Life-size embryo model

For the first time, a living embryo was grown from stem cells

Anna Govorova, Infox.ru

Bioengineers from the University of Cambridge have managed to achieve great success in the field of regenerative medicine – from different types of embryonic stem cells they have grown a real mouse embryo, whose age was 13 days after fertilization, reports Infox. 

(From what is written below, it is easy to understand that this is not a real embryo capable of further development, but its shell. But obtaining a viable embryo was not part of the researchers' tasks – VM.)

As the authors themselves say, their research will help to better understand the processes that occur at the earliest stages of embryogenesis, including finding out when and how something goes wrong, and problems arise that lead to termination of pregnancy and miscarriage.

The authors report on the results of their work in the latest issue of the journal Science (Harrison et al., Assembly of embryonic and extra-embryonic stem cells to mimic embryogenesis in vitro).

Human and mammalian embryogenesis is a complex process and has not yet been fully studied. It is known that after fertilization (fusion of an egg with a sperm), a zygote is formed. Then the complex process of preparing the zygote for crushing lasts about 30 hours. As a result of crushing, a morula is formed (it resembles a raspberry berry). On the 2-5 day after fertilization, a blastocyst is obtained – this is already a contented complex structure consisting of different types of stem cells. Blastocyst for some time (up to 13-14 days after fertilization) it also floats freely in the uterus, and then attaches to its wall.

The blastocyst contains three different types of cells: embryonic stem cells – the whole body is formed from them, trophoblastic stem cells – from which the inner layer of the embryo and the placenta are obtained. The third group of cells is endodermal stem cells, from which the yolk sac is formed, which supplies the embryo with nutrients before it attaches to the uterine cavity and begins to receive nutrition from the placenta.

In their experiment, the scientists used two groups of mouse cells – embryonic and extratrophoblastic stem cells. They were placed in a three-dimensional frame where they could grow and develop.

Surprisingly, these cells began to interact with the help of signaling molecules. As a result, the process went exactly as it should happen in the body: embryonic stem cells occupied one part of the skeleton, and extratrophoblastic cells occupied the opposite. A cavity formed between them. It is precisely in it that the embryo should be formed in the future. The process took 14 days. Everything is exactly as it happens in the uterine cavity.

Blastocyst grown in vitro on the fourth day (left). Blastocyst on the second day (right). Embryonic stem cells are shown in red, extratrophoblastic stem cells are shown in blue. Photo: Sarah Harrison and Gaelle Recher, Zernicka-Goetz Lab, University of Cambridge.

As the authors say, the further development of the blastocyst grown in the laboratory would not have gone anyway. Since they used only two types of cells, and without stem cells giving rise to the yolk sac, the blastocyst does not live long.

"In our experiment, two types of cells began to interact with each other, and that's why the development process started. Otherwise, nothing would have happened. That is why previous attempts to grow an embryo from stem cells have not been successful. This interaction between different types of cells determines the position for each of them in the right place and at the right time," says the lead author of the study, Professor Magdalena Zernicka–Goetz (Magdalena Zernicka-Goetz).

"We knew that cell interaction was important, but we were surprised that cells really direct each other to the right place, pointing the way with the help of various signaling molecules," the scientists add (in a press release from the University of Cambridge Scientists create artificial mouse 'embryo' from stem cells for the first time – VM).

Portal "Eternal youth" http://vechnayamolodost.ru  03.03.2017