Thousands of people die each year waiting for an organ transplant as there aren’t enough human organs available, so researchers are turning to an unlikely source: genetically modified (GM) pigs. And these pigs could apparently offer something human donation can’t – an almost unlimited supply of organs.

Researchers have announced that they were able to keep a pig heart alive in a baboon for 945 days. They were also able to shatter records with their kidney transplant between these species, which lasted for 136 days. The previous record was 90 days, though researchers suggest that survival for more than 30 days is unusual. Their findings, detailed in the journal Xenotransplantation, brings us one step closer to pig-to-human transplants. Researchers believe that young pigs are an ideal animal for transplants because their organs are the right size.

The research is being pioneered by scientists at Revivicor, which focuses on regenerative medicine as part of the biotechnology company United Therapeutics. The co-CEO Martine Rothblatt told MIT Technology Review that their goal is to create “an unlimited supply of transplantable organs” and eventually carry out the first successful pig-to-human lung transplant.

The history of cross-species organ transplantation highlights the difficulties of achieving this surgical feat. During the 1960s, Keith Reemtsma transplanted chimpanzee kidneys into 13 human patients. While most of the transplants failed within four to eight weeks, one of Reemtsma’s patients survived for nine months and even returned to work as a school teacher. She eventually collapsed and died from what doctors’ think was an acute electrolyte disturbance. To learn from previous failures, researchers have to find a way to overcome the recipient’s powerful immune response and significantly reduce the risk of infection.

The study builds on previous research that removed a sugar molecule that played a significant role in hyperacute rejection. Researchers went on to genetically modify pigs, giving them human genes to make the organs more compatible and increase the success of an organ transplant. Researchers hope that by adding human genes, the organ will repress the immune response, so patients depend less on huge doses of immunosuppressant drugs. By next year, researchers hope to add eight genes to some of the pigs.

There’s still a great deal of progress to be made, and researchers have their eyes on a more ambitious goal: To successfully complete a pig-to-human lung transplant within the next few years. Lung transplants are a lot more difficult, but Rothblatt is eager to push through with the research.

[H/T MIT Technology Review]