Pig kidneys survive year-long freezing and transplantation
Donor organs can only survive outside the body for hours. That keeps transplant waiting lists long and costly. Researchers have now managed to freeze pig kidneys for up to a year and successfully transplant them afterwards.
The technique is called vitrification: freezing tissue so rapidly and with such precision that no ice crystals form to damage cells. The challenge with large organs is that both the freezing and the rewarming must happen evenly and quickly enough throughout the entire mass. Until now, this had only been achieved with small tissue samples or with rodent kidneys.
Nanoparticles as an internal heat source
The researchers solved the rewarming problem using a method called nanowarming. Before freezing, iron oxide nanoparticles were perfused through the kidney’s vascular system. When exposed to an alternating electromagnetic field, these particles generate heat from within the organ, producing a more uniform and rapid warm-up than surface-based methods allow.
The kidneys, which were around 100 times larger than any previously nanowarmed organ, were stored at -150 degrees Celsius for up to one year. After rewarming, they demonstrated vascular, metabolic and excretory function. They produced urine immediately after transplantation. Their functional recovery approached outcomes seen with kidneys preserved using standard cold storage alone.
A path toward organ banking
The method requires preparation before freezing, meaning it cannot be applied to organs already preserved without nanoparticles. That is a meaningful limitation. Even so, the researchers describe the results as an important step toward organ banks where kidneys and other organs could be available for months or years. Whether the technique works in human-scale kidneys or other organ types remains to be tested.
Search terms to explore further: organ vitrification cryopreservation transplantation, nanowarming iron oxide nanoparticles tissue, cryoprotectant large organ freezing