Synthetic Embryos: Science Fiction Meets Reality

Think of every sci-fi, superhero, and dystopian movie you've watched. I'm sure you can recall the mad scientist who tries to create a superhuman serum, clone some monster, or create a form of synthetic life. That's fiction though, it's not real, although… What if it was? What if scientists could model and mimic life at its very beginning? Well, they already have! In 2022 Professor Magdalena Zernicka-Goetz and her team at the University of Cambridge made a mouse embryo model derived exclusively from embryonic stem cells. In other words, a synthetic embryo1. 

Before you jump to conclusions, let me first explain what I mean by synthetic embryos. They are clumps of cells that closely resemble an early human embryo, without using sperm, eggs, or a womb. They can even produce hormones that turn a pregnancy test positive in a lab. They allow scientists an insight into the first weeks of fertilisation, a period of dramatic change, and when most miscarriages and birth defects are instigated. This time is poorly understood in the scientific field and these models give scientists access to the developing structure of an embryo without ever having to implant in a womb, whilst remaining completely visible, allowing them to see the embryo’s progression through that critical developmental stage. This usually isn't possible with embryos in the womb due to legal, ethical, and technical constraints.  Professor Jacob Hanna, from the Weizmann Institute of Science, said this time is usually "a black box and that's not a cliche - our knowledge is very limited."2 

So how exactly do these scientists turn stem cells (the body’s master cells, which can develop into almost any cell type in the body) into a group of cells that almost identically model an embryo? Well, to start with, they mimic the natural process of gastrulation in the lab by using chemicals to coax the stem cells into becoming the four types of cells found in the earliest stages of mammalian development. Epiblast cells, which become the embryo proper (or foetus), trophoblast cells, which become the placenta, hypoblast cells, which become the supportive yolk sac, and extraembryonic mesoderm cells. Those cells are then mixed in a precise ratio and the expression of certain genes is induced to encourage the stem cells to ‘talk’ to each other. Lastly, around 1% of that mixture self-organises into a structure that resembles, but is not identical to, a human embryo, and voila you have what is otherwise known as a synthetic embryo!

Why does it matter? 

Now as extraterrestrial and supernatural as that sounds, there are many scientific reasons for creating these models that go beyond being able to see the first stages of pregnancy and all the benefits that come from doing so. One hope is that they will also provide scientists with both a powerful tool for improving in-vitro fertilisation (IVF) success rates as they will help researchers to understand why some embryos fail and a means for assessing whether medicines will be safe during pregnancy. They also offer a valuable alternative to natural human embryos for research purposes, which could reduce the reliance on donated IVF embryos. Not only are these often unavailable, but they also avoid the ethical concerns associated with their use or destruction. Lastly and maybe most importantly, synthetic embryos could pave a new path for regenerative medicine and biotechnology. For example, the models could be used to generate specific cell types, and tissues for transplantation, such as blood, nerve, heart, and liver cells. Although doing so is still a long way off as Professor Neil Vargasson from the University of Aberdeen said through email discussions with me, “There are some basics in developmental biology we need to understand before we can regenerate human tissues. Synthetic embryos will certainly help, but more basic developmental biology research is also needed.”. 

The Ethical and Legal Debate 

As with any scientific research, ethical and practical considerations must be considered, especially when it involves embryos, even synthetic ones. One ethical concern at the moment is the fear around carrying these synthetic models to term and creating a ‘synthetic child’. Although researchers have clearly stated it would be unethical, illegal, and impossible to achieve a pregnancy using these embryo models. On a more legal front, the laws and rules related to the development of synthetic embryos vary widely across different countries and regions. Some countries including Germany, Italy, and Ireland have a complete prohibition. On the other hand, Sweden, the UK, and the US have more permissive regulations that allow some forms of human embryo research under certain conditions and oversight. However, not all these regulations explicitly address synthetic embryos or other types of stem cell-based embryo models.

The Future of Synthetic Embryos 

Synthetic embryos are part of the future of developmental biology and an exciting addition to the field of science. They have the potential to enhance our understanding of early development and revolutionise healthcare, but they also come with issues regarding their ethics which require careful consideration and regulation. The world needs to continue speaking more openly about the tough questions in science and not be afraid of the unknown, even if it does resemble a Captain America comic. 

By Tagatha Stokes, 16 years old, Scotland, UK. 

Reference

1. Gianluca Amadei et al. ‘Synthetic embryos complete gastrulation to neurulation and organogenesis.’ Nature (August 2022). DOI: 10.1038/s41586-022-05246-3

2. BBC News(2023). Scientists grow whole model of human embryo, without sperm or egg. Available from: Scientists grow whole model of human embryo, without sperm or egg - BBC News [Visited: December, 2024]