Japanese Hybrid Human-Rat Embryo Research
- Elements of Science
- Aug 29, 2019
- 3 min read
Updated: Oct 13, 2019
July 2019
Before March of this year, David Cyranoski from Nature[2] documented that Japan had an explicit set of rules governing scientific research that banned the growth of animal embryos containing human cells. However, Japan's science and education ministry released a revised set of rules that month, one of the changes being the removal of that specific ban on hybrid human embryo research.
After just a few months, Hiromitsu Nakauchi of the University of Tokyo and Stanford University received approval from the Japanese government to attempt to grow human pancreases in rats. According to Nakauchi and his team, the primary objective of these experiments is to be able to transplant the developed pancreases to people in need. This could potentially save the lives of many people with pancreatitis, pancreatic cancer, or other pancreatic disorders. The above infographic summarizes the research procedure. If successful and with little drawbacks, this kind of research could have other medical applications, potentially expanding to other organs such as the liver or kidneys.
However, there is controversy in this type of research. Many bioethicists are concerned that the injected human cells could have effects beyond localization to the pancreas; for example, perhaps an injected cell could travel to the rodent’s brain and give it some kind of human-like cognition. Furthermore, since the injected human cells are iPS cells, or induced pluripotent stem cells, the manner of harvesting such cells may also be subject to debate. Stem cells like iPS cells are basic cells that have the ability to differentiate (or develop) into more specific cells, such as liver cells or pancreas cells; scientists have taken an interest in stem cells because this ability to become other types of cells could have medical applications, including regrowing otherwise irreparably damaged human tissues. Stem cell research has historically been controversial from its inception: while iPS cells can be harvested from an adult human being and avoid the need to destroy an embryo, the iPS cells themselves have the potential to develop into an embryo. In essence, using human iPS cells would be like messing around with a potential human clone; it is for this and other reasons that many countries have banned human cloning experiments.
Finally, there are still barriers standing in the way of success for this experiment. One of the biggest obstacles is the genetic distance between humans and rats; that is, humans and rats are different enough that it is rather difficult to grow normal human cells in rats. Although there exists animals more genetically similar to humans than laboratory rats such as chimpanzees and other primates, they are not as frequently used as rats are. While the source cited below does not explain why this is the case, the reason for this discrepancy likely has to do with primates having much longer life cycles than rats do (making the process more inefficient) and greater ethical opposition from animal rights activists.
Regardless, using stem cells like iPS cells can help mitigate this issue, but Nakauchi himself states that Japan’s approval of this experiment will allow him to try growing different stages of human iPS cells in rats to help determine the limits set by natural genetic distance.
Although the applications of such an experiment are astounding, the obstacles to success are plenty and the controversy behind doing such experiments are not negligible. In regards to the future, Nakauchi and his team are prepared to advance with this research one step at a time, under government supervision.
By Vincent Tse
Works Cited
- Infographic overview of hybrid embryo research.
- Nature magazine’s documentation of the Japanese government approval of the experiments and Nakauchi’s involvement in the whole process.
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