Researchers in Japan are one step closer to being able to implant human induced pluripotent stem (iPS) cells into an animal embryo. Their aim is to grow a fully-grown human pancreas in an animal, a pig, and ultimately harvest and transplant such organs into patients.
Like human embryonic stem (hES) cells, iPS cells can develop into any cell in the body, but crucially, they are derived from adult human tissue, rather than embryos, which have to be destroyed to harvest hES cells.
Current regulations in Japan stipulate that 'chimeric' embryos (animal embryos containing human cells) can only be developed in the laboratory for 14 days, after which time they must be destroyed.
Professor Hiromitsu Nakauchi from the University of Tokyo has explained that Japan's highest science advisory body, the Expert Panel on Bioethics of the Council for Science and Technology Policy, has recommended a review of those regulations in view of his research proposal.
'This recommendation is a very important step forward and one that has taken us three years to achieve', Professor Nakauchi commented. In his proposal the chimeric embryo would be implanted in a sow and raised after birth until such time as its pancreas could be harvested and analysed.
His team has already successfully injected stem cells from a breed of black pig into the embryo of a white pig that was engineered not to develop its own pancreas. The resulting organ was genetically matched to the black pig and not its host.
Professor Nakauchi's work now focuses on pigs because, he says, 'pigs have organs that are similar to humans', in terms of both size and shape'. He is far from the first to make such an observation; pig heart valves are widely used in transplant medicine, for example.
The panel's recommendation will now be sent to an education ministry committee and continue the process of being transmuted into law. This should 'take another year or two', Professor Nakauchi told ScienceInsider, and even then the outcome is not assured. The government 'doesn't want to take risks', he added.
However, if the regulations are relaxed, Professor Nakauchi believes the first pig carrying a human organ could be produced 'quite quickly, because the technique has been established already'.
Speaking to ScienceInsider, Professor Nakauchi acknowledged the potential of his work to provoke alarmist headlines. 'People think we're making a human-pig monster', he said.
But for him the most important question was whether his technique would produce working human pancreases. If it did, he said, there could be around a decade of safety testing ahead before wider clinical use.