GM pigs raise hopes for human organ transplants

Posted Agosto 14, 2017

At the time of writing, 117,000 people in the United States are on a waiting list for an organ, with 22 people dying each day waiting for a transplant. "This could be a path to a transplant for them". "While using pig organs, we can in principle use as many as we need".

Scientists have for the first time eliminated a risky type of virus found in live pigs that could make it safe for potential organ transplants into humans. "As a result, xenotransfusion was banned in France for a number of years".

Such xenotransplantation would be one way to address the organ shortage of organs for transplant. "Many previous works have demonstrated that the immunological incapability can be alleviated through tailoring the pig genome". These are known as endogenous retroviruses which, although normally silent, can be activated to become fully infectious for human cells when pig cells carrying these retroviruses are co-incubated with human cells. Then the scientists cloned the edited cells.

The adult cells were not as nature made them, however.

In a bold scientific step that helps open the door to organ transplants from animals, researchers at Harvard and a private company have created gene-edited piglets cleansed of viruses that might cause disease in humans. In most of the rest, CRISPR missed its mark. In any event, said Dr. A. Joseph Tector, a transplant surgeon at the University of Alabama at Birmingham, pig retroviruses are very sensitive to the drugs used to treat HIV. Apparently, in its zeal to attack so many PERV genes, CRISPR had shredded the cells' genomes - fatally.

"The next major step is to solve the problem of vigorous immune responses, such as complement activation, coagulation and thrombosis, triggered by xenotransplantation", Lin said. "That can happen when you make two or three [CRISPR edits], and we're dealing with 25".

Now they've announced their PERV-free embryos are healthy PERV-free piglets, the oldest being 4 months old. And CRISPR did not change any DNA it wasn't supposed to; there were no "off-target" effects. The unreliability of cloning means that, out of thousands of attempts, just 15 piglets remain alive.

Not all were brought to term and over half of the population had their lives ended in order for scientists to check in on how their organs were developing. "Our team will further engineer the PERV-free pig strain to deliver safe and effective xenotransplantation". The viruses, he added, were genetically inactivated, as opposed to deleted.

Organ transplantation is a controversial topic at the best of times. They used the gene editing tool CRISPR to deactivate all 25 genomic sites. It is an issue that emerged in the early 1980s when surgeons put a pig heart into a baboon. The supply is way below the demand and the gap is only expected to grow wider.

There is disagreement about whether pig organs would have to be PERV-free to be successfully transplanted into people.

Separately, researchers have also been working toward another possible solution for the donated organ shortage: 3-D printing.