brain death, such as fatty livers and the livers from elderly donors with multiple comorbidities, may be accepted for machine perfusion in Japan in the near future.

Evaluation of the ex vivo liver viability using a nuclear magnetic resonance relaxation time-based assay in a porcine machine perfusion model

There is a dearth of effective parameters for selecting potentially transplantable liver grafts from expanded-criteria donors. In this study, we used a nuclear magnetic resonance (NMR) relaxation analyzer-based assay to assess the viability of ex vivo livers obtained via porcine donation after circulatory death (DCD). Ex situ normothermic machine perfusion (NMP) was utilized as a platform for viability test of porcine DCD donor livers. A liver-targeted contrast agent, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), was injected into the perfusate during NMP, and the dynamic biliary excretion of the Gd-EOB-DTPA was monitored by measuring the longitudinal relaxation time (T1). The longitudinal relaxation rate (R1) of the bile was served as a parameter. The delay of increase in biliary R1 during early stage of NMP indicated the impaired function of liver grafts in both warm and cold ischemia injury, which was correlated with the change of alanine aminotransferase. The preservative superiority in cold ischemia of dual hypothermic oxygenated machine perfusion could also be verified by assessing biliary R1 and other biochemical parameters. This study allows for the dynamic assessment of the viability of porcine DCD donor livers by combined usage of ex situ NMP and NMR relaxation time based assay, which lays a foundation for further clinical application.

Impact of human-derived hemoglobin based oxygen vesicles as a machine perfusion solution for liver donation after cardiac death in a pig model

The recent clinical application of perfusion technology for the machine preservation of donation after cardiac death (DCD) grafts has some advantages. Oxygenation has been proposed for the preservation of DCD liver grafts. The aim of this study is to clarify whether the use of HbV-containing preservation solution during the subnormothermic machine perfusion (SNMP) of the liver graft improves the graft function of DCD porcine livers in an ex vivo reperfusion model. Pig livers were excised after 60 minutes of warm ischemic time and were preserved under one of three preservation conditions for 4 hours. The preservation conditions were as follows: 4°C cold storage (CS group; N = 5), Hypothermic machine preservation (HMP) with UW gluconate solution (HMP group; N = 5), SNMP (21°C) with UW gluconate solution (SNMP group; N = 5), SNMP (21°C) with HbVs (Hb; 1.8 mg/dl) perfusate (SNMP+HbV group; N = 5). Autologous blood perfusion was performed for 2 hours in an isolated liver reperfusion model (IRM). The oxygen consumption of the SNMP and SNMP+HbV group was higher than the HMP groups (p < 0.05). During the reperfusion, the AST level in the SNMP+HbV group was lower than that in the CS, HMP and SNMP groups. The changes in pH after reperfusion was significantly lower in SNMP+HbV group than CS and HMP groups. The ultrastructural findings indicated that the mitochondria of the SNMP+HbV group was well maintained in comparison to the CS, HMP and SNMP groups. The SNMP+HbVs preservation solution protected against metabolic acidosis and preserved the liver function after reperfusion injury in the DCD liver.

Impact of Machine Perfusion on Sinusoid Microcirculation of Liver Graft Donated After Cardiac Death

BACKGROUND

The present study examined the impact of oxygenated machine perfusion on preservation of liver grafts donated after cardiac death by measuring sinusoidal endothelial injury and microcirculatory disturbances.

MATERIALS AND METHODS

Fifteen porcine livers were retrieved 60 min after warm ischemia and allocated into three groups as follows: (1) CS group: static cold storage, (2) HMP group: oxygenated hypothermic perfusion preservation, (3) SNMP group: oxygenated subnormothermic perfusion preservation. The liver grafts donated after cardiac death were preserved for 4 h in different treatment conditions mentioned previously, then subject to ex vivo reperfusion for 2 h using diluted allogeneic blood. The hemodynamic parameters, liver function tests, tissue adenosine triphosphate (ATP) levels, and immunohistochemical findings were investigated.

RESULTS

The number of sinusoidal epithelial cells and trabecular structures were maintained after 4 h of preservation in the CS, HMP, and SNMP group. Liver tissue ATP levels after 4 h of preservation in the HMP and SNMP groups were significantly higher compared with that in the CS group. The sinusoidal epithelial cells were significantly exfoliated to a more severe extent in the CS group than in the HMP and SNMP groups. Intrasinusoidal platelet aggregation occurred more frequently in the CS group than in the HMP and SNMP groups.

CONCLUSIONS

The results indicated that oxygenated machine perfusion preservation was important to prevent the depletion of tissue ATP and maintain sinusoidal homeostasis regardless of the perfusate temperature. Our findings suggest oxygenated machine perfusion preservation as an effective alternative to static cold storage.

Initial perfusate purification during subnormothermic machine perfusion for porcine liver donated after cardiac death

Improvement of machine perfusion (MP) technologies is required to enhance organ quality for donor after cardiac death (DCD) grafts. Installing a dialyzer or a filter into the perfusion circuit to maintain the perfusate condition has some advantages. However, the consequences of purification perfusate during subnormothermic machine perfusion (SNMP) remain unexplained. In this study, the effects of initial purification perfusate with simple method of replacing the first 0.5-L perfusate during SNMP were investigated to consider installation effect of the filter or the dialyzer. Porcine liver grafts, which have 60-min warm ischemia time, were procured to imitate the DCD graft condition. Purified SNMP (PSNMP) results were compared with simple cold storage and conventional SNMP. In PSNMP, initial perfusate of 0.5 L was removed to substitute for purification. After preservation process, the preserved grafts were reperfused with diluted autologous blood for 2 h under normothermic machine perfusion condition to evaluate the liver function using an isolated reperfusion model. The vascular pressures, enzyme release rates and the metabolic indexes during reperfusion were analyzed. The pressures in the hepatic artery after reperfusion 60 min were significantly lower in PSNMP group compared with cold storage (CS) and SNMP groups. In addition, lactate dehydrogenase and alkaline phosphatase were significantly lower after PSNMP than after the CS or SNMP. Also, the metabolic indexes of hyaluronic acid and lactate were significantly decreased by purifying the perfusate in MP preservation than in CS or SNMP. The effectiveness of initial purification perfusate during SNMP was investigated.