What is Myelin?

Neurons are the structures in the nervous system that allow us to think, see, hear, speak, feel, eliminate (bowel/bladder) and move. Each neuron is made up of a cell body and an axon (the extension of the cell body that carries messages). Most of the axons in the central nervous system are wrapped in myelin, a substance rich in lipids (fatty substances) and proteins. Like the coating around an electrical wire, myelin insulates and protects the axon and helps speed nerve transmission.Myelin is present in the central nervous system (CNS) and peripheral nervous system (PNS); however only the central nervous system is affected by MS. CNS myelin is produced by special cells called oligodendrocytes. PNS myelin is produced by Schwann cells. The two types of myelin are chemically different, but they both perform the same function — to promote efficient transmission of a nerve impulse along the axon.

In MS, an abnormal immune system response produces inflammation in the central nervous system. This process:

• Damages/destroys myelin and oligodendrocytes
• Causes damage to the underlying nerve fiber
•  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

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, including testing existing drugs, finding ways to stimulate oligodendrocytes to produce myelin, and ways to protect oligodendrocytes and myelin from further damage.