SCHWANN CELLS: ROLE, CLINICAL SIGNIFICANCE, AND THEORY

SCHWANN CELL: AN IMPORTANT COMPONENT OF THE PERIPHERAL NERVOUS SYSTEM

Through this article, we endeavor to furnish information related to Schwann cell. We have encompassed all the details which would be helpful for you.

Information such as what is Schwann cell; their production, structure, role, and discovery have been included.

Also, for a better understanding, the difference between the Schwann cell and the myelin sheath is provided.

What is the Schwann cell?

Named after a German physiologist Theodor Schwann, Schwann Cells are derived from the neural crest.

They are the most abundant glial cells in the PNS which includes two major phenotypes – myelinating and non-myelinating Schwann cells.

They are the cells in the peripheral nervous system which are responsible for producing the myelin sheath around the neuronal axons.

They play a substantial role in the regeneration and maintenance of the sensory and motor neurons of the peripheral nervous system.

During the process of embryonic development, Schwann cells differentiate from the cells of the neural crest.

They are accelerated to propagate buy some constituent of the axonal surface.

Schwann Cells are imperative for replenishing nutrients to the exams and for the purpose of myelinating.

Myelinating enhances the axonal conduction velocity which supports the proper supply of electrical signals through the nervous system.

The non-myelinating Schwann Cells function to provide a cushioning effect to the non-myelinated axons.

They do not wrap the axons to improve conduction rather they provide trophic support to the axons.

Where are Schwann cells found?

Schwann cells are found in the Peripheral Nervous system (PNS). They regulate the formation of the node of Ranvier and the perineurium.

Also, they wrap around the Axons to form the myelin sheath. Moreover, they have a crucial role in the functioning and stimulation of the Peripheral Nervous system.

What is the structure of Schwann Cells?

Each Schwann cell constitutes a single myelin sheath on a peripheral axon, where each ensuing myelin sheath is developed by a different Schwann cell.

It is because numerous Schwann cells are needed to myelinate the length of an axon.

However, this disposition is in contraposition to Oligodendrocytes, the myelinating cell present in the central nervous system.

Oligodendrocytes form myelin sheaths for multiple surrounding axons, unlike the Schwann cells.

Schwann cells are surrounded by a basal lamina, while Oligodendrocytes are not.

Between adjoining myelin sheaths, there are gaps of approximately 1 micrometer which are called nodes of Ranvier.

The concentration of voltage-gated sodium channels is present at the node, which is the site of saltatory conduction.

Schmidt-Lanterman incisures are cytoplasmic outpouchings that interrupt compact myelin in heavily myelinated neurons.

They contain a high density of gap junctions and other cell junctions, serving a role in communication and maintenance of the Schwann cell.

Formation of Myelin sheath from Schwann cells

The plasma membrane of Schwann cells, which contains a high amount of lipid, forms the myelin sheath.

The cholesterol present in the plasma membrane is essential for assembling the myelin sheath.

Both survival and maturation of Schwann cell precursors, as well as the extent of myelination, depend on the expression of Neuregulin-type III on the axonal surface. 

Schwann cells perform the process of myelinating the axons with a large diameter that transmit electrical signals at the highest speed.

On contrary, slow-conducting axons are arranged together to form bundle-like structures, which are engulfed by non-myelinating Schwann cells.

Role of the Schwann cell

Schwann Cells have a vital role to play in the Peripheral nervous system.

Schwann Cell

The role and functions of myelinating Schwann Cells are as follows:-

  • Serves as the myelinating cells of the peripheral nervous system
  • Provide support to the cells of peripheral neurons
  • Form the myelin sheath around the inner Axon by wrapping its plasma membrane concentrically
  • The high-lipid content and cholesterol present in the plasma membrane of the cells support the assembling of the myelin sheath
  • The sheath escalates the conduction velocity and insulates the Axon segment
  • Responsible for furnishing energy metabolites to Axons
  • Play a crucial role in Axon regeneration by clearing the dead cell content and promoting its regeneration

What would happen if Schwann cells were destroyed?

In an instance of the destruction of Schwann Cells, the process which initiates the myelin sheath formation is obstructed. The insulating myelin of axon segments is also lost.

Moreover, it affects the conduction of nerve impulses down the axon which can lead to blockage as well.

The electrical conduction process is blocked as well. Also, it reduces the cushioning effect to the axons and the nerve cells which affects its functioning.

In another instance, where injury has occurred primarily to the axons, it leads to damaging the Schwann cells as well. This is called “secondary demyelination”.

Are Schwann Cells present in the Central Nervous System?

No, Schwann Cells are not present in the Central Nervous System.

In the central nervous system, Oligodendrocytes are present which performs similar functions as the Schwann cells.

However, they are different from Schwann cells to a certain extent which is discussed further.

Who discovered Schwann cells?

Schwann Cells were discovered in the year 1839 by a German Physiologist, Theodor Schwann. The cells are named after him.

The first description of the cells is found in his famous book “Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants”.

He also endeavored to grasp the origin of Schwann cells and their meaning.

His further efforts developed as a result of the cell-chain theory of the development of nerve fibres.

What is the Clinical Significance of Schwann Cells?

The clinical significance of Schwann cells can be studied in various syndromes and medical contingencies. 

Various neuropathies involve Schwann cells such as:-

  • Charcot-Marie-Tooth Disease
  • Guillain-Barre Syndrome
  • Schwannomatosis
  • Chronic Inflammatory Demyelinating Polyneupathy
  • Leprosy
  • Zika Virus

Since 2001, several clinical experiments and studies have attempted to induce demyelination in multiple sclerosis-afflicted patients.

This was done by implanting Schwann cells into the affected individual.

Various studies and experiments conducted over the past two decades demonstrated prospects for Schwann cell transplantation.

The positive results and potential of the cells paved the way for spinal cord injury therapy. The therapy could derive the regrowth and myelination of the damaged Central Nervous System axons.

Moreover, Schwann cell transplants, when studied in combination, with other therapies demonstrated efficiency in functional recovery from a spinal cord injury.

How are Schwann cells and Myelin sheath different?

Schwann CellsMyelin Sheath
Schwann Cells are special cells present in the Peripheral nervous System which forms the myelin sheath by wrapping around the Axon of the neuron cellsMyelin Sheath acts as an insulating and conduction cover surrounding the axon. It accelerates the speed of nerve impulses while travelling along the axons.
These are a variety of glial cells in the PNSThe sheath is formed of a material called myelin

What is the difference between the Schwann cell and Oligodendrocytes?

Although the function of Oligodendrocytes and Schwann cells is myelinating axons, they differ in certain ways.

Schwann CellsOligodendrocytes
Their location marks the major difference between the two.
Schwann cells are found in the Peripheral Nervous system (PNS)Oligodendrocytes are found in the Central Nervous system (CNS)
The process of myelination of Axons also differs in both.
Schwann cells wrap their body around the Axons to complete the myelinating processOligodendrocytes secrete myelin sheaths around the Axons to complete the process

Various studies are being conducted to decode the response of Schwann cells to functioning as well as nerve injury.

Prominent differences between the categorization of Schwann cell will be promoting additional future studies.

Their role in neuropathic pain and nerve injury is the major concern of study today.

The conclusions could lead to better therapeutic strategies against neuropathic pain and injuries.

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