Background: The composition of cold storage solutions is a critical factor to maintain the quality of the transplanted grafts. The University of Wisconsin (UW) preservation solution is the most used in liver transplantation. However, it shows important limitations, especially when grafts are derived from extended criteria donors, such as steatotic livers or they are submitted to prolonged ischemic periods. The UW solution contains HES (inducing erythrocyte aggregation), high-K+ concentration (causing hyperkalemic cardiac arrest) and some drugs like allopurinol, GSH or adenosine which do not confer any protection. We have developed a new liquid called PERLA® (patented by Barcelona University; PCT/ES2009/000267). It is a high-Na+ liquid containing polyethylene glycol-35, carvedilol, trimetazidine and tacrolimus. These three last molecules are potent modulators of the main pathways responsible of ischemia-reperfusion (I/R) injury. We evaluated the effectiveness of PERLA® compared to UW solution in preserving non-steatotic and steatotic rat livers.

Methods: Two models were used: the isolated perfused liver and the orthotopic liver transplantation. Homozygous (obese) and heterozygous (lean) Zucker rats between 16 and 18 weeks were used. In the ex vivo perfused model, grafts were cold preserved for 24 h using either UW or PERLA® solution and then, they were perfused ex vivo for 120 min at 37°C. In in vivo model, steatotic and non-steatotic grafts were cold stored for 6 h using either UW or PERLA® solutions and transplanted to rats. Hepatic functionality and damage were measured by quantifying transaminases (ALT/AST), bile flow rate, malondialdehyde (MDA), bromosulfophthalein (BSP) clearance, purine nucleotide phosphorylase (PNP), ATP and caspase-3 levels. The animal survival after 14 days was also assessed.

Results: By using the ex vivo model, the cold conservation of non-steatotic and steatotic livers in PERLA® solution reduced hepatic injury, ameliorated liver functionality, preserved energy metabolism and prevented oxidative stress as well as apoptosis, as compared to conservation with UW solution. After transplantation, PERLA® solution reduced necrosis and attenuated hepatic damage in the recipients of either non-steatotic or steatotic grafts, as compared to UW solution. The survival of the transplanted animals was higher in the PERLA® group for both non-steatotic and steatotic liver grafts compared to UW group. We noted that the recipient transplanted with steatotic livers showed 75 % and 40 % survival for PERLA® and UW groups, respectively. For recipients transplanted with non-steatotic livers, we found 92% and 83% survival in PERLA® and UW groups, respectively.

Conclusion: PERLA® is an effective liquid to preserve grafts collected from extended criteria donors. It allows increasing the tolerance of non-steatotic and steatotic livers against cold ischemia reperfusion damage, diminishing the risk of primary failure following transplantation.