Kidney Metabolism During Normothermic Machine Perfusion Differs Substantially From In Vivo Conditions

Background. – Normothermic machine perfusion (NMP) is being explored as a promising method to assess pretransplant viability and potentially enhance the functional performance of deceased-donor kidneys. To realize NMPs full potential, however, understanding ex vivo kidney metabolism and its differences from our clinical in vivo reference frame is essential. Here, a multiomics approach including metabolomics, transcriptomics, and proteomics analyses was used to explore metabolic differences between ex vivo and in vivo kidneys and assess the additional impact of warm ischemia on ex vivo kidney metabolism. Methods. – Paired kidneys from laboratory pigs (n = 30) sustained either minimal or 75 min of warm ischemia. All kidneys underwent 6 h of oxygenated hypothermic machine perfusion followed by 6 h of NMP. Cortical tissue samples were collected in vivo, after cold preservation, and after NMP for metabolomics, transcriptomics, and proteomics analyses. Results. – Metabolomics analysis revealed increased branched-chain amino acid metabolism and decreased uracil- and cytidine-containing pyrimidine metabolism after NMP compared with in vivo. Subsequent analyses demonstrated enhanced glycolysis, decreased gluconeogenesis, impaired tricarboxylic acid cycle activity, and nicotinamide adenine dinucleotide depletion. Multiomics analysis showed associations between metabolic alterations and increased immune response and cell death processes during NMP. Conclusions. – Together, our findings indicate substantial differences between in vivo and ex vivo kidney metabolism and reveal a link between metabolic alterations and potentially detrimental cellular processes.