How’s this for some sci-fi anime tropes turning to reality? Specifically one involving human-animal chimera hybrids?

In March 2019, the Japanese Science Ministry lifted the ban for the growth of animal embryos containing human cells beyond 14 days. Stem-cell biologist Hiromitsu Nakauchi will be leading the first government-approved human-animal embryo experiment in Japan.

His end goal? To produce human organs in animals so that they can be transplanted into people who need them.

According to Nature, Nakauchi has already experimented on rats and mice. In 2017, the biologist worked together with a few colleagues to produce a mouse pancreas in a rat. They basically injected mouse cells into the embryo of a rat. The rat then formed a pancreas made entirely of mouse cells and the pancreas was transplanted into a mouse that had diabetes. The new organ successfully cured the mouse of diabetes.

A rat embryo. Credit: Science Pictures ltd/SPL

For his human-animal experiment, Nakauchi and his team will be carrying out something similar to the rat-mouse experiment. They will attempt to grow human cells in mouse and rat embryos and then transplant those embryos into surrogate animals.

It’s hard for me to write about all the scientific aspect of this undertaking because honestly, I don’t really understand it all that well myself.

The more pressing concern is the debate on whether or not this is an ethical thing to do. Some bioethicists are worried that the human cells might go beyond simply developing the intended organs and travel to the developing animal’s brain, potentially affecting its mental capabilities.

By the way, bioethicists are academic professionals whose job is to determine if a practice or development in biology and medicine are ethical or unethical. Issues like this are why we need them.

On the positive side, this could be an amazing way of preparing new organs for people who need them. On the very scary and not-so-positive side, we might get animals asking us to play with them with actual words instead of just making animal noises.

Actually, that’s really far-fetched but hey, it’s still really scary.