Pig Liver Keeps Patient Alive
A genetically modified pig liver successfully kept a human patient alive until a suitable human liver transplant could be performed. This pioneering xenotransplantation used specific gene edits to remove rejection triggers — a remarkable step forward that could dramatically reduce organ waitlist times.
The recent procedure was an *extracorporeal* perfusion performed at the University of Pennsylvania. Collaborating companies eGenesis and OrganOx used a device to circulate a brain-dead donor's blood outside the body and through the pig liver for 72 hours, where it successfully filtered blood without signs of rejection. This research is driven by a severe organ shortage. In the United States alone, more than 100,000 people are on the national transplant waiting list, with about 10,000 awaiting a liver. It is estimated that 17 people die each day in the U.S. while waiting for an organ transplant. Pigs are considered the most suitable animal for organ harvesting due to their similar organ size, but their genes must be altered to prevent immediate rejection by the human body. Using CRISPR gene-editing technology, scientists remove pig genes that trigger an immune response and can add human genes to improve compatibility and reduce blood clotting risks. The primary immunological barrier is hyperacute rejection, where the human immune system rapidly attacks the foreign organ. Another significant concern is the potential transmission of porcine endogenous retroviruses (PERVs), which are embedded in the pig's genome, though genetic engineering aims to inactivate these. This liver experiment follows other recent xenotransplantations. Surgeons have previously transplanted genetically modified pig hearts and kidneys into living human patients. One pig kidney with 69 genomic edits survived in a non-human primate for up to two years, showcasing the rapid advancements in the field. The immediate goal for the external pig liver is to act as a "bridge" therapy. This approach could temporarily support patients with acute liver failure, giving their own liver a chance to recover or keeping them stable long enough to receive a human organ transplant. Following the successful 72-hour test, eGenesis and OrganOx plan to apply to the U.S. Food and Drug Administration (FDA) to begin a first-in-human clinical study of their external liver perfusion system.
