Breakthrough by Chinese scientists could lead to pig livers being used to keep people alive while they await a suitable human donor which can take months or even years
A pig liver has been successfully transplanted into a human for the first time. Scientists say pig livers could eventually be used to keep people alive while they await a suitable human donor which can take months or even years.
Chinese scientists genetically modified a miniature pig to minimise the risk of organ rejection before transplanting its liver into a brain dead human patient. It successfully produced bile and maintained stable blood flow and researchers say pig livers could now “solve the problem of severe liver failure”.
Study author Professor Lin Wang, of the Fourth Military Medical University in Xi’an province, said: “The liver collected from the modified pig functioned very well in the human body. This surgery was really successful. We examined the blood flow in the different vessels and arteries. The flow is very smooth. It functioned very well. 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.”
In the UK there are currently over 600 people with end stage liver disease in need of a transplant. The life-saving surgery is also performed for some patients with primary liver cancer and children with metabolic diseases.
The breakthrough findings, published in the Nature journal, suggest genetically modified pig livers could survive and function in human bodies. Scientists also monitored the liver’s ability to perform core functions, blood flow and its immune and inflammatory responses over a period of 10 days.
Demand for liver donor livers far exceeds the supply so pigs have long been considered a possible alternative given the similarity of their organs to that of humans. Previously scientists have been able to transplant pig kidneys and hearts to humans but these organs have mostly one function.
Transplanting a liver had proved elusive during over a decade of research because it performs so many vital functions, which Professor Wang said was a “huge obstacle for us to overcome”. These functions include filtering blood, metabolizing nutrients, detoxifying harmful substances, producing bile for digestion and storing essential nutrients. In 2013 scientists performed the first pig-to-monkey liver transplant.
Rafael Matesanz, founder of the National Transplant Organisation 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.”
Mr Matesanz added that similar transplants could be carried in living organisms “in the near future”.
The experiment was terminated after 10 days because of requests made by the brain dead patient’s family. Scientists insist further research on long-term outcomes is needed.
The liver had six of its genes modified to improve compatibility when transplanted into the human. Professor Wang added: “The pig liver could survive together with the original liver of the human being and maybe it will give it additional support.”
Professor Wang said his team wants to transplant pig livers into non-brain-dead humans in future, but stressed there are “many rules” around this in China.
Only basic liver functions were assessed and the team were unable to collect longer term data on more complex liver functions such as drug metabolism, detoxification or immune function.
Professor Iván Fernández Vega, expert at the University of Oviedo in Spain, said: “We have to be cautious. The study represents a milestone in the history of liver xenotransplantation. Sophisticated genetic modifications have been applied to the graft to prevent hyperacute rejection, one of the most critical complications. Optimising this approach could expand the pool of available organs and save lives in liver emergencies.”