World First "Synthetic" Mouse Embryos Grown Without Need For Egg, Sperm, Or Womb

The novel methodology may one day enable us to grow organs for transplantation using synthetic embryo models.


Rachael Funnell

Social Editor and Staff Writer

clockAug 3 2022, 15:58 UTC
mouse embryo stem cell
The new approach could bypass ethical issues which surround some mouse embryo research. Image credit: © 2022 S Tarazi et al, Published by Elsevier Inc.

Scientists have successfully grown mouse embryos using stem cells cultured in a petri dish. The novel method for embryonic development research meant they could create synthetic mouse embryo models without the need for a natural embryo formed from a fertilized egg and a womb, and is published in Cell.

Embryonic development research took a leap forward when the Weizmann Institute of Science in Rehovot, Israel, found a way to keep mouse embryos alive for several days. Ferris-wheel-like incubators that carefully spin liquid enabled the embryos to develop to a far greater age than ever before, growing to roughly the size of a grain of rice with a visibly beating heart.


Now, reported in the journal Cell, scientists have gone one step further in creating those embryos for development without the need for what’s generally considered to be the basic building blocks of mammalian life: an egg, sperm, and a womb to cook it all in.

The synthetic mouse embryo models developing outside of the womb.

Instead, scientists have found a way to use stem cells cultured in a petri dish that had been programmed into a naïve state. By getting the stem cells to their earliest stage, they can increase their potential for development, creating stem cells that have the capacity to become almost anything.


“The embryo is the best organ-making machine and the best 3D bioprinter – we tried to emulate what it does,” said Professor Jacob Hanna of Weizmann’s Molecular Genetics Department in a statement sent to IFLScience.

“Until now, in most studies, the specialized cells were often either hard to produce or aberrant, and they tended to form a mishmash instead of well-structured tissue suitable for transplantation. We managed to overcome these hurdles by unleashing the self-organization potential encoded in the stem cells.”

Mouse embryo development up to day eight.


Where the new approach has such merit, say the researchers, is that it could bypass the ethical issues that surround more traditional approaches to embryonic development research, which more often relies on natural embryos rather than synthetic ones.

By replacing mouse embryos with mouse embryo models derived from stem cells that can develop in lab incubators, the approach also increases their research potential as a greater number can be included in studies, improving the validity of their findings.

A beating heart, blood stem cell circulation, brain, and intestinal tract was visible in the embryo models created using this approach. However, these self-assembled complex embryos only represented a small number of outcomes from the technique (reportedly around 50 in every 10,000).


It’s therefore the team’s intention to try and better understand how and why some embryos are able to gather themselves in this way.

“Our next challenge is to understand how stem cells know what to do – how they self-assemble into organs and find their way to their assigned spots inside an embryo,” Hanna continued. “And because our system, unlike a womb, is transparent, it may prove useful for modeling birth and implantation defects of human embryos.”

  • tag
  • animals