New 'supercooling' technology increases organ preservation time

Scientists have developed a new supercooling technique to increase the amount of time human organs could remain viable outside the body.

According to the researchers, if it succeeds in humans, it would enable a world-wide allocation of donor organs, saving more lives and allow for more time to prepare the patient and ease logistics at the donor hospital site, reduce the urgency of rushing the organ to its destination, and expand the donation area to allow for transcontinental and intercontinental transplantations.

The researchers said that the technology would also increase the chances of patients finding better matches while simultaneously significantly reducing costs.

Martin Yarmush, M.D., Ph.D., and Korkut Uygun, Ph.D., investigators in the Center for Engineering in Medicine at Massachusetts General Hospital (MGH), Boston, have developed a four-step preservation technique that has tripled the amount of time that rat livers can be stored before transplantation.

The researchers said that the first step is to employ the use of machine perfusion-a way of delivering oxygen and nutrients to capillaries in biological tissues while outside the body-to supercool the liver tissue without causing irreversible damage to the cells. In order to accomplish this, the MGH team added 3-OMG (3-O-methyl-D-glucose), a non-toxic, modified glucose compound, to the solution being delivered to the liver.

The 3-OMG is taken up and because it cannot be metabolized by cells, accumulates in the hepatocytes (liver cells), acting as a protectant against the cold. The team also modified the solution by adding PEG-35kD (polyethylene glycol) to specifically protect cell membranes. Ethylene glycol is the active ingredient in anti-freeze, and it works by lowering the freezing point of a solution.

The livers were then slowly cooled below the freezing point, to 21 degrees Fahrenheit, without inducing freezing-thereby supercooling the organ for preservation. After storing the organs for several days, the researchers again used machine perfusion to rewarm the organ, while also delivering oxygen and other nutrients to prepare the organ for transplantation.

The study was published online in Nature Medicine.