FASTER, PLEASE: Genetically Modified Pigs Could Ease Organ Shortage.

Researchers have been trying for decades to make animal-to-human transplants work, a process known as xenotransplantation. Pigs are a particularly promising source of organs. They produce big litters. Organs such as the kidney and liver are similar in size to those of humans. “Nobody has come up with a better animal,” says Joseph Tector, a professor of surgery who runs the xenotransplantation program at the University of Alabama at Birmingham.

A previous push into xenotransplantation by companies and scientists in the 1990s faltered due to a number of factors. In early experiments with nonhuman primates, their immune system attacked and rejected the pig organs. There were concerns that remnants of retroviruses in pigs’ genetic makeup, while harmless to the pigs, might end up infecting humans. Trying to modify the pig genome was a slow process; it often took years to successfully modify a single gene.

Then last year, a group led by George Church of Harvard University published a paper describing their use of a new gene-editing technology called Crispr-Cas9. Unlike previous gene-editing systems, Crispr allowed the researchers to make multiple changes simultaneously to inactivate viral remnants in the pigs’ genes.

Crispr has helped renew enthusiasm for xenotransplantation.

In the meantime, if you’re eligible, please sign your donor card.