WHEN PROTO MAGAZINE LAUNCHED IN 2005, there was new hope that pigs would someday be used as organ donors for humans. Researchers had recently discovered how to genetically remove a substance in pig tissue that was rejected by human immune systems.

In this video, Joren Madsen, director of the Massachusetts General Hospital Transplant Center, talks about what happened in the years after that discovery, and why researchers are once again optimistic.

“There are now published examples of pig to baboon heart transplants going for over a year,” says Madsen. But to solve the problem of organ failure, the research field must have several other runners in that race—developing synthetic organs, making machines that can assist failing organs and keeping organs from failing in the first place. “We don’t know who’s going to win the race, we just want to make sure that someone wins it soon.”

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