Key Takeaways

  • Texas A&M University researchers preserved pig kidneys at -4 C for as long as 72 hours without ice formation or added cryoprotectants.
  • Transplanted kidneys recovered faster than organs stored on ice for 24 hours, with one remaining healthy after 200 days.
  • Longer storage could reduce organ waste, widen recipient matching and support the emerging xenotransplantation supply chain.

Researchers led by Matthew Powell Palm at Texas A&M University have demonstrated a pressure-controlled system that keeps pig kidneys below freezing for up to 72 hours and preserves their ability to function after transplantation. The work could turn organ storage from a race measured in hours into a logistics window measured in days.

That distinction matters. More than 104,000 people are waiting for a kidney transplant in the US, while an estimated 17 people die each day while waiting. In some years, around one in three donated kidneys is discarded, often because its condition deteriorates before a suitable recipient can be reached.

Conventional practice generally places kidneys on ice at about 4 C. Static cold storage and devices that mimic some conditions inside the body typically provide a window of up to roughly 24 hours. Beyond that point, cellular damage increasingly threatens organ function.

Powell Palm’s team instead cools kidneys to -4 C inside a hermetically sealed, pressure-controlled chamber. The organ is submerged in a preservation solution already used in transplantation, while sensors monitor temperature and detect ice formation. No cryoprotective chemicals are added.

Colder storage is useful only if ice stays out. Crystals can disrupt cells, blood vessels and the kidney’s intricate internal structures. By controlling pressure and the kinetics of ice formation, the Texas A&M University system slows metabolism without freezing the tissue.

For the experiment, researchers removed one kidney from each pig and flushed it to remove blood. Comparison organs were kept on ice for either two or 24 hours. Others were supercooled for 24, 48 or 72 hours. Each stored kidney was then returned to its original donor, whose second kidney was removed, leaving the animal dependent on the preserved organ.

The kidneys stored for 24 hours under supercooled conditions began producing urine immediately after transplantation. Functional markers returned to normal levels within about 10 days. Kidneys held for 48 and 72 hours performed similarly, according to the research team, and recovered faster than those stored on ice for 24 hours.

The team also reported longer-term survival data. According to the researchers, during 30 days of observation, the pigs grew by around 30%, while the transplanted kidneys almost doubled in size as they compensated for the animals’ growth and the absence of a second kidney. One pig was monitored for 200 days, after which researchers noted its kidney still appeared healthy.

The findings add another route to a rapidly expanding preservation field. The NSF Engineering Research Center ATP-Bio previously reported restoring function to a pig kidney cryopreserved for 10 days. Canadian researchers have also transplanted pig kidneys stored below zero for up to 48 hours, although that protocol used a cryoprotectant and followed the organs for one week.

These methods are not interchangeable. Supercooling offers a relatively near-term extension of cold storage, while cryopreservation targets substantially longer storage and requires more complex cooling, warming and protection against ice. Both could eventually complement machine perfusion rather than replace it.

Why does an extra two days change the business case? Organ procurement organizations such as LifeGift could gain more time for testing, allocation and transportation. Transplant centers could schedule procedures with less operational pressure. A 72-hour window might also support international shipment and lower-cost ground transport instead of relying as heavily on chartered aircraft and urgent courier networks.

The opportunity extends to xenotransplantation. The FDA approved clinical trials of pig kidney xenotransplantation in 2025, while programs involving Massachusetts General Hospital and Revivicor have advanced gene-edited organs toward clinical use. A gene-edited porcine kidney has functioned in a living human for 271 days, according to case data summarized by the National Kidney Foundation. Harvard Gazette has also documented Massachusetts General Hospital’s progress in pig-to-human kidney transplantation.

Important questions remain. The Texas A&M University work involved pig kidneys returned to their original donors, so it did not test immune rejection between different animals or species. Human trials will also require validated transport performance, standardized rewarming, manufacturing controls and evidence that pressure exposure does not create subtle long-term damage.

Preliminary tests found that kidneys stored for 120 hours appeared healthy, but those organs have not yet been transplanted. Powell Palm and the research team plan to launch a company focused on the technology and related protocols for stopping biological time. If later studies reproduce the 72-hour performance in human transplantation, preservation may become more than packaging. It could become core infrastructure for a broader, more flexible organ supply chain.