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Bioethical framework for human-animal embryo research proposed

05 September 2016

By Anneesa Amjad

Appeared in BioNews 867

A prominent bioethicist in the USA has suggested that most of the ethical concerns surrounding the creation of animal-human chimera embryos using human pluripotent stem cells could be reasonably addressed, and that the research may be justified to help patients in need of organ transplants.

Insoo Hyun, associate professor of bioethics at the Case Western Reserve University, made the comments following an announced by the US National Institutes of Health (NIH) that it is considering lifting a ban on this type of research (reported in BioNews 863). Professor Hyun, whose views are consistent with those of the International Society for Stem Cell Research which he helped establish, proposed an ethical framework for the use of human-animal chimeras to grow human organs.

In September 2015 the NIH introduced a funding moratorium on research involving stem cell chimeras. Although this moratorium currently still stands, the NIH has held a consultation on the option of public funding for this type of research may become available under certain conditions and where an ethics committee oversees the research.

Researchers are interested in finding a solution to the shortage of organs for transplantation. It is believed that human stem cells could be one day be transplanted into pig embryos which have had the genes for pancreatogenesis 'switched off', in order to grow a human pancreas in a pig. The idea comes from research that used a similar method to grow a rat pancreas inside a mouse.

In his opinion piece published in PLOS Biology, Professor Hyun responds to a number of ethical concerns that underpin the NIH's current moratorium on chimera stem-cell research funding, noting that many of these are common to all forms of chimera research including that which is currently publicly funded.

One ethical concern is that the genetically modified animals, along with their human organs, may have human moral status. Also, if off-target effects were to occur and result in chimerisation of other organs – particularly the central nervous system – would the resulting animal be 'too human' for research purposes? Professor Hyun suggests that this would not be the case.

A technique called 'targeted organ generation', which ensures that the stem cells only differentiate into the intended organ, can reduce off-target effects. Professor Hyun also suggests that the appearance of human features in animals would not increase their moral status. Only the development of a human level of self-consciousness, which Professor Hyun defines this as 'an existential awareness and concern for oneself as a temporally extended agent with higher-order beliefs about one's own mental experiences', would grant more moral status. This level of self-consciousness is unlikely to appear in chimeric embryos, he said. 

Professor Hyun adds that an ethical framework for this research should involve maximising animal welfare, while understanding the need to prioritise patients in need of organ transplants.


14 August 2017 - by Cara Foley 
Ancient viral genes have been eliminated from pigs using the genome editing tool CRISPR, according to research...
30 January 2017 - by Annabel Slater 
The first early human–pig embryo chimeras have been created by researchers at the Salk Institute, California...
30 January 2017 - by Arit Udoh 
Insulin-producing cells from pancreases grown in rats can cure diabetes when transplanted into mice, according to a study...

08 August 2016 - by Antony Blackburn-Starza 
The US National Institutes of Health is considering lifting a ban on the funding of research to create human-animal 'chimeras' and replacing it with an ethical review process...
13 June 2016 - by Dr Jane Currie 
Scientists have used CRISPR to create part-pig, part-human embryos in an attempt to grow human organs for transplant...
09 November 2015 - by Dr Jane Currie 
A group of researchers have called for an overturn of a recent decision by the National Institutes of Health to suspend funding for research on human–animal chimeras...

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