Embryos recreated from stem cells


Synthetic embryos in an artificial uterus

The synthetic embryos differ fundamentally from embryo-like stem cell colonies created earlier – primarily because of their high degree of development. Analyzes show that apart from the placenta, all cell types typical of an embryo are represented. An artificial uterus developed by Hanna’s team was crucial for the technology. With this, in 2021, it kept mouse embryos alive outside the body for more than half the duration of a pregnancy for the first time. The synthetic embryos also grew in these nutrient solutions. However, the process is still extremely inefficient. Only a small proportion of the stem cell clumps took an embryo-like developmental path – in Hanna’s work only 0.5 percent. The team led by Zernicka-Goetz did not specify a success rate. However, experts estimate that it will not be much higher.

However, experts expect that more experience with the technology will increase the success rate – and that biomedical applications will also be opened up as a result. The team led by Zernicka-Goetz showed that an inactivated gene called Pax6 has the same effect in the synthetic embryo as in a real embryo. This is particularly interesting if it is possible to produce synthetic human embryos, which may only be a matter of time. “From a technical point of view, it is easy to imagine transferring these results to humans,” explains Michele Boiani from the Max Planck Institute for Molecular Biomedicine. However, the artificial uterus does not just have to function for a few days, but for weeks or months. That is a big challenge.

How much trouble does technology cause?

The working group led by Jacob H. Hanna has already proposed such experiments. Synthetic human embryos would allow experiments that are prohibited on real embryos for ethical reasons. It is possible that tissue for transplantation could also be obtained in this way. Both the working groups involved and other experts emphasize that the synthetic embryos are similar to the real ones, but they are not. It is crucial that “these synthetic embryos – as the mouse model shows – no matter how embryo-like they look, have no organismic potential: they cannot lead to a live birth,” says Jesse Veenvliet from the Max Planck Institute for Molecular Cell Biology, for example and genetics.



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