Japan Approves Scientist’s Plan to Create World’s First Human-Animal Hybrids

human animal hybrid

The Japanese government has approved a scientist’s plan to create the world’s first human-animal hybrids, if all goes well.

Hiromitsu Nakauchi, a stem cell researcher, plans to grow human cells in mouse and rat embryos before transporting them into surrogate animals, according to Nature.


Japan had previously prohibited the growth of animal embryos with human cells beyond 14 days as well as their transplant into a surrogate uteruses. This was lifted in March of this year, when its science ministry released new guidelines that removed such bans. 

Nakauchi, who leads teams at the University of Tokyo and Stanford University, ultimately aims to develop animals with organs made of human cells, which can be transplanted into people when the need arises.

“Finally, we are in a position to start serious studies in this field after 10 years of preparation,” Nakauchi said in an interview with the Asahi Shimbun.

“We don’t expect to create human organs immediately, but this allows us to advance our research based upon the know-how we have gained up to this point.”

In the study, Nakauchi and his team will engineer embryos — or fertilized eggs — of mice and rats that are not capable of making pancreases. They will then place human induced pluripotent stem (iPS) cells into the eggs, essentially developing “human-animal embryos.”

The researchers will eventually transplant the embryos into wombs of mice and rats. It is expected that the infant rodents, as a result, will grow human pancreas in their systems.

After the birth of the rodents, the researchers will spend up to two years monitoring their development. Suspension of an experiment can occur, however, in the event that human cells exceed more than 30% of the brain of an embryo.

Human-animal embryos — including pig and sheep — have already been created in the past, but none were ever brought to term. Nakauchi, who awaits a final approval next month, claims to proceed with the study slowly.

The study raises concerns on both ethical and technical grounds. It attracts some confidence, however, as Nakauchi succeeded in creating the first human-sheep embryo last year, which had only about one human cell in 10,000 sheep cells or less before its termination after 28 days.

“We are trying to ensure that the human cells contribute only to the generation of certain organs,” Nakauchi told Stanford Medicine’s Out There. “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.”

Featured images via Pixabay and YouTube / DazedDamien (right)

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