The world’s first ‘synthetic embryo’: why this research matters more

In a world first, biologists have grown mouse embryo models in the laboratory without the need for fertilized eggs, embryos or even a mouse, using only stem cells and a special incubator.

This achievement, published in the journal Cell by a team led by researchers from the Weizmann Institute of Science in Israel, is a very sophisticated model of what happens during early mouse embryo development at the stage just after implantation.

This is a crucial stage: in humans, many pregnancies are lost during this stage, and we don’t know exactly why.

Models offer a way to better understand what can go wrong and potentially insights into what we might be able to do about it.

The smallest bunch

What is particularly interesting about the newly released model is its very complex structure; It not only mimics the cellular specification and layout of an early-stage body plan, including precursors of the heart, blood, brain, and other organs, but also the supporting cells such as those found in the placenta and other tissues responsible for establishment and maintenance of pregnancy are required.

The earliest stages of pregnancy are difficult to study in most animals. The embryos are microscopic clusters of cells that are difficult to locate and observe in the uterus.

But we know that at this stage of development things can go wrong; For example, environmental factors can affect and disrupt development, or cells do not receive the proper signals to fully form the spinal cord, such as B. Spina bifida. With models like this, we can wonder why.

While these models are a powerful research tool, it is important to understand that they are not embryos.

They only replicate some aspects of development, but do not fully reproduce the cellular architecture and developmental potential of embryos formed after fertilization of oocytes by sperm, so-called natural embryos.

The team behind this work emphasizes that they could not develop these models beyond eight days, while a normal mouse pregnancy lasts 20 days.

Are synthetic human embryos on the horizon?

The field of embryo modeling is advancing rapidly, with new advances emerging every year.

In 2021, several teams managed to get human pluripotent stem cells (cells that can transform into any other cell type) to self-aggregate in a Petri dish, mimicking the blastocyst.

This is the earliest stage of embryonic development just before the complex process of implantation, when a mass of cells attaches itself to the wall of the uterus.

Researchers using these human embryo models, often referred to as blastoids, have even been able to begin studying implantation in a shell, but this process is much more difficult in humans than in mice.

Breeding human embryo models with the same complexity now achieved with a mouse model remains a distant proposition, but one we should nonetheless consider.

It is important that we are aware of how representative such a model would be; A so-called synthetic embryo in a petri dish will only be able to teach us a limited amount about human development, and we need to be aware of that.

Ethical pitfalls

Without a source of stem cells, embryonic modeling cannot be done. So when it comes to thinking about future uses of this technology, it’s important to ask where these cells come from. Are they human embryonic stem cells (obtained from a blastocyst) or induced pluripotent stem cells?

The latter can be produced in the laboratory from skin or blood cells, for example, or even obtained from frozen samples.

An important consideration is whether using cells for this particular type of research attempting to mimic an embryo in a dish requires special consent.

We should think more about how this research area will be governed, when it will be used and by whom.

However, it is important to realize that there are existing laws and international stem cell research guidelines that provide a framework to regulate this area of ​​research.

In Australia, research using human stem cell embryo models would require a license similar to that required for the use of natural human embryos under the law that has been in place since 2002.

However, unlike other jurisdictions, Australian law also dictates how long researchers can grow human embryo models, a limitation some researchers would like to see changed.

Regardless of these or other changes in how and when human embryo research is conducted, there needs to be a larger community discourse on the issue before a decision is made.

There is a difference between banning the use of this technology and technologies like human cloning for reproductive purposes and allowing research using embryo models to improve our understanding of human development and developmental disabilities that we do not answer by other means be able.

Science advances rapidly. While this stage is mostly about mice, now is the time to discuss what this means for humans, and consider where and how we draw the line in the sand as science advances.

(The Conversation: By Megan Munsie, Professor Emerging Technologies (Stem Cells), The University of Melbourne)