Japan allows scientist to grow rat embryos spliced with human cells

A Japanese scientist has been granted permission to bring a human-animal hybrid to term.

After a ban on the practice was lifted this year, Hiromitsu Nakauchi — who leads teams at the University of Tokyo and Stanford University in California — is planning to splice human cells to see if they will grow beyond the current limit of two weeks, Nature reports.

If Nakauchi accomplishes this, it will be the first successful experiment of its kind in Japan.

His ultimate goal is to grow a human pancreas inside an animal so that it can later be transplanted into a patient.

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“If we are able to generate human organs in animals we could help many, many people,” Nakauchi told the Stanford Medicine magazine last year.

Japan has overturned a rule that forbid researchers from growing animal embryos spliced with human cells for longer 14 days.

Nakauchi aims to grow mouse and rat embryos with human cells until 14.5 and 15.5 days old, respectively, according to Nature.

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Later, he hopes to grow pig embryos spliced with human cells for up to 70 days, pending government approval.

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Though similar experiments have been done in countries like the United States, they’ve never been brought to term.

Nakauchi’s research has raised concerns about the potential for human cells to travel beyond the targeted organ, resulting perhaps in the animal’s cognition being affected.

“It is good to proceed step wise with caution, which will make it possible to have a dialogue with the public, which is feeling anxious and has concerns,” Tetsuya Ishii, a science policy researcher at Hokkaido University in Sapporo, told Nature.

But Nakauchi says he and his team have considered this, and have been preparing for this for a decade.

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“We are trying to do targeted organ generation, so the cells go only to the pancreas,” he explained.

The Japanese government has said researchers will monitor the animal-human hybrids for up to two years and will stop the experiment if they find more than 30 per cent human cells in an animal’s brain, The Asahi Shimbun reports.

Japanese officials are expected to make a final ruling on the project in September.

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meaghan.wray@globalnews.ca