A Japanese stem cell scientist has obtained permission to create human-animal chimeras and transplant them into surrogate animals. Hiromitsu Nakauchi, a researcher at the University of Tokyo and at Stanford University, plans to insert induced pluripotent human cells into mouse embryos. His ultimate aim is to grow human organs in animals.
This kind of procedure was banned in Japan until March, when the government issued new guidelines permitting scientists to create human-animal embryos which can be brought to term. The creation of chimeras in the laboratory is permitted in other countries, like the United States, but the human-animal hybrids cannot be brought to term.
Nakauchi says that he will proceed cautiously and slowly, first with mice, then with rats, and then with pigs. “It is good to proceed stepwise with caution, which will make it possible to have a dialogue with the public, which is feeling anxious and has concerns,” science-policy researcher Tetsuya Ishii, of Hokkaido University, told Nature.
Bioethicists fear that the human stem cells could migrate to the brain of the developing embryo and create some form of human consciousness. But Nakauchi says that this will not happen in his experiment. “We are trying to ensure that the human cells contribute only to the generation of certain organs,” Nakauchi told a Stanford magazine. “With our new, targeted organ generation, we don’t need to worry about human cells integrating where we don’t want them, so there should be many fewer ethical concerns.”
Michael Cook is editor of BioEdge
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