How lessons from frogs could boost supplies of transplant livers



Copy-frog: Scientists believe cooling transplant livers slowly, the way a frog cools down during hibernation, could protect them and boost supplies

A hibernating technique used by frogs could boost the supply of transplant livers, reports say.

Scientists have pioneered a process that freezes the organ very slowly, as some frogs do when they hibernate, to prevent the formation of damaging ice crystals.

They have already tested the system by successfully freezing, thawing and transplanting a pig's liver.

If human livers are found to survive the process, more of the organs would be made available to patients.

Transplant livers deteriorate rapidly without a blood supply, becoming useless after between 12 and 24 hours.

Some frog species employ a similar slow-cooling technique when they allow parts of their bodies to freeze during hibernation.

Dr Amir Arav, who developed the new freezing method at the Israeli Agricultural Research Organisation in Bet-Dagan, told New Scientist magazine: "We didn't invent this process, nature did."

His team cooled the pig's liver at a rate of 0.3C per minute, reducing its temperature to minus 20C in about an hour-and-a-half.

The liver was then allowed to thaw for 20 minutes before being transplanted into another pig. The animal's original liver was left in place.

After about two hours the pig was killed and analysis of the transplanted liver showed its cells were alive.

Dr David Winter, president of Human BioSystems, a company in Palo Alto, California, that is looking at organ freezing, said it would have been better if the transplant liver had been tested on its own.

"One pig liver in a piggyback transplant is not very convincing as there's no evidence the thawed liver can really support the animal," he said.

Dr Arav said his work had been restricted by animal welfare regulations.

He hopes to evaluate how long livers can be stored, and work out the best storage temperature.

The team also found that rat livers stored at minus 80C for up to three weeks regained function, although they were not transplanted into living animals.

Rat hearts, human ovaries connected to fallopian tubes, and parts of human knee joints have also been frozen by Dr Arav.

