(Newswire.net — November 15, 2019) — A long history of human-animal hybrids is described in mythologies from all across the globe: Ancient Greeks called them “chimeras”.
Chimeras can now become a reality, as the Japanese government has allowed scientists to not only grow human organs inside animal embryos, but also to allow these embryos to fully develop to their end stages – which is crucial.
The research is led by Hiromitsu Nakauchi from the University of Tokyo and Stanford. During the procedure, scientists will inject human stem cells into modified embryos of rats and mice to form the pancreas. The embryos will then be transplanted into surrogate animals.
The ultimate goal is for these organs to be transplanted into humans.
Until recently, scientists in Japan had to destroy animal embryos into which human cells were implanted after 14 days and they were forbidden to grow these embryos in surrogate animals. But those restrictions have now been lifted, and researchers can seek individual licenses for research projects.
Professor Nakauchi’s research is not the first in this field: he and other researchers have already grown human cells in embryos of mice, rats, pigs, and even sheep. The goal of scientists is to provide human organs for transplantation, especially those most in need – like the pancreas.
In 2017, Professor Nakauchi practically cured a diabetic mouse by breeding a healthy mouse pancreas in a rat embryo and then transplanting it into a diseased mouse. Until now, human cell experiments have had to be suspended either because of legal requirements or because the tests were unsuccessful.
This research raises ethical questions about the possibility that human cells end up in the animal brain, potentially “humanizing” the consciousness of animals. However, Professor Nakauchi pledged to carry out the experiment so that “the cells end up in the pancreas only.”
In July, a panel of experts at the Japanese Ministry of Education, Culture, Sports, Science and Technology approved his research under certain conditions and procedures.
The technique involves genetically modifying animal embryos to remove genes associated with the production of a particular organ – in this case, the pancreas, but in the future possibly even the liver and kidney. Scientists then inject the human embryo into an animal embryo, and now they will be able to grow the embryo to its fullest.
The ministry’s license obliges Professor Nakauchi to conduct experiments only on small animals, genetically distant from humans. In addition, at each stage of development, the team must check for human cells in the fetal brain. It will spend up to two years overseeing development after the birth of the rodent.
In an experiment conducted at Stanford University in California, Professor Nakauchi previously placed human stem cells in fertilized sheep eggs and then transplanted the embryos into sheep. The embryos were destroyed after 28 days of development. They contained very few human cells and did not develop any human characteristics, Professor Nakauchi said.
“The number of human cells that grew in the bodies of sheep was extremely small, about one in a thousand or one in tens of thousands,” he said.
“At that level, an animal with a human face will never be born,” Professor Nakauchi said.