Heart transplants don't usually make headlines around the world. But earlier this month, a 57-year-old man with terminal heart failure was the first to receive a heart transplant from a very special source: a genetically modified pig.
From all accounts so far, the man, David Bennett, seems to be doing well.
And it's not just pig hearts in the news. There’s been a bit of action on the pig kidney transplant front, too.
These aren't the first instances of pig tissue being transplanted into people — not by a long shot.
Heart valves from pigs, as well as cows and horses, have been transplanted into human hearts for 30 years.
But entire organ transplants are another kettle of fish, both technically and ethically.
So what are some of these ethical quandaries around the practice of transplanting organs and tissues between species — a technique called xenotransplantation — and can we expect to see pig hearts in chests in Australia soon?
Ethical questions and high stakes
University of Sydney bioethicist Diego Silva said xenotransplantation, and growing replacement parts in animals such as pigs, presented a raft of ethics questions.
"We're genetically modifying pigs, in this case, and using them as tool for the benefit of humans," he said.
"But we have to recognise that all of this is happening on the backdrop of a shortage of organs. People are dying.
"We're not seeing if we can [transplant pig organs into humans] because it's interesting, but we're doing this to save people's lives."
Julian Koplin, a bioethics researcher at the University of Melbourne and Monash University, said ethical considerations could be broadly split into issues for humans and animal welfare.
The first, and perhaps most obvious, is that a heart taken from a pig may save a person's life, but it means death for the donor.
"We currently rear and kill pigs — sometimes under factory farming conditions, which are quite horrible — so we get to enjoy a tasty source of protein," Dr Koplin said.
Then there's the donor pig's quality of life. Pigs are intelligent, social creatures.
Donor pigs are bred and raised in medical-grade facilities to protect them from diseases that may be passed onto humans.
"And that means that the life of a transplantation pig might not have many opportunities for environmental enrichment," Dr Koplin said, compared to, say, a pig that's allowed to snuffle around on a farm.
"But again, the purpose it's serving is a crucially important one, so potentially it's a trade-off worth making."
On the human side, while Mr Bennett's nine-hour operation was done by transplant surgeons in a hospital, it's important to remember that it's still an experimental procedure.
"What kind of consent standards are needed to trial the technology, and who should be eligible?" Dr Koplin said.
In the case of Mr Bennett, it was either get the pig heart transplant or die. He had terminal heart disease but was ineligible for a human heart transplant.
"The worst case scenario if he participates in this experimental treatment isn't much worse than the expected scenario if he doesn't."
Then if the technique eventually moves into more routine clinical care, more questions will be raised around historical disparities in health — will it make health care more or less equitable for minority populations? — not to mention how the business of animal organ transplants will run, Dr Silva said.
"And what will regulators want to see in order to say, 'yes, these are the parameters by which you can scale this up'?"
"To a large extent, it's a scientific question, but there's an ethical aspect to it as well. What risks are we willing to take?"
What's the deal in Australia?
Organ transplantation from pigs and other animals has a long history stretching back to the middle of last century.
And while clinical trials are allowed in Australia now, subject to regulatory clearances, that's not always been the case.
From 2004 to 2009, the National Health and Medical Research Council (NHMRC) recommended that xenotransplant clinical trials should not be conducted in Australia "as it was still a developing area of science".
A major concern was the risk of spreading diseases between pigs and people. That's because your standard, run-of-the-mill pig DNA doesn't just contain instructions to build the pig.
It also contains genetic code for a bunch of viruses, some of which can infect human cells where they might cause disease and spread.
In recent years, gene-editing techniques such as CRISPR have allowed researchers to trim that virus DNA from a pig's genome, resulting in virus-free animals.
They can also add and snip out genes to lower the risk of organ rejection.
Nowadays, the biggest scientific hurdle to overcome is stopping the human body from rejecting the transplanted organ, according to Peter Cowan, Immunology Research Centre science director at Melbourne's St Vincent's Hospital.
But even if that problem was solved tomorrow, we wouldn't be seeing whole pig organ transplants or even clinical trials in humans happening in the short- to mid-term, said Professor Cowan, who is involved in pig-to-human xenotransplantation research.
"Due to our quarantine rules, we can't import live pigs. We couldn't say 'OK, let's take pigs from the US and bring them here and start doing transplants'."
Then there's the problem of where we'd keep them, even if the pigs could be brought over, he added. In Australia, we don't have any medical-grade pig facilities — needed for human clinical trials — and they're expensive to set up and run.
Still, the pig heart transplant "really stirred up interest in the whole area", Professor Cowan said.
"I'm hoping it takes off. We really want to get things established here in Australia as well."
Dr Silva says as progress in whole organ xenotransplantation continues, so too will discussions around ethics and regulations.
"It won't so much be asking, 'is this the right thing to do?'" he said.
"It's more, 'how do we do this in the right way?' And that should be the question that's guiding us."
