It was announced yesterday that in an effort to create better models for studying neurological disorders, a team of scientists from the Salk Institute led by Dr. Fred Gage have successfully bio-engineered mice to be born with a small percentage of human brain cells. The process involves injecting 2-week-old mouse embryos with roughly 100,000 human embryonic stem cells. The mice created could be a valuable asset to scientists as they struggle to understand and combat neurological disorders like epilepsy and Parkinson’s disease.
Although the total percentage of human cells in the mice brains barely approaches 0.1%, the work, by some people’s judgment, falls into an ever-expanding ethical gray area that seems to encompass stem cell research and to even greater extent, cloning research. One fear centers on the idea of “humanizing” animals by mixing human and animal cells. Researchers defend their work saying that the only way to advance stem cell research is by mixing human and animal cells in animal hosts since it is still too risky to experiment with humans, and research is necessary since the field holds such great promise.
“The worry is if you humanize them too much you cross certain boundaries,” said David Magnus, director of the Stanford Medical Center for Biomedical Ethics. About Gage’s work he does, however, say, “…I don’t think this research comes even close to that.”
Other researchers agree. “It’s true that there is a huge amount of [genetic] similarity, but the difference are huge,” said Dr. Evan Snyder, a stem cell researcher at the Burnham Institute in San Diego. “You will never ever have a little human trapped inside a mouse or monkey’s body.”