Israeli scientists grow human embryos from stem cells

Groundbreaking experiment based on research team's previous experience in creating synthetic stem cell–based models of mouse embryos.

Researchers like Prof. Liran Shlush are studying how rare blood stem cells signal early signs of disease. Credit: Weizmann Institute.
Researchers like Prof. Liran Shlush are studying how rare blood stem cells signal early signs of disease. Credit: Weizmann Institute.

The Weizmann Institute of Science in Israel has succesfully created complete models of human embryos from stem cells cultured in a lab. 

The groundbreaking experiment was based on the research team’s previous experience in creating synthetic stem cell–based models of mouse embryos, and managed to grow the embryos outside the womb up to day 14.

Weizmann Institute said that previous studies could not be considered genuinely accurate human embryo models, but that the new experiment had all the structures and compartments characteristic of this stage, including the placenta, yolk sac, and chorionic sac.

“The drama is in the first month, the remaining eight months of pregnancy are mainly lots of growth. 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 this box. It closely mimics the development of a real human embryo, particularly the emergence of its exquisitely fine architecture,” said  Prof. Jacob Hanna, the research team chief.

“An embryo is self-driven by definition; we don’t need to tell it what to do – we must only unleash its internally encoded potential. It’s critical to mix in the right kinds of cells at the beginning, which can only be derived from naïve stem cells that have no developmental restrictions. Once you do that, the embryo-like model itself says, ‘Go!’” he added.

(l-r) Dr. Noa Novershtern, Dr. Vladyslav Bondarenko, Prof. Jacob Hanna, Dr. Bernardo Oldak and Emilie Wildschutz. Credit: Weizmann Institute.

The research team’s results indicate that their models emulated the process by which an early embryo gains all the structures it needs for beginning its transformation into a fetus.

“Many failures of pregnancy occur in the first few weeks, often before the woman even knows she’s pregnant. That’s also when many birth defects originate, even though they tend to be discovered much later. Our models can be used to reveal the biochemical and mechanical signals that ensure proper development at this early stage, and the ways in which that development can go wrong,” Prof. Hanna said.

In fact, the study has already produced a finding that may open a new direction of research into early pregnancy failure. The researchers discovered that if the embryo is not enveloped by placenta-forming cells in the right manner at day 3 of the protocol (corresponding to day 10 in natural embryonic development), its internal structures, such as the yolk sac, fail to properly develop.

Prof. Hanna said that because an embryo isn’t static, it must have the right cells in the right organisation, and it must be able to progress. “It’s about being and becoming. Our complete embryo models will help researchers address the most basic questions about what determines its proper growth”

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