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Toward human-animal hybrids

To be published tomorrow in the Federal Register, the massive, Byzantine thousands-upon-thousands of pages repository for all of the rules and regulations that constitute so much of de facto law in the contemporary United States: a Request for Public Comment on the Proposed Changes to the NIH Guidelines for Human Stem Cell Research and the Proposed Scope of an NIH Steering Committee’s Consideration of Certain Human-Animal Chimera Research.  

As always, the technical issues are complex.  But, briefly, some scientists are working on putting human “pluripotent” stem cells—like embryonic stem cells, the kind that can produce many different organs or tissues or even a full human being—into early embryos of other mammals, such as mice or pigs.  Why?  To try to understand a disease better, or, in the case of some of the pig work, event to “grow” a human organ in an animal for future transplantation.

The National Institutes of Health (NIH) limits the scope of what it will pay for, because, frankly, we don’t know what we will get.  Concerns include having an animal with a more “human-like” brain, or one that can make human sperm and egg cells, or one that could breed to “spawn,” if you will, a part-animal, part human or even a human baby in a female animal.  More generally, what percentage of human cells does it take for a living being to be considered human, and how far might we experiment with adding human cells to animal embryos and animal cells to humans?

Farfetched?  Some scientists have reportedly looked at human stem cells in mice to see if brain function is affected in a way that can help understand psychiatric conditions.  See this discussion from the New York Times.

The proposed revisions to the NIH rules purport to make restrictions tighter by prohibiting government funding of experiments in which any pluripotent cells, not just the specific ones in the current guidelines, are inserted into early embryos from non-human primates (monkeys, apes) or breeding animals when the work may have contributed to human sperm or egg cells having been produced. 

But they would open introduction of human cells into other mammals’ embryos, or in non-breeding situations, as long as a committee determines that there could not be “a substantial contribution or a substantial functional modification to the animal brain by the human cells.”  Even here, they exclude rodents, presumably to permit such work in mice or rats to proceed.

The NIH wants to claim that this work can be carefully monitored and regulated to keep it from getting out of hand.  But non-government funded research would not be affected, and intrepid actors will invariably try to stretch the boundaries.  And some are concerned that even in the specific case, much less the “field” as a whole, we can’t predict where it will all lead.

If the society could, it should slow much more of this work down, if not call a halt entirely.  But legal bans are likely to be circumvented, and appeals to potential benefits generate continual pressure to move ethical boundaries further.   I think that ultimately it will not do to argue that eventual risks outweigh benefits.  Rather, we would have to convince our fellow humans that ethics require that we just forego some opportunities.  And that’s a hard sell.

This entry was posted in Health Care, Stem Cells and tagged , , , . Posted by Jon Holmlund. Bookmark the permalink.

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