Ex Vivo Reperfusion Model to Evaluate Utility of Machine Preservation for Porcine Liver Donated After Cardiac Death

Continuous oxygen monitoring to enhance ex-vivo organ machine perfusion and reconstructive surgery

Continuous oxygenation monitoring of machine-perfused organs or transposed autologous tissue is not currently implemented in clinical practice. Oxygenation is a critical parameter that could be used to verify tissue viability and guide corrective interventions, such as perfusion machine parameters or surgical revision. This work presents an innovative technology based on oxygen-sensitive, phosphorescent metalloporphyrin allowing continuous and non-invasive oxygen monitoring of ex-vivo perfused vascularized fasciocutaneous flaps. The method comprises a small, low-energy optical transcutaneous oxygen sensor applied on the flap's skin paddle as well as oxygen sensing devices placed into the tubing. An intermittent perfusion setting was designed to study the response time and accuracy of this technology over a total of 54 perfusion cycles. We further evaluated correlation between the continuous oxygen measurements and gold-standard perfusion viability metrics such as vascular resistance, with good agreement suggesting potential to monitor graft viability at high frequency, opening the possibility to employ feedback control algorithms in the future. This proof-of-concept study opens a range of research and clinical applications in reconstructive surgery and transplantation at a time when perfusion machines undergo rapid clinical adoption with potential to improve outcomes across a variety of surgical procedures and dramatically increase access to transplant medicine.

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.

Applicability of Hypothermic Oxygenate Machine Perfusion Preservation for Split-Liver Transplantation in a Porcine Model: An Experimental Study

Background

Split-liver transplantation can be useful in situations of limited donor resources. However, novel preservation methods are required to help the recipient recover from severe ischemic reperfusion injury incurred due to receiving a relatively small liver graft.

Material/Methods

Our experiment was performed using porcine livers without warm ischemia time, assuming a brain-dead organ. We made porcine split-liver grafts by 75% liver resection at the back table and divided the specimens into 4 groups. Group 1 was preserved with simple cold storage after splitting (CS; n=3), Group 2 was preserved with hypothermic perfusion preservation (HMP) after splitting (SBP; n=3), Group 3 was preserved with HMP after splitting under perfusion preservation (SDP; n=4), and Group 4 had the whole liver perfused as control grafts (Whole Liver; n=3). To assess potential methods of preservation and their effects, all grafts were evaluated by an ex vivo isolated liver reperfusion model using diluted autologous blood.

Results

Portal vein pressure resistances during reperfusion were low in Group3 (SDP). Hepatic artery pressure resistances during reperfusion were markedly higher in Group 1(CS) than in the other groups. The levels of AST and LDH were high and increased at 2 h after reperfusion in Group 1 (CS). The histological findings show that the liver cell structure was irregular in Group 1 (CS) but remained regular in Groups 2 (SBP) and 3 (SDP). Histological Suzuki scores were also significantly better in Groups 2 (SBP) and 3 (SDP) compared with Group 1 (CS).

Conclusions

Splitting the liver under machine perfusion preservation may help restore the function and reduce ischemia-reperfusion injury.

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.