Super-cooled livers could bring new flexibility to organ transplants

In liver transplantation, the biggest inequity is geographic. When organs become available, they are generally offered first to patients nearby. A big part of the reason is that once a liver is harvested from a cadaver, it remains viable for no more than 12 hours.

As a result, waiting times vary dramatically across the country depending on supply and demand. Liver patients in Los Angeles, for example, typically wait years longer — and become far sicker prior to surgery — than those in northern Florida.

Now a group of Harvard University researchers has come up with a preservation technique that could one day allow livers to be shared more easily around the world.

In a paper published this week in the journal Nature Medicine, the scientists describe an experiment in rats in which livers were preserved for up to four days before transplantation.

Of the 12 rats that received four-day-old livers, seven survived for at least three months. Transplantation after three days worked perfectly: All six rats in that group survived.

In comparison, no rats survived after receiving three- and four-day-old livers preserved in the standard ice-cold solution — a breakthrough in transplantation when it was invented at the University of Wisconsin in 1980.

The new method relies on super-cooling. Livers were stored at minus 6 degrees Celsius in a chemical bath that prevented them from freezing. Freezing destroys delicate cell membranes.

The livers were slowly warmed before surgery.

The experiment marks the first time that a liver has been successfully transplanted after four days of storage — in any species.

But will the technique work in people? The scientists wrote that preserving human livers could require changes to the chemical solution or the protocol of cooling and warming.

One challenge is that human livers are more vulnerable to freezing than rat livers because of their size. There are other differences in liver biology as well.

But if the researchers can make it work, extending preservation time could have profound effects on the transplant system. Livers could be flown around the country or the world where they are needed most, equalizing waiting times and reducing organ shortages in the places with the highest demand and the lowest supply.

More than 15,700 people in the U.S. are waiting for liver transplants.

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