Scientists from the University of Cambridge have successfully replicated the experiment that was made public a few days ago and which consisted of creating mouse embryos in the laboratory without using eggs, sperm or a uterus. Synthetic embryos have been able to develop more complex brains and, although their success rate is very low, only 1%, it has exceeded that of the previous experiment, which was 0.5%.
They have done it again. Scientists have managed to make mouse embryos from embryonic cells, but without using eggs or sperm or a uterus . For this they have used an incubation device that could well look like a Ferris wheel, since it is shaped like a cylinder and contains small glass jars where the embryos float in a nutrient solution and rotate rapidly. The idea is to simulate how blood and nutrients go to the placenta.
The embryos survived 8.5 days , which is almost half of the duration of the mouse’s pregnancy. During this time, the embryos developed yolk sacs, which serve to supply them with nutrients. Digestive tracts, neural tubes, beating hearts, and brains with well-defined subsections, including the forebrain and midbrain , also emerged. The latter is an advance compared to the previous experiment.
“This has been the dream of our community for years and a main goal of our work for a decade, and we have finally achieved it,” lead study author Magdalena Zernicka-Goetz, a developmental and life sciences biologist, said in a statement. stem cells with laboratories at the University of Cambridge (UK) and at the California Institute of Technology in Pasadena.
The new study, which has been published in the journal Nature , yields very similar results to those obtained in a previous study that appeared in Cell on August 1 and was led by the biologist at the Weizmann Institute of Sciences in Israel, Jacob Hanna, who has also participated in the most recent experiment. In the Cell experiment, the scientists started with different stem cells, but used the same incubator that Hanna had devised. The embryos obtained developed digestive tracts, beating hearts and brains. They lived 8.5 days.
Although both studies produced similar embryos, the experiments started slightly differently . In the first study, Cell, the scientists induced mouse stem cells to a naïve state, meaning that they could become any type of cell, such as heart, brain or intestinal cells. From there, the team divided these naive cells into three groups. In one group, they turned on the genes to make the placenta, and in another group, they turned on the genes to make the yolk sac. The last group was left to develop into embryos.
The experiment published in Nature began with three types of mouse stem cells, rather than naive cells. One type of stem cell gave rise to the embryo, while the other two developed into the tissues of the placenta and yolk sac. Throughout the experiment, they watched as these three types of stem cells interacted, exchanging chemical messages and physically bumping into each other in the glass vials. Precisely studying these exchanges could give clues about how the first stages of embryonic development in humans proceed, and what happens when things go wrong.
“This period of human life is very mysterious, so to be able to see how it develops in a dish – to have access to these individual stem cells, to understand why so many pregnancies fail and how we might prevent it – is very special,” says Zernicka-Goetz. . “We have studied the dialogue that has to take place between the different types of stem cells at that moment; we have shown how it happens and how it can go wrong.”
In both the study published in Cell and Nature , the synthetic embryos closely resembled the natural ones , albeit with some slight differences and flaws in the way the tissues were organized. However, in both experiments, a very low proportion of stem cells gave rise to embryos, suggesting that the efficiency of both systems could be improved . Furthermore, neither of the two sets of synthetic embryos survived to the ninth day of development, a hurdle that would have to be overcome in further studies. They also did not develop umbilical cords so it is impossible for them to be implanted in a uterus to be born.
The research also raises ethical questions about whether this technology could be applied to human cells in the future.
Referencia: Amadei, G., Handford, C.E., Qiu, C. et al. Synthetic embryos complete gastrulation to neurulation and organogenesis. Nature. 2022. DOI: https://doi.org/10.1038/s41586-022-05246-3
