Procurement and ex-situ perfusion of isolated slaughterhouse-derived livers as a model of donors after circulatory death

Ex-situ machine perfusion (MP) techniques are increasingly used in clinical settings, especially on grafts derived from donors after cardiac death (DCD). However, comprehension of biological effects elicited during MP are largely unknown and a substantial number of animal studies are presently focused on this topic. The aim of the present study was to describe a model of DCD based on ex-situ perfusion of liver grafts derived from animals dedicated to food production. Procurement took place within a slaughterhouse facility. A clinically fashioned closed circuit normothermic MP (NMP) was built up. Autologous blood-enriched perfusion fluid was adopted. Perfusate and tissue samples were collected to asses NMP functionality. Grafts were classified as transplantable (LT-G) or not (n-LT) according to clinical criteria, while histopathological analysis was used to confirm graft viability. After cold storage, the liver grafts were connected to the NMP. During the rewarming phase, temperature and flows were progressively increased to reach target values. At the end of NMP, 4 grafts were classified as LT-G and 3 nLT-G. Histology confirmed absence of major damage in LT-G, while diffuse necrosis appeared in nLT-G. Interestingly, in nLT-G an early impairment of hepatocyte respiratory chain, leading to cell necrosis and graft non-viability, was documented for the first time. These parameters, together with indocyanine-green dye and citrate clearance could contribute to graft evaluation in clinical settings. In conclusion, this model provides a promising and reproducible method to replace dedicated experimental animals in DCD and MP research, in line with the 3Rs principles.