At Texas A&M, pig kidneys were stored at −4 °C for three days and then transplanted back into the same animals

At Texas A&M, pig kidneys were stored at −4 °C for three days and then transplanted back into the same animals

On July 23, MIT Technology Review reported results from Matthew Powell-Palm's team that were presented in June at the American Transplant Congress. After 72 hours of storage, the kidneys were transplanted back into the pigs. One of the animals was monitored for 200 days.

After removal, a kidney is usually kept on ice for 18–24 hours. During this period, physicians assess the organ, identify a recipient, transport the kidney, and prepare for surgery. The organ continues to sustain damage even when cold, so long-distance transport narrows the choice of recipients.

The Texas A&M team tried to extend this window by cooling the kidney below zero. They flushed the kidney with a standard transplant solution and placed it in a sealed chamber under constant pressure. At −4 °C, the pressure prevents the water from forming ice: the temperature is below zero, but crystals do not yet form and rupture the cells. This method did not require a cryoprotectant, a substance that acts like antifreeze.

The experiment tested whether the transplanted organs would function. Some kidneys were kept on ice for two or 24 hours, while others remained in the chamber for 24, 48, or 72 hours. Each kidney was then transplanted back into the same pig, and the other kidney was removed. The preserved kidney therefore had to filter the blood and produce urine on its own. After one day in the chamber, the kidneys began producing urine immediately, and their measurements returned to normal levels within about ten days. According to Powell-Palm, organs stored for 48 and 72 hours recovered in a similar way.

One pig lived with such a kidney under observation for 200 days. During the first month, the animal grew by about one-third, while the kidney nearly doubled in size as it took over the workload of the removed paired organ. After removing the kidney, the team described it as healthy.

In the pig experiment, the entire process worked: the tissue was preserved without ice, warmed, and produced a functioning kidney after transplantation. For transplant logistics, the additional two days would provide time to compare several recipients, reassess the organ, and select a transport route.