- Scientists successfully froze a pig kidney to a glass state and restored its function.
- The research team used chemical cryoprotectants and iron oxide nanoparticles for freezing.
- Long-term storage of organs can improve matching and transportation flexibility.
- The current urine output of the kidney is below expectations and requires further study.
For the first time, scientists have announced the successful freezing of an entire pig kidney to a glass state, storing it for months at approximately -238 degrees Fahrenheit (-150 degrees Celsius), and subsequently restoring its function. Reports indicate that one kidney was frozen for over a year, and after reheating, it regained color and began to urinate, a key indicator of organ function.
This research was led by transplant surgeon Erik Finger and bioengineer John Bischof. They first injected the kidney with chemical cryoprotectants, which act like antifreeze, followed by the injection of iron oxide nanoparticles. The organ reached a glass state at approximately -184 degrees Fahrenheit (-120 degrees Celsius) under the influence of cold nitrogen gas, and was then maintained at -238 degrees Fahrenheit. This method avoids damage caused by ice crystals.
Innovations in Freezing Technology
The reheating process is relatively complex. The research team utilized electromagnetic fields to release heat from the nanoparticles and controlled the heating rate by adjusting the strength of the electromagnetic field. The pig kidney weighs about 100 times that of the mouse kidney frozen by the research team in 2023, and Bischof noted that the formulation of the cryoprotectant needed adjustments, a change that took three years.
The reheated kidney was tested on a perfusion machine and was transplanted into a pig for two hours. Finger noted that in both cases, "they immediately turned pink." These kidneys began to urinate within about a minute, although only two-thirds of the normal amount. The one-year-old kidney tested on the perfusion machine urinated immediately and appeared to perform better than many other kidneys.
Potential Impacts on Organ Preservation
The significance of this research lies in the fact that the current preservation time for human organs is only 24 to 36 hours, making matching and transportation urgent. Long-term storage of organs could give doctors more time to match donors and recipients, and may allow patients' immune systems to prepare, potentially reducing the need for lifelong immunosuppressive medication. Finger stated, "Now it's the organs waiting for patients."
Kevin Myer, who oversees the organ procurement organization LifeGift, envisions an organ bank ready to respond to emergencies such as drug overdoses and gunshot wounds. This achievement follows a milestone from the National Science Foundation's Engineering Research Center ATP-Bio in 2025. According to the University of Minnesota, researchers at Massachusetts General Hospital previously stored a pig kidney for 10 days at approximately 5 degrees Fahrenheit (-15 degrees Celsius) before transplanting it into a live pig, restoring its function.
Future Research Directions
However, these kidneys are not perfect. Their urine output is below expectations, and they exhibit damage that researchers believe is related to the cryoprotectants. Greg Fahy, a pioneer in cryobiology who did not participate in the study, stated that these experiments do not demonstrate whether the kidneys can support life. Another cryobiologist who did not participate, Peter Kilbride, called this work a "major breakthrough that solves half the problem." Next steps include conducting longer tests in pigs, using less toxic cryoprotectants, and experimenting with human kidneys.
Potential Applications and Challenges of Pig Kidney Freezing Technology
The success of this technology brings new hope to the field of organ transplantation, particularly with breakthroughs in organ storage time. Current limitations on organ preservation restrict the flexibility of transplantation, while the results of this research could significantly extend the availability of organs, thereby improving patients' chances of acceptance. Additionally, despite the current challenges in restoring kidney function, this research lays the groundwork for future experiments, especially in using safer cryoprotectants and conducting tests on human kidneys. These advancements could facilitate the realization of the organ bank concept to address urgent medical needs.