Synthetic human embryos raise ethical questions among experts

A team of UK and US scientists has announced that it’s created “synthetic human embryos”: embryos made from stem cells rather than human eggs or sperm.

The research, which is not yet peer-reviewed, was presented at the International Society for Stem Cell Research’s annual conference in Boston.

This breakthrough, which has previously been demonstrated in mice, could allow scientists to study human development during a period where comparatively little is known about how the foetus develops.

Currently, regulations in most countries stipulate that embryos and embryo-like structures cannot be cultivated in a lab for research beyond 14 days.

Stem-cell synthetic embryos are not caught up in the ban, and therefore could be used to sidestep the rule and study foetal development beyond two weeks.

The researchers, who are based at the University of Cambridge and the California Institute of Technology, have cultivated their synthetic embryos to “just beyond” the equivalent of 14 days of development, according to The Guardian, which was the first to report on the discovery.

But it’s not yet clear whether these embryos could actually develop into humans, or if they should be subject to the same rules as other embryo-like structures.

“It is extremely important to develop a much deeper understanding of the earliest stages of human development, particularly as these are essential for developing better clinical responses to infertility, miscarriage, and developmental errors,” says Professor Rachel Ankeny, a researcher at the University of Adelaide who watched the presentation in Boston.

“We need to engage various publics about their understandings of and expectations from this sort of research, and more generally about their views on early human development, as these biological processes are deeply tied to our values and what we think counts as human life.”

Dr Kathryn MacKay, from the University of Sydney, points out that, while they didn’t need a full egg and sperm cell, the embryos still needed human embryonic cells to grow.

“If human embryonic stem cells are needed to create these human-like embryos for research, then synthetic embryos may not avoid having to use human embryos for research. This is an ongoing moral issue around respect for human life,” says MacKay.

“Further, there is a moral issue involved in creating something for research that may or may not have the potential to live as its own full entity. If they could live as their own full entities, then we must ask whether it is morally permissible to create living beings purely for research purposes.

MacKay says that, based on animal models, the synthetic embryos shouldn’t be able to grow into a human baby.

“This raises two further questions: One, if they are not the sort of thing that can really grow into a human baby, then how useful are they really for scientific knowledge into human reproduction and development? And two, will researchers decide that ‘fixing the problem’ of these embryos not being able to grow into human babies is something worth pursuing, for questionable ends?”

Other experts point out that, in addition to fertility and foetal development, synthetic embryos could be used to understand more about genetic diseases, longevity and ageing.

“It is likely that this work will allow us to develop new strategies to treat different developmental dysfunctions, and perhaps even extend lifespan,” says Professor Wojciech Chrzanowski, from the University of Sydney.

“This work on the one hand mitigates any ethical concerns related to fundamental biology research on embryos, but on the other hand, raises substantial concerns about whether such embryos will not be misused to generate some ‘super forms’ of life. Similarly, to the use of AI, the regulatory, ethical and integrity aspects are important to consider.”

Associate Professor Karinne Ludlow, from Monash University’s Faculty of Law, compares the discovery to a similar one announced by a Monash team in 2021: iBlastoids, structures also made from stem cells that closely resemble human embryos.

Read more: Ethics of making human blastocysts in a lab

“The regulator ultimately determined that iBlastoids met the definition of a human embryo and were therefore subject to existing laws on embryo research. However, this decision was controversial,” says Ludlow.

Much remains to be learned about the synthetic embryos, including how similar they really are to human embryos, and what research they could help to encourage.

Professor Ankeny says: “It is critical that researchers be transparent about this type of research and what is known and unknown, in order to ensure that our regulatory processes address the necessary issues and that the public is assured that there are adequate oversight mechanisms and safeguards.”