In the name of lifesaving humanitarian discovery, the government of Japan became the first in the world to authorize the scientific study of how to cross human and animal cells to create hybrid creatures. The Japanese ruling overturned a former ban on the practice.
But don’t expect to see a hawk-headed man walking like an Egyptian any time soon – or ever. The object of this exercise is to grow human cells in rat and mouse embryos so they can be transplanted into a surrogate animal.
Hiromitsu Nakauchi, a Japanese stem cell scientist, received the green light from his government to launch the first-ever experiment into human-animal embryos.
Nakauchi directs the Center for Stem Cell Biology and Regenerative Medicine at the University of Tokyo and is also team leader at Stanford’s Nakauchi Lab whose staff is “working on uncovering new diseases, elucidating the causes of disease, and developing therapeutic modalities by connecting the knowledge and methodology of basic science including immunology, molecular biology, cell biology, and developmental engineering with clinical medicine.”
Nakauchi’s team wants to help establish “new frontiers of stem cell therapy and to make clinical applications of stem cells a reality.”
To achieve those goals, the team plans to create lab-grown animals whose organs are generated from human cells. Hopefully, such hybridized organs would not be rejected by human patients and could be added to the pool of organs for needy recipients currently on long waitlists.
Before March 2019, Japan had laws that prohibited growing animal embryos that contained human cells beyond 14 days or to transplant them into a host uterus out, worried that the practice could result in the birth of creatures with mixed animal and human genes.
Then, on July 24, a committee of the Ministry of Education, Culture, Sports, Science, and Technology approved a request from the University of Tokyo researchers to carry out a project to create human pancreases in rodents by using human-induced pluripotent stem (iPS) cells.
After 10 years of preparation, Nakauchis’s team would be permitted to create human-animal embryos that could be transplanted into surrogate animals and brought to term. The specially appointed professor at the Institute of Medical Science of the University of Tokyo said:
“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.”
Scientists in the United States succeeded in creating pig-human fetuses in early 2017 but never brought them to term. These “chimaeras” could be useful for testing drugs and helping researchers better understand early human development.
But making them is as hard as it sounds:
“To create chimaeras, scientists generally inject pluripotent stem cells — which can become any type of organ — from one species into the early embryo of a second species. In theory, the foreign cells should differentiate and spread throughout the body, but in practice, producing viable hybrid embryos has proven difficult.”
This type of stem cell research is legal in the U.S. but the National Institutes of Health (NIH) has suspended funding for this line of medical inquiry since 2015.
Nakauchi plans to proceed slowly and surely. The genetics expert will not try to grow any hybrid embryos to term at first. Instead, hybrid mouse embryos will grow until 14.5 days, at which time the animal’s organs are almost completely formed and the fetus is almost to term.
The same experiments will be conducted in laboratory rats, growing the hybrids about 15.5 days to near term. Only after that will Nakauchi to apply for government approval to grow hybrid embryos in pigs for up to 70 days. The lead bioengineer explained his team’s methodical approach to hybridizing human and animal cells:
“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.”
One public concern revolves around the chance human cells might wind up outside the targeted organ before traveling to the brain of the developing animal where they might alter its cognition (thinking).
Nakauchi has a ready answer to calm that fear:
“We are trying to do targeted organ generation, so the cells go only to the pancreas.”
According to Nakauchi, if his team finds that human cells exceed more than 30 percent of the brains of the laboratory rodent embryos, the experiment will be suspended.
The next steps for these bioengineers are to create human livers and kidneys grown in pigs and sheep.
As for the public fear that ambiguous creatures, part-human and part-beast, Nakauchi scoffed at the idea, dismissing it as the stuff of science fiction:
“The number of human cells grown in the bodies of sheep is extremely small, like one in thousands or one in tens of thousands. At that level, an animal with a human face will never be born.”
Tell that to Doctor Moreau.