Scientists create “simulated embryos” with a few days of life in the laboratory – 03/17/2021 – Science

Two different research groups have developed a biochemical recipe that can be used to convert adult cells into structures that are very similar to embryos that are just a few days old. Progress promises to understand fundamental aspects of embryonic development and pregnancy in our species, but it also creates a complex ethical debate about the nature of such cellular structures, even when they appear incapable of becoming viable fetuses.

Detailed data on the feat can be found in articles in this week’s edition of the scientific journal Nature, one of the most important in the world. The “simulated embryos” were called blastoids – analogous to blastocysts, since real embryos are known that are about a week old. At this point in time, they are a tenth of a millimeter in diameter and have several hundred cells arranged in layers whose properties the researchers are trying to imitate.

Using slightly different techniques, the teams led by the Argentinian José Polo from Monash University in Australia and the Chinese Jun Wu from the University of Texas (USA) adapted what is already known about the ability to convert adult cells into “more primitive” Convert cells. to cultivate their blastoids.

In fact, this type of trick has become relatively common over the past few decades and is dominated by scientists around the world. Such techniques are based on a simple assumption: most of the cells in the organism share the same genetic material, a “recipe book” written using the DNA alphabet that has existed since the egg was fertilized by the sperm.

The original cell that emerged from this union already contained all the instructions that were necessary for the construction of the entire organism. If the same DNA is still present in many of our cells, it means that it is at least theoretically possible to reconstruct the entire body from one of them.

Based on this principle, mammalian cloning was developed from the 1990s, starting with the famous Scottish sheep Dolly. However, the scientists found that it wasn’t even necessary to make clones. When the researchers realized that simply activating certain genes (roughly functional sections of DNA) was enough to bring adult cells into a state very close to that of the embryo, they began using them to control various aspects of development examine. The idea is that in the future the same technique will help create bespoke tissues for transplants and other therapies.

For a long time, the main interest was to create cells that correspond to those found in the so-called MCI (internal cell mass) of blastocysts. These are the ones who are responsible for building the embryo itself and can lead to any part of the body, from the heart to the brain.

However, it happens that the cells of the blastocyst also give rise to the placenta and other accessory structures that are essential for the embryo to implant in the mother’s uterus and develop properly.

This time around, both Polo’s and Wu’s team were able to activate some of the genes that are already widely used to reprogram adult cells and build structures very similar to blastocysts in special containers.

Both the shape and the biochemical properties of the blastoids produced by the two groups are very reminiscent of those of the different layers of the real embryos. There are some differences, however: Blastoids also contain some cells with their own properties that are not found in natural blastocysts. Based on these and other details, as well as what is known from developing similar structures with mouse cells, “blastoids are unlikely to have the full potential for embryonic development,” says Martin Johnson, Professor Emeritus of Reproductive Science at Cambridge University, commented on the Study at the request of the journal Nature.

Even so, the researchers made it clear that for the time being they did not intend to exceed what is known as the 14-day rule, a limit set by scientists today for research using real human embryos (which can only be used until then age). Blastoids would be useful for studying problems of early embryonic development and infertility, and also as a drug testing platform, as they can be tailored from a particular patient’s cells with the same genetic material as that patient. We are a family business.

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