Multiple sclerosis is an autoimmune disease, a condition in which the body’s immune system attacks the body’s own tissues. The immune system attacks are directed at the central nervous system (brain and spinal cord) — specifically at myelin, a substance that serves as a protective covering for nerves. This is why MS is also known as a demyelinating disease. The damage to the myelin sheath can cause symptoms of MS such as muscle weakness, numbness, and vision problems.
What role does myelin damage play in the MS disease course? To learn more, MyMSTeam talked to Dr. Barry Singer, director and founder of The MS Center for Innovations in Care at Missouri Baptist Medical Center in St. Louis. His award-winning MS website, MS Living Well, started in 2007 and has been a valuable resource in more than 190 countries. He is also the host of the MS Living Well Podcast, including the episode “Remyelination: Repairing Multiple Sclerosis.”
Myelin protects axons in the CNS. Axons are extensions of individual neurons (nerve cells), which allow them to communicate with other cells. Most axons are protected by myelin, similar to how electrical wire is protected by its coating.
The normal transmission of nerve signals allows our bodies to carry out normal functions without our having to think about it. This includes seeing, hearing, and controlling our bodily functions.
Researchers believe that in MS, the immune system responds abnormally, producing inflammation in the CNS. This inflammation then damages both myelin and oligodendrocytes, the cells that create myelin.
Myelin damage in MS can result in lesions and scar tissue on nerves, which can slow or even stop nerve signals from reaching the rest of the body. This can cause MS symptoms.
People with MS most often have a relapsing-remitting disease course, in which they experience periods of new or worsening symptoms (called flares), alternating with periods of remission, when symptoms fade or disappear. Another type of disease course is progressive. This type of MS worsens gradually over time without periods of remission.
Although there’s evidence that suggests demyelination plays a role in how MS progresses, some researchers argue that more research is necessary to know for certain. Myelin plays an important role in keeping axons healthy. Loss of myelin may make neurons more vulnerable to injury over time, leading to progressive disease. When a person loses axons more quickly than their CNS can compensate for the damage, they may transition from relapsing-remitting MS to progressive MS.
Some DMTs have shown that they’re capable of protecting the brain from further damage and shrinkage, Dr. Singer said. Although a degree of brain shrinkage is an inevitable part of getting older, MS can speed up the process. DMTs could help guard against that shrinkage, Dr. Singer noted. DMTs can also prevent new relapses.
“They prevent disability progression over time, so a group of people on a placebo would progress more rapidly than people on a drug,” he said. “They prevent future disease activity.”
Although DMTs show promise, they cannot reverse MS: People who’ve lost function due to MS won’t get it back through the use of DMTs, Dr. Singer added. “Unfortunately, these disease-modifying therapies aren’t going to bring back old function,” he said. “They are not repair drugs.”
Dr. Singer added that some people who take these drugs have difficulty sticking to their treatment. Some people who start taking these drugs stop when they don’t see a reversal in their symptoms because they assume the medications aren’t working. However, it’s vital that people with MS understand that these medicines are meant to prevent future damage, not reverse existing symptoms by creating new myelin, he said. A 2022 study found that people with MS who stuck with their treatments had a significantly higher life expectancy than those who did not.
“Unfortunately, we do have patients as they age who have had a lot of disease in their spinal cord or brain, and they start to have cognitive problems and more balance problems,” Dr. Singer said. “They feel like they’re getting worse despite treatment — but I think off of disease-modifying therapies, things may be getting worse a lot faster.”
Dr. Singer explained that in addition to taking DMTs, people with MS can do things on their own to keep their physical and cognitive states as sharp as possible. He recommends:
All of these activities have proven benefits. “Brain health is really important,” Dr. Singer said. “Exercise has been shown to help keep your brain reserves healthy.”
He also recommended that anyone with MS should quit smoking, which damages both physical and cognitive abilities. Researchers have found that smoking can have a negative impact on the course of MS progression.
Research laboratories and leading MS centers are continually studying ways to repair damaged myelin, a process called remyelination. No remyelination treatments are ready for approval by the U.S. Food and Drug Administration (FDA), according to Dr. Singer, but scientists continue to work toward creating effective remyelination treatments for people with MS.
“We’re looking at antibody therapies [and] oral therapies, so we’re hopeful that one day we’ll be able to have remyelination treatment,” he said. “In the animal models, you can see when you get these experimental treatments, they turn on myelin production and actually can recoat the nerves.”
Oligodendrocytes wrap around nerve cells and create myelin, Dr. Singer said, noting that in people with MS, 5 percent to 8 percent of the brain and spinal cord cells are immature oligodendrocytes, lying dormant (not active). The goal is to turn on these cells, allowing them to mature so they can be recruited into the MS plaques.
Future remyelination treatments aim to activate these oligonucleotides, thereby preventing further bodily degeneration and progression of MS, and — perhaps someday — restoring or improving function in those living with MS.
“I’ve been involved in a number of clinical trials,” Dr. Singer said, referring to research studies that test the effectiveness and safety of potential treatments. “My center has been a site for five early phase 1 and 2 clinical trials using antibodies for myelin repair that unfortunately didn’t work.”
Dr. Singer remains optimistic and determined. He is planning future trials with new compounds. Large phase 3 trials would be the next step to prove a treatment is safe and effective.
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