Research out this week appears to show the potential longevity of transplanted organs from genetically engineered pigs. Scientists gave monkeys kidneys from these animals, finding that some were able to live for one to two years. Many of the genetic changes evaluated in this study could make pig-to-human transplants a more viable treatment to test out in clinical trials, the team says.
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Animal-to-human transplantation, or xenotransplantation, has become a promising avenue for addressing the perpetual shortage of donated organs. By editing the genes of pigs to make them more compatible with human biology, the hope is that their organs can be safely tolerated by the recipient’s immune system.
Early tests of the technology in humans have either involved the use of brain-dead patients (with the permission of their families) or living but terminally ill patients who are ineligible for conventional transplants. These studies have found that the organs can be transplanted and remain functional without being immediately rejected by the body for up to two months.
The scientists behind this new research are from the biotech company eGenesis and Harvard Medical School. They argue that larger-scale clinical trials will require creating engineered pigs with organs that can clearly survive longer-term tests in nonhuman primates. And their findings, published Wednesday in the journal Nature, suggest that such pigs are indeed possible.
The researchers bred Yucatan miniature pigs with up to 69 different genetic edits. These edits included knocking out genes from pig-specific retroviruses inserted long ago, as well as adding human genes intended to improve compatibility. The researchers then transplanted their organs into cynomolgus monkeys, with some monkeys given organs from only lightly edited pigs.
The monkeys given organs from the least-edited pigs survived less than two months on average. Of the rest, nine monkeys survived for longer than two months, five survived for over a year, and one monkey made it to just over two years (as of the study’s publication, three monkeys are reportedly still alive, with the longest living over 670 days). Other tests found that the edited organs in these monkeys could perform as well as native kidneys, at least for a time.
The findings are only a proof-of-concept for the technology. There are still many questions about the best way to make xenotransplantation safe and effective in humans. Many researchers have been experimenting with far fewer genetic edits than the ones seen here, for instance. But the team says their results should bring “us closer to clinical testing of porcine renal grafts for human transplantation.”