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A stem cell-derived human embryo model at a developmental stage equivalent to a 14-day embryo. © Weizmann Institute of Science
Researchers have succeeded in growing a human-like organism without human cells. Pregnancy hormones were also released.
Frankfurt – A research team from the Weizmann Institute of Science has managed to grow an organism that would correspond to a human embryo at 14 days old. With the help of stem cells, the researchers succeeded in creating a human-like organism like the institute in one without a uterus, eggs or sperm press release had explained. Pregnancy hormones were also released.
Research team cultivates embryo outside the uterus for two weeks
The scientific team, led by Jacob Hanna, managed to grow the embryo model outside a uterus for two weeks using cultured stem cells in the laboratory. The organism would have all the characteristics common to the stage of a human embryo at the same time period. These include the placenta, yolk sac, chorionic sac and other external tissues. Only recently have researchers succeeded in producing synthetic embryos.
Experiments from previous studies could therefore not have been viewed as human embryos because these properties have not yet been proven. In particular, these would not have contained several cell types that are essential for the development of the embryo, for example those that form the placenta and the chorionic sac. In addition, they did not have the structural organization characteristic of the embryo and did not show a dynamic ability to progress to the next stage of development.
“Unprecedented opportunity”: Artificially grown embryo offers glimpse of early human stages
The results could provide researchers with an “unprecedented opportunity to shed new light on the mysterious beginnings of the embryo,” according to the press release. So far, little is known about this stage because it is difficult to investigate for both technical and ethical reasons.
However, it is precisely this period of time that is crucial. In this phase, the clump of cells that implants itself in the uterus on the seventh day of its existence would become a well-structured embryo within three to four weeks that already contains all of the body’s organs.
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Researcher sees “ethical and accessible possibility” in artificial embryo model
Scientist Jacob Hanna explains: “The drama takes place in the first month, the remaining eight months of pregnancy are mainly growth months,” says the author of the study. “But this first month is still largely a black box. Our stem cell-derived human embryo model offers an ethical and accessible way to look into this box.” Accordingly, it closely imitates the development of a real human embryo, in particular the formation of its extremely fine architecture.
Researchers use a method to return cells to their original state
The researchers obtained the biological material for this from, among other things, adult skin cells that had been converted into stem cells. The team also relied on descendants of human stem cell lines that had been cultivated in the laboratory for years. Twins were born last year whose genetic material had been frozen for more than 30 years. With a recently developed method, it is possible to reprogram stem cells and turn their clock back to an even earlier state – the so-called naive state.
Science team puts human cells in a naive state – and allows embryo to develop
In this state, cells are able to develop into any type of cell. For a human embryo, this would correspond to day 7 of its development. The team has been researching the first steps of this method since 2013 in order to continue improving it over the years.
Once the cells are in the naive state, the embryos will organize themselves: “An embryo is by definition self-controlled; “We don’t have to tell it what to do – we just have to unlock its internally encoded potential,” says Hanna. “It is crucial to mix in the right cell types at the outset, which can only be obtained from naive stem cells that are not subject to developmental constraints. As soon as you do that, the embryo-like model itself says, ‘Go!'”
Jacob Hanna, professor of molecular genetics, works on embryo samples in his laboratory at the Weizmann Institute of Science in Rehovot. © Ilia Yefimovich / dpa
Cultured embryo without sperm and eggs opens up new research avenues
The study has already led to a result that would open a new direction for research into early pregnancy failure. “Our complete embryo models will help researchers answer the most fundamental questions about what determines its proper growth.” The experiments also produced pregnancy hormones.
It could help uncover the causes of many birth defects and types of infertility. It could also lead to new technologies for growing transplant tissues and organs. And it could provide a way to bypass experiments that can’t be done on living embryos – for example, determining the effects of drugs or other substances on fetal development.
2023-09-09 16:50:46
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