Two Compartment Evaluation of Liver Grafts During Acellular Room Temperature Machine Perfusion (acRTMP) in a Rat Liver Transplant Model

Abstract

BackgroundSubnormothermic machine perfusion (SNMP) of liver grafts is currently less clinically developed than normothermic and hypothermic approaches, but may have logistical advantages. At intermediate temperatures, the oxygen demand of the graft is low enough to be satisfied with an acellular perfusate, obviating the need for oxygen carrying molecules. This intermediate metabolic rate, however, is sufficient to support the production of bile, which is emerging as an important indicator of graft injury and viability. In this study, we hypothesized that the biliary compartment would be more sensitive than perfusate in detecting graft injury during SNMP.MethodsTo test this hypothesis in a rat model, we performed liver transplants with DCD and control liver grafts after 1 h of acellular room temperature machine perfusion (acRTMP) or static cold storage (SCS). Point of care liver function tests were measured in biliary and perfusate samples after 1 h of machine perfusion. Following transplantation, rats were sacrificed at 24 h for assessment of post-transplant graft function and histology.ResultsAll point-of-care liver function tests were significantly more concentrated in the biliary compartment than the perfusate compartment during acRTMP. DCD liver grafts could be distinguished from control liver grafts by significantly higher markers of hepatocyte injury (AST, ALT) in the biliary compartment, but not in the perfusate compartment. Classical markers of cholangiocyte injury, such as gammy-glut amyl transferase (GGT), amylase (AML), and alkaline phosphatase were detectable in the biliary compartment, but not in the perfusate compartment. In comparison to SCS, graft preservation by acRTMP produced a significant survival benefit in DCD liver transplantation (75 vs. 0%, p < 0.0030).ConclusionTogether, these findings demonstrate that during acRTMP, the biliary compartment may be a more sensitive indicator of graft injury than the perfusate compartment. Moreover, acRTMP provides superior graft preservation to SCS in rat DCD liver transplantation.

Optimizing DCD Liver Grafts With Prolonged Warm Ischemic Time Using Stabilized Plasmin in a Static Cold Storage Orthotopic Rat Liver Transplant Model

“…After 3–5 min, the portal vein was clamped with a microsurgery vascular clamp and the hepatic artery was ligated with 7-0 ties and divided to induce warm ischemic time. After 30 min, the donor liver was procured as previously described 11 and prepared for implant via a modified vascular cuff technique. 12 Preparation of the liver graft was performed at ambient temperature, rather than on ice, to account for the last 15 min of warm ischemia time.…”

“…The liver was then transplanted into the recipient using the modified vascular cuff technique as we have previously described. 11 The bile duct anastomosis was performed using a stent between the recipient and donor bile ducts. No hepatic artery anastomosis was performed.…”

“…Following the 45-min warm ischemic period, the liver was flushed with 50 mL of HTK containing either plasmin or albumin through the portal vein. Then, the donor liver procurement was done as previously described, 11 and the organ was prepared for implant via a modified vascular cuff technique 12 while on ice. After cuffing, the graft was flushed for a second time with 50 mL of HTK containing either plasmin or albumin and then stored on ice at 4 °C for 1 h. After 1 h, the graft was flushed for a third and final time with 50 mL of HTK containing either plasmin or albumin.…”

Sterile inflammation in liver transplantation

“…Lastly, other groups such as ( 187 , 188 ) have illustrated the efficacy of optimizing the balance between metabolic demand (controlled by temperature) and oxygenation level of the perfusate. In doing so, they have introduced a modality termed subnormothermic machine perfusion (SNMP): perfusion of an organ at room temperature (21°C), in an effort to keep the organ metabolizing at a level sufficient to allow assessment and treatment while keeping its demand for oxygen low enough to prevent IRI injury ( 187 ). This also allows for the use of an acellular perfusate, which is more readily available than blood based perfusates.…”

Comprehensive review of the application of MP and the potential for graft modification

“…In the clinical trial, HMP was demonstrated to be a safe and feasible option, with potential superiority to SCS in terms of liver injury and postoperative complications (5). Since then, several experimental studies, along with a handful of clinical trials, have aimed to demonstrate the superiority of dynamic preservation methods-MP systems-in the reduction of ischemia reperfusion injury of the liver graft when compared to SCS (6)(7)(8)(9). Thus, under the premise of reducing graft injury before transplantation, research efforts have been toward the evaluation of the potential role of MP as a pathway to lessen the unfavorable shortage of liver organs by increasing the usage of all available organs.…”