Last week, Israeli scientists announced that they had created a model human embryo without using sperm or eggs; are we heading for a future where procreation is an entirely technological, not biological, phenomenon? Genetics and reproduction specialist Dr Güneş Taylor explains what this means for the future of human reproduction.

It was recently reported that researchers have created models of human embryos out of stem cells in a lab environment, without the use of sperm or eggs, grown outside the womb. Can you explain what exactly this means? Is this a biological entity that could grow further, and go on to be become a human? 

A few years ago, scientists found to their surprise that, when under the right conditions, mouse stem cells within the lab can self-organise into structures akin to those seen during early mouse development. This caused much excitement as people wondered whether it would be possible to do the same with human stem cells. This very recent news reported that when scientists mixed four different types of human stem cells together, they organise themselves into these structures that look recognisably like human embryos at an early stage of development – complete with cells that would form a placenta etc.

At present, these human stem cell-based embryo models develop at rates slightly different to human embryos and are inefficient to generate in the lab, indicating that more work is required to perfect their growing conditions. Even further work will be required to see if these models do accurately replicate early human development – it is still very early days. Ultimately, until they are tested by growing further it is not possible to say definitively if they could become a human.

It sounds like an amazing achievement, but what’s the point in growing artificial embryos from stem cells? What are the possible benefits?

Human embryos spend a critical period of their early development hidden away inside the lining of the mother’s womb, which makes it hard to study them. Many important biological events occur within the embryo during this time and there is also a high incidence of embryo loss. Therefore, understanding what is happening within human embryos during this period of early embryonic development will help us better understand early pregnancy loss and how birth defects occur.

Currently, scientists rely upon non-human animal models such as mice to try and understand these early stages of development. The hope for this new field of generating embryo models from stem cells is to allow scientists to grow structures that resemble human embryos outside of the human body, therefore allowing them to be studied. As these models use human cells, it is becoming possible for the first time to start really understanding what goes on during this black box of our development.

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What are the implications of this development for the internationally recognized ethical limit (the “14-day rule”) for growing embryos outside of the womb? Do you expect the ethical guidelines on this to change given this recent development?

The 14-day rule was developed in the 1970s in response to public concerns regarding in vitro fertilisation (IVF). Through innovative and extensive public dialogue and consultation, the Warnock Committee established that human embryos should not be cultured in a lab beyond 14 days of development. This new and growing field of stem cell-based embryo models did not exist when the “14 day rule” was established. Therefore, whether or not the 14-day rule applies to these new models comes down to your definition of an ‘embryo’. An international group of scientists working within the field have proposed a series of ‘tipping points’ for when these human embryo models could eventually be afforded similar legal and ethical protection as that of human embryos. Consequently, I do expect that ethical guidelines on this will change, as will the definition of what an embryo is.

Fertility technology and genetic engineering technology such as CRISPR raise numerous ethical questions. Are there new ethical questions that are raised because of this new achievement?  

Of course. New innovations always raise new perspectives and questions, and I am certain there will be many. For me personally, one of the most interesting ethical questions that has immediately sprung to mind is: is it more ethical to use animal models or generate enough human embryo models to do meaningful experiments directly in the human context? Of course, adult disease experiments will still need animal models, but these stem cell-based embryo models do present a tantalising opportunity to reduce the number of animals used in research.

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Our clear sense of what it means to be human is being challenged by these kinds of experiments – just as IVF once challenged what it means to have a baby.

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How might lab grown embryos redefine what it means to be human?

This is at the heart of the matter. Our clear sense of what it means to be human is being challenged by these kinds of experiments – just as IVF once challenged what it means to have a baby. Only time will tell which facets are the most important to different cultures and how the diversity of human perspectives and values will be translated into legal and ethical frameworks to regulate these embryo models.

What will the future of human development look like if reproduction no longer requires a sperm, egg or womb? Are we heading for utopia, where our current reproductive problems are all solved, or a dystopia where genetic engineering creates a new underclass?

These new embryo models replicate the very earliest stages of pregnancy – not the whole 9 months!  So while this is a great opportunity for us to reflect on how we think the tools we have at our disposal should be used to improve lives in the future, it remains to be seen if it is even possible to grow a baby without a womb. It’s much too early to be celebrating the advent of a reproductive utopia, sadly!

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Having knowledge does not mean it must be utilised nor guarantees it will be used.

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With new technology, like AI and CRISPR, arises the question of whether scientists should be doing something just because they can, because they are capable of pushing new boundaries. What’s your view on this? Should there be no-go areas or moratoriums when it comes to new technology that can alter the future in ways we can’t predict? 

Personally, I don’t see that not knowing something is protection from it. I believe that pushing the boundaries of knowledge and what is possible is the function of science. Also, that knowledge permits us to assess our options, and the courses of action we have available in any given moment, to make the changes we wish to make. However, we all know intuitively that there is a difference between having knowledge and using knowledge… Having knowledge does not mean it must be utilised nor guarantees it will be used.

The recent paper: https://www.nature.com/articles/s41586-023-06604-5

Key review of the policy and governance of embryo models: https://www.sciencedirect.com/science/article/pii/S0959437X23000837

 Key statement on the ethical framework of embryos: https://www.cell.com/cell/fulltext/S0092-8674(23)00807-3