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Hybrid embryos and interspecies organ transplants: The new chimerae

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Are chimeric organisms a viable medical and ethical resource?

Last January, a team of researchers at the Salk Institute for Biological Studies in La Jolla, California, published a study in the journal Cell announcing they had “successfully produced the first human-pig chimera,” an embryo containing cells from two different species. Researchers transformed cells from an adult human into stem cells, then injecting those cells into first-stage pig embryos, then implanting them into female pigs, allowing them to develop for some weeks, according to the article published by the Smithsonian Institute. Moreover, National Geographic reports 186 of these embryos developed into “later-stage chimera embryos,” implying that “one in every hundred thousand cells of the embryo was human derived.”

The study aims towards the production of human organs hosted in non-human animals, for transplantation. Needless to say, such research is not without controversy, as it straightforwardly poses questions regarding both animal rights — those referring to in vitro studies using embryos and also in vivo research involving fully grown, sentient animals — and, evidently enough, on what we consider to be a human being.

According to Dr. Daniel Garry — in an interview published by Hannah Devlin at The Guardian — a cardiologist leading yet another project on chimeric organisms in the University of Minnesota, the experiment was carried out responsibly, both medically and ethically speaking. The possibility of a half-man/half-beast organism (literally, a chimera) is absolutely out of the question, as this kind of research only seeks to know if is it really possible to “guide” human cells “into forming a particular organ in pigs.”

However, as Göran Hermerén, a Swedish philosopher from the University of Lunds, explains, the fact that our culture considers human beings to be different from animals — that is to say, holding both ethically and a legally different status — has several implications on these experiments. The first difference refers to the fact that “being human” is not only a biological but a moral concept: humans are moral, responsible agents, able of intentional action. Here, a line is drawn. Hermerén explains:

“Concerning the goal of growing human organs in animals such as pigs (as discussed above), a key challenge is the xenogenic barrier – these two species are estimated to have diverged almost 100 million years ago, so is it even feasible to use a pig as an ‘incubator’ for human organs? If this barrier cannot be overcome, could we use primates? Or, taking this to the extreme, might one even conceive of using people in a permanent vegetative state or suffering from senile dementia (who might not display the key characteristics of intentional action, self-reflection and self-understanding mentioned above) as incubators? This might sound like science fiction or a dystopia, but should be discussed before it becomes scientifically feasible.”

Still, Hermerén’s ethical approach to this issue allows for certain room, if and only if the methods used to achieve the goals of this research are indeed feasible and if there are no less controversial methods available for achieving these ends, as the research objective is indeed important. A final word, either on the medical or the ethical end of the discussion, has not yet been pronounced.

This story is tagged under:
bioethics
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