Chimera breakthrough opens ethical debate

News that US researchers have successfully grown human cells in monkey embryos, has opened a heated debate on the ethics surrounding the procedure.

The announcement by Juan Carlos Izpisua Belmonte at the Salk Institute in California and his colleagues to say they had have produced what are known as human-monkey chimeras, with human stem cells – special cells that have the ability to develop into many different cell types – inserted in macaque embryos in petri dishes in the lab, has been described as a Pandora’s box.

In humans, chimerism can naturally occur following organ transplants, where cells from that organ start growing in other parts of the body.

Izpisua Belmonte added the team’s work could pave the way in addressing the severe shortage in transplantable organs.

“These Chimeric approaches could be really very useful for advancing biomedical research not just at the very earliest stage of life, but also the latest stage of life,” he explained.

Prof Julian Savulescu, Uehiro Chair in Practical Ethics, and Director of the Oxford Uehiro Centre for Practical Ethics, and Co-Director of the Wellcome Centre for Ethics and Humanities, University of Oxford, said the news created a number of serious questions.

“The most difficult issue lies in the future,” he said. “This research opens Pandora’s box to human-nonhuman chimeras. These embryos were destroyed at 20 days of development but it is only a matter of time before human-nonhuman chimeras are successfully developed, perhaps as a source of organs for humans. That is one of the long term goals of this research. The key ethical question is: what is the moral status of these novel creatures? Before any experiments are performed on live born chimeras, or their organs extracted, it is essential that their mental capacities and lives are properly assessed. What looks like a nonhuman animal may mentally be close to a human. We will need new ways to understand animals, their mental lives and relationships before they used for human benefit.

“Perhaps this will lead us to rethink how animals are treated more generally by humans in science, medicine and agriculture.”

“This study essentially undermines the commonly held understanding that human embryos wouldn’t be studied beyond 14days in vitro,” Prof Martin Johnson, Emeritus Professor of Reproductive Sciences, University of Cambridge, said. “Although not formally doing so given that stem cells, and not embryonic human cells, were injected into monkey blastocysts on day 6.5, nonetheless the experiments amounted to a circumvention of the 14day rule. This sort of experiment would not be necessary if the 14 day rule was changed and thus provides us with a powerful reason to change this rule.”

Sarah Norcross, director of the Progress Educational Trust, added: “Substantial advances are being made in embryo and stem cell research, and these could bring equally substantial benefits. However, there is a clear need for public discussion and debate about the ethical and regulatory challenges raised.

“Issues raised by this particular research concern the combination of human and nonhuman material (although the embryos in this case were predominantly nonhuman) and how long embryos may be cultured for in the laboratory.

“A related area that deserves further discussion is the creation of synthetic human entities with embryo-like features (SHEEFs) – structures that resemble human embryos, but do not originate from ordinary fertilisation.”

However, Dr Anna Smajdor, Associate Professor of Practical Philosophy, University of Oslo, said the research asked serious questions.

“This breakthrough reinforces an increasingly inescapable fact: biological categories are not fixed – they are fluid,” she explained. “This poses significant ethical and legal challenges. Many of the frameworks we rely on to govern our behaviour are based on false assumptions, for example that there is a biological answer to the question ‘what is a human being’?

“The scientists behind this research state that these chimeric embryos offer new opportunities, because ‘we are unable to conduct certain types of experiments in humans. But whether these embryos are human or not is open to question.”

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