November 2020 Pulse

In August 2019, The Guardian reported that a team of researchers led by Prof Juan Carlos Izpisúa Belmonte from the Salk Institute in the US has produced monkey-human chimeras by combining the cells of the two species. The exact nature of the research remains somewhat hazy although it was reportedly conducted in China ‘to avoid legal issues’.

According to the article, Izpisúa Belmonte and other scientists have in the past succeeded in producing pig-human and sheep-human chimeras by injecting human cells into the respective animal hosts, although, it is claimed, human cells are used only in tiny proportions – only one cell in 10,000 is human.

Scientists have provided a number of reasons why the creation of inter-species – especially human-animal – chimeras is important for their research. They claim that human-animal chimeras could help them to better study certain diseases because they provide animal models within which these diseases can be emulated.

For example, in the 1980s scientists created the SCID-hu mice by grafting human stem cells, human foetal liver cells, foetal thymus cells and bone marrow to immune-deficient mice. The studies conducted on these mice, which now possess the human immune system, are regarded by some as the cornerstone of research in human immunology.

Other scientists believe that the creation of the chimera could address the problem of the lack of supply of transplantable organs for the millions of people who need them.

For example, in 2002, Benjamin Dekel and his team at the Weizman Institute in Israel induced the growth of miniature kidneys in mice by transplanting kidney precursor cells from human embryos into the mammals. Scientists hope that one day they will be able to grow transplantable human organs in bovine hosts to address the current shortage.

Needless to say, the creation of human-animal chimeras has provoked profound ethical concerns. These ethical concerns go beyond the question of safety, such as the issue of unknown zoonotic infections transmitted by the animal host to the human organ it is carrying.

They have to do with the possibility of the animal hosts becoming ‘humanised’ as the result of the introduction of undifferentiated human stem cells, especially when these hosts are genetically close to humans, such as monkeys.

Put differently, how are we to assess the moral status of the chimeric creature when it begins to exhibit human capacities such as self-awareness or rationality, as a result of the introduction of human pluripotent stem cells?

When the animal recipient acquires or displays human capacities such as thought and feelings as a result of the presence of human stem cells, the identity of the animal or its ontological status has changed. This must also mean that its moral status has also changed.

The chimeric animal that now displays human capacities can no longer be considered as non-human. It must be seen as a human being, albeit a severely disabled and compromised human being.

And it is the scientists that are responsible for bringing this compromised human being into existence!

As Robert Streiffer has put it, ‘in status-enhancing research, what would have been animal confinement, pain, suffering, and death, becomes the moral equivalent of – and, on an anthropocentric view, also becomes – human confinement, pain, suffering, and death.’

Some scientists are of the view that such an outcome is highly unlikely. But the truth is that with the current knowledge of the interaction of malleable human stem cells in animal hosts, scientists are simply not able to assert this with certainty.

As Streiffer has pointed out, it is precisely because ‘it is not now possible to predict the extent of human contribution to such chimeras’ that scientists should be extremely cautious in conducting such research.

In an article entitled ‘Chimeras and “Human Dignity”’ published in The American Journal of Bioethics, Josephine Johnston and Christopher Eliot argue that certain forms of human-nonhuman chimera research are a violation of human dignity.

In addition, intentionally creating chimeras that are part-human beings (for example, creatures that possess compromised human faculties, but are unable to fend for themselves and are kept in cages) is blatantly cruel.

Legalising the creation of such creatures and allowing research to be conducted on them also reflects badly on scientists, the scientific community and society. Such research smacks of the immoral use of seriously compromised human beings (that would otherwise not have existed in the first place if not for the experiments) as a means to an end.

In 2010, the National Council of Churches of Singapore (NCCS) participated in a consultation on ‘Human and Animal Mixtures: Ethical, Legal and Social Issues’ conducted by the Bioethics Advisory Committee of Singapore.

The Council’s positions on a variety of research involving human-animal chimeras may be summarised as follows:

• The insertion of ex vivo human embryos into the bodies of animals should be prohibited.
• The insertion of an animal embryo into a human should be prohibited.
• The insertion of human sperm into an animal should be prohibited.
• The insertion of an animal sperm into a woman should be prohibited.
• The insertions of human nuclei into non-human eggs should be prohibited.
• The insertion of human nuclei into animal eggs stripped of their chromosomes should be prohibited.
• The mixing of human and animal gametes to form human-animal entities should be prohibited.
• The transplantation of (1) human pluripotent stem cells into a non-human blastocyst or early embryo (2) non-human pluripotent stem cells into a human blastocyst or early embryo should be prohibited.
• The transplantation of (1) human pluripotent cells into post-blastocyst stages of animal embryo and (2) non-human pluripotent cells into post-blastocyst of human embryos should be prohibited.
• The transference of human neural stem cells into nonhuman animals should be prohibited until scientists are sure that such procedures will not result in ‘higher order’ brain functions in the nonhuman hosts.
• The creation of human and animal chimeras through xenotransplantation should proceed with caution and should abide by established international laws.

Dr Roland Chia is Chew Hock Hin Professor at Trinity Theological College (Singapore) and Theological and Research Advisor of the Ethos Institute for Public Christianity.