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Breakthrough in gene editing gives hope to organ transplant waitlist

Scientists have found a way for the human body, especially an immunocompromised body, to not reject pig organs by using CRISPR to genetically remove porcine retroviruses.
CRISPR-Cas9 are basically "scissors" that snip out the unwanted DNA to make room for the genes scientists would like to replace it with. Photo: Flickr/A.Sparrow

More than 117,000 Americans are currently on a transplant wait-list and 22 people die every day awaiting a match, according to federal figures. A scientific advance using genetically edited piglets could lower the fatality rate and make using pig organs, similar to our own, a common practice.

Using the “molecular scissors” CRISPR–Cas9 gene-editing system, scientists in Massachusetts were able to inactivate all 25 viruses in the pig genome. The retroviruses don’t harm pigs, but would make xenotransplants, cross-species transplants, impossible.

“Our animal is probably the most [genetically] modified animal on the Earth,” said Luhan Yang, co-founder and chief science officer of eGenesis, the Cambridge–based start-up that led the research. “We are pushing the envelope of technology day by day. I think that such innovation is required to tackle as challenging a problem as xenotransplantation.”

Many of the porcine embryos and fetuses cloned in the CRISPR experiments died before birth or shortly after, but scientists ended up with 15 living female piglets, the oldest now 4 months old. All are retrovirus-free.


George Church, a Harvard Medical School geneticist who co-founded eGenesis and is a co-author of the paper, said piglets would need to be roughly four months old for their organs to be used for transplants.

“I generally hesitate to say we’ve solved a two-decade-old problem, but in this case, we have,” he said, Scientific American reported.

Pig heart valves are already used in humans, but dead tissue doesn’t carry the same HIV transmission risk, according to Scientific American. Burn patients sometimes receive skin grafts of pig skin, which is eventually rejected by the body but was never intended to be permanent.

Pig organs are roughly the right size and similar enough that using them to save lives makes sense, but other concerns have been raised.

An estimated 100 million pigs are killed in the United States each year for food, The New York Times reported. Major religious groups have concluded that pig organs are OK for live-saving transplants, although some Jewish and Muslim leaders believe dialysis is sufficient for patients with renal failure.

CRISPR was recently used to remove a genetic disease from a human embryo in a huge step for the genetics community.