New technique could stop transplant organ waste

Senior author John Bischof and a sample.

However, they still need several years until the technology is optimized perfectly for use on human organs. This will be very helpful in eliminating waiting lists for organ transplants.

Scientists now plan to begin testing the technology on rat and rabbit organs, then scale it up to pig organs.

The cryopreservation of organs is a step closer to becoming a reality after scientists used nanotechnology to defrost frozen tissue without damaging it.

To address this issue, researchers at the University of Minnesota developed a new heating method using iron oxide nanoparticles, which surround the frozen tissues. Speed and even heating are the keys to preventing this from happening. Now, in a first, researchers at the University of Minnesota have discovered a way to thaw animal heart valves and blood vessels using a process called "nanowarming", said the report in Science Translational Medicine. The process was tested on several human and pig tissue samples, and it showed that nanowarming achieves the same speed of thawing as the use of traditional convection techniques.

But the biggest problem has been with the rewarming, which often leaves tissues massively damaged and useless for transplantation.

"These sort of approaches always take longer than you would expect to reach clinical use", said Dr. David Klassen, chief medical officer of the United Network for Organ Sharing, which manages the U.S. transplant network. "In cryobiology, we do try to stay science-based".

Vitrification is the prevailing method for long-term tissue preservation, and it works by super-cooling the samples to a liquid so high in viscosity it's basically a glassy, non-crystalline (meaning, non-ice) solid. Once thawing is complete, the nanoparticles simply wash away.

Previous studies have successfully thawed miniscule tissue samples that were only 1 to 3 milliliters in volume. After more than five years of work, they were rewarded by seeing a vitrified system successfully heated in an entirely novel way. Their new method can heat samples up to 80 ml and it can heat them at the rate of more than 130 degrees Celsius per minute.

In addition, perfusing organs that are more dense may present its own challenges, as an even distribution of nanoparticles is necessary for the method to work.

Others saw more potential in the approach.

"I can tell you from a scientific point of view that the scale-up into the organs is going to be a major undertaking with many different investigators". The researchers say it is very likely that the technique could be scaled up to the larger organ sizes. "But the technology for those tissue banks and those types of tissues, the technology exists now and that's really why I think this paper is getting as much interest as it is".

"We will have to actually go to a larger system if we want to move into human organs but there's nothing that precludes us from doing that". Why not freeze the organs, you might ask?

"Once you have done a whole organ, there is a certain intellectual connecting of the dots that takes you from the organ to the person", Bischof says. Co-author Dr Kelvin Brockbank said: 'I'll have to say that the cryonicist movement will probably distort the importance of this to being able to preserve whole human bodies quite quickly. Instead of having donors wait anxiously for organs to become available, the technology may flip the situation, allowing the organs to wait for us.

  • Joanne Flowers