Rise of the Pigoons
Human-pig chimeras: from science fiction to science fact.
Charlotte Barker |
"The goal of the pigoon project was to grow an assortment of foolproof human tissue organs in a transgenic knockout pig host - organs that would transplant smoothly and avoid rejection, but would also be able to fend off attacks by opportunistic microbes and viruses, of which there were more strains every year. A rapid-maturity gene was spliced in so the pigoon kidneys and livers and hearts would be ready sooner, and now they were perfecting a pigoon that could grow five or six kidneys at a time.”
This somewhat prophetic quote comes from “Oryx and Crake” by Margaret Atwood. Snowman, the novel’s narrator, lives alone in a hostile landscape – a plague has wiped out the rest of humanity. In childhood flashbacks, we see the genesis of the catastrophe, including his parents’ work at OrganInc Farms. Back in 2003, the pigoons felt very much like science fiction; Atwood couldn’t have known that, just 13 years later, researchers in California would successfully create part-human, part-pig embryos (1).
The chimeras were created by knocking out a gene crucial for pancreas development in pigs and injecting human induced pluripotent stem cells (iPSCs) into the modified embryo. The majority of the human cells are outcompeted by the pig’s own cells but, because there are no pig pancreas cells to compete with, the embryos develop a human pancreas. In theory, cells from the transplantee could be used to make the iPSCs, so that the resulting organ would be a perfect copy of the patient’s own pancreas; harsh immunosuppressive regimes could be consigned to the history books.
There’s no denying that we need a better source of donor organs – and the science is very clever indeed. But are we entering an ethical minefield? The NIH think so – they imposed a moratorium on funding human chimera research in 2015. A key concern is that the human cells won’t be confined to the target organ and may integrate into other parts of the pig – maybe even the brain.
Snowman spends much of Atwood’s book on the run from feral pigoons, whose part-human brains and massive size make them a formidable adversary. But don’t fret; we won’t be terrorized by murderous hybrid pigs just yet – scientists are terminating the chimeric embryos at just 28 days gestation. Before the first chimeric piglets are born, it would be wise to pause for serious reflection. Regardless of the great potential for therapeutic benefit – and setting aside any hysteria over “mutants” – the scientific community must engage with the public and ethicists to ensure that we’re heading in a direction that wider society is comfortable with.
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- N Davis and K Rawlinson, “Scientists attempting to harvest human organs in pigs create human-pig embryo”, The Guardian (6 June 2016).