On the final day of March, surgeons at Massachusetts Normal Hospital started an operation that they hoped may result in a everlasting change in how kidneys are transplanted in individuals.
That morning’s affected person was not an individual. It was a pig, mendacity anesthetized on a desk. The pig was lacking one kidney and wanted an implant.
Whereas kidneys usually have to be transplanted inside 24 to 36 hours, the kidney going into the pig had been eliminated 10 days earlier than, frozen after which thawed early that morning.
By no means earlier than had anybody transplanted a frozen organ into a big animal. There was a lot that would go incorrect.
“I feel there’s a couple of 50 p.c probability that it’ll work,” Korkut Uygun, a professor of surgical procedure and a frontrunner of the crew, stated earlier than the surgical procedure. Dr. Uygun is on the scientific advisory board of Sylvatica Biotech Inc., an organization that’s creating freezing strategies to protect organs.
However the promise from freezing and storing organs is nice.
There’s a extreme and ongoing scarcity of kidneys for transplants — greater than 92,000 individuals are on ready lists. One motive is that the window of 24 to 36 hours is so transient that it limits the variety of recipients who’re good matches.
How a lot better it is perhaps to have a financial institution of saved, frozen organs so an organ transplant might be nearly like an elective surgical procedure.
That, at the least, has been the decades-long dream of transplant surgeons.
However the makes an attempt of medical researchers to freeze organs had been thwarted at each flip. In lots of circumstances, ice crystals fashioned and destroyed the organs. Different occasions, the substance meant to cease the crystals from forming, a cryoprotectant, was poisonous and killed cells. Or the frozen organ grew to become so brittle it cracked.
Then, stated John Bischof, a cryobiology researcher on the College of Minnesota who was not concerned with the pig kidney venture, even when the freezing appeared to go properly, there was the issue of thawing the organ.
Once they froze an organ, scientists tried to be sure that any ice crystals that fashioned had been so tiny they didn’t harm the organ. However these crystals had a bent to develop because the organ warmed, slashing delicate cells.
“It’s important to outrun the ice crystals as they develop,” Dr. Bischof stated.
“The important perception was: You may’t go quick sufficient in the midst of an organ if all you do is heat it on the edges,” he stated. “If heating begins solely on the skin of the frozen organ, the temperature variations from the sting to the middle of within the organ can result in stress that fractures the organ like an ice dice that cracks if you put it in your drink.”
He added, “It’s important to warmth uniformly, from the within.”
His colleague, Dr. Erik Finger, a transplant surgeon additionally on the College of Minnesota who was additionally not concerned within the Mass Normal experiment, stated that whereas the freezing needed to happen slowly to stop ice harm, rewarming must go quick, 10 to 100 occasions sooner than the cooling course of.
Investigators tinkered with their techniques, finally studying to efficiently freeze, thaw and transplant rat kidneys.
However larger animals launched new issues.
“For 4 many years, rewarming was the problem,” Dr. Finger stated. “However as you improve the dimensions of the organ, cooling turns into a problem.” Immediately, the cryoprotectants that labored with tiny rat organs had been now not adequate.
At Massachusetts Normal, researchers tried a unique strategy. It started with Shannon Tessier, a postdoctoral fellow in Dr. Uygun’s lab and now an affiliate professor of surgical procedure at Harvard Medical Faculty who’s on an advisory board for Sylvatica Biotech and has a patent software associated to the tactic used within the March surgical procedure. Some years in the past, she was finding out Canadian wooden frogs.
When the climate turns chilly, the frog’s metabolism adjustments, permitting it to freeze itself. All its mobile processes cease. Its coronary heart stops. It’s primarily useless.
The frog is so brittle that lab employees need to be very light. “You may break off its arm in case you are not cautious,” stated McLean Taggart, a technician within the lab.
“Shannon got here into the lab and stated, ‘Is it doable to translate this to human organs?’” Mr. Taggart stated.
That led to work to find out how the frog goes into its deep freeze. Simply earlier than it hibernates, the frog begins producing giant quantities of glucose. The glucose accumulates inside cells, the place it reduces the freezing level of water, stopping ice from forming.
However a frog is an amphibian. Would one thing like that technique work on a warm-blooded mammal, or its organs?
It seems that it does. A mammal, the arctic squirrel, supercools itself when the temperature drops by utilizing an analogous technique. Its cells attain a temperature beneath the freezing level of water — chilled, however not sufficient for ice to type. Its metabolism slows a lot it doesn’t need to eat.
Just like the researchers earlier than them, the group at Mass Normal began with rat livers and tried to imitate the method. They determined to work with lately eliminated however nonetheless reside organs utilizing the identical course of because the wooden frog -— chilling them sufficient to cease metabolic processes, however not sufficient to danger the formation of enormous ice crystals.
They started by infusing a man-made glucose that may’t be metabolized. The sugar accumulates in cells, however as a result of it’s unusable, the cells enter a type of suspended animation, their metabolic processes paused.
On the identical time, the investigators add a diluted antifreeze — propylene glycol — which replaces water left within the cells. The result’s that little or no ice varieties inside cells, which is the place harm from organ freezing happens.
Their storage answer is a mix of the dilute propylene glycol and synthetic sugar, plus Snomax, the substance used to make synthetic snow on ski slopes. Snomax creates tiny uniform ice crystals, which helps be certain that the ice that varieties doesn’t trigger harm.
To thaw the organs, the group reverses the method, placing the livers in a heat answer containing propylene glycol and the substitute glucose and progressively diluting the chemical compounds till they’re gone.
It took about 5 years of trial and error to get the method proper, the researchers stated.
The following step was to maneuver as much as bigger mammal species. They’d attempt to freeze and thaw pig kidneys.
Their final purpose was formidable — they wish to make banks of frozen pig kidneys that had been genetically modified for use in human sufferers.
Different transplant surgeons at Dr. Uygun’s hospital are starting to experiment with genetically modified pig kidneys. They’ve transplanted them into a number of human sufferers, with combined outcomes. On Friday, a affected person whose kidney had lasted longest thus far — 130 days — needed to have it eliminated as a result of her body rejected it.
Nobody knew if the tactic utilized by Dr. Uygun and his colleagues would succeed.
“The protocol was optimized for livers,” Dr. Uygun stated. “We didn’t suppose it will work.”
But it surely did.
The crew examined the tactic, freezing and thawing 30 of pig kidneys, ensuring the organs remained wholesome after the freezing course of. They realized they may preserve the kidneys frozen for as much as a month with no apparent harm.
However would a beforehand frozen kidney operate if it was transplanted right into a pig?
Within the take a look at in March, the kidney had remained frozen for 10 days and was to be transplanted again into the pig from which it had been taken.
At 3 a.m. the crew began thawing the kidney, a course of that took two hours.
At 9 a.m., Dr. Alban Longchamp and Dr. Tatsuo Kawai, transplant surgeons at Mass Normal, opened the pig’s stomach and ready the animal for the surgical procedure.
At 10:30, they sewed the kidney in.
The whitish grey organ rapidly turned pink as blood flowed into it.
Lastly, success: Earlier than they sewed up the pig, the researchers watched because the transplanted kidney produced pee.
