The sustainability of an organ after it is removed from the body becomes a race against time as its cells begin to deteriorate by the hour. A new technique developed at the Massachusetts General Hospital (MGH) in Boston dubbed “supercooling,” which involves filling an organ with nutrients and oxygen before cooling it to below the freezing point, has the potential to keep organs fresh for up to 72 hours.
“The next step will be to conduct similar studies in larger animals,” Dr. Rosemarie Hunziker from the National Institute of Biomedical Imaging and Bioengineering (NIBIB) said in a statement. “It is exciting to see such an achievement in small animals, by recombining and optimizing existing technology. The main point here is that using all of these approaches at once was what led to success. Halfway measures did not do. Such a tour de force reflects this team’s very deep understanding of the complex processes at work here, and how they relate simultaneously to each other.”
Researchers from the Center for Engineering in Medicine at the Massachusetts General Hospital/Harvard Medical School developed their four-step organ preservation technique using rat livers. They started by using machine prefusion to deliver oxygen and nutrients to the liver’s tissues while outside of the body without causing irreversible cell damage. To protect cells against the cold, the research team combined the solution that was delivered to the liver with a non-toxic, modified glucose compound known as 3-OMG (3-O-methyl-D-glucose). The solution also included PEG-35kD (polyethylene glycol) to protect cell membranes.
Following the delivery of nutrients and oxygen, the livers were slowly cooled to 21 degrees Fahrenheit without inducing freezing, effectively supercooling the organ for preservation. Supercooled rat livers were stored for three to four days at 21 degrees Fahrenheit. When the liver was ready for transplantation several days later, the machine prefusion technique was used to rewarm the organ while delivering a steady flow of oxygen and nutrients. While none of the rats who received organs kept fresh using current techniques survived, the rats that received supercooled livers stored for three days ended up surviving for up to three months. Rats that received supercooled livers that were stored for four days had a survival rate of 58 percent.
“The longer we are able to store donated organs, the better the chance the patient will find the best match possible, with both doctors and patients fully prepared for surgery,” Hunziker added. “This is a critically important step in advancing the practice of organ storage for transplantation.”
According to the Organ Procurement and Transplantation Network, there are currently 123,049 people in the United States waiting for a new organ. For most of these people, the amount of time they are kept waiting for their organ transplant could mean the difference between life and death. Current organ preservation techniques involving cold temperatures and a chemical solution can only sustain the organ for up to 24 hours, meaning a good deal of organs do not reach their intended recipient in time.
Source: Berendsen T, Bruinsma B, Puts C. Supercooling enables long-term transplantation survival following 4 days of liver preservation. Nature Medicine. 2014.