Astrocytes of the Brain: Retinue Plays the King

Besides neurons, there are many other cells in the brain tissue grouped under the name “glia.” According to our current knowledge, humans have the approximately same number of neurons and glial cells. Among glial cells, astrocytes occupy a special position because of their fantastic multifunctionality, which can be uncovered from new angles. The history of the study of astrocytes goes back over 100 years. During that time, they have been firmly considered as supportive and service cells and, therefore, have always been “in the shadow” of neurons. New tools of molecular genetics that allow cell labeling, cell manipulations in vitro and in vivo, experimental gene knock-out, and regulation of gene expression—coupled with new methods of cell imaging—have opened wide possibilities for solving problems of fundamental biology. They have led to two important discoveries: (1) astrocytes are close in function to neurons and (2) they play an important role in brain repair and regeneration. There has been intensive research in the areas associated with each of these discoveries since the 1990s. However, research in each of them has followed separate paths, and there has been little overlap. This is not surprising since modern research is often highly specialized and focused on details so deep that a sense of the integrity of the object and the problem is lost. In the case of astrocytes, this is the case. One direction of research, extremely important for understanding brain function, has focused on the physiology of astrocytes and their involvement in the regulation of synaptic activity of neurons. Research in the other direction has involved the study of neural stem cells. They have revealed the properties of stem cells in astrocytes as well as their ability to be reprogrammed into neurons. The amount of data generated by studying astrocytes is huge. Therefore, each of the reviews devoted to them usually covers only one narrow topic. Therefore, the aim of our review is to combine the information from two areas of research mentioned above. This will provide the most complete picture of the current state of knowledge in astrocyte biology and will outline new ways of studying normal brain functioning and its reconstruction.