The prospect of using genetically modified pig organs to cut transplant waiting lists has moved forward with the creation of the first versatile pig stem cells. Scientists in China have successfully reprogrammed pig skin and bone marrow cells into an embryo-like state with the potential to form every type of body tissue. The achievement promises to provide a tool for breeding pigs that are genetically engineered to carry human immune system proteins so that their organs are less likely to be rejected for transplant. It also raises the possibility of modifying pigs to resist infections such as swine flu, and to grow pig tissues and organs as models for human diseases.

Lei Xiao, of the Shanghai Institute of Biochemistry and Cell Biology, who led the research, said: “Pig pluripotent stem cells would be useful in a number of ways, such as precisely engineering transgenic animals for organ transplantation therapies. The pig species is significantly similar to humans in its form and function, and the organ dimensions are similar to human organs. We could use embryonic stem cells or induced stem cells to modify the immune-related genes in the pig to make the pig organ compatible to the human immune system. Then we could use these pigs as organ donors to provide organs for patients that won’t trigger an adverse reaction from the patient’s own immune system.”

Several other important safety barriers remain before pig organs can be transplanted into human beings. Scientists remain concerned, for example, about exposing people to pig viruses. While embryonic stem cells have been derived from many animals, including human beings, attempts to culture these master cells from pig embryos have previously failed. In the research, published in the Journal of Molecular Cell Biology , the scientists have produced embryo-like stem cells by modifying several genes in adult tissue. The resulting induced pluripotent stem cells, or IPS cells, have similar properties to embryonic stem cells.

This would be useful to science because embryonic stem cells are important tools in genetic engineering. The main method of producing GM animals is to alter the DNA of embryonic stem cells and then add these to an embryo. The resulting animal will be a chimera containing some modified and some normal cells. If two chimeras breed with one another, some of their offspring will contain only the modified cells. Chris Mason, Professor of Regenerative Medicine at University College London, said that the research could have medical applications within ten years. “This potentially reinvigorates the quest to grow humanised pig organs such as pancreases for diabetics and kidneys for chronic renal failure,” he said.

“The clinical use of humanised porcine tissues and organs [xenografts] has moved a long way forward in recent months with successful small-scale clinical trials for the treatment of diabetes by Living Cell Technology in Australia. While the xenograft approach may not necessarily be the long-term solution, it may represent a step change in the treatment of organ failure, which could deliver real benefit to millions of patients within a decade.”