Genetically modified pig lungs or lab-grown lungs: Which is the future of our organ supply?

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Your loved one might be saved by a lung transplant grown inside a genetically engineered pig.

This is the future promised by efforts to genetically modify pigs to grow “humanized” organs. Already a close match for humans in many aspects of their biology, it should take relatively little modification to make pig organs viable substitutes for human.

The idea has been around since at least 2006, but biotech pioneer J. Craig Venter has brought it back into the headlines by making a deal between his private company Synthetic Genomics and United Therapeutics’ Lung Biotechnology with the explicit goal of making genetically engineered pig organs for human use a reality.

Despite the close similarity of pig and human organs in terms of size and functionality, the genetic differences between human host and donor animal leads the immune system to attack the donor organ as a foreign object. Hence the need to create organs which will not set of the immune system’s hair trigger.

“We’re going to start with generating a brand new super-accurate sequence of the pig genome, and then go through in detail and compare it to the human genome,” Venter told Reuters reporter Julie Steenhuysen.

“The goal is to go in and edit, and where necessary, rewrite using our synthetic genomic tools, the pig genes that seem to be associated with immune responses,” he said. “We want to get it so there is no acute or chronic rejection.”

Steenhuysen summarizes Venter’s plans:

Venter’s team is tasked with editing and rewriting the pig genome and providing the United Therapeutics group with a series of altered cells. United Therapeutics will take those cells and transplant them into pig eggs, generating embryos that develop and are born with humanized lungs.

If all goes well, Venter thinks his team will be able to deliver the cells in a few years. Testing the humanized organs in clinical trials to ensure they are safe in people will take many more years.

So this future of pig-grown organs is still far off at best. And in the meantime efforts are are moving forward to grow human organs de novo in a lab. In February of this year a team at University of Texas announced their success at growing the first human lung in a lab using stem cells.

According to David McNamee at Medical News Daily:

Taking lungs from two children who had died from trauma (most likely a car accident), the researchers stripped one of the lungs down to a bare “skeleton” of just collagen and elastin – the main proteins in connective tissue.

Using this stripped-down lung as a “scaffold,” they then harvested cells from the other lung, which were applied to the scaffolding.

This lung structure was then placed in a chamber filled with a nutritious liquid […]

After 4 weeks of immersion, the team extracted a complete human lung from the liquid.

Unfortunately, according to the McNamee “the reality of lab-engineered lungs being used in transplants could be at least 12 years away”

With both methods of creating donor organs still far from clinical use, there doesn’t seem to be much ethical buzz around either approach yet. I can’t help but expect that pig-grown organs would see push-back, not least of all because creating a supply of genetically modified pigs would raise all the same ethical concerns as raising the animals for meat in addition to pushing the “unnatural” button common in opponents of biotech.

Regardless, pig-grown organs do seem to be coming. Venter’s team isn’t the only one trying to perfect the process of genetically modifying pigs to act as organ donors. Steenhuysen reports that “researchers at the National Heart, Lung, and Blood Institute […] grafted a genetically altered pig heart into the abdomen of a baboon and kept it functioning, aided by the baboon’s natural heart, for more than a year.”

Kenrick Vezina is Gene-ius Editor for the Genetic Literacy Project and a freelance science writer, educator, and naturalist based in the Greater Boston area.

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