If you’ve ever watched a hospital drama series on TV, you’ve probably seen an episode where the cast is racing against the clock to transplant an organ. While certain aspects of the show may be dramatized, the time crunch for an organ transplant is very real.

One of the most pressing concerns in a transplant operation is making sure the organ is preserved until it can get to the recipient. Keeping an organ viable during transport is difficult because it has be cool enough to prevent the tissue from breaking down, but not so cold that the organ freezes and incurs an ice injury.

Currently, most donated organs are transported on ice in coolers, and at best those organs can last anywhere from four to twelve hours. But a lot has to happen in that window for the transplant be a success:

The transplant recipient has to be notified and brought to the hospital, the surgical team has to be ready to operate, and the organ has to be safely transport to the operating suite.

Doctors have been trying for decades to figure out a way to give these organs and the transplant teams more time, and it looks like one Mass General team has just made it possible.

For the first time, researchers at the Center for Engineering in Medicine have successfully “supercooled” a human liver and returned it back to normal body temperatures without any ice injury.

Using this supercooling technique, the research team, led by Reinier de Vries, MD, were able to triple the shelf-life of human livers from about nine hours to 27 hours.

The Current State of Organ Transport

When a donor organ becomes available, transplant teams feverishly work to coordinate transportation logistics, which are often very complicated.

Since donor livers are generally only viable for about nine hours, coordinating efforts puts extreme stress on the transplant team and the recipient, leaving very little time to prep.

Matching the donor organ to the best recipient can also be a challenge.

When a recipient goes on the transplant list there are a number of factors which are considered when making a donor match, such as body size, blood type, condition severity and distance.

But, depending on the circumstances certain factors such as proximity to the donor organ become more important. “This can sometimes result in an individual receiving a good match, but maybe not the perfect match,” says de Vries.

If organs could be preserved for longer periods of time, it could result in more people receiving their perfect matches, increased viability of the organ after transplant and fewer donor organs lost when they are not able to reach a recipient in time.

How Donor Organs Become “Supercool”

Supercooling is the process of cooling something to subzero temperatures without the formation of ice crystals. While this may sound counter intuitive, it is possible.

Water typically freezes below 32°F, but that is due in part to its interaction with other external factors, says de Vries.

When cold water interacts with air, certain proteins and other impurities it can aid in fixing freely moving water molecules in place to form ice. But pure water on its own can remain in liquid form below the freezing point in small volumes.

So how did researchers take the largest solid organ in the human body, made mostly of water, and supercool it without any damage?

In most cases, before transporting an organ it is flushed with a cleansing solution and infused with a preservative solution using an intravenous line.

While this process gets the job done, it can result in uneven distribution of the preservative. And even if he organ is fully flushed, there is still a risk of freezing since the tissue itself contains a lot of water.

As an alternative to an IV line, the researchers team used machine profusion—a pressure-controlled pump that provides a slow and steady circulation of cooling solution throughout the liver.

To enhance the organ’s freeze-resistance, the team incorporated higher levels trehalose and glycerol—two naturally-occurring sugar molecules—into the solution. At higher levels, these molecules work as the body’s natural version of antifreeze.

Finally, before placing the organ into a chiller that circulates a special freeze-resistant solution, the enclosed the liver in a plastic bag with a small amount of solution and used removed all of the air bubbles to create a vacuum seal.

These three steps allowed the research team to triple the preservation time from nine to 27 hours without tissue damage.

How Supercooling Can Be Used in the Future

Supercooling can become challenging as the size of the transplanted organ increases, but since DeVries and his team managed to succeed with the liver, the largest solid organ in the human body, they are confident they can apply this technique to other donor organs.

They are currently exploring various protocols for supercooling organs such as the kidneys, ovaries and hearts as well as for larger transplants such as limbs for those who have suffered traumatic injuries.

The next step is to conduct more trials using laboratory models to monitor post-operation health of animals that have received supercooled organs and ensure the technique is safe for humans.

If successful, the technique could help preserve countless organs for longer periods of time and save numerous lives.

About the Mass General Research Institute
Research at Massachusetts General Hospital is interwoven through more than 30 different departments, centers and institutes. Our research includes fundamental, lab-based science; clinical trials to test new drugs, devices and diagnostic tools; and community and population-based research to improve health outcomes across populations and eliminate disparities in care.
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