Welcome to Ethics Consult -- an opportunity to discuss, debate (respectfully), and learn together. We select an ethical dilemma from a true, but anonymized, patient care case, and then we provide an expert's commentary.
Last week, you voted on whether a researcher should be allowed to conduct an experiment that involves injecting human brain cells into mice embryos.
Should the researcher be allowed to go ahead with the experiment?
Yes: 55%
No: 45%
And now, bioethicist Jacob M. Appel, MD, JD, weighs in:
Until the 1970s, animal chimeras -- cross-species hybrids -- were largely the stuff of mythology. Yet starting with the success of biologists Paul Berg and Richard Mulligan at Stanford University in transplanting rabbit hemoglobin genes into primate kidneys, scientists managed to generate a slew of rapid advances in the field: A hematologist at the University of Nevada, Reno, claimed to have produced sheep with livers that were partially "humanized"; a lab at the Mayo Clinic produced "pigs with human blood." In China, researchers fused human skin cells with rabbit eggs. Yet the most significant and controversial step in the field occurred when Irving Weissman, a professor in the departments of pathology and developmental biology at Stanford, asked for -- and received -- permission from the university to create mice embryos with brains derived from human neurons. Weissman had previously produced mice embryos whose neural tissue was 1% human, but he hoped that using only human neurons, coupled with mouse glial cells, would generate a model for studying human neural tissue in the laboratory.
Opponents of human-animal chimera research are particularly concerned about the use of neural tissue in these experiments. Critics fear that mice with human brain cells could develop some human cognitive qualities and could even experience human-like suffering. These bioethicists often see the hybrids as an affront to human dignity. They also express concerns related to species integrity and human uniqueness -- or what columnist Wesley J. Smith refers to as Making mice more human, according to some commentators, also makes humans more like mice. Former Sen. Sam Brownback (R-Kan.) introduced legislation multiple times to prohibit human-animal hybrids in research, but the bills failed to gain traction.
Even ethicists who favor such research in principle have urged considerable caution on the part of researchers. Legal scholar Henry Greely and his colleagues, in an in the prestigious American Journal of Bioethics, noted that these experiments would be problematic, even if not inherently unethical, if they so unsettled the public that they "undermined support for ... other useful biomedical research." However, any initial popular concern over Weissman's request has largely evaporated, and human-mouse hybrids are increasingly part of scientific endeavors. The most striking feature of the scenario at the start of this chapter may be that at many universities today, the prospect of mice with half-human brains is neither surprising nor particularly controversial among researchers -- although the idea of such chimeras still remains highly objectionable to a large segment of the U.S. public.
Jacob M. Appel, MD, JD, is director of ethics education in psychiatry and a member of the institutional review board at the Icahn School of Medicine at Mount Sinai in New York City. He holds an MD from Columbia University, a JD from Harvard Law School, and a bioethics MA from Albany Medical College.
Check out some of our past Ethics Consult cases:
Let Look-Alike Sisters Commit Insurance Fraud?