Without eggs and spermatozoa
Biologists for the first time assembled a mouse "embryo" directly from stem cells
Anatoly Glossev, Vesti
Scientists have created a prototype of a full-fledged embryo from stem cells. It forms all the necessary cell types and, when implanted into the uterus, causes pregnancy. This result was achieved for the first time without the use of eggs and spermatozoa. The details of the study are described in a scientific article published in the journal Nature by a team led by Niels Geijsen from Utrecht University in the Netherlands (Rivron et al., Blastocyst-like structures generated solely from stem cells).
Why do scientists need artificial embryos when it's so easy to get a natural one? The fact is that in the case of a mouse, there are no problems with conducting any experiments on a real embryo. But with a potential human being, it will not be possible to "play around" like that. There are still heated ethical discussions about this, and at the moment embryos are destroyed no later than 14 days after fertilization.
The "model" obtained from stem cells has many properties of an embryo and at the same time obviously cannot develop into an adult organism. Later, the technology developed on mice can be applied to the study of human embryos without causing sharp criticism about the moral side of such actions.
The current artificial mouse embryo was created using two types of stem cells: embryonic and trophoblastic. The latter are responsible for the formation of the placenta.
The blastocyst consists of the outer layer of cells from which the placenta develops, and the inner one – the future baby. Here and below are illustrations by Nicolas Rivron.
Scientists want to learn more about the development of the embryo in the early stages. Let us explain that the cells of the embryo send chemical signals to each other during its development and growth. This is a kind of instruction on how to position yourself in space in order to form an embryo and placenta. And these signals are still very poorly understood.
"In a natural embryo, the same stem cells in three dimensions talk to each other in a language that we barely understand," explains the first author of the study, Nicolas Rivron from Utrecht University, whose words are quoted by the resource phys.org with reference to the AFP news agency.
In the experiments of researchers, embryonic stem cells, apparently, also turned out to be quite "chatty". The creation of biologists evolved into an analogue of a 3.5-day-old blastocyst. Recall that at this stage of development, the embryo is a hollow ball consisting of less than a hundred cells. Its thin wall in the future becomes a placenta, and a small seal in the center becomes a fetus.
Such "embryo models" will help to understand the processes occurring in the first stages of pregnancy.
When transplanted into the mouse uterus, this "quasi-embryo" initiated pregnancy. However, scientists emphasize that this is still not a real embryo, and it could not be tolerated. But, since this is its fairly accurate analogue, it will help answer many questions of scientists.
"This breakthrough has opened [to us] the black box of early pregnancy," says Rivron.
Such "embryo models" will help to better study the first stages of fetal development. Scientists hope that this will increase the effectiveness of artificial insemination. After all, so far two-thirds of such manipulations end in failure, and mostly after implantation of the embryo into the uterus. Why this happens, in many ways, is not yet clear.
In addition, artificial embryos can become a model for drug testing. Finally, the authors hope that they will help to clarify the mechanisms of a number of hereditary pathologies, including some types of diabetes and cardiovascular diseases.
"Our research helps to find the ideal path that an early embryo must take to develop healthy," Rivron concludes in a university press release Forming model embryos from stem cells in the lab.
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