To many, human-animal chimeras--animals that contain human cells--sound like the stuff of nightmares. If you can picture a frog with a human head, a monkey with human vocal chords or a dog with opposable thumbs, you can see why some people want to put the brakes on any sort of scientific experiment that mixes cells from different species.

The reality of chimeras is much less dramatic: Picture instead a pig that produces human insulin or a mouse getting chemotherapy for its human cancer cells. But inter-species blends still raise concerns, even among scientists. The British Academy of Medical Sciences just released a report calling for new rules to avoid ethical missteps. The report expressed particular concern over several types of research, including anything that would implant human brain cells into animals. During a comment period, some members of the public worried that such experiments could give animals human memories.

That sounds like a great premise for a science fiction short story: The mouse who remembers growing up in a dysfunctional family in the suburbs. But even the academy acknowledges that an animal with human thoughts or consciousness is pretty far-fetched. Indeed, many of the fears surrounding chimeras are based on a misunderstanding of the real-world applications.

Human-animal chimeras are especially useful for studying medical applications of stem cells, an approach that, inconveniently for the scientists involved, combines two controversial, emotionally charged practices. For example, studies have found that stem cells from human embryos can strengthen the limbs of rats plagued by strokes. There’s no chance that these rats will wax philosophically about the fickle nature of fate, but there’s a good chance that such research could lead to new treatments for human stroke victims.


Still, some find the idea of chimeras deeply unsettling. In 2005, Sen. Sam Brownback (R-Kansas) introduced a “Human Chimera Prohibition Act.” The title speaks for itself. Brownback added that the bill would prevent experiments that would “blur the lines between human and animal, male and female, parent and child, and one individual and another individual.” (The legislation went nowhere.) Similarly, the U.S. National Council of Churches has said that it opposes “the creation of chimeras or any experimentation that might lead to an intermediary human/animal species.”

Of course, any experiment involving animals requires a commitment to ethics. No scientist should be causing suffering for no reason, and no scientist should be creating chimeras simply to see how strange things can get. Scientists who create chimeras are already bound by the rules of their universities or their funding sources.

As the British Academy of Medical Sciences or any other body pursues new laws governing chimeras in research, they have two basic options: They could target the hypothetical scientists creating monsters in petri dishes, or they could take a close look at the science that’s really happening in labs around the world.

The chimeras in the labs definitely aren’t as scary as the ones in our nightmares.


healthkey@tribune.com

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