Diluted blood reperfusion as a model for transplantation of ischemic rat livers: alanine aminotransferase is a direct indicator of viability.

Donors after cardiac death present a significant pool of untapped organs for transplantation, and use of machine perfusion strategies has been an active focus area in experimental transplantation. However, despite 2 decades of research, a gold standard has yet to emerge for machine perfusion systems and protocols. Whole blood reperfusion has been used as a surrogate for organ transplantation, especially as a model for the short-term response posttransplantation, and for optimization of perfusion systems. Although it is known that there is a strong correlation between liver function in whole-blood reperfusion and survival, the exact nature of these correlations, and to what extent they can be considered as an indicator of viability for transplantation/recipient survival, remain unclear. In this work, we demonstrate that diluted whole-blood reperfusion can be used as a direct model for transplantation of ischemic rat liver grafts. Specifically, we show that recipient survival can be predicted based simply on the value of alanine aminotransferase during perfusion, providing quantitative criteria of viability for use in this animal model. These results indicate that in the rat model graft survival is highly correlated with hepatocellular damage.

Sequential cold storage and normothermic perfusion of the ischemic rat liver.

Extending transplant criteria to include livers obtained from donors after cardiac death (DCD) could increase the liver donor pool, but conventional simple cold storage of these ischemic organs can lead to poor graft function after transplantation. Experimental normothermic machine perfusion has previously proven to be useful for the recovery and preservation of DCD livers, but it is more complicated than conventional cold storage, and, therefore, is perhaps not practical during the entire preservation period. In clinical situations, the combined use of simple cold storage and normothermic perfusion preservation of DCD livers might be more realistic, but even a brief period of cold storage prior to normothermic preservation has been suggested to have a negative impact on graft viability. In this study we show that rat livers subjected to 45 minutes of ex vivo warm ischemia followed by 2 hours of simple cold storage can be reclaimed by 4 hours of normothermic machine perfusion. These livers could be orthotopically transplanted into syngeneic recipients with 100% survival after 4 weeks (N = 10), similar to the survival of animals that received fresh livers that were stored on ice in University of Wisconsin (UW) solution for 6 hours (N = 6). On the other hand, rats that received ischemic livers preserved on ice in UW solution for 6 hours (N = 6) all died within 12 hours after transplantation. These results suggest that normothermic perfusion can be used to reclaim DCD livers subjected to an additional period of cold ischemia during hypothermic storage.