Using the gene-editing tool known as CRISPR, scientists have successfully edited the genome of pigs to produce piglets whose organs aren’t coated with a marker that would make those organs unsuitable for transplant into human patients, the New York Times reports, citing an article published today in the journal Science.
This represents a major breakthrough in medicine and in the use of science to extend people’s lives. In the US alone, 22 people die every day on waiting lists for organ transplants.
Yet the use of this technology to raise pigs whose only purpose would be organ harvesting raises ethical questions, which are bound to get an audience with politicians, religious organizations, animal rights groups, and others.
The problem with using pig organs
You may wonder why we allow so many people to die every day when all they need is a new liver or a new kidney to keep them alive a little longer. Science fiction and just general fiction have created literature where humans are brought into the world simply because a sick relative needs an organ, and siblings are the most likely source of compatible organs.
The reason siblings make good donors is that the genes in their organs’ cells are likely to be similar to those of the recipient. So, when the organ is transplanted, the immune system of the recipient wouldn’t recognize anything about that organ as being foreign. The recipient’s immune system would be less likely to attack the organ, in other words, than it would if the organ had come from a non-family member.
Pigs have scattered throughout their DNA several remnants of ancient viral infections known as porcine endogenous retroviruses, or PERVs. If the organs are transplanted, these viral infections could infect a person who receives the pig organ. That person’s immune system would then attack the organ, kill it, and kill the person.
Scientists tried to transplant a pig organ into a baboon once, and the baboon died within minutes as a result of the baboon’s immune system attacking the organ.
But what if, using CRISPR, scientists were able to take all the viral infection remnants out of the pig’s genome? They could theoretically make pigs without the problem-causing coatings on their organs and try again.
Where we are
Scientists at Harvard and at the private company eGenesis have done exactly that. They say trials with transplanting pig organs into human recipients could be just a few years away.
“If this is correct, it’s a great achievement,” Science quoted virologist Joachim Denner of the Robert Koch Institute in Berlin, who has studied the mysterious PERV sequences, as saying.
Scientists need to see if removing the PERVs is the only modification needed so the organs won’t be rejected by the human immune system. The organs may also have other issues that need to be addressed before any inter-species transplantation occurs, and transplant surgeons are always concerned about rejection and infection, even when the donor is of the same species.
Still, Mr Denner says, “If it is possible to knock [PERVs] out, you should do it.”
But once we do, the risk of infection and other problems that may arise from any pig-to-human transplant can’t be overlooked. Doctors will need to consider how the animal is sacrificed, any risks to healthcare workers, any danger not only to the patient but to family members, and so on.
There’s a long way to go, but this is ultimately a huge step.