On the last day of March, surgeons at Massachusetts General Hospital started a business that hoped that it could lead to a permanent change in the way they are transplanted to the kidneys to humans.
That morning he was not a person. It was a pig, lies stunned at a table. The pig was missing a kidney and needed an implant.
While the kidneys should usually be transplanted within 24 to 36 hours, the kidney entering the pig had been removed 10 days before, frozen and then thawed early in the morning.
Never before had anyone transplanted a frozen organ into a large animal. There was so much that they could go wrong.
“I think there is about 50 percent like it will work,” said Korkut Uygun, a professor of surgery and leader of the team before surgery. Dr. Uygun is on the scientific advisory council of Sylvatica Biotech Inc., a company that develops freezing methods to maintain organs.
But the promise of freezing and storing the organs is great.
There is a serious and ongoing lack of kidney for transplants – more than 92,000 people are on waiting lists. One reason is that the 24 to 36 -hour window is so short that it limits the number of recipients that are good matches.
How much better it would be to have a stored, frozen organs bank so that an organ transplant can be almost like selective surgery.
This, at least, has been the dream of decades of transplant surgeons.
But the efforts of medical researchers to freeze the organs were canceled at every turn. In many cases, the ice crystals formed and destroyed the organs. Other times, the substance intended to stop the crystals from formation, a cryoprotective, was toxic and killed cells. Or the frozen organ became so fragile.
Then said John Bischof, researcher of cryoviology at the University of Minnesota, who did not participate in the work of the kidney pigs, even when the freezer seemed to go well, there was the problem of defrosting the organ.
When an organ was frozen, the scientists tried to make sure that any ice crystals formed were so tiny that they did not hurt the organ. But these crystals tended to grow as the organ was heated, reducing sensitive cells.
“You have to overcome ice crystals as they grow older,” Dr. Bischof said.
“The essential knowledge was: you can’t go quickly in the middle of an instrument, if all you do is warm it up to the edges,” he said. “If heating only starts on the outside of the frozen organ, the temperature differences from the edge to the center of the instrument can lead to anxiety that record the organ as an ice cube that breaks when you put it in your drink.”
Added, “you must heat evenly, from within.”
His colleague, Dr. Erik Finger, a transplant surgeon at the University of Minnesota, who also did not participate in the general experiment of the mass, said that while the freezer had to be done slowly to prevent the ice damage, the return of 10 times.
The researchers dug with their systems, eventually learning to freeze, thaw and transplant rat kidneys.
But the larger animals have introduced new problems.
“For four decades, Rewarming was the issue,” Dr. Finger said. “But as you increase the size of the instrument, cooling becomes a problem.” Suddenly, the cryoprotections that worked with tiny rats were no longer sufficient.
In Massachusetts, the researchers tried a different approach. He started with Shannon Tessier, a postdoctoral partner in Dr. Uygun and now Associate Professor of Surgery at Harvard Medical School, who is on an advisory council for Sylvatica Biotech and has a patent diploma related to the method used in March surgery. A few years ago, he was studying Canadian wood frogs.
When the weather is cold, the frog metabolism changes, allowing it to freeze itself. All his cellular processes stop. His heart stops. He is essentially dead.
The frog is so fragile that laboratory workers must be very kind. “You can break his hand if you are not careful,” said McLean Taggart, a laboratory technician.
“Shannon came to the lab and said,” Is it possible to translate this into human organs? “, Mr Taggart said.
This led to work to find out how the frog goes to its deep freeze. Shortly before inactivation, the frog begins to produce large amounts of glucose. Glucose accumulates in cells, where it reduces the water freezing point, preventing ice from forming.
But a frog is amphibious. Would something like this method work in a warm mammal or its organs?
It turns out to do so. A mammal, the squirrel of the Arctic, was overwhelmed when the temperature drops using a similar method. Its cells reach a temperature below the water freezing point – heat sink, but not enough to form the ice. Its metabolism slows down so much that it does not need to eat.
Like the researchers in front of them, the team at Mass General started with rat liver and tried to imitate the process. They decided to work together recently, but they still live instruments using the same procedure as the frog wood -to cool enough to stop the metabolic processes, but not enough to risk the formation of large ice crystals.
They began with the injection of an artificial glucose that cannot be metabolized. Sugar accumulates in cells, but because it is useless, cells enter a form of suspended moving images, their metabolic processes have stopped.
At the same time, the researchers add a diluted antifreeze – propylene glycol – which replaces the remaining water in the cells. The result is that very few forms of ice in cells, where damage is damaged by the freezing of the organs.
The storage solution is a mixture of sparse propylene glycol and artificial sugar, as well as snomax, the substance used to make artificial snow on slopes. Snomax creates tiny uniform ice crystals, which helps to ensure that the ice it forms does not cause damage.
To thaw the organs, the group reverses the process by placing the livers in a warm solution containing propylene glycol and artificial glucose and gradually dilute the chemicals until they leave.
It took about five years of testing and error to get the right process, the researchers said.
The next step was to move on to larger species of mammals. They would try to freeze and thaw the kidneys of pigs.
Their ultimate goal was ambitious – they would like to do the banks of frozen kidney pigs that were genetically modified to be used in human patients.
Other transplant surgeons at Dr. Uygun begin to experiment with genetically modified pig kidney. They have transplanted them into several people, with mixed results. On Friday, a patient whose kidney had lasted farther so far – 130 days – had to remove it because her body rejected it.
No one knew if the method used by Dr. Uygun and his colleagues would succeed.
“The protocol was optimized for the livers,” Dr. Uygun said. “We didn’t think it would work.”
But he did.
The group examined the method, freezing and thawing 30 kidney pigs, ensuring that the organs remained healthy after the freezer process. They learned that they could keep the kidneys frozen for a month without obvious damage.
But would it be a previous frozen renal function if transplanted into a pig?
In the test in March, the kidney remained frozen for 10 days and had to be transplanted back into the pig from which he was taken.
At 3am The team began to thaw the kidney, a process that took two hours.
At 9am, Dr. Alban Longchamp and Dr. Tatsuo Kawai, transplant surgeons at Mass General, opened the pig’s belly and prepared the animal for surgery.
At 10:30, they took the kidney inside.
The white gray instrument became pink as the blood flows into it.
Finally, success: Before sewing the pig, the researchers watched that the transplanted kidney was a pee.
