Will pigs keep humans alive? Future of transplants may rest on tiny hooves

Scientists have dreamed for centuries about using animal organs to treat ailing humans. In recent years, those efforts have begun to bear fruit: Researchers have begun transplanting the hearts and kidneys of genetically modified pigs into patients, with varying degrees of success.

But lungs are notoriously difficult to transplant, even from human to human, and mortality rates are high. Now, in the first procedure of its kind, Chinese scientists on Aug 25 reported of transplanting a lung from a pig into a brain-dead man.The organ sustained damage after it was transplanted but functioned to some degree, scientists at Guangzhou Medical University reported in the journal Nature Medicine. It was rejected after nine days.

Given the global shortage of organs, especially lungs, experts were upbeat yet cautious. “If there is a way to actually source organs from animals and have them work in genetically modified ways, that would be very exciting,” said Dr Stephanie Chang, an associate professor in cardiothoracic surgery at NYU Grossman School of Medicine and surgical director for the lung transplant program.

Research teams across the world have been increasing the number of experiments with organs from genetically modified pigs bred by different companies, with various sets of gene edits.

In March, a team of Chinese scientists reported that they had transplanted a genetically altered pig’s liver into a brain-dead person, where it functioned for 10 days, producing bile and porcine albumin and maintaining stable blood flow without signs of rejection.

The US company eGenesis is also studying the transplantation of pig livers in addition to other organs. In April, the company received authorization from the US Food and Drug Administration to start clinical trials using pig livers to treat patients with a condition called acute-on-chronic liver failure. The treatment involves circulating the patients’ blood outside the body through the animal’s liver.

In February, the FDA also gave the go-ahead to United Therapeutics Corporation to start a clinical trial transplanting kidneys from genetically engineered pigs into patients with kidney failure.

One American man who received a kidney from a genetically altered pig produced by eGenesis has been living with the organ since January. He is the longest survivor with a pig’s kidney to date.

“Just imagine, you have kidney disease and know your kidneys are going to fail, and you have a pig’s kidney waiting for you — and you never see dialysis,” said Mike Curtis, president and chief executive at eGenesis, envisioning a future where gene-clipped pig organs would get so compatible with humans that powerful immune-suppressants that raised risks of infection and cancer would become redundant. Pig organs could serve as bridge transplants for many in the waitlist, whether its babies born with heart defects or people needing new livers.

Too early to rejoice
But there are miles to go before that dream is realised. The humans receiving pig organs have only lived for months so far. Even if such transplants are successful, they could potentially let pig viruses find their way to humans. “A potential zoonotic transference could happen at any point after a transplant — in perpetuity,” said bioethicist Christopher Bobier from the Central Michigan University College of Medicine, warning that it may be decades before symptoms surfaced. In fact, the first pig heart given to a Maryland man had a porcine virus that had gone undetected despite rigorous pre-transplant screening.
But doctors are still optimistic. “We forget, but the first person to receive a human heart transplant also died within two weeks,” said Dr Robert Montgomery, a surgeon at NYU Langone. Dr Montgomery has had a human heart transplant himself and had successfully kept a brain-dead man with a pig’s kidney stable for two months.

Ethical questions
However, ethical concerns remain. Some have criticised the cloning of animals to harvest their organs even as pigs are being bred in millions for human consumption. Cooper, who is also an eGenesis consultant, said, “Is it ethical to let thousands of people die each year on a waiting list when we have an alternative therapy that looks pretty encouraging? I think that’s ethically unacceptable.”

NYT news service