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What Is Myelin?

New Hope in Myelin Repair

Stem cell therapies show early successes in lab models. 

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In this article

Overview of myelin and multiple sclerosis

Myelin is a fatty substance that surrounds and insulates axons (or nerve fibers) much as insulation does an electrical wire. It is an electrical conductor composed mostly of lipids, water and proteins.

Myelin is present in the central nervous system and peripheral nervous system. However, only the central nervous system is affected by multiple sclerosis. Central nervous system myelin is produced by special cells called oligodendrocytes.

Myelin sheath function

The coating of myelin around axons is often referred to as a “myelin sheath.” The myelin sheath protects the axons and helps speed nerve transmissions. If the myelin sheath is damaged, these nerve signals will travel more slowly or be blocked completely.

Abnormal immune response and multiple sclerosis

Our immune systems are responsible for protecting our bodies from infection. In MS, something triggers the immune system to attack the central nervous system. This attack produces inflammation and:

  • Damages or destroys myelin and oligodendrocytes (a process referred to as demyelination)
  • Causes damage to the axons
  • Produces damaged areas (lesions or scars) along the nerve, which can be detected on magnetic resonance imaging (MRI)
  • Slows or halts nerve conduction — producing the neurologic signs and symptoms of MS

Diagram of normal nerve versus MS-stricken nerve

Learn more about what causes MS.

Research efforts underway to stimulate myelin repair

Scientists have discovered that the body heals some lesions naturally by stimulating oligodendrocytes in the area — or by recruiting young oligodendrocytes from further away — to begin making new myelin at the damaged site. However, this natural repair process is slow and incomplete. Scientists are investigating several different strategies for stimulating the repair of myelin. They are testing existing drugs and finding ways to stimulate oligodendrocytes to produce myelin. In addition, they are researching ways to protect oligodendrocytes and myelin from further damage.


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