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Jumping Genes Inactivated with CRISPR in Pigs

11 Août 2017

Scientists may have stumbled upon a solution to stop the 500 people who die in the United Kingdom every year waiting for an organ transplant - pigs. Despite pig organs posing as prime candidates for human transplantation considering their similar size and function, they generally, and unsurprisingly, trigger significant immune rejection responses in humans.

In 2014 Margaret Mann, a retired carer from West Sussex, became the first patient in the world to have a heart valve made of pig tissue.

Now, in what one medical expert tells the New York Times could be a "real game changer," researchers from eGenesis, a spinoff of Harvard University, have scrubbed dozens of viruses from pig DNA to create genetically modified piglets that may one day serve as organ donors for humans. "We are pushing the envelope of technology day by day". Dr. Fishman said the risk of transplanted organs spreading the virus to others is low.

"We got perfectly healthy piglets", Church tells The Verge, "so that's incredible". But one concern has been the potential for the zombies of pig infections past, known as porcine endogenous retroviruses (PERVs), to reanimate and infect human organ recipients. "If you could help them with a pig organ, wouldn't that be wonderful?"

Another pleasant surprise, Church adds, is that the piglets did not get reinfected with the viruses in the womb. So far, the animals have lived more than a year with no problems, Tector said. Scientists have noticed the shortage and they have been trying to address the issue in more than one way, and recently they have also tried tweaking the organs of mammals and use them for humans in a compatible way. Church says his lab is already doing work on that, and expects to publish a paper on it soon. The challenge is to identify which pig genes are necessary and sufficient to change so that the animals' organs have a shot at working in people.

These human cells then had the ability to infect other human cells, which raised concerns that transplanting the organs into humans could activate the virus and create a new human disease. "This is a great step forward for xenotransplantation", says Joachim Denner of the Robert Koch Institute in Germany. If this happened, it may cause diseases like cancer.

Fears that pig organs would infect humans with freaky retroviruses brought the research to a halt.

In the new report, scientists detail how they took pig cells and edited them using the gene-editing technology CRISPR-Cas9 to target and hinder their virus-related DNA.

"At least for those who are four months old, we did not observe difference in physiology between the modified piglets and normal ones", Yang said.

When asked about it, Dixon Kaufman, the President of American Society of Transplant Surgeons said that it will only be years before xenotransplantation comes into existence.

Jumping Genes Inactivated with CRISPR in Pigs