Supercooling makes livers for transplants last longer
Chilling to subzero temperatures greatly increased survival time of rats’ organs outside the body
By Nsikan Akpan
“Supercold but unfrozen” is the idea behind a new procedure that tripled the time a rat liver can survive outside the body. If the procedure works similarly well for humans, the method may grant life-saving transplants a passport for traveling across the world, scientist report June 29 in Nature Medicine.
Organs quickly stop working once removed from the body. To stay viable, donated organs are stored inside plastic bags filled with a liquid preservative and kept on ice. But even with this procedure, a human liver lasts only 12 hours, a time frame that instills geographical limits between organ donors and recipients. Patients waiting for a liver in New York are 20 times as likely to receive one as those in Washington state or Kentucky. If the technique works for humans, it could introduce parity, meaning an organ donated in Houston could help a patient in Honolulu or even Hong Kong.
Prolonging the time frame could save lives, but attempts at long-term preservation have floundered. Most researchers have tried freezing the organs, but the process damages cells and blood vessels, says study coleader Korkut Uygun, a chemical engineer at Harvard University. “We wanted to reduce the temperature but avoid freezing at all costs,” he says. “We didn’t think that we could bring the cells back from a frozen state, given that’s been tried for 20 years now with no success.”
So rather than freeze, the team supercooled organs, a process whereby tissue chills to subzero temperatures without its water turning to ice. The key was finding the right cryopreservatives — ones that could maintain cellular architecture without being toxic. The team settled on two compounds: 3-O-methyl-D-glucose, which prevents ice from forming inside cells, and polyethylene glycol, which does the same for the exterior. Uygun is seeking Food and Drug Administration approval for use of the chemicals as cryopreservatives in humans.