The synthetic embryo developed under the leadership of Weizmann researchers: a senior researcher in the field explains why this is a breakthrough

Many pregnancies are terminated at the stage when the fetus is implanted in the uterus and begins to develop. The discovery will make it possible to investigate this phase in detail

By Megan Munsey, Professor of Emerging Technologies (Stem Cells), University of Melbourne

In what is reported to be a world first achievement, Biologists have grown mouse embryo models in the lab without the need for fertilized eggs, in embryos or even in a mouse (male or female) - 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, it is a very sophisticated model of what happens during the early development of mouse embryos - in the immediate phase after embryo implantation.

This is a crucial step: in humans, many pregnancies are lost during it and we really don't know why. Having models provides a way to better understand what can go wrong, and perhaps insights into what we can do about it.

The smallest cluster

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

This eight-day-old mouse embryonic model has a beating heart, yolk sac, placenta, and developing blood flow. Weitzman Institution of Science.

The earliest stages of pregnancy are difficult to study in most animals. Embryos are microscopic, tiny clusters of cells that are difficult to locate and examine inside the womb.

But we do know that at this stage of development, things can go wrong; For example, environmental factors can affect and interfere with development, or the cells fail to receive the correct signals to fully form the spinal cord, such as in the syndrome spina bifida. Using such models, we can begin to ask why.

However, although these models are powerful research tools, it is important to understand that they gone Passing

They reproduce only certain aspects of development, but do not fully reproduce the cellular architecture and developmental potential of embryos derived from fertilization of eggs by sperm - so-called natural embryos.

The team behind this work emphasizes that they were unable to develop these models beyond eight days, while a normal mouse pregnancy lasts 20 days.

Are human 'synthetic embryos' on the horizon?

The field of embryo modeling is advancing rapidly, with significant steps emerging every year.

In 2021, several teams They succeeded in causing human pluripotent stem cells (cells that can transform into any other type of cell) to accumulate by themselves in a Petri dish, imitating the "blastocyst". This is the earliest stage of embryonic development just before The complex process of transplantation, when a mass of cells attach to the uterine wall.

Researchers using these human embryo models, called Often blastoids, even managed to start investigating the transplantation in a plate, but this process is much more challenging in humans than in mice.

Growing human embryo models of the same complexity now achieved with a mouse model remains a distant vision, but one we still have to consider.

More importantly, we must be aware of how representative such a model would be; A so-called synthetic embryo in a petri dish will have limitations on what it can teach us about human development, and we need to be aware of that.

Ethical pitfalls

It is impossible to create embryonic models without a source of stem cells, so when it comes to thinking about the future use of this technology, it is important to ask - where do these cells come from? Are they human embryonic stem cells (derived from the blastocyst), or are they induced pluripotent stem cells (adult stem cells)? Such stem cells can be derived in the laboratory from skin, or blood cells, for example, or even from frozen cell samples.

An important consideration is whether the use of cells for this particular type of research - an attempt to mimic the development of an embryo in a dish - requires any specific consent. We need to think more about the way the field of research will be controlled, when it should be used, and by whom.

However, it is important to recognize that existing laws exist and international guidelines for stem cell research that provide A framework for regulating this field of research.

In Australia, research involving human stem cell embryo models will require licensing, similar to that required for the use of natural human embryos under a law that has been in place since 2002. However, Unlike other countries, Australian law also dictates how long researchers can grow human embryo models, a limit some researchers would like to change.

Regardless of these or other changes in the way and time in which human embryo research is conducted, there needs to be a larger community discourse around this issue before a decision is made.

There is a distinction between prohibiting the use of this technology to clone humans for reproductive use, and allowing research using embryo models to advance our understanding of human development and developmental disorders that we cannot study by any other means.

Science is advancing rapidly. While it's mostly mice at this point, it's time to discuss what the technology means for humans, and consider where and how we draw the line in the sand as science develops.

For an article in The Conversations

More of the topic in Hayadan:

• No egg, no sperm and no uterus: Weizmann Institute of Science scientists created an artificial model of mouse embryos
• The very first program to create an embryo by creating artificial embryonic and placental stem cells
• Weizmann Institute scientists grew mouse embryos outside the womb