312 First Vascularized Composite Allotransplantations in Rats after 6 Hours of Ex Vivosubnormothermic Machine Perfusion Using an Hemoglobin Oxygen Carrier: A Proof of Concept Study

Abstract Introduction Vascularized composite allotransplantation (VCA) remains the most advanced treatment option to restore motor function and aesthetics in patients living with devastating disfigurements. However, the current method of organ preservation (static cold storage), successfully used in solid organ transplantation, can jeopardize the quality of VCA grafts and could accelerate the risk of chronic rejection. Ex vivo subnormothermic oxygenated machine perfusion (SNMP) is a novel method of preservation demonstrated to improve the quality of solid organs prior to transplantation. The aim of this study was to transplant a VCA (heterotopic hind limb model) after 6 hours of SNMP. Methods Seven rodent hind limbs were procured after systemic heparinization (300 IU). All limbs were perfused for 6 hours via the femoral artery using a pressure-controlled system, and the venous outflow was prepared for sample collection. The perfusion solution base consisted of a mixture of muscle media with growth factors, bovine serum albumin, polyethylene glycol and an acellular oxygen carrier. Arterial flow and vascular resistance were monitored. Lactate levels and oxygen consumption were evaluated as markers of viability of muscle tissue. After 6 hours of SNMP, 5 limbs were prepared for biopsy collection. Muscle biopsies analyzed with liquid chromatography-mass spectrometry for energetic cofactors, referred to as energy charge. In solid organ transplantation, peri-transplant energy status significantly correlates with post-transplant outcome. Furthermore, muscle biopsies were prepared for cell culture to assess viability. Two limbs were transplanted in a heterotopic fashion. Results Arterial outflow and vascular resistance remained stable throughout perfusion, between 0.5-3.0 mL/min and 20-40 mmHg/mL/min respectively. During 6 hours of perfusion, lactate levels decreased while potassium levels and oxygen consumption remained stable. Energy charge levels were comparable to fresh controls. After 6 hours of perfusion muscle biopsy had 80% viability and cells grew great in culture with no signs of contamination. Median post-operative follow up was 48 hours and grafts showed no signs of early graft failure or infection. Conclusions This study demonstrates that 6 hours ex vivo SNMP of rat hind limbs is feasible and viability of the grafts are confirmed with both cell culture and in a transplant model. Current studies are investigating superiority of SNMP over SCS in our tran