Damaged Myelin Is Not The Cause Of Multiple Sclerosis
It is estimated that in the US alone, there are currently 400.000 people suffering from multiple sclerosis or MS. Worldwide there are more than 2.1 million diagnosed cases of multiple sclerosis. MS is a demyelinating disease (which leads to the disappearance of myelin, lipid substance that surrounds nerve fibers of the white matter) of the central nervous system, that leads to sclerosis (hardening caused by an abnormal deposition of connective tissue), appearing in the form of plates of white matter. Myelin is a soft substance that formes the nerve sheath and participates in the correct transmission of nerve electrical signals.
There are many assumptions without a scientific basis on the onset and development of multiple sclerosis and one of them, has now been proved to be incorrect by University of Zurich researchers: also known as the neurodegenerative hypothesis, the destruction of oligodendrocytes (cells that produce myelin) does not lead to multiple sclerosis.
The study which aimed to make the neurodegenerative hypothesis obsolete, was based on the fact that some patients presented some kind of myelin damage without the presence of an autoimmune disturbance. The neurodegenerative hypothesis claims that the immune system does not play a key role in triggering characteristic myelin damage and the autoimmune attack against myelin is the result and not the determining factor of the disease.
In order to prove this hypothesis wrong, scientists used mouse models in which, by altering the genetic code, they were able to damage the myelin without triggering an immune response. Myelin damage, very similar to that which can be observed in multiple sclerosis patients has not determined an MS-like autoimmune response in any mouse model. Next researchers tried to observe if an active immune defence due to a combination between infection and damage of the myelin leads to MS. The conclusion was firm: “We were unable to detect an MS-like disease – no matter how intensely we stimulated the immune system,” says Ari Waisman, a professor from the University Medical Center Mainz. “We therefore consider the neurodegenerative hypothesis obsolete.”
The term Multiple Sclerosis comes from the Latin multus plus plica meaning “fold”, and the Greek sklerosis meaning “hardening”. According to MediLexicon’s medical dictionary, Multiple Sclerosis (MS) is a “common demyelinating disorder of the central nervous system, causing patches of sclerosis (plaques) in the brain and spinal cord; occurs primarily in young adults, and has protean clinical manifestations, depending on the location and size of the plaque; typical symptoms include visual loss, diplopia, nystagmus, dysarthria, weakness, paresthesias, bladder abnormalities, and mood alterations; characteristically, the plaques are “separated in time and space” and clinically the symptoms show exacerbations and remissions”.
With MS the central nervous system (CNS) is attacked by the person’s own immune system. That is why MS is known as an auto-immune disease. The CNS includes the brain, spinal cord and optic nerves.
Nerve fibers are surrounded by myelin, which protects the nerve fibers. Myelin also helps conduct electrical signals, also termed impulses - i.e. myelin facilitates a good flow of electricity along the nervous system from the brain.
Researchers expressed their wish to continue their work and eventually find the exact cause of multiple sclerosis focusing more on the immune system and less on the brain and spinal cord.
What is myelin?
Myelin is a fatty material that coats, protects, and insulates nerves, enabling them to quickly conduct impulses between the brain and different parts of the body. Myelin also contains proteins that can be targeted by the immune system. Myelin coats the nerves of both the central nervous system and the peripheral nervous system; the destruction of the myelin in the central nervous system is what triggers many of the symptoms of multiple sclerosis (MS).
Nerve cells are coated with sections of myelin, and the tiny spaces between the sections are called nodes. As the brain sends messages through the nerves of the spinal cord, the impulses jump from node to node. Myelin prevents these impulses from escaping from the nerve at the wrong point.
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Burkhard Becher
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University of Zurich