Raphael ThysScientists are in a race against time to perfect a process that transforms pig livers into human organs that could save the 105,000 people waiting for transplants.
A team at a Miromatrix laboratory in Minneapolis is working on a method that completely washes away the animal cells in the organ, leaving behind a rubbery honeycomb structure.
Human liver cells are then oozed back into the liver, filling in the nooks and crannies to restart the organ's functions.
Miromatrix plans first-of-its-kind human testing in 2023, starting with the initial experiment outside of the patient's body - but this all depends on approval from the Food and Drug Administration.
The team removes all animal cells from the pig liver (pictured), leaving behind the organ's structure. They then fill the organ with human cells
The initial experiment would place a pig-turned-humanlike liver next to a hospital bed to temporarily filter the blood of someone whose own liver suddenly failed. And if that novel 'liver assist' works, it would be a critical step toward eventually attempting a bioengineered organ transplant.
'It all sounds science fiction-ey, but it's got to start somewhere,' said Dr Sander Florman, a transplant chief at New York's Mount Sinai Hospital, one of several hospitals already planning to participate in the liver-assist study.
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'This is probably more of the near future than xenotransplantation,' or directly implanting animal organs into people.'
US surgeons transplant a PIG heart into a human in world's first op
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Xenotransplantation is the transplanting of organs or tissues of one species into a different one, which was recently done in January when a dying man became the world's first patient to receive a heart transplant from a genetically-modified pig.
David Bennett, the patient, died two months after the groundbreaking experiment.
Doctors did not give an exact cause of death, saying only that his condition had begun deteriorating several days earlier.
Miromatrix is looking to bioengineer the animal organ before putting it into a human.
The first step is to shampoo away the pig cells that made the organ do its work, its color gradually fading as the cells dissolve and are flushed out.
This is the process that leaves behind a rubbery scaffolding, which is filled with donated human liver cells.
Jeff Ross, CEO of Miromatrix, told AFP: 'We essentially regrow the organ. Our bodies won't see it as a pig organ anymore.'
Ross said that stripping away the pig cells removes some of the risks of xenotransplantation, such as lurking animal viruses or hyper-rejection.
The FDA already considers the decellularized pig tissue safe for another purpose, using it to make a type of surgical mesh.
More complex is getting human cells to take over.
Here is the pig organ being filled with human cells. Scientists said this method is more successful than transplanting the organ directly into a human
'We can't take billions of cells and push them into the organ at once,' Ross said. When slowly infused, 'the cells crawl around and when they see the right environment, they stick.'
The source of those human cells are donated livers and kidneys that will not be transplanted.
As long as enough cells function when donation groups offer an organ, Miromatrix biologists can isolate usable cells and multiply them in lab dishes.
The laboratory says it can grow enough cells from one rescued human organ to repopulate several pig liver or kidney scaffolds, cells responsible for different jobs - the kind that line blood vessels or filter waste, for example.
In 2021, Miromatrix announced it successfully implanted its bioengineered liver transplant into five pigs with liver failure.
The transplant was part of a preclinical study in collaboration with researchers at Mayo Clinic, designed to assess the initial transplantation and functionality of a bioengineered liver in an acute liver failure model.
It utilized decellularized porcine liver scaffolds recellularized with human vascular cells and porcine hepatocytes, implanted into pigs suffering acute liver failure.
All pigs were monitored for up to 48 hours.
During that time, the transplanted organ showed critical performance metrics, including the ability to sustain blood flow and key liver function before and after transplantation.
This experiment was conducted in October and the team submitted a pre-IND request to the FDA in December 2021.
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