Safe Human Embryo Analog Was First Grown from Stem Cells

This will help scientists, in particular, find out what leads women to infertility and learn how to prevent it.

For the first time, scientists have grown from stem cells a structure that is similar to the first phases of embryo development.

“Our model reproduces part of the human development program. It was incredibly interesting to trace those processes that were previously hidden from the human eye and were inaccessible for experimental study,” – said one of the authors of the study, University of Cambridge professor Alfonso Martinez-Arias.

In recent years, scientists have become actively interested in how the genetic development program is arranged and how it works, which turns a fertilized egg into an embryo, placenta and other essential components of the fetus. If scientists learn how malfunctions occur in this program, it will be possible to understand how many forms of infertility arise, as well as learn the mechanisms of occurrence of many serious congenital diseases.

The first experiments on the embryos of mice and monkeys showed that observing the development of the embryos of these animals will not help scientists understand something definite. Therefore, researchers are looking for alternative ways. For example, three years ago, British and Korean geneticists conducted the world’s first experiment to edit the DNA of viable human eggs, during which they turned off one of the key genes associated with the work of the human development program.

Martinez-Arias and his colleagues figured out how to conduct similar experiments on less controversial material. With the help of the technique they have developed, it is possible to grow structures from stem cells, which in their structure and behavior are similar to one of the first forms of an embryo – the so-called gastrula.

Artificial embryos

Gastrula consists of three separate layers of cells – ectoderm, mesoderm and endoderm, which serve as the basis for the formation of all the most important parts of the human body. The first tissue is a “building material” for the nervous system and skin, the second is for muscles, and the last is for the intestines and internal organs.

The process of gastrula formation and the peculiarities of its development still remain a mystery to biologists. The fact is that due to modern legal regulations, scientists cannot conduct experiments on embryos that have lived for more than two weeks. British researchers got around this problem by discovering a set of molecules that can be used to transform stem cell cultures into an analogue of gastrula.

To do this, the scientists found out which genes are activated during the formation of gastrula in the embryos of mice and tried to reproduce a similar environment in the culture of human stem cells. As it turned out, they can be forced to turn into an analogue of gastrula by growing a culture of stem cells of a certain density and treating them with a substance that blocks the work of the GSK3B gene.

This section of DNA serves as a kind of stop-signal that prevents stem cells from transforming into various types of “blanks” of body tissues, including three types of embryonic gastrula tissues. After the researchers blocked it, in just a few hours, the stem cells began to transform into miniature gastrula resemblances with a distinct three-layer structure and an elongated shape.

By measuring the activity of genes in the “head” and “tail” of the gastrula, scientists have found characteristic differences in their work, which are characteristic of the developmental programs of other mammals. By the way, the scientists found groups of cells that were “blanks” of muscles, skin, bones and cartilage, but inside these artificial gastrula there were no cells that could turn into neurons.

On the one hand, this poses new questions for scientists about how the program of development of the embryos of humans and other animals differs. On the other hand, the absence of nerve cells removes many ethical questions, including fears that such artificial embryos could be grown to the very last stages of development.