Temperature Dependency of Machine Perfusion Preservation with Histidine-Tryptophan-Ketoglutarate Solution on Ultrastructure of Porcine Liver Donated after Cardiac Death.

Introduction: The University of Wisconsin (UW) and histidine-tryptophan-ketoglutarate (HTK) are the most popular organ-preservative solutions. Ultrastructure of organelles reflects the functionality of cells, but less is understood about ultrastructural changes of hepatocytes after machine perfusion (MP) with HTK, than with UW solution.

Methods: We evaluated the ultrastructure of hepatocytes preserved in HTK solution during hypothermic (4°C) and midthermic (22°C) MP (HMP and MMP, respectively) temperatures using osmium maceration scanning electron microscopy.

Results: The functional ultrastructure of mitochondria in hepatocytes was maintained immediately after HMP and MMP. After 2 h in a porcine isolated liver reperfusion model (IRM) that simulates transplanted liver grafts, mitochondrial cristae became denser and some large vacuoles that we assumed were autophagosomes were detected in hepatocytes after HMP. Autophagy functions in the suppression of reactive oxygen generation and subsequent apoptosis, and these findings indicated that HMP is more effective than MMP when livers are preserved in HTK solution.

Conclusion: The present findings contradict the previous findings of the UW solution that MMP is more effective than HMP. Thus, various combinations of conditions for MP should be carefully optimized before changing preservatives.