Preserved Kidneys Rewarmed and Transplanted in Rats
Published in Nanowarming, Vitrification.
For the first time in history, scientists have been able to freeze, preserve, rewarm, and transplant rat kidneys with a new method of organ cryopreservation.
The rewarming problem
Today, organ transplantation is severely limited by the fact that organs can only be preserved for a short time in near-freezing temperatures. Long-term cryopreservation of organs could save countless lives, but it has eluded scientists for decades, even though we can freeze and unfreeze blood, sperm, and embryos.
Many hurdles must be overcome on the way to successful organ cryopreservation. First, the organ must be frozen in a way that avoids the formation of tissue-destroying ice crystals. This demands quick freezing and the use of cryoprotective agents (CPAs), which can themselves be toxic. The second major problem is achieving quick and uniform rewarming. While the former has been mostly solved by a freezing technology called vitrification , the latter remains.
Central heating for a kidney
In this new paper published in Nature Communications, a group of researchers from the University of Minnesota reports using a groundbreaking rewarming technique to successfully transplant vitrified and rewarmed kidneys into rats.
The researchers call their technique “nanowarming” because it involves adding iron oxide nanoparticles to the CPA solution that the kidney is flooded with prior to vitrification. When it’s time to rewarm the kidney, a radiofrequency coil induces alternating magnetic fields that heat the nanoparticles uniformly, regardless of how deep in the organ tissue they reside. Essentially, the organ is heated from the inside instead of outside. After the kidney is rewarmed, the CPAs, along with the nanoparticles, are flushed out of it, and the organ is ready for transplantation.
Success in vitro and in vivo
First, the researchers vitrified several rat kidneys, which involved quickly cooling the organs to below the vitrification temperature of -128?°C. The kidneys were then stored at the same temperature for up to 100 days.
The researchers then tested the function of several rewarmed kidneys ex vivo by connecting the organs to machines instead of transplanting them into actual animals. As controls, they used kidneys that had been cold-stored at 4?°C for 24 hours and kidneys that were flushed with the CPA solution without the iron oxide nanoparticles, and neither of these vitrified nor rewarmed.