Understand The Times, International

Japanese scientists are expecting to be granted approval to grow human organs in animals and then harvest them for transplant within the next year. A panel of scientists and legal experts appointed by the government has drawn up a recommendation that will form the basis of new guidelines for Japan�s world-leading embryonic research.

There is widespread support in Japan for research that has raised red flags in other countries. Scientists plan to introduce a human stem cell into the embryo of an animal � most likely a pig � to create what is termed a �chimeric embryo� that can be implanted into an animal�s womb. When the adult animal is slaughtered, the organ will then be harvested and transplanted into a human. That will then grow into a perfect human organ, a kidney or even a heart, as the host animal matures. When the adult creature is slaughtered, the organ will then be harvested and transplanted into a human with a malfunctioning organ.

Nakauchi�s team have 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. At present, the Japanese guidelines permit scientists to develop chimeric embryos in laboratory conditions for a maximum of 14 days, but the next stage in the process � the embryos being implanted into an animal�s womb � is prohibited.

As soon as government officials agree on the details of the revised guidelines � a process that is expected to take 12 months � Nakauchi believes the first pig carrying a human organ can be produced �quite quickly, because the technique has been established already.�

The scientists plan to initially breed a pig with a human pancreas as it is a relatively easy organ to create, Nakauchi said, and perfecting the technique will bring relief to millions of people with diabetes. Creating kidneys and a human heart will be far more complicated, he said, but are feasible. He suggested that practical use for the organs may be as little as five years away. Eventually, he hopes to be able to have numerous human organs within each donor animal that can be harvested all at the same time.