A team led by transplant surgeon Erik Finger and bioengineer John Bischof at the University of Minnesota has successfully rewarmed pig kidneys that were vitrified and stored at -150 °C for months, in one case more than a year. After rewarming, the organs were tested in machines and transplanted into pigs, where they regained color and produced urine. Finger said that a decade ago he had low expectations for the approach, but after the last transplant he knew it was "a big deal."
The research, shared on the preprint server bioRxiv, is not yet peer-reviewed, and the team has not shown that the organs can sustain life over the long term. Still, outside experts described the result as a milestone. Cryobiologist Peter Kilbride said the field has finally reached a step many have tried and failed to achieve, while Harvard Medical School's Korkut Uygun called the work amazing and predicted it could lead to truly indefinite organ banking. Such banking would address the current 24-to-36-hour limit for preserving human organs, giving doctors time to match organs and prepare recipients, potentially reducing reliance on lifelong immunosuppressive drugs.
The breakthrough builds on earlier work with rat kidneys, but scaling up to pig organs—which are similar in size to human ones—required overcoming new hurdles. The team had to redesign the cryoprotectant cocktail used to prevent damaging ice crystals, a process Finger and Bischof said took three years. They also infused the organs with iron oxide nanoparticles that, when activated by an electromagnetic field, allowed for even rewarming throughout the larger tissue.