In a groundbreaking development, scientists have grown synthetic human embryos for 14 days – without eggs, sperm or a womb.
In a new study published in Nature, biologist Prof Jacob Hanna and their research team at the Weizmann Institute of Science, Israel, demonstrate their complete model of a human embryo using lab-grown stem cells.
They generated the model using genetically unmodified pluripotent stem cells. These are cells that have the potential to develop into many different cell types. The resulting model mimics the 3D structure and key characteristics of a human embryo.
And, in a first for science, this model includes placenta and a yolk sac to ensure the synthetic embryo’s growth.
The group has been competing with Prof Magdalena Żernicka-Goetz's team, of the University of Cambridge and the California Institute of Technology, in a race to create human embryo models. Żernicka-Goetz’s team presented their unpublished results at a conference in June 2023.
However, previous models have been missing the crucial ‘hallmarks’ of a post-implantation embryo, including the cells that form the placenta and yolk sac.
In this new study, the model embryo even contains the cells that make the hormone detected by pregnancy tests to determine their results. When Hanna’s team conducted a pregnancy test on the synthetic hormones, the result was positive.
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The legal limit on non-synthetic embryo experimentation is 14 days, meaning scientists currently know very little about early embryo development.
But that’s when all the ‘drama’ happens, according to Hanna. That's because this is the stage when a group of cells begins to form the embryo’s structure that, within four weeks, already contains all of our organs.
“The drama is in the first month, the remaining eight months of pregnancy are mainly lots of growth,” said Hanna. “But that first month is still largely a black box.”
“Our stem cell–derived human embryo model offers an ethical and accessible way of peering into [the black] box,” Hanna added. “It closely mimics the development of a real human embryo, particularly the emergence of its exquisitely fine architecture.”
The researchers underline that while the models resemble embryos, they are not real embryos. Scientists are still unsure how long they would survive if allowed to develop beyond 14 days.
While it is currently illegal to implant synthetic embryos into a human womb, there is currently no legal framework addressing the ethical issues of synthetic embryos. Despite this, so far they have not been grown for longer than 14 days.
Darius Widera, Professor of Stem Cell Biology and Regenerative Medicine, University of Reading, was not involved in the research. According to Widera, “This research and other recent reports on models of the early human embryo show that models are getting more sophisticated and closer to [...] normal development, highlighting that a robust regulatory framework is more needed than ever before.”
The team hopes that the findings will facilitate deeper investigation into early human development, as well as infertility and the growth of tissues for transplants.
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