Before conducting research that involves putting human stem cells into the brains of nonhuman primates such as monkeys or apes, scientists and oversight committees should consider a series of ethical criteria, according to a policy paper released in the July 15 issue of Science.
The policy paper was written by a 22-member committee that included Hank Greely, JD, a law professor at Stanford University and chair of the Stanford Center for Biomedical Ethics steering committee. Greely previously chaired an informal working group that reviewed the ethics of similar work in mice.
Greely said that although many of the concerns are the same, research in monkeys and apes raises some distinct ethical issues. "The possibility that human cells might create human-like abilities is much larger in nonhuman primates than in mice," he said. The recent ability to create animals containing some human brain cells has spurred an ongoing national debate about the ethics of such work-research that has only become possible with the growing availability of human adult or embryonic stem cells.
Overall, Greely and his colleagues found no ethical reason for prohibiting research involving human stem cells in nonhuman primate brains. This type of work may even be required by the U.S. Food and Drug Administration to show that a potential therapy involving human stem cells is effective.
However, the group found that oversight boards at universities or funding agencies should consider six factors when overseeing such research: 1) the number of human cells used compared with the number of cells in the animal's brain, 2) the developmental stage of the animal receiving the cells (i.e. fetus or adult), 3) the species, 4) the animal's brain size, 5) the site where the stem cells are placed and 6) whether the animal's brain was injured or diseased.
Greely pointed out that if a large number of human cells were to be injected into a part of the brain where those cells may be involved in thinking or emotions, that experiment may not be ethical. But injecting a smaller number of cells into a region of the brain that controls movement may be acceptable.
"People need to think responsibly about how to minimize ethical risks these sorts of experiments might entail," Greely said.