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The nerve cells are not only nerve cells. According to the distinction finely, there are several hundred to several thousand different types of nerve cells in the human brain according to the latest calculations. These types of cells vary in their function, in the number and length of their cellular appendages and in their interconnections. They emit different neurotransmitters in our synapses and, depending on the brain region – for example, the cerebral cortex or the average brain – different types of cells are active.

When scientists produced nerve cells from stem cells in petri boxes for their experiences in the past, it was not possible to take into account their great diversity. Until now, researchers have only developed procedures to cultivate a few dozen different types of in vitro nerve cells. They reached it using genetic engineering or by adding signaling molecules to activate specific cell signaling routes. However, they have never got closer to the diversity of hundreds or thousands of different types of nerve cells that really exist.

Neurons derived from stem cells are frequently used to study diseases. But so far, researchers have often ignored the precise types of neurons with which they work. “”

Barbara Treutlein, professor, Biosystems Department of Science and Engineering in Eth Zurich, Basel

However, this is not the best approach to such work. “If we want to develop cell culture models for diseases and disorders such as Alzheimer’s disease, parkinson and depression, we must take into account the specific type of nerve cells. »»

Systematic screening was the key to success

Treutlein and his team have successfully produced more than 400 different types of nerve cells. In doing so, scientists have paved the way for a more precise basic neurological research with cell culture experiences.

ETH researchers have succeeded by working with a cultivation of multi -patent stem cells induced by the man who had been generated from blood cells. In these cells, they used genetic engineering to activate certain geneal regulator genes and treated cells with various morphogens, a special class of signaling molecules. Treutlein and his team adopted a systematic approach, using seven morphogens in different combinations and concentrations in their screening experiences. This resulted in nearly 200 different sets of experimental conditions.

Morphogenic

Morphogens are known messengers of embryonic development research. They are not uniformly distributed in an embryo but occur in a variety of concentrations forming space models. In this way, they define the position of the cells in the embryo, for example if a cell is near the axis of the body or in the back, the abdomen, the head or the torso. Consequently, morphogens help to determine what is developing in the embryo.

The researchers used various analyzes to prove that they had produced more than 400 different types of nerve cells in their experience. They examined RNA (and therefore genetic activity) at the level of individual cells, as well as the external appearance of cells and their function: for example, what type of cell appendix they had in the quantities and impulses of the electrical nerve they have emitted.

The researchers then compared their data with information from databases from human brain neurons. In doing so, they were able to identify the types of nerve cells that had been created, such as those found in the peripheral nervous system or the brain cells and the part of the brain from which they come, that they perceive pain, cold or movement, etc.

In vitro neurons for research on active ingredients

Treutlein specifies that they are still far from producing all types of nerve cells that exist in vitro. However, researchers now have access to a much larger number of different types of cells than before.

They would like to use in vitro nerve cells to develop cell culture models to study serious neurological conditions, including schizophrenia, Alzheimer’s, parkinson, epilepsy, sleep disorders and multiple sclerosis. Cell -cultivation models of this type also have a great interest in pharmaceutical research to test the effects of new compounds active in cell cultures without animal tests, in order to be able to remedy these conditions.

In the future, cells could also be used for cell replacement therapy, which consists in replacing sick or dead nerve cells in the brain with new human cells.

But there is a challenge to be overcome before it can happen: researchers have often produced a mixture of several different types of nerve cells in their experiences. They now work to optimize their method so that each experimental condition produces only one type of specific cell. They already have some initial ideas on how it could be achieved.