US researchers have managed to transplant kidneys from genetically modified pigs into baboons, a development that could pave the way for animal-to-human organ transplants, Nature magazine reports. Scientists at the Massachusetts General Hospital, US, used kidneys from pigs that have been genetically altered to reduce rejection by the human and monkey immune systems. They transplanted pig kidneys into eight baboons, which enabled them to survive for up to 81 days, compared to around 30 days for kidneys from non-genetically altered pigs.
The use of animal organs for human transplants (xenotransplantation) has been suggested as a way to overcome the massive shortage of donated organs for human patients. But there are many technical obstacles to overcome with this approach, including the rejection of foreign tissue by the body's immune system. To address this problem, researchers have bred miniature pigs whose body cells lack a key sugar molecule, called alpha-1,3-galactose, which normally triggers an aggressive immune response. The pigs, produced by US company Immerge BioTherapeutics, lack a gene called GGTA1, which makes a protein that normally adds the sugar molecules to the outside of the cell. In addition, the size of the miniature pigs' organs is closer to that of humans than organs from ordinary-sized pigs.
The latest results, presented by team leader David Sachs at the International Xenotransplantation Congress in Glasgow earlier this year, provide evidence that tissue rejection can be overcome. Eighty-one days is apparently the longest that researchers have managed to extend a baboon's life using a pig organ. But there are still other problems to overcome, reports Nature, such as the tiny blood clots that killed some of the baboons. There are also other safety and ethical issues to address before researchers can consider human xenotransplantation trials, including the concern that pig organs could transfer new viruses to human patients.