Five new things to know about myelin repair

Tue 25 August 2020

Dr Catherine Godbold

Last week, our Stop MS Scientific Ambassador Professor Anna Williams was part of an international team of MS researchers who published a whirlwind review of recent progress in myelin repair research. We dived in so you don’t have to…

Myelin is the fatty sheath that protects our nerves from damage and helps send messages efficiently. In MS, the immune system attacks myelin. For a recap on why repairing damaged myelin is key to stopping MS, read our webpage on myelin repair.

1. We can now see myelin repair happening on MRI scans

Most of our knowledge of myelin repair comes from experiments with cells in a dish or animals. Until recently, it was hard to observe in humans. So we didn’t know whether experimental results would be true for people with MS.

New imaging techniques let researchers pinpoint areas where myelin has been repaired in human brains.

One pilot study tested a technique to measure changes in myelin in MS lesions over several months. Myelin repair differed dramatically between people and between different lesions. Higher levels of repair were associated with lower disability scores and reduced brain shrinkage (in an area called the thalamus).

2. Old oligodendrocytes repair myelin

Our bodies naturally repair myelin. Special stem cells travel to the site of damage and turn into new myelin-making cells called oligodendrocytes.

Recently, researchers discovered older pre-existing oligodendrocytes can also repair myelin. How did they find out? By looking at after-effects of nuclear bomb testing in the middle of the last century.

This technique has already advanced our understanding in lots of different areas of medical research. Concentrations of a molecule released into the atmosphere match concentrations in our DNA. By measuring the level in different cells, you can work out their age. Tissue from people with MS showed lots of older cells.

We don’t know to what extent old vs. new oligodendrocytes repair myelin. Research has focussed on ways to help stem cells turn into new oligodendrocytes. Now researchers can explore how to help older oligodendrocytes repair myelin more effectively too – opening up another avenue for potential treatments.

3. More electrically-active nerves get preferential treatment

Over a decade ago, researchers discovered that using toxins to block or stimulate electrical activity in nerve cells in a dish affected their myelin.

Recently we’ve seen that actively stimulating electrical activity increases myelin on nerves in mice. And in zebrafish, myelin sheaths are more likely to form around nerves with more electrical activity.

Although we don’t yet know what causes this link between electrical activity and myelin repair, it could offer an exciting new route for treatment.

4. Immune cells aren’t always the bad guys

In MS, different types of immune cells contribute to myelin damage. The chief culprits are white blood cells called T and B cells. Other cells, like macrophages and microglia, have also been implicated.

But researchers believe some immune cells actually help repair myelin. Mice without certain types of T cell show less myelin repair than healthy mice. Putting white blood cells from people with MS into areas of damaged myelin in mice can promote myelin repair.

And we know there’s an important role for macrophages in clearing away debris left over from attacks.

5. Thirteen myelin repair drugs have made it to phase II trials

Researchers have identified numerous new and existing drugs with the potential to boost myelin repair, ranging from steroids to antifungals. Thirteen of these have made it to phase II clinical trials, with varying results.

So far, only a few trials have involved people with MS. Most focussed on optic neuritis, and we don’t know how whether those findings will be true for other areas of the brain.

But trials that have included people with relapsing MS have reported some improvements on MRI scans, like fewer lesions and reduced brain shrinkage. And more drugs are being discovered, like metformin, the diabetes drug that mimics the effect of fasting.

We’re supporting world-leading research into myelin repair for MS. This includes funding two dedicated centres of excellence and dozens of individual projects around the UK.

Discover more about myelin repair research