Reinier J. de Vries et al successfully developed a supercooling protocol that could preserve human livers at –4 °C to extend the ex-vivo life of the organ by upto 27 hours. The team had previously shown that supercooled ice-free storage at –6 °C could extend viable preservation of rat livers. They were able to do this by adding a modified glucose compound, 3-OMG, and PEG-35kD to the protective solution that they use to cool the livers. The risk of scaling supercooling preservation to human organs which were intrinsically limited because of increased ice crystal formation was successfully resolved. The scientists removed air from the storage solution bag prior to supercooling to effectively eliminate the chance of spontaneous ice nucleation on the surface of the organ. The team added ingredients like trehalose and glycerol to protect and stabilize the hepatocytes. In addition, researchers used subnormothermic machine perfusion to deliver oxygen and nutrients to capillaries in liver tissues while outside the body. This enabled the organ to adjust and remain at -4oC with the protective solution spreading throughout the organ more uniformly. Findings showed that the viability of livers before and after supercooling remains unchanged.
Source: Nature Biotechnology 9 September 2019 https://www.nature.com/articles/s41587-019-0223-y