A new system allowed researchers to successfully transplant rat livers after a preservation of at least four days; this triples the amount of time that organs can be preserved.
The protocol includes below-freezing temperatures as well as two protective solutions and machine perfusion, the Massachusetts General Hospital said. The work was published in the journal Nature Medicine.
"To our knowledge, this is the longest preservation time with subsequent successful transplantation achieved to date," Korkut Uygun, PhD, of the MGH Center for Engineering in Medicine (MGH-CEM), co-senior author of the report, said. "If we can do this with human organs, we could share organs globally, helping to alleviate the worldwide organ shortage."
Once the oxygen supply is cut off from an organ it begins to deteriorate. Organs are normally stored at temperatures just above freezing, which reduces deterioration for up to 12 hours. Extending that preservation time could increase the distance the organ could be transported as well as the amount of time that could be spent on an operation.
Keeping organs at below-freezing temperatures in a process called "supercooling" could extend their preservation by slowing metabolism, but this process can damage the organ in several ways. To reduce this risk the MGH-CEM protocol involves using polyethylene glycol (PEG), which protects cell membranes, and a glucose derivative called 3-OMG, which is used in liver cells.
After the organs were removed from the donor the livers were attached to a machine perfusion system that supports basic organ function. They were loaded with 3-OMG and flushed with UW and PEG solutions. They were then stored for either 72 or 96 hours at 6 degrees Celsius (21 degrees Fahrenheit) before being gradually increased to 4 degrees Celsius. They were submerged in a room temperature solution for three hours before being transplanted into rodents.
"This ability to assess the livers prior to transplantation allows us to determine whether the supercooled organ is still good enough for transplantation," explained study co-author Bote Bruinsma, MSc, of the MGH-CEM. "Even among the livers preserved for four days, if we had only used those in which oxygen uptake, bile production and the flow of perfusion solution were good, we would have achieved 100 percent survival."
"By reducing the damage that can occur during preservation and transportation, our supercooling protocol may permit use of livers currently considered marginal - something we will be investigating - which could further reduce the long waiting lists for transplants," Martin Yarmush, MD, PhD, founding director of MGH-CEM and co-senior author of the paper said.
