The first transplant of a pig's liver into a human recipient has been carried out by scientists in China, according to a new study.
Researchers at the Fourth Military Medical University in Xian, in northwestern China, used a liver taken from a miniature pig that had been genetically modified to reduce the risk of rejection.
The liver successfully produced bile and maintained stable blood flow after being placed into a brain-dead, but still-living, person.
Scientists then monitored the liver's ability to perform core functions, blood flow and its immune and inflammatory responses over 10 days.
Researchers hope the organ could be used as a possible future treatment for patients with liver failure awaiting human donors.
Professor Lin Wang, author of the study, published in the Nature journal, said: "The liver collected from the modified pig functioned very well in the human body. It's a great achievement."
"This surgery was really successful," Wang added.
"We examined the blood flow in the different vessels and arteries," Wang said. "The flow is very smooth. It functioned very well."
The experiment was terminated after 10 days because of requests from the patient's family members.
The liver had six of its genes modified to improve compatibility when transplanted into humans.
The findings suggest the modified livers can survive and function in human bodies, but further research on long-term outcomes is needed, the study said.
Wang added: "We have the opportunity in the future to solve the problem of a patient with severe liver failure. It is our dream to make this achievement."
"The pig liver could survive together with the original liver of the human being and may give it additional support," the professor continued.
Wang also expressed a desire to conduct further research on living, non-brain-dead human beings in the future, but stressed the complications and "many rules" around this.
Rafael Matesanz, founder of the National Transplant Organization in Spain, said: "This is the world's first case of a transplant of a genetically modified pig liver into a brain-dead human."
"The ultimate goal of the experiment was not to achieve a standard liver transplant, but to serve as a 'bridge organ' in cases of acute liver failure, while awaiting a human organ for a definitive transplant," he said.
Matesanz said the procedure was "successful for its intended purpose" and that similar transplants could be carried out in living organisms "in the near future."
Liver transplantation is the most effective treatment for end-stage liver diseases, but the demand for donor livers far exceeds the supply, according to the researchers.
Pigs are being considered as an alternative source of organs owing to their compatible physiological functions and size.
The pig for this surgery was provided by Dr. Deng-Ke Pan at Clonorgan Biotechnology Company.
The transplant follows more than 10 years of research into this process on animals. In 2013, scientists performed the first pig-to-monkey liver transplant.
Previous studies into kidney and heart transplants from pigs to humans have also been successful but whilst those organs have mostly one function, the multi-functionality of the liver was a "huge obstacle for us to overcome," Wang said.
