Scientists have grown a 'textbook' human embryo from stem cells in a lab

The aim is to study the earliest moments in human life

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Scientists have grown a “model” of a human embryo without using a womb, eggs or sperm.

The Weizmann Institute team say their “embryo model” was created using stem cells, and looks like a textbook example of a real 14-day-old human embryo.

It even released hormones that turn a pregnancy test positive in the lab.

A stem-cell derived human embryo model showing blue cells (embryo), yellow cells (yolk sac) and pink cells (placenta) (Image: The Weizmann Institute of Science)A stem-cell derived human embryo model showing blue cells (embryo), yellow cells (yolk sac) and pink cells (placenta) (Image: The Weizmann Institute of Science)
A stem-cell derived human embryo model showing blue cells (embryo), yellow cells (yolk sac) and pink cells (placenta) (Image: The Weizmann Institute of Science)

The ambition for embryo models is to provide an ethical way to study the earliest moments in the development of human life - not to create life. 

The research published in Nature demonstrates that the synthetic embryo models have all the structures and compartments characteristic of human embryos, including the placenta, yolk sac, chorionic sac and other external tissues.

The research “may provide an unprecedented opportunity to shed new light on the embryo’s mysterious beginnings,” according to the institute. It explained: “Little is known about the early embryo because it is so difficult to study, for both ethical and technical reasons, yet its initial stages are crucial to its future development.

“During these stages, the clump of cells that implants itself in the womb on the seventh day of its existence becomes, within three to four weeks, a well-structured embryo that already contains all the body organs.”

Professor Jacob Hanna, who led the research, said in a release: “The first month [of pregnancy] 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.”

This entity was created through the use of pluripotent stem cells taken from adult human skin - which have the potential to become a number of different cell types. The cells were treated to revert them to an earlier state of being, known as the naïve state – in which they are capable of specializing into any type of cell.

“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,” Professor Hanna says. “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!’”

Then the embryo-like structures “developed normally outside the womb for eight days, reaching a developmental stage equivalent to day 14 in human embryonic development“.

It is hoped the research could provide crucial insight into the causes of miscarriages and pregnancy complications.

Professor Hanna said: “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 Roger Sturmey, professor of reproductive medicine at the Hull York Medical School, said the work shows programmed stem cells “are capable of self-organising into a structure that looks very much like an early embryo at the stage around when they begin to engage in implanting into the womb”.

He added that “significant further work is required to understand the degree to which these, and many other embryo models resemble native embryos” – though it “remains prohibited to transfer an embryo model into the uterus of an animal or person”.

Prof Alfonso Martinez Arias of Pompeu Fabra University, said: “The 14th day of human development is a crucial landmark associated with the moment in which a human embryo earns its right to legal protection.”

He added: “The work from the Hanna lab just published has, for the first time, achieved a faithful construction of the complete structure from stem cells, in vitro, thus opening the door for studies of the events that lead to the formation of the human body plan.”

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