Ependymal Cells: Definition, Classification, Physiology and Repair of the Cerebral Ventricles

Ependymocytes are cells that make up the ependyma, the membrane that lines the inside of the ventricular cavities of the central nervous system.

Classification

There are four types of glyocytes in the central nervous system and two types of glyocytes in the  peripheral nervous system .

In short, the glyocytes of the central nervous system form neuroglia, which literally means “nerve glue.”

Their number is much higher (9 times) than that of neurons in the central nervous system, thus constituting half of the total mass of the  brain  (part of the nervous system located in the skull).

Neuroglia consists of:

Astrocitos

Astrocytes are the cells that belong to the macroglia. They come in the form of star-shaped cells and provide nutrition protection support function.

These cells are provided with numerous radiating extensions that attach to capillaries (small vessels) and neurons. Finally, astrocytes allow neurons to heal in case of injury and appear to communicate with each other.

Oligodendrocitos

Oligodendrocytes mean cells with little (oligos).

Small oligodendrocytes are aligned along the axons corresponding to the central portion of the cylindrical end of the body of the neuron, and allowing the transmission of nerve impulses, and more particularly around the thick axons of the central nervous system and their cytoplasmic extensions.

They wrap around them forming an insulating envelope: the myelin sheath. Myelin is the lipid (fat) substance that surrounds and protects axons.

Physiology

These cells are lined up inside the cavities that contain the cerebrospinal fluid, a fluid that circulates in all the cavities of the central nervous system, these cavities are in relation to each other.

The ependyma is the canal located in the middle of the spinal cord, which carries cerebrospinal fluid from the cerebral ventricles.

Ependymodia are a permeable barrier between the cerebrospinal fluid and the fluid interstitial fluid in which the cells of the central nervous system are immersed.

Thanks to the beating of your eyelashes, these cells ensure the circulation of cerebrospinal fluid, also called cerebrospinal fluid.

Ependymodies provide a protective cushion for the brain and spinal cord.

For specialists in cell biology, pendimary cells are attached to each other by means of apical junctions: zonula adhaerens more particularly gap junctions. It is a layer of cells that is not completely impermeable except for the choroid plexus.

There is the presence of other structures called aquaporins. This is a variety of channels that carry water.

Ependymal cells play a particularly important role in the reabsorption secretion between the brain parenchyma (functional brain tissue) and the cerebrospinal fluid, also called cerebrospinal fluid.

Therefore, it is a set of structures that constitute a protective barrier, but also an interface between two complementary histological systems.

The neuroglia is the tissue (set of cells) that supports the nervous system. It serves, among others, the protection of neurons (nerve cell bodies).

The nervous tissue, which is the set of all the cells that make up the nervous substance as such, seems very complex. In fact, it is not, this tissue is made up of two main types of cells which are:

  • Neurons, nerve cells themselves, which have the ability to excite, produce and transmit electrical signals.
  • Gliocytes or glial cells called glial cells, are smaller, enveloping and protect neurons.

All neurons are associated with glyocytes. They do not have the property of excitability and therefore cannot transmit nerve impulses like neurons.

Repair of the cerebral ventricles

Ependymal cells are capable of closing lesions caused by mechanical lesions in the wall of the cerebral ventricles.

This observation by researchers from the Department of Medicine at the University of Freiburg offers a better understanding of the origin of certain brain diseases such as edema and hydrocephalus.

The eponymous to fight against brain injuries and diseases: Department of Medicine, Dr. Viktoria Szabolcsi Prof. Marco Celio’s research group has shown that in the brain of mice, ependymal cells are capable, thanks to their mobility, to heal mechanical injuries of the cerebral ventricles.

These cells are a particular form of epithelial tissue that covers the ventricles of the brain, the cavities of the brain that contain cerebrospinal fluid. Composed of a single layer and equipped with movable tabs, they are highly specialized and can hardly be regenerated.

They form an important barrier between the cerebrospinal fluid and the brain. As it is impossible for them to multiply, their disappearance leads to irreversible scars, cerebral edema or even ventricular enlargement (hydrocephalus).

Although ependymal cells have received increasing attention in the last twenty years, their exact role in brain damage is still largely unknown.

Healing through movement

In the mouse brain, mechanical damage to ependymal cells was found to cause overexpression of parvalbumin, a calcium-binding protein that is also expressed in specific nerve cells and fast-twitch muscles.

Parvalbumin overexpression provides increased mobility to ependymal cells, allowing rapid recovery from injury.

In mice lacking parvalbumin, this re-epithelialization process is inhibited, underscoring the role played by this protein in cell motility.

When the healing of a lesion of the ependymal layer, based on the proliferation of ependymal cells, is not possible, which increases their motility is an alternative for the repair of said damage.

The results will serve as the basis for future research on the influence of parvalbumin on cerebral edema and hydrocephalus. Furthermore, this protein could also be used as a potential marker in the diagnosis of diseases related to the ependyma.