Chimeras with benefits? Transplants from bioengineered human/pig donors

By Brad Segal

In January of this year, Cell published a study modestly titled, Interspecies Chimerism with Mammalian Pluripotent Stem Cells. It reports success bioengineering a mostly-pig partly-human embryo. One day before, Nature published a report that scientists had grown (for lack of a better word) a functioning genetically-mouse pancreas within the body of a genetically-modified rat. The latest study raises the likelihood that before long, it will also be scientifically possible to grow human organs within bioengineered pigs.

The implications for transplantation are tremendous. But hold the applause for now. Imagine a chimera with a brain made up of human neurons which expressed human genes. Would organ procurement without consent be okay? That troubling possibility raises  questions about whether manufacturing chimeras with human-like properties for organs is even appropriate in the first place. Here’s what University of Montreal bioethicist Vardit Ravitsky told the Washington Post:

“I think the point of these papers is sort of a proof of principle, showing that what researchers intend to achieve with human-non-human chimeras might be possible … The more you can show that it stands to produce something that will actually save lives … the more we can demonstrate that the benefit is real, tangible and probable — overall it shifts the scale of risk-benefit assessment, potentially in favor of pursuing research and away from those concerns that are more philosophical and conceptual.”

I respectfully disagree. Saving more lives, of course, is good. Basic science is also valuable – even more so if it might translate to the bedside. This line of research, though, is positioned to upend our entire system of transplantation, and so its implications go beyond organ supply. In this post I will argue that to assess this technology’s implications for organ procurement in particular, there is good reason to focus on harms, not benefits. Continue reading