Scientists from the University of Cambridge have created model embryos from mouse stem cells that form a brain, a beating heart, and the foundations of all the other organs of the body. It represents a new avenue for recreating the first stages of life.
The team of researchers, led by Professor Magdalena Zernicka-Goetz, developed the embryo model without eggs or sperm. Instead, they used stem cells – the body’s master cells, which can develop into almost any cell type in the body.
“It’s just unbelievable that we’ve got this far. This has been the dream of our community for years, and major focus of our work for a decade and finally we’ve done it.” — Magdalena Zernicka-Goetz
By guiding the three types of stem cells found in early mammalian development to the point where they start interacting, the researchers mimicked natural processes in the lab. The scientists were able to get the stem cells to ‘talk’ to each other by inducing the expression of a particular set of genes and establishing a unique environment for their interactions.
The stem cells self-organized into structures that progressed through the successive developmental stages until they had beating hearts and the foundations of the brain They also had the yolk sac where the embryo develops and gets nutrients from in its first weeks. Unlike other synthetic embryos, the Cambridge-developed models reached the point where the entire brain, including the anterior portion, began to develop. This is a further point in development than has been achieved in any other stem cell-derived model.
According to the team, their results could help researchers understand why some embryos fail while others go on to develop into a healthy pregnancy. In addition, the results could be used to guide the repair and development of synthetic human organs for transplantation. The study, which is the result of more than a decade of research that progressively led to more and more complex embryo-like structures, was reported on August 25, 2022, in the journal Nature.
“Our mouse embryo model not only develops a brain, but also a beating heart, all the components that go on to make up the body,” said Zernicka-Goetz, Professor in Mammalian Development and Stem Cell Biology in Cambridge’s Department of Physiology, Development and Neuroscience. “It’s just unbelievable that we’ve got this far. This has been the dream of our community for years, and major focus of our work for a decade and finally we’ve done it.”
A “dialog” between the tissues that will form the embryo and the tissues that will connect the embryo to the mother is necessary for the healthy development of a human embryo. Three different stem cell types begin to form in the first week following fertilization; one of these will eventually develop into the bodily tissues, while the other two support the embryo’s development. One of these extraembryonic stem cell types will become the placenta, which connects the fetus to the mother and provides oxygen and nutrients. The second is the yolk sac, where the embryo grows and where it gets its nutrients from in early development.
Many pregnancies fail at the point when the three types of stem cells begin to send mechanical and chemical signals to each other, which instruct the embryo on how to develop properly.
“So many pregnancies fail around this time, before most women realize they are pregnant,” said Zernicka-Goetz, who is also Professor of Biology and Biological Engineering at Caltech. “This period is the foundation for everything else that follows in pregnancy. If it goes wrong, the pregnancy will fail.”
Professor Zernicka-Goetz’s group in…
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