Scientists Revive Frozen Pig Kidneys After One Year

These kidneys were frozen using a 'vitrification' method and then rewarmed in a magnetic field to prevent tissue damage.

These kidneys were frozen by the "vitrification" method and then reheated with a magnetic field so as not to damage the tissues.

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For the first time, researchers managed to rewarm some frozen pig kidneys and observe signs of activity in them. These kidneys were kept at minus 150 degrees and one of them was frozen for more than a year. After being warmed, the kidneys regained their normal color and produced urine.

This achievement paves the way for long-term preservation of transplanted organs. However, the research has not yet been scientifically judged and researchers have not been able to show that these kidneys can maintain the life of a living organism in the long term.

The University of Minnesota research team used a process called "vitrifying" to preserve the organs. In this method, the tissue becomes glass-like to prevent the formation of harmful ice crystals. This process works for reproductive cells and embryos, but it is more difficult to do in whole organs.

The researchers first impregnated the kidney with antifreeze. These substances are like antifreeze, but may be toxic to tissues. Then iron oxide nanoparticles were injected into the organ. In the heating process, an electromagnetic field activated these particles to spread the heat evenly throughout the kidney.

This method solves an important problem: heating large organs quickly and evenly, without parts of them getting too cold or too hot. Earlier in 2023, researchers had tested this technology on mouse kidneys. In that experiment, the kidneys were rewarmed and transplanted after 100 days of storage.

In the new experiments, the researchers examined heated kidneys with both perfusion devices and transplanted them into pigs. Perfusion devices both maintain the flow of fluids and nutrients in the organ and help doctors evaluate the function of the transplanted organ.

After rewarming, the kidneys received blood flow and made urine. However, their urine output was about two-thirds of what was expected. Also, signs of tissue damage were observed, possibly caused by cryoprotectants.

If these issues are resolved, organ banks can provide more time to find a suitable recipient. Nowadays, the preservation of human organs is usually limited to about 24 to 36 hours. Long-term storage can make it easier to coordinate transplants and reduce the likelihood of organ by-pass.

The next step is to investigate kidney function in pigs over longer periods and find protective agents with less toxicity. Researchers also plan to test this method on human kidneys.

The researchers have posted the pre-refereed version of their study on the bioRxiv website.