An innovative new technique has been tested (on animals only, for now) at the University of Minnesota. Kidneys are “vitrified” in liquid nitrogen at -150 degrees Celsius and then restored to full functionality using nanoparticles.
Vitrify. This is the word that could open up new possibilities in the transplant sector, allowing organs to be stored for a long (very long) time before being transplanted into patients in need. A pilot experiment in this field has been successfully conducted for the first time by a group of bioengineers and surgeons at the University of Minnesota (United States) on lab animals (rats). The researchers harvested kidneys from healthy animals and, using extremely rapid cooling with liquid nitrogen, froze them to -150 °C (this is the process of vitrification); then, after several days, they rewarmed them using a special system (nanowarming). Finally, they used them for transplants, confirming that the kidneys were once again viable and perfectly preserved.
The vitrified kidneys—as the researchers explain in the scientific journal Nature Communications—can be stored for up to 100 days, and this technique, if it can also be used in human beings in the future, will allow for much better planning for transplants, so that, as the researchers point out, this procedure “more equitably reaches patients regardless of geographical and time constraints.”
A long journey marked by disappointments
Vitrification was first researched by the Swiss priest Basile Luyet in the ’30s, but the many attempts at organ cryopreservation that followed all failed, until today, chiefly due to ice formation, which causes irreversible damage.
Vitrification, on the other hand, allows organs to be brought to a glass-like, stable state. “However,” the researchers go on to explain, “the rewarming of vitrified organs can similarly fail due to ice crystallisation, if rewarming is too slow” or due to the cells “cracking from thermal stress, if rewarming is not uniform.”
Nanowarming turned out to be the right answer. How does it work?
The organ to be preserved is injected with a solution that contains magnetic nanoparticles (particles, in other words, that are in the order of one millionth of a millimetre in size), plus a liquid that preserves biological tissue. When it is time to rewarm the organ, alternating magnetic fields are used to heat the nanoparticles within the organ’s vasculature, after which the nanoparticles are removed by draining the liquid in which they are contained. Within 45 minutes of the transplant, the kidney begins to function—that is, to produce urine—and, within three weeks, all parameters return to normal.
As we stated above, this is the first time that rewarming of this sort has been successful in overcoming the current limitations of transplants, which can only be performed using organs harvested a short number of hours beforehand, given how quickly tissue deteriorates. Many factors still require optimisation, however, given that, for example, we still do not know how long rewarmed and transplanted organs will remain functional in the long term (months or years), as well as the fact that what has been observed in animal models may not necessarily be replicated in humans.
Nevertheless, the researchers have predicted that the technique could be optimised and made available for initial clinical trials within just a couple of years. After that, at least five more years will be needed to complete all necessary testing.