From Bioethics
It was just a matter of time after the successful creation of pig and cow embryos grown with human cells that some researcher somewhere would think it might be worth trying to find out whether it is possible to grow more closely related monkey embryos with human cells, and so they did.1 The experiment reportedly has not been a straightforward runaway success, but, of 132 monkey embryos injected with human extended pluripotent stem cells, three embryos were still alive at day 19. The low success rate may be a consequence of the fact that the researchers, led by a stem cell biologist at the Salk Institute, have not quite figured out yet how to manipulate which cells grow into which kind of tissue.
The primary objective of such research is not to develop more human-like monkeys, or more monkey-like humans, but to create new pathways towards making new organs for transplant purposes. This does raise interesting ethical questions. First among them is the question of what the moral status of such chimeras would be, should they ever be birthed. Then there are other issues, such as whether such research is itself ethically defensible, seeing that its primary objective is to—essentially—create a new source of organs for humans. Would it be ethically acceptable to create highly developed monkey–human chimeras only to kill them in order to extract organs for xenotransplantation purposes? Arguably the shortage of organs for transplant purposes can be addressed by changing how we go about sourcing them. Options available to us range from paying prospective donors for their organs to making it more difficult for those opposed to the use of their organs after their demise to opt out. Creating a new class of highly developed chimeras for xenotransplantation purposes does not appear to be necessary to achieve what is otherwise an uncontroversially desirable objective.
What about the uncertainty about moral status mentioned earlier? Let us assume that at least one of the remaining embryos could be successfully implanted (something not planned by this research team) and carried to term. What would be the moral status of the newborn chimera, seeing that it is a hybrid made up of both monkey and human cells? Those of us not hung up on species membership will focus on the capabilities of the newborn and base our answer to the moral status question on those capabilities. Is there sentience? Then inflicting pain and suffering on it matters morally. If, as was the case when human glia cells were injected into mice brains, mental capacities turned out to increase as a result of the monkey–human stem cell mix,2 then the moral status of the chimeras should rise. What matters for the determination of your moral status should be your capabilities, not how those capabilities came about. If anything, such a finding should give us further cause to reconsider using such chimeras as a convenient solution to our organ-shortage problem.
Julian Savulescu and Julian Koplin have considered a different solution. They propose a two-step solution: ‘Firstly, the cells which cause human brain development should be knocked out through gene editing, if possible. And secondly, the live-born chimeras should not immediately be “used”, instead, they are allowed to develop in social groups and are studied for their cognitive capacities and potential for non-verbal communication’.3 This strategy would permit us to study the chimeras carefully, and make a considered determination of what their moral status is, and of what is and what is not morally owed to them.
Of course, those opposed to the use of non-human primates for research purposes will likely be opposed to their use as living human organ banks, too, whether they are primate–human chimeras or ‘just’ primates. We do not need to rehearse those ethical arguments here, as readers of the journal will be very familiar with them.4 Berna Sozen, a stem cell biologist at Yale University, is quoted as saying that ‘it is really hard to say that it will ever be possible to grow organs for transplantation by creating these animal–human chimeras, but this research should continue for us to understand whether we will ever achieve this’.5 My view would be that it serves no apparent purpose to find out, if one is not also prepared to use such chimeras as mere means-type vessels carrying organs for transplant purposes. That seems difficult to justify.
