CRISPR makes piglets that may be better organ donors for humans

CRISPR slices virus genes out of pigs, but will it make organ transplants to humans safer?

Scientists announced Thursday they have discovered a gene editing method that could clear the way for growing human organs in pigs meant for transplants.

Pig organs are about the same size as humans, ' so some scientists and transplant surgeons see them as candidates to solve the problem of a shortage of organ donors, reports The New York Times.

"There's a big gap between organ supply and organ demand", he told The Times. Between 2012 and 2016, there was a almost 20 percent increase in the number of transplants that happened in the United States, and that number is only expected to increase as the population grows older, according to the United Network for Organ Sharing. "Even if organs from these gene-edited pigs could be safely used to overcome virus transmission, there remain formidable obstacles in overcoming immunological rejection and physiological incompatibility of pig organs in humans".

The findings represent an important breakthrough in the potential for xenotransplantation, or the use of animal organs in humans. It is an issue that emerged in the early 1980s when surgeons put a pig heart into a baboon.

It's a huge step, as those viruses (more specifically known as porcine endogenous retroviruses, or PERVs) pose a not-yet-fully-understood ― but potentially significant ― health threat to humans.

The eGenesis scientists used the CRISPR-Cas9 version of the genome editing tech to slice off the PERV-causing genes in porcine embryos. However, pigs also have many viruses embedded in their DNA, passed down the generations in sperm and eggs.

Gene editing technology has been making waves for the past year for its revolutionary medical promise. The retroviruses don't harm pigs, but would make xenotransplants, cross-species transplants, impossible.

Those virus-free cells were then used to fertilize several pig embryos, which were implanted in sows who have since given birth to virus-free pigs.

Through their private company called eGenesis, Harvard researchers, together with Chinese and Danish collaborators, have created genetically engineered piglets that are free of viruses that might harm humans.

They successfully transplanted hearts and kidneys from those pigs into monkeys and baboons. But one of the largest safety concerns has been the fact that most mammals including pigs contain repetitive, latent retrovirus fragments in their genomes - present in all their living cells - that are harmless to their native hosts but can cause disease in other species.

Next, the company needs to make sure it can consistently replicate virus-free pigs, which it's already well on its way to doing.

An average of 22 Americans die each day waiting for an organ. As a result, Church had wondered if they play an essential role in the pig's survival and whether the animals could develop properly without them.

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