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02/03/2017

Can We Be Okay With Chimeras?

In a post yesterday, Jon Holmlund, in typically erudite fashion, addressed the ethical issues that arise from the findings of a published study which looked at the potential use of genome technologies to (someday) produce human organs in animals. I will begin by saying that I have no particular disagreement with Jon’s assessment. There is a lot that is troubling in this research, as much good as it could eventually do, and we need not embrace it just because it has the chance to help people. Many of us have have taken an ethical stand against embryonic stem cell research, for example, because it ultimately violates the dignity of human beings, regardless of its intended benefits.

Yet I do find myself troubled, aesthetically and emotionally, at least, by the contention of the esteemed Charles Krauthammer that this research would ultimately provide “spare parts.” I suspect that, to the parent of a child with a congenital liver disease, a donor organ would hardly be considered such. That doesn’t constitute an ethical argument, for there are many unethical ways to procure organs and we invent more all the time. But it is a reminder that these discussions aren’t restricted to the theoretical firmament of the molecular biologists.

It’s in the public forum now. A recent article in the New York Times addressed this research and spoke to the continued disparity between the tremendous need for healthy human organs in waiting patients and the great scarcity of those organs available from donors. The article estimates 76,000 people are currently on a waiting list. Stem cell therapy, for all its successes in treating a host of diseases by way of human adult stem cells, has not had success with in vitro development of human organs for transplantation. Enter “chimeras.”

To be honest, there is much about the very notion of “chimeras” (which are a blend of the cells of two or more species, in this case: human and non-human animal, which this post addresses) and “human-animal hybrids (a blending of the DNA of both species) that I find troublesome, or even “creepy,” in an Island of Doctor Moreau-kind of way. And concern is warranted. Much of the research for which some scientists are seeking advocacy would do exactly what Jon (and Dr. Krauthammer) expressed: place pluripotent stem cells into another species (likely pigs or, less likely, sheep) and “pull the trigger.” In the article there is an implicit assumption that we must be cautious. The Times tries to be clever here: “No-one wants a talking pig.” But even a slight risk that this could place human cells into the central nervous system or reproductive germline of animals should be chilling.  And yes, we need to have a compelling explanation of this concern to offer the suffering and those who wait with them for new organs.  This is a risk not worth taking.

But I am also haunted by a bit of an escape clause: there is technology that could avoid the bulk of what I find ethically problematic. I have less fear of some mix of human and animal tissue…certainly “xenotransplantation,” like implanting a pig’s heart into a human being, whatever its successes or failures, isn’t really an ethical problem to most. What if the use of  the “CRISPR-Cas” gene editing system, which would allow for specific genes that code for targeted organs, could be used?

This technology, to which the original Cell (and NYT) article alludes, would mean that the animal embryo with implanted human stem cells did indeed avoid involving any human tissue in the non-specific organs of the host animal, particularly the brain and reproductive systems. Could that blunt much of our argument against this…one that says that the brain and germline are “off-limits,” but that we could find ethically-acceptable ways to provide organs for waiting patients using animals we already use for human food?

To be honest, I have my own qualms about CRISPR-Cas, largely because I don’t know a lot about it. It may indeed involve its own ethical problems, despite any protestations from its proponents. And once we go down this road, it makes it harder to say that, in particular, brain tissue is “off limits.” I get that. I would need to be convinced that this technology would do exactly what it is supposed to do. But I want to be sure my acceptance or rejection of any technology is soundly rooted in a consistent ethic that is appropriately nuanced.

I say all this to open the conversation…perhaps more to have the wiser inform me. But I do wonder…in this very specific way, are we able to keep the door slightly ajar without rejecting the technology outright? Does that keep us in the conversation? Within strict boundaries, can we be, indeed, be okay with chimeras?

This entry was posted in Genetics, Health Care, Stem Cells and tagged , , , . Posted by Jerry Risser. Bookmark the permalink.

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