Radial Glia: What Is It And What Functions Does It Have In The Brain?
Thinking about the brain or the nervous system in general is equivalent to thinking about neurons. And the neuron is the basic unit of the nervous system, which is why we usually focus on them when we are exploring the functioning of said system. But there are not only neurons in the brain. We can also find glial cells, which support, protect and keep neurons alive. Among the multiple types of glial cells that we can find, in this article Let’s focus on the so-called radial glia an essential element for our development.
We understand glia or glial cells to be that set of cells derived from the embryonic epithelium that cover the nervous system and form a network of support, protection, nutrition and maintenance of neurons. Initially it was believed that they were a substance that only held neurons together, although this hypothesis was rejected after the discovery of the existence of synapses.
Its functions are multiple: in addition to contributing to providing a structure to the nervous system, it has been observed that glial cells are those that bring neurons into interaction with the cells of the cerebrovascular system, acting as a filter. This means that the glia can provide nutrients and oxygen to the neurons, something that refers to one of its main and most relevant roles: that of providing nutrients and keeping the nervous system alive. A final, especially relevant role of this type of cells is the fact that they eliminate waste and maintain stability in the environment in which the neurons are located.
But although they were traditionally considered mainly as sustainers, recent research proposes that they are capable of both capturing and releasing information-transmitting substances with a possible influence on synaptic transmission that occurs between neurons. Thus, they have an effect on information processing beyond mere neuronal support.
Glial cells are essential for the proper functioning and survival of the nervous system. But the term glia includes a large number of cell types. Among them we can find astrocytes, oligodendrocytes, Schwann cells or the one we are dealing with in this article, radial glia.
Radial glia: basic elements
Regarding the radial glia, we are faced with a type of glial cell with generally bipolar morphology that extends throughout the cerebral and cerebellar cortex (although in the latter case there are more elongations, being multipolar). These are cells that serve as a structural pillar and contribute to the development of the nervous system.
They have often been linked to another type of glial cell, astrocytes, because they perform typical roles of this type of glial cell and, like these, present similar cytoskeletal and membrane proteins (possessing, among other things, glutamate receptors or GABA). In fact, radial glia can become or derive from these.
Radial glia, also called aldainoglia, are primarily known to serve as path or guide for neurons during fetal development This guidance occurs due to the interaction of glia and neuron, through a process of attraction at a chemical level and the role of glia in promoting the growth and migration of nerve fibers.
However, this role is reduced over time: once the migration of the neurons of the cortex towards their final position has occurred and once new neurons stop being born in most areas of the nervous system, their role becomes focus on supporting the neural network.
Radial glia fulfill different roles within the organism, but we have already mentioned the most prominent, investigated and known of all of them: It is the type of cell that allows and acts as a guide for neurons during neuronal migration allowing them to reach the positions that concern them.
This process is especially visible during fetal development, seeing how the newly formed neurons travel through the glial cells, using them as a guide to the cortex. Although it is not the only method of neuronal migration available, it is the best known and most widely used, especially with regard to the cerebral cortex.
In addition to this guidance and transport function, the radial glia It has also been related to neuronal generation and synthesis itself: It has been observed that they can act as progenitors of other cells such as neurons. This neurogenesis is especially linked to childhood, but its involvement is suspected in the birth of new nerve cells in the adult brain in the few areas in which it has been detected (in the hippocampus and the olfactory bulb is where it has been observed the most). ). Likewise, they have been related to the recovery of some functions after the presence of brain lesions, and their link has been observed with processes such as synaptic and neuronal pruning that occurs during growth.
It has been seen that glial cells also have a very important role in generating a complex cerebrovascular network, functional and stable in the brain, especially at the beginning of life but also throughout the life cycle. In experiments with mice, it was observed that its inhibition generates a degradation of the cerebral vascularization network and brain metabolism, something that greatly facilitates the appearance of neurodegeneration (something that in fact is discussed regarding its involvement in diseases such as Alzheimer’s). .
Finally, it is worth mentioning that like the rest of glial cells, radial glia also have an important role in supporting and keeping alive the neurons that surround them, facilitating their growth and nourishing them.
