The Globe and Mail, Monday, October 30, 2000
Buying time with frozen frogs
Chilled out amphibians may allow MDs to preserve human organs longer and avoid the rush to transplant
By Anne McIlroy
The frogs, nestled in Tupperware, are chilling out in the fridge next to somebody's lunch. Soon, Ken Storey of Carleton University will put them in the freezer and they will become curvy, amphibian mounds of ice, hard as rock, with no heartbeat, no other sign of life.
Yet the frozen woodland frogs are still very much alive. They thaw out after about 20 minutes at room temperature, sit for a while, then are ready to ribbett. This seemingly miraculous ability, it turns out, is perfectly natural.
Wood frogs, spring peepers and several other species of terrestrial frog survive the Canadian winter by becoming part of the frozen landscape. Dr. Storey is trying to figure out exactly how they do it, but his quest is about more than understanding one of nature's curiosities. He believes the molecular secrets of his frozen frogs will one day allow human organs to be safely frozen, and doctors won't have to race against time to transplant livers and hearts once they are taken from the donor.
He has been freezing frogs in his Ottawa lab for about 15 years. Early on in his research he discovered that some species have a natural cryoprotectant, something that protects their cells from being killed when frozen.
"It is glucose. The same blood glucose you use as fuel, the same blood glucose you get from a chocolate bar or any food," he explained.
When ice starts forming on their rubbery skin, frogs start filling each cell in their body with glucose, which stops the life-killing ice from forming within each cell.
Alas, chocolate bars will not save human beings from freezing to death. If humans had as much blood sugar in their cells as frozen frogs, they would be diabetic and extremely sick. What saves the frogs from freezing to death would never work for us. But it just might work for individual human organs.
Identifying glucose as the mystery cryoprotectant was only the first step. In the years that followed, Dr. Storey has also isolated more than 20 genes out of the 10,000 in frog chromosomes that are turned on when the animal starts to freeze. It appears those genes shut down the frog's metabolism and pack its cells with sugar.
The idea is to get those same genes working in human organs.
"Here is the joy of biochemistry. The basic structure and function of all cells of all vertebrates are the same. You have the same types enzymes and proteins as a frog and a fish. You have genes of similar sequence and you have the same control of genes over all. All you have to do is learn what genes and enzymes to regulate, then learn how to turn them on or off. All we have to do is learn to twiddle them," Dr. Storey said.
He has a jumpy, manic energy, explaining that his field is called cryobiology, which differs from cryonics, the practice of preserving the whole body, head, or brain of persons recently declared legally dead, in the hope of revival at some time in the future. Cryonics is on the scientific fringe, and not largely accepted by the research community. Cryobiology, on the other hand, gets significant government funding and provides insight into how living cells work.
Human livers taken from donors for transplant can last six to eight hours after death, a heart and lung only four to five hours. If, by freezing organs, doctors could avoid the mad rush to transplant, they could wait for the perfect match. In the Second World War scientists did experiments and figured out how to safely freeze blood. After the war, they tried the same approach with organs, but failed to freeze them without destroying them.
In the late seventies and early eighties, Dr. Storey says, the research community realized they had to start looking for a natural mechanism that would allow for freezing. A scientist in Minnesota froze frog specimens he left in his trunk overnight and realized they could survive. Dr. Storey, who in 1984 was recognized with a Steacie Award as one of Canada's most promising scientists, began what would become his life's work with funding from the Natural Sciences and Engineering Research Council.
He works in a laboratory decorated with pictures of frogs, frog magnets, frog toys, frog cartoons, frog stickers and frog posters. But he has branched out since he first started his frog research 15 years ago, and researchers in his lab now study ground squirrels, bats, snails and turtles. (Some turtles can hibernate for three or four months under water without breathing.)
The process is not identical in each species, but it does seem to involve similar mechanisms and processes.
Hibernating ground squirrels, for example, don't freeze solid as do frogs, but they do turn off their metabolism.
"The genes in a hibernating ground squirrel largely shut off, just like in a frozen frog," Dr. Storey said.
If he could figure out how, he could get livers or other organs for transplants to do the same thing. That would mean they would last hundreds of times longer.
"These animals are living in a state of suspended animation, and if you think about suspended animation, that is exactly what you want for organs for transplant. Squirrels aren't dead at 5 degrees. We want mammalian organs to act like that in fridges everywhere."
But that, he says, could take years. This kind of science works slowly, solving one piece of the mystery at a time.
Each new discovery shows how complicated a hibernating squirrel or a frozen frog really is.
When Dr. Storey started out freezing frogs, he was pretty much alone in his field. Now scientists around the world have begun studying unusual animal models to understand basic cell function.
He's still the leading expert in frozen frogs, however, and seems genuinely fond of his specimens, some as small as a thumbnail.