New supercooling technique to boost organ transplant

Scientists have discovered how to 'supercool' organs so that they can be transplanted days after being harvested from a donor, a breakthrough that offers new hope to thousands awaiting organ transplants.
A new system developed by researchers allowed successful transplantation of rat livers after preservation for as long as four days, more than tripling the length of time organs currently can be preserved.
The team describes their protocol which combines below-freezing temperatures with the use of two protective solutions and machine perfusion of the organ.
"To our knowledge, this is the longest preservation time with subsequent successful transplantation achieved to date," said Korkut Uygun, of the Massachusetts General Hospital center for Engineering in Medicine (MGH-CEM), co-senior author of the report.

"If we can do this with human organs, we could share organs globally, helping to alleviate the worldwide organ shortage," said Uygun who is also on the faculty of Harvard Medical School.
Once the supply of oxygen and nutrients is cut off from any organ, it begins to deteriorate.

Since the 1980s, donor organs have been preserved at temperatures at or just above freezing (zero degrees Celsius) in a solution developed at the University of Wisconsin (UW solution), which reduces metabolism and organ deterioration ten-fold for up to 12 hours.
The new protocol involves the use of two protective solutions - polyethylene glycol (PEG), which protects cell membranes, and a glucose derivative called 3-OMG, which is taken into liver cells.

After removal from donor animals, the livers were attached to a machine perfusion system - in essence, an 'artificial body' that supports basic organ function - where they were first loaded with 3-OMG and then flushed with a combination of UW and PEG solutions while being cooled to 4 degrees Celsius.
The organs were then submerged in UW/PEG solution and stored at 6 degrees Celsius for either 72 or 96 hours, after which the temperature was gradually increased back to 4 degrees Celsius.
The organs were then machine perfused with UW/PEG solution at room temperature for three hours before being transplanted into healthy rats.

All of the animals that received organs supercooled for 72 hours were healthy at the end of the three-month study follow-up period.
Although only 58 per cent of animals receiving organs supercooled for 96 hours survived for three months, analysis of several factors done while the organs were being rewarmed could distinguish between the organs that were and were not successfully transplanted.
The findings appear in the journal Nature Medicine.