Optimization of Ex Vivo Machine Perfusion and Transplantation of Vascularized Composite Allografts.

Background Machine perfusion is gaining interest as an efficient method of tissue preservation of Vascularized Composite Allografts (VCA). The aim of this study was to develop a protocol for ex vivo subnormothermic oxygenated machine perfusion (SNMP) on rodent hindlimbs and to validate our protocol in a heterotopic hindlimb transplant model. Methods In this optimization study we compared three different solutions during 6 h of SNMP (n = 4 per group). Ten control limbs were stored in a preservation solution on Static Cold Storage [SCS]). During SNMP we monitored arterial flowrate, lactate levels, and edema. After SNMP, muscle biopsies were taken for histology examination, and energy charge analysis. We validated the best perfusion protocol in a heterotopic limb transplantation model with 30-d follow up (n = 13). As controls, we transplanted untreated limbs (n = 5) and hindlimbs preserved with either 6 or 24 h of SCS (n = 4 and n = 5). Results During SNMP, arterial outflow increased, and lactate clearance decreased in all groups. Total edema was significantly lower in the HBOC-201 group compared to the BSA group (P = 0.005), 4.9 (4.3-6.1) versus 48.8 (39.1-53.2) percentage, but not to the BSA + PEG group (P = 0.19). Energy charge levels of SCS controls decreased 4-fold compared to limbs perfused with acellular oxygen carrier HBOC-201, 0.10 (0.07-0.17) versus 0.46 (0.42-0.49) respectively (P = 0.002). Conclusions Six hours ex vivo SNMP of rodent hindlimbs using an acellular oxygen carrier HBOC-201 results in superior tissue preservation compared to conventional SCS.