Remyelination in Multiple Sclerosis: Progress and Therapies

Remyelination is the process of repairing myelin in MS. The erosion of myelin reduces the speed of nerve signal delivery. While there is no cure for MS, remyelination therapy could offset progression.

Multiple sclerosis (MS) is a neurological condition where the body’s own immune system attacks myelin, a fatty tissue that wraps around nerve cells. Myelin protects the nerve cells but, more importantly, it acts as “insulation”.

Like the covering on an electrical wire, this insulation prevents outside signals from getting in and the signals inside from getting out. This allows the signal traveling through the neuron to reach its destination loud and clear.

When the myelin gets damaged, the nervous system cannot function properly. Leading to a wide range of symptoms including:

• mood imbalances
• cognitive problems
• issues related to movement and balance
• gait challenges

Previously, doctors believed that damage to the nervous system, including multiple sclerosis, could not be healed. Once the damage was done, it was done forever. However, more recently, researchers are finding that the nervous system could slowly be restored. That includes the restoration of the myelin sheaths around the nerve cells.

This process is called “remyelination.” It is thought to be a natural process that the body uses to shore up and repair injury or wear-and-tear on the myelin sheaths.

Early Thoughts

Remyelination has been seen in the spinal cord and other parts of the nervous system, and appears to restore the myelin sheath to a healthy condition (or has the potential to do so). A major issue in MS is the scar tissue that grows as a way to try to compensate for the damaged myelin. This scar tissue is very non-conductive and makes it difficult for the nervous system to function properly. With remyelination, this does not appear to be the case.

There is a lot we do not know about remyelination – what triggers it, what increases it, and how it can be induced. As our understanding  of this healing process grows, we will be better able to make remyelination happen through specific therapies. Potentially, further study could lead to other treatments for MS as well.

Here is what we know so far:

How Does Remyelination Work?

We don’t know what triggers remyelination. But, cells – possibly immature oligodendrocytes (oligodendrocyte progenitor cells, or OPCs) – detect the damage and begin the process of repairing the myelin.

These cells are important. They produce myelin in the nervous system and the brain, as well as having many other important neurological functions. Remyelination is complicated — the body has to produce many different building blocks of myelin, including lipids (fats) and cholesterol. They also need to be put together properly and arrayed on the neurons. 

What we do know is that remyelination appears to be a constant process. The only way to see it, when it is active, is to slow down and reduce the de-myelination.

Immune system suppressing or inflammation-reducing drugs, alongside stress-reduction techniques, stop the damage being done to the myelin and allow the recovery to take a better hold. This makes treatment more than just holding back the flood – it is important to healing.

Myelin Production

The remains of damaged myelin prevent the repair of the myelin. In MS, these scraps are not properly cleared out by macrophages and other immune system cells. When treated with the right medications, the immune system is better able to do its actual job.

Myelin production is also affected by age. As people get older, these repair processes are less effective. Also, the longer that someone has lived with MS, the less effective the remyelination is. Nervous system activity, however, encourages remyelination. So, keeping the brain and nervous system active and stimulated is important to recovery.

Current treatments for MS are imperfect; the damage is still being done. This means that remyelination is slow and may be easily overwhelmed by inflammation. Ideally, MS treatments would include some form of medication or therapy that stimulates remyelination.

Future Therapies for Remyelination

Immunomodulatory medications, anti-inflammatories, and other medications used to combat autoimmune diseases such as MS might also help with remyelination. When the immune system is working properly, it may actually encourage healing instead of hindering it.

Ocrelizumab (Ocrevus) is a medication used to treat MS. More specifically, it is a monoclonal antibody. Monoclonal antibodies, which are designed to turn the immune system on its own misbehaving cells, are an especially promising therapy for MS. These antibodies are capable of crossing the blood brain barrier and targeting the MS damage. And have been approved by the US Food and Drug Administration for trials. Ocrelizumab requires an IV injection. It also comes along with several severe side effects and reactions.

Bexarotene, a retinoid, is a cancer drug that stops the growth of cancer cells. Because the immune system is also a rapidly growing and dividing cell-type, it can be used to treat autoimmune diseases by suppressing the immune system. This may give a person with MS some space to repair their neurons, though it comes with the cost of a suppressed immune system. This suppression leaves people vulnerable to illness and infection.

Future therapies might also target how the oligodendrocyte cells process cholesterol. Certain treatments might encourage these cells to be more active, and thus more regenerative. Most of these therapies are still under research, or undergoing early clinical trials. These include stem cell therapy and oral antihistamines (used for allergies.) These therapies are hints to a promising future for remyelination treatments.

In either case, it is a bright future – and more therapies for remyelination may soon be found.