This kidney was frozen for 10 days. Can surgeons transplant this?

On the last day of March, surgeons in Massachusetts General Hospital began the surgery that they hoped could lead to a lasting change in kidney transplantation in humans.

The patient of this morning was not a person. It was a pig, lying anesthetized on the table. The pig was missing one kidney and needed an implant.

While the kidneys usually have to be transplanted within 24 to 36 hours, the kidney entering the pig was removed 10 days earlier, frozen and then thawed early in the morning.

Never before has had a frozen organ with a immense animal. There was so much that it could go wrong.

“I think there is about 50 percent of the chance that it will work,” said Korkut Uygun, a professor of surgery and team leader. Dr. Uygun is a member of the Sylvatica Biotech Inc. Scientific Council, a company that develops freezing methods to preserve the organs.

But the promise of freezing and storing organs is great.

There is a solemn and continuous lack of kidneys for transplants – more than 92,000 People are on waiting lists. One of the reasons is that a window from 24 to 36 hours is so compact that it limits the number of recipients who have good matches.

If it is better to have a bank stored, frozen organs so that organs can be almost like an operation to choose from.

At least it was a decades of transplant surgeons.

But the attempts of medical researchers to freeze organs were thwarted at every step. In many cases, ice crystals formed and destroyed organs. Another time, a substance aimed at stopping crystals, a cryoprotectant, was toxic and killed cells. Or the frozen organ became so feeble that it broke.

Then, said John Bischof, a Kriobiology researcher at the University of Minnesota, who was not involved in the pig kidney design, even when the freezing seemed good, the problem of softening of the organs occurred.

When the organ froze, scientists tried to make sure that all formed ice crystals were so miniature that they did not damage the organ. But these crystals tended to grow when heating organs, cutting tender cells.

“You must overtake ice crystals when they grow,” said Dr. Bischof.

“The necessary insight was: you can’t go quickly enough in the middle of the organ, if everything you do is heating on the edges,” he said. “If the heating begins only outside the frozen organ, the temperature differences from the edge to the organs on the organs can lead to stress that breaks organs like ice cubes, which breaks after putting it in the drink.”

He added: “You must heat uniformly, from the inside.”

His colleague, Dr. Erik Finger, a transplant surgeon also at the University of Minnesota, who was also not involved in a mass general experiment, said that although freezing had to take place slowly to prevent ice damage, re -embrying would have to go quickly, 10 to 100 times faster than the cooling process.

Researchers tinked their systems, ultimately learning to effectively freeze, defrost and transplant rat kidney.

But larger animals have introduced novel problems.

“For four decades, re -cultivation was checked,” said Dr. Finger. “But when you boost the size of the organ, cooling becomes a problem.” Suddenly, the cryoprotectants who worked with miniature ratios were no longer enough.

In Massachusetts general, scientists tried a different approach. It started with Shannon Tessier, doctoral students in the Dr. Uygun laboratory, and now a professor of surgery at the Harvard Medical School, who is a member of the Sylvatica Biotech advisory board and is patent applications related to the method used in the marching operation. A few years ago she studied Canadian wood frogs.

When the weather becomes frigid, the metabolism of the frog changes, allowing it to freeze. All his cellular processes stop. His heart stops. Is essentially dead.

The frog is so feeble that laboratory employees must be very tender. “You can take your hand if you’re not careful,” said McLean Taggart, a technician in a laboratory.

“Shannon entered the laboratory and said:” Can it translate into human organs? ” – said Taggart.

This led to work to find out how the frog goes into deep freezing. Just before his hibernate, the frog begins to produce immense amounts of glucose. Glucose accumulates in internal cells, where it reduces the temperature of freezing water, preventing the formation of ice.

But a frog is a amphibian. Was something like this to work on toasty mammals or his organs?

It turns out that yes. A mammal, arctic squirrel, Supercool when the temperature drops using a similar method. Its cells reach the temperature below the water freezing point – chilled, but insufficient to produce ice. His metabolism slows down so much that he doesn’t have to eat.

Like the researchers before them, the group in Mass General began the rat liver and tried to imitate the process. They decided to work with recently removed, but still live organs using the same process as the wood frog -relieving them enough to stop metabolic processes, but not enough to risk creating immense ice crystals.

They started by saturating artificial glucose, which cannot be metabolized. Sugar accumulates in cells, but because it is useless, the cells enter into the form of suspended animation, their metabolic processes stop.

At the same time, researchers add diluted counteracting – propylene glycol – which replaces the water left in the cells. As a result, very little ice creates cells in cells where the organs are freezed.

Their storage solution is a mixture of diluted propylene glycol and artificial sugar, as well as Snomax, a substance used for the production of artificial snow on ski slopes. Snomax forms miniature uniform ice crystals, which helps to ensure that the formation of ice does not cause damage.

To defrost organs, the group reverses the process, placing the liver in a toasty solution containing propylene glycol and artificial glucose and gradually dilutes chemicals until they disappear.

Scientists have found that it took about five years of attempts and mistakes to improve this process.

The next step was to move to larger species of mammals. They tried to freeze and defrost the pig’s kidneys.

Their final goal was ambitious – they would like to make frozen pig kidney banks, which have been genetically modified to apply in humans.

Other transplant surgeons at the DR UYGUN hospital begin to experiment with genetically modified pig kidneys. They transplanted them to several human patients, with mixed results. On Friday, the patient whose kidney lasted the longest time – 130 days – had to remove him because her body rejected him.

Nobody knew if the method used by Dr. Uygun and his colleagues were successful.

“The protocol has been optimized for the liver,” said Dr. Uygun. “We didn’t think it would work.”

But yes.

The team tested the method, freezing and defrosting 30 kidneys of pigs, making the organs remain robust after the freezing process. They learned that they could maintain frozen kidneys for a period of up to a month without obvious damage.

But is the previously frozen kidney function if he were transplanted into a pig?

During the test in March, the kidney remained frozen for 10 days and was to be transplanted back to the pig she was taken from.

At 3 in the morning the team began to defrost the kidney, a process that lasted two hours.

At 9am, Dr. Alban Longchamp and Dr. Tatsuo Kawai, transplant surgeons in Mass General, opened the belly of the pig and prepared the animal for surgery.

At 10:30 they sewed in the kidney.

In whitish, the gray organ quickly became pink when the blood flowed into it.

Finally, success: before they sewed the pig, scientists watched the transplanted kidney produced pee.