Introduction: Extending the maximum preservation time of donor organs could dramatically improve the outcome of organ transplantation. Static cold storage (SCS) at +5[deg]C is the clinical standard and allows for maximum liver preservation times of 12 hours. Recently, rat livers were supercooled to -6[deg]C for 3 days and transplanted with 100% long term survival. The main goal of this study is to translate supercooling to human livers. We hypothesized that the human liver preservation time can be doubled to 24 hours, by storing the organ at -4[deg]C in an ice-free, supercooled state, followed by recovery with sub-normothermic machine perfusion (SNMP).

Method: Marginal human livers were recovered from conventional SCS and loaded with the cryoprotectant agent (CPA) 3-O-methyl-D-glucopyranose using SNMP. Next, the livers were gradually cooled and flushed with UW supplemented with the CPAs polyethylene glycol, glycerol and trehalose. Subsequently, the livers were supercooled and stored for 20 hours at -4[deg]C. After supercooling the CPAs were washed out and the livers were recovered using SNMP. Pre- and post-supercooling SNMP conditions were identical. Vascular resistance, blood gas parameters, electrolytes, urea, liver enzymes and bile production were measured every 30 minutes during pre- and post- supercooling SNMP. Bilateral wedge biopsies for the measurement of energy status and conventional histology were also sampled throughout the protocol.

Results: Post-supercooling livers showed preserved energy status, which is correlated to graft viability. Also, no differences were observed between arterial resistance and oxygen consumption comparing pre- and post-supercooling SNMP. Viable livers produced bile and urea pre-supercooling and continued production post supercooling. Similarly, histology shows minimal necrosis, no edema, preserved billiary stem cells and limited endothelial injury. Common markers of liver damage, such as ALT and AST, were slightly elevated post-supercooling, as compared to pre-SNMP conditions.

Conclusion: Preliminary results demonstrate the feasibility of storing whole human at sub-zero temperatures in the supercooled state to double the preservation duration, as compared to clinical standards. Moreover, we identified important CPAs, perfusion- and supercooling conditions which are critical for success.

CITATION INFORMATION: de Vries R., Tessier S., Banik P., Ozer S., Napgal S., Cronin S., Markmann J., Yeh H., Uygun K. Supercooling of Human Livers to Extend the Preservation Time for Transplantation Am J Transplant. 2017;17 (suppl 3).

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