A mouse with a human heart? Japanese scientist plans to grow human organs in the bodies of mice

While Japanese scientist Hiromitsu Nakauchi's research could lead to new sources of human organs for transplant, the question of animal rights is also crucial.

 |  4-minute read |   01-08-2019
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The lines of evolution are blurring. Very soon, it might be normal to sight a human-animal chimaera, for science is now attempting to create animal embryos that will contain human cells and transplant them into surrogate animals.

To put it simply — we will now have rats or mice bearing human hearts, lungs or livers.

We are not making up a tale of Frankenstein-ish experiment.

A Japanese stem-cell scientist, Hiromitsu Nakauchi, has received government support for human-animal embryo experiments.

Nakauchi, who leads teams at the University of Tokyo and at Stanford University in California, plans to grow human cells in mouse and rat embryos and then transplant those embryos into surrogate animals.

His ultimate goal is to produce animals with organs made of human cells — that can, eventually, be transplanted into people.

main_nakauchi_stanfo_073119073840.jpgHiromitsu Nakauchi: The man who aspires to create human-animal hybrids. (Photo: Stanford Medicine)

Don’t be surprised or alarmed. This is not the first time this kind of experiment has been attempted.

In 2010, Nakauchi successfully generated adult mouse-rat chimaeras by injecting rat pluripotent stem cells (stem cells with an ability to rise to several different cell types) into mouse blastocysts (embryo). When mouse embryos — unable to make their own pancreases — were supplemented with rat pluripotent stem cells, the adult animals were found to have a functioning pancreas comprised of rat cells. Similarly, in March 2013, Nakauchi showed that pig pluripotent stem cells were able to grow a pancreas in a pig that had been genetically engineered to be unable to generate one of its own.

The experiments established the viability of Nakauchi’s dream — of having the organs of one species develop in the bodies of another species.

The stage was set for similar experiments — using human cells.

However, the Japanese government in 2014 was wary of such experiments and banned the necessary tests to determine whether Nakauchi’s plan would work. Nakauchi moved the base from Tokyo to Stanford where the federal laws about animal-human hybrid research and funding were less restrictive. While in the United States, human cells had been introduced into embryos of pigs, cows and rats, they had never been brought to full-term.

Japan was not the only one banning chimeric experiments though.

Many countries have restricted, defunded and even outright banned such experiments on the grounds of questionable ethics.

However, earlier this year, Japan not only lifted the ban but also made it legal to transplant hybrid embryos into surrogate animals and bring them to term.

main_lab-mice_reuter_073119074617.jpgWhat about them? How ethical is it to transplant hybrid embryos into surrogate animals? Do we have the moral right to play God? (Photo: Reuters)

In a recent interview to Stanford Medicine, Nakauchi reportedly said, “If we are able to generate human organs in animals we could help many, many people. Furthermore, we could also use animal-grown human cells or tissue for toxicology studies or drug screening. Surgeons could practice surgery on intact human organs before operating on patients, and we could study aspects of early human development that have never before been accessible to researchers."

Nakauchi’s experiments are reportedly the first to be approved under Japan’s new rules, by a committee of experts in the science ministry. Final approval from the ministry is expected in August. Nakauchi says he plans to proceed slowly with mice and then subsequently plans to apply for government approval to grow hybrid embryos in pigs for up to 70 days.

Indeed, if Nakauchi’s experiments are successful, and if organs are grown in lab animals, it will make a world of difference to the medical world that is perpetually in desperate need for organ donors. However, the question of ethics that raises its head again is whether scientists should be allowed to play God? We are talking of altering entire genetic codes and pulling the developmental strings of multiple species to create human-animal chimaeras.

Further, another question is whether human cells can potentially affect the brain and cognition of the animals born in the process? What if a rat is trapped in the body of the rat — with the brain and cognition of a human? More importantly, is it ethical to create animals for the sole purpose of growing organs for human transplants? Does it not violate their right to life?

While this line of argument might not find many takers except the animal welfare fraternity, it is important to raise this question.

Today, it is rats we experiment on; tomorrow, it could be fellow humans. The line of demarcation is now very blurred indeed. 

Also read: Wrong in every way: If his claim is true, a Chinese scientist says he could have created the world's first genetically edited babies


Rajeshwari Ganesan Rajeshwari Ganesan @rajeshwaridotg

Assistant Editor, DailyO

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