How do I repair myelin

Psychiatry, psychosomatics & psychotherapy

19.02.2018

Formation and repair of the myelin layer around nerve fibers examined "live" for the first time

The extensions of nerve cells are surrounded by a myelin layer. A team from the Technical University of Munich (TUM) observed for the first time "live" how it is formed and how damage is repaired. It was found that characteristic patterns of the myelin layer are established early. If necessary, however, they can adapt, presumably controlled by the nerve cells themselves.

The myelin sheath around nerve cell extensions (axons) can be compared to the insulation around electrical cables. Myelin shields the axon and makes the rapid transmission of electrical signals possible in the first place. If the insulation is damaged, for example in diseases such as multiple sclerosis, it can lead to severe failure symptoms.

Myelin segments determine transmission speed

However, the myelin does not form a continuous tube around the axon, but is divided into segments. These can be of different lengths and are each separated from one another by so-called Ranvier lacing rings. In the complex network of the central nervous system, it is not a matter of making all connections as quickly as possible. What is more important is the fine-tuning: impulses have to be in the right place at exactly the right time. How fast information is transmitted through an axon is also influenced by the number and length of the segments.

Patterns remain stable

The bodies of humans and animals are at least partially able to repair damaged myelin sheaths. Dr. Tim Czopka, neuroscientist at TUM, observed this process “live” for the first time. Using specially developed marker substances, he and his team were able to make visible how myelin segments are formed around axons in the spinal cord of zebrafish. They found that characteristic patterns with myelin segments of different lengths along an axon are established within a few days after the onset of myelin formation. After that, the segments continue to grow - after all, the body of the fish also grows - but the pattern is retained.

In the next step, Tim Czopka and his team deliberately destroyed individual segments. “We had a surprise,” says Czopka. “After the destruction, the myelin layer began to change dynamically. In the end, the damage was repaired and in most cases the original pattern was restored. ”The reconstruction followed a fixed scheme: First, the neighboring segments expanded, as if to close the gap. Then a new segment grew between them and they shrank back to their original size.

Axons affect segmentation

This leads to an important question: Who controls the creation and restoration of the segment pattern? "Our observations suggest that it is not the myelin-forming cells, the oligodendrocytes, but the axons that determine where myelin is formed," says Tim Czopka. "You could say that they know best which pattern is needed for the ideal transmission speed."

He and his team are currently researching how segment patterns change as a result of specifically triggered nerve cell activity and the messenger substances released in the process. “If we understand the role of the axons in myelin regeneration, new approaches to control them could emerge,” explains Czopka. "That would be relevant for the treatment of diseases such as multiple sclerosis, for example."

Publication: F. Auer, S. Vagionitis, T. Czopka, “Evidence for Myelin Sheath Remodeling in the CNS Revealed by In Vivo Imaging”, Current Biology (2018). DOI: 10.1016 / j.cub.2018.01.017.

Full text (Open Access):
http://www.cell.com/current-biology/fulltext/S0960-9822(18)30019-8

Source: Technical University of Munich on idw