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Supercooling preserves donor livers for more than a day

The breakthrough could mean that fewer organs go to waste before they make it into a transplant recipient.

ByKatherine J. WuNOVA NextNOVA Next

By perfusing organs with a chemical cocktail that keeps them from freezing at subzero temperatures, researchers can preserve human livers for more than a day. Image Credit: Massachusetts General Hospital

With the help of a chemical treatment that keeps organs from freezing at subzero centigrade temperatures, a team of researchers has tripled the typical shelf life of donated livers from nine to 27 hours.

By extending the amount of time tissue remains viable outside the body, the new “supercooling” method could someday reduce the number of donor organs that expire—and must be discarded—before they make it to a recipient. That could be a boon for the many patients on transplant waiting lists, including more than 110,000 people in the United States alone.

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After donor organs are removed from a body, they’re typically stored on ice at around 4 degrees Celsius (39 degrees Fahrenheit)—a temperature that keeps them viable for just a few hours. In the case of livers, doctors have somewhere between nine and 12 hours to transport the organ to its recipient, making every transplant “a race against the clock,” study author Reinier de Vries of Harvard Medical School told Clare Wilson at New Scientist.

That timeline could be extended if organs could be stored at temperatures below freezing—that is, 0 degrees Celsius (32 degrees Fahrenheit)—but as ice crystals form (and then later melt), they can damage organs and even render them unusable. The method devised by de Vries’ team, described in a study published today in the journal Nature Biotechnology, is the first to develop a workaround to this problem.

In the study, the researchers acquired human livers that had gone up for transplant, but weren’t claimed. They then used a machine to perfuse each organ with a cocktail of chemicals, including two compounds called trehalose and glycerol, that acted like a gentle antifreeze. Because ice tends to form where liquid contacts gas, the storage bag containing the mixture was also purged of air. (The sugars are later flushed out with a similar perfusion procedure.)

None of the preserved livers ultimately made it into bodies. But when the researched pumped three of them up with blood at body temperature to simulate a transplant, they found the livers had survived the ordeal unscathed, and could still take up oxygen, produce bile, and perform other normal liver functions—even after 27 hours outside a human body.

“That is impressive,” Ina Jochmans, a researcher and transplant surgeon at KU Leuven who was not involved in the study, wrote in an email to Sarah Zhang at The Atlantic.

The researchers didn’t check for viability past this point, but de Vries thinks they haven’t yet hit their limit, Wilson reports. Further down the road, the team wants to see how the supercooled organs fare in large animals like pigs, study author Shannon Tessier, a biomedical engineer also at Harvard and Mass General, told Maria Temming at Science News. “We actually want to show that the animals survive transplantation,” she said. “Then, hopefully we can think about clinical trials.”

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Top left: The machine perfusion system. Top right: A liver recovering from perfusion. Bottom left: A liver in the supercooling process. Bottom right: A liver being perfused with blood at the end of the procedure. Image Credit: de Vries et al., Nature Biotechnology, 2019

Malcolm MacConmara, a transplant surgeon at the University of Texas Southwestern Medical Center in Dallas who was not involved in the study, praised the new study for its elegance, Temming reports. Although the researchers used only livers in their trial, other organs, such as hearts—which can begin to deteriorate after just four hours—stand to benefit from the technology as well. (Notably, lungs, which are full of air, could pose a challenge.)

If that’s the case, the number of donated organs that end up going to waste could decrease in the future, Jedediah Lewis of the nonprofit Organ Preservation Alliance, who was not involved in the study, told Zhang. The tight timelines of current protocols restrict organs to certain geographical areas, reducing the number of potential patient matches. If doctors don’t find a good candidate within the few hours they have, the organ never finds a home.

A brief (and protected) plunge below freezing, however, means organs can—quite literally—go further. As James Shapiro, a transplant surgeon at the University of Alberta in Canada who wasn’t involved in the study, tells Temming, that “could really open up the possibility of saving more lives.”

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