Growing a Kidney Inside a Pig Using your own DNA: The Ethics of ‘Chimera Organs’

Guest post by David Shaw

Imagine that you’re in dire need of a new kidney. You’re near the top of the waiting list, but time is running out and you might not be lucky enough to receive a new organ from a deceased or living donor. But another option is now available: scientists could take some of your skin cells, and from them derive stem cells that can then be added to a pig embryo. Once that embryo is implanted and carried to term, the resulting pig will have a kidney that is a perfect genetic match to you, and the organ can be transplanted into your body within a few months without fear of immune rejection. Would you prefer to take the risk of waiting for an organ donated by a human, which would require you to take immunosuppressant drugs for the rest of your life? Or would you rather receive a “chimera organ”?

This scenario might seem far-fetched, but it is quite likely to be a clinical reality within a decade or so. Scientists have already used the same technique to grow rat organs inside mice, and it has also been shown to work in different types of pig. Although clinical trials in humans have not yet taken place, using these techniques to create human organs inside animals could solve the current organ scarcity problem by increasing supply of organs, saving thousands of lives each year in Europe alone. As illustrated in the example, organs created in this way could be tailored to the individual patient’s DNA, allowing transplantation without the risk of immune rejection. However, the prospect of growing organs of human origin within (non-human) animals raises several ethical issues, which we explore in our paper.

Although chimera organs are ‘personalised’ and unlikely to be rejected, one of the major concerns about using organs transplanted from animals is the risk of ‘zoonosis’ – the possibility that an animal virus might be transmitted along with the organ, resulting in a new disease that could cause a pandemic. Any pig used to create an organ for transplant would be kept in a very sterile environment to minimize any such risk. But even if the risk of zoonosis is extremely small, we also need to consider the magnitude of the harm that might result should the worst-case scenario be realized. A new source of organs sounds like a wonderful thing, but it’s not if they go on to cause a pandemic of “pig flu” that kills thousands of people. However, there have been no documented cases of zoonosis following xenotransplantation (transplants from animals); transplanting organs that are genetically human is likely to be safer still, provided that animals are raised in sterile environments and organ recipients are closely monitored after transplantation.

Another worry about adding human stem cells to pig embryos is that the resulting pigs might acquire human features. If a pig grew a human foot, it could be disconcerting. But what if it showed signs of human self-awareness? The risk of this happening is even lower than the risk of zoonosis, but if it did, could we still confidently draw the line between humans and animals? Luckily, there are technical ways of making sure that this is simply not a possibility. This could be done by ‘knocking out’ the genes for morally sensitive aspects of human development (such as brain and reproductive system) in the stem cells added to the pig embryo, so that there really was no risk at all of the pig developing these human characteristics.

But there is a more obvious ethical issue that cannot be so easily dealt with: every time a pig is used to create an organ, a pig will be sacrificed. To someone who eats meat, this might seem like a trifling objection: surely it’s ok to use an animal to save a human life if we eat them every day? But defenders of animal rights will argue that the creation of chimera organs involves using animals purely as a means to the end of saving human lives, and that doing so is deeply unethical. Why should we use animals to supply humans with organs when so many people refuse to donate their organs after their death? Shouldn’t we increase donations from humans rather than instrumentalising animals in this way? It’s true that efforts to encourage humans to donate should certainly continue, but the truth is that we really need a new source of organs. Lab-grown organs still seem a long way off, and chimera organs also offer the advantage over normal donations that they will not be rejected by the recipient’s immune system. Given the way animals are currently exploited by humans, using them to create lifesaving organs actually seems more ethical than eating them or using them for research.

A last concern relates to human dignity. Conservative commentators have long argued that it is against human dignity to mix our DNA with that of animals. We explore this objection at length in our paper; our view is that human dignity is a very fuzzy concept which can be used to argue both against and for the use of chimera organs. Is it dignified to let people suffer and die when we could use this new biotechnology to provide them with organs that will let them live long and happy lives? In the UK alone, 3 people die every day waiting for an organ, and creating organs in chimera pigs could save these lives and improve the lives of the thousands of people who must undergo dialysis every week. Ultimately, hearts and other organs could perhaps be created in this way too. While this source of organs is not entirely without risks, we believe that they are worth taking.

  • 572ec13f

    Re zoonosis. Since there are no cases of clinical x-t (as far as I know, all there is are various experiments rather far from what a bona fide clinical procedure might look like), citing lack of cases of zoonosis is rather weak an argument. What we have isn’t a proved low risk but lack of evidence for either low or high risk. This goes especially for the PERV risk, where the statement “transplanting organs that are genetically human is likely to be safer still, provided that animals are raised in sterile environments and organ recipients are closely monitored after transplantation” would not seem to hold. With the PERV, the worry is that inert viruses already present in the animal DNA are re-activated by the X-T procedure, and then the insertion of human tissue may instead add to the risk and sterility in the lab is of no consequence whatsoever. Of course, you can monitor patients, but if what results is a new black death, that won’t help much unless recepients are to be subjected to draconian security measures (for how long, one may ask?). Therefore, it seems to me that this new idea is in a similar situation to the trad. X-T: lots needs to be proved beyond patient efficacy before clinical application is anything to think about.

    Christian Munthe

    • David Shaw

      Thanks for the comment, Christian. I agree that more than patient efficacy needs to be proven, but this technique does reduce (almost to zero) the amount of animal DNA that’s present in the transplanted tissue.
      David Shaw

  • Arianna

    Dear David Shaw, on the basis of which anaylsis of the state-of-the-art
    on xenotransplantation and tissue engineering is your statement
    :”Lab-grown organs still seem a long way off, and chimera organs also
    offer the advantage over normal donations that they will not be rejected
    by the recipient’s immune system.”? in my opinion, purely argumenting
    with advantages , tissue engineering seems more promising than
    xenotransplantation.
    But foremost:It is a profoundly problematic
    aspect to use the current ethical status
    quo to argue for further exploitation fo sentient beings. Along with the
    ethical issues related with nonhuman animals, there are also many legal
    concerns (about compatibility of xenotransplantation with human rights
    due to the risks) as well as issues of distributive justice connected
    with xenotransplantation, so that at the very end xenotransplantation is
    a practice which will be based on the exploitation of thousands of
    existing and future nonhuman animals and the discrimination of future
    human beings. As you well know, research at this stage is a matter of
    allocation of research founding. i think we should defend the best
    possible allocation of resources believing that scientific research can
    contribute significantly to moral progress and thus to reduce the
    suffering of sentient beings, beings humans and nonhumans.

  • Rita Wing

    “This could be done by ‘knocking out’ the genes for morally sensitive
    aspects of human development (such as brain and reproductive system) in
    the stem cells added to the pig embryo, so that there really was no risk
    at all of the pig developing these human characteristics.” Surely the whole idea of use use-up-and throw-away a life (a pig’s in this case) shows that human beings do not have moral sensibility at all. Growing human features, or, alternatively, “contaminating” our human dignity – both seem to deal with non-existent features of our lamentable species.