Background: Hibernation is a complex and multi stage process that leads to unique metabolic changes over an extended period of time. Regulatory genes and transcription factors involved in this processes are also present in non-hibernator mammals. This study compares ex-vivo metabolic and genomic pathways of porcine livers perfused at 21[deg]C over a 9 hour period with published data from hibernating Ursus americanus (UA).

Methods: Six swine livers were preserved with MP and perfused with a novel hemoglobin-based oxygen carrier (HBOC). Perfusate samples were collected every three hours and post-transplantation bile samples were collected daily for 5 days. Metabolomics studies were performed through the analysis of 600 metabolites. Liver biopsies were obtained at baseline and after preservation and 25,000 genes were assessed by microarrays. All liver allografts were subsequently transplanted and compared with a group (n=6) preserved with cold storage (CS).

Results: Porcine liver oxygen consumption during MP was similar to that of hibernating UA (0.096 vs 0.083 ml/g/h) and bile production was very limited (1ml/h). Most of the signature hibernation metabolic pathways described in the UA were also observed in the porcine livers at 21[deg]C. 1) Significant reduction in the expression of genes involved in glycolysis. 2) Gluconeogenesis was significantly upregulated. 3) Increased carbohydrate synthesis was confirmed by remarkable increase in levels of glucose (↑7.24 folds, p<0.001) and fructose 4) β-oxidation of fatty acids and the production of ketone bodies significantly increased [3-hydroxybutyrate (↑154 folds, p<0.001) and acetoacetate (↑13 folds, p<0.001)]. 5) Fatty acid synthesis was downregulated. 6) Amino acid levels were significantly higher [alanine (↑12 folds, p<0.001), glutamate (↑230 folds, p<0.001), serine (↑417 folds, p<0.001), glycine (↑90 folds, p<0.001), tyrosine (↑8 folds, p<0.001), and glutamine (↑230 folds, p<0.001)]. 7) Expression ratio of known hibernation regulatory genes were kept above 90% during MP and NF-kB expression was significantly higher (p<0.001) after MP.

Conclusion: MP at 21[deg]C appears to simulate/induce a hibernation-like metabolic profile in a non-hibernator mammal. Future investigations on transcription factors, miRNAs and in the genomic expressions of hibernation specific proteins are underway. Livers preserved within a hibernation-like environment had a significantly (p<0.05) better allograft survival (100%) when compared to cold storage (33%) over a 5 day period.

CITATION INFORMATION: Banan B, Dobrowolski S, Michalopoulos G, Fontes P. Machine Perfusion (MP) at 21[deg]C Simulates Hibernation Metabolic Pathways in a Non-Hibernator Mammal. Am J Transplant. 2016;16 (suppl 3).

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