Human livers can be stored at - 4 °C using an improved supercooling method described in a paper published this week in Nature Biotechnology. This protocol can extend the life of the organ outside the body by 27 hours.
The lack of technology to preserve organs for more than a few hours is one of the fundamental causes of the donor organ shortage crisis. The current standard for hypothermic maintenance at + 4 °C preserves livers for less than 12 hours. Korkut Uygun and colleagues have previously shown that supercooled, ice-free storage at - 6 °C can extend the preservation of rat livers. However, the ability to scale this supercooling method to human organs is limited by several factors.
In this study, Reinier de Vries, Shannon Tessier, Korkut Uygun and colleagues describe an improved supercooling method that prevents the freezing of human livers. The authors were able to store livers at - 4 °C with supercooling, extending the life of the donor organs by 27 hours, when compared to current methods of preservation. They used subnormothermic machine perfusion, a technique that continuously pumps oxygen and nutrients at about 20 °C through the liver, to recover the organs from supercooling. The viability of the livers before and after supercooling was unchanged, and supercooled livers were able to withstand the stress of simulated transplantation.
The authors conclude that this research supports the use of subzero organ preservation in the clinic. However, long-term survival experiments with transplanted supercooled livers in large animal models will be needed first.