Japanese scientists have developed a process for forming a chimeric embryo by planting a human stem cell into an animal embryo, usually a pig. The organs would then mature inside the animal until scientists harvest and transplant them into a human body.
Led by Professor Hiromitsu Nakauchi of the University of Tokyo, they want to plant the embryo in a female pig's womb, inducing pregnancy and creating a new-born pig with human organs such as pancreas or liver. The organs would then mature inside the hybrid offspring as it grows until it is slaughtered and scientists harvest the organs and transplant them into a human body.
Creating the chimeric embryo is legal, but so far implanting it in an animal's womb is not. Right now, a Japanese regulatory body is deciding whether to lift the ban on implanting chimeric embryos in animals, and these scientists are confident they could successfully grow a pig with human organs within a year if they win approval.
Japan supports researches that have raised red flags in other countries, such as its scientists’ plan to introduce a human stem cell (infant cells that can develop into any part of the body) into the embryo of an animal to create what is termed a "chimeric embryo" that can be implanted into an animal's womb. That will then grow into a perfect human organ, a kidney or even a heart, as the host animal matures. Prof. Nakauchi's team has already succeeded in injecting stem cells from rats into the embryos of mice that had been genetically altered. “We can apply the same principles to human stem cells and pigs, although the guidelines have not permitted us to do this yet,” he said.
There is little public opposition to research of this kind in Japan, with domestic media coverage overwhelmingly positive, reflecting relatively high levels of scientific literacy in the country. Until the discovery of iPS cells (human “induced Pluripotent Stem” cell) several years ago, the only way to obtain stem cells was to harvest them from human embryos. This is controversial because it requires the destruction of the embryo, a process to which religious conservatives, among others, object.
Similar to embryonic stem cells, iPS cells are also capable of developing into any cell in the body, but crucially their source material is readily available. “We'll see if the experiment goes well, but if we succeed in producing a human organ, the rest of the work toward practical use would be done within five years,” Nakauchi told AFP. He said creating kidney and human heart will be far more complicated, but they are feasible. He and his team will initially breed a pig with a human pancreas as it is a relatively easy organ to create, and perfecting the technique will bring relief to millions of people with diabetes.