Astrocytes: Nerve Path Builders

Astrocytes are part of the glial cell group. Its importance has varied over time. At first, its function was underestimated, since all the protagonism was taken by the neurons. However, it has been shown that they do not only fulfill a passive function, that is, their task is not simply to complement neurons.

These types of glial cells are responsible for building nerve pathways, which among other functions:

• Guide neurons during migration.
• They induce the formation of the blood-brain barrier.
• They are the metabolic support of neurons.
• Collaborate in neuronal regeneration.

Therefore, there is a lot to discover and know about astrocytes. In fact, it’s amazing how they react to neuronal activity and how they repair and communicate. Let’s go deeper.

Types of astrocytes

Astrocytes completely surround the capillaries of the brain and form a physical barrier between blood and neurons. They have different types that give rise to different varieties:

• Protoplasmic astrocytes: are found in gray matter. They have a balloon shape with branches that give rise to other branches and irregular curves. The ends of its branches cover the blood vessels, the meningeal surface and the synapses.
• Fibrous astrocytes: are found in the white matter. They have thin, long and unbranched extensions in the form of fibers. Their endings involve Ranvier’s nodules of axons and blood vessels.

As a curiosity, we mentioned that the term astrocytes comes from the way these cells are presented, which is similar to a star in which you can see extensions that project themselves onto neighboring cells.

In addition, astrocytes contain in the cytoskeleton a protein called glial fibrillary acidic protein (GFAP), which is the characteristic that differentiates them, since it is only found in this type of cell. cxc

Roles

Astrocytes build the information transmission pathways in our brain. Thanks to the neural connections they provide, they are responsible for helping to guide the journey made by axons, through molecules that attract or repel.

As good builders, astrocytes are aware of what happens “in real time” in nervous functioning. Therefore, they are responsible for maintaining the balance of neurons or cerebral homeostasis, which is why they act as a metabolic support, which is achieved by preserving the ionic balance of nerve cells.

In addition, they participate in the maturation, training and maintenance of neuronal synapses. Through astrocytes, neurons are supplied with oxygen, nutrients and protective isolation.

Now, through a process called phagocytosis, these cells are able to eliminate waste from brain metabolism. This process is beneficial because it allows the elimination of waste and pathogens and is carried out by transporting the waste products into the blood so that they can be eliminated. Also, when brain damage occurs, astrocytes travel to the site of damage to eliminate dead neurons.

On the other hand, they are part of the important blood-brain barrier (BME), which makes them intermediaries between the circulatory system and neurons as a filtering mechanism. Therefore, they are also responsible for regulating the passage of molecules from the blood to the brain.

Astrocytes are linked to neurotransmitters because they respond to them actively and have receptors for their union. This is a true communication method for this type of glial cell that is complemented by another way of sending messages, isolating the space at synaptic junctions and acting as signal modulators between neurons.

Astrocytes and reactive gliosis

There is a pathological process whereby the number of astrocytes increases rapidly and disproportionately. This process is what accompanies inflammatory phenomena and is called reactive gliosis.

Two types of astrocytes are found when this type of proliferation occurs: the A2, which have repair functions, and the A1, which favor the degradation of nervous tissue.

Reactive gliosis occurs when there is damage to the nervous system and is followed by a proliferation of these cells in regions that have suffered damage. This phenomenon has been reflected in many studies.

Pros and cons?

Reactive gliosis is beneficial because it causes a synthesis of neurotrophic factors responsible for promoting the survival of neurons. And, on the contrary, it is harmful because it generates a glial scar, which is a barrier to axonal growth.

This phenomenon is vital in clinical research, as it is a great hope for new therapeutic models. For example, stem cell transplants are studied using neurotrophic factors that favor neuronal regeneration. In fact, they are being researched to treat neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

Why are they the great builders of the nervous system?

Astrocytes are responsible for establishing communication bridges between different cells of the nervous system. Furthermore, since they are responsible for isolating and eliminating harmful substances, they act against brain damage and allow the re-establishment of these communication pathways.

Astrocytes are prepared to forge links between different locations and anatomical-functional elements, such as the circulatory system and the blood-brain barrier, the neurons with each other and with brain neurotransmitters, among others. Also, they are fantastic when it comes to maintaining the nerve pathways, as they keep the nervous system in internal balance.

In light of all these discoveries, we can only hope that neuroscience, through the continuous study of these cells and their possible applications, will lead us to great advances in health related to this type of glial cell.