A new supercooling technique to increase the amount of time that organs can remain viable outside of the body has succeeded in clinical trials involving rats, and could improve transplantation outcomes in humans. The study results were published in the journal Nature Medicine and supported by the National Institute of Biomedical Imaging and Bioengineering and the National Institute of Diabetes and Digestive and Kidney Disease.
Presently, human livers can be preserved outside of the body for up to 24 hours with cold temperatures and a chemical solution to help liver tissue stay alive while in transit to the recipient site. While single cells and simple tissues have been successfully cryopreserved at temperatures of -320.8 degrees Fahrenheit, extensive tissue damage can occur to organs in this process due to multiple cell types and reactions of other structures to the cold in organs.
Researchers at the Center for Engineering in Medicine at Massachusetts General Hospital in Boston created a process that uses machine perfusion (the delivery of oxygen and nutrients to capillaries in biological tissues while outside the body) to add 3-OMG (3-O-methyl-D-glucose) for preventing irreversible cell damage. The 3-OMG collects in the liver cells because it cannot be metabolized by the cells and proceeds as a protectant against the cold. PEG-35kD (polyethylene glycol) was also added to protect cell membranes as ethylene glycol lowers the freezing point of the solution. The livers were slowly cooled to 21 degrees Fahrenheit without inducing freezing and the organs were preserved via supercooling. The organs were stored for several days that then rewarmed using machine perfusion while administering oxygen and other nutrients to prepare the organ for transplantation.
The supercooled livers were stored for 72 hours and 96 hours at 21 degree Farenheit. The rats with the 72 hour supercooled livers survived 3 months, with those receiving the 96 hour supercooled livers having a 58% survival rate. No rats receiving transplants with current methods survived. Next steps for research include conducting similar studies on larger animals and eventually humans for optimal organ transplant outcomes.
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