Scientists at the Technical University of Munich discovered that the characteristic patterns of the myelin layer are determined at an early stage, but these patterns can be adjusted as needed in a process controlled by the nerve cells themselves. The authors said that if the role of the axons in myelin generation and remodeling can be understood, it may offer new approaches to controlling it. That would be relevant for the treatment of multiple sclerosis.

The team used newly developed markers to visualize the formation of myelin segments surrounding axons in the spinal cord of zebrafish. They found that characteristic patterns made up of myelin segments with different lengths along an axon are defined within a few days after myelin formation begins. Although the segments continue growing from that time onward – as the body of the zebrafish grows – the pattern remains preserved.

Following this observation, the researchers destroyed selected segments. They discovered that after the destruction of the segments, the myelin sheaths began to dynamically remodel. In the end, the damage was repaired and in most cases the original pattern was restored. The regeneration followed a fixed sequence: First, the adjacent segments expanded to close the gap, then a new segment then formed between them, and they contracted to their original size.

For researchers, this raises an important question: What controls the emergence and the restoration of the segment pattern? The team said that observations suggest that it is not the oligodendrocytes – the cells that form myelin – that decide where it is formed, but rather the axons.

Results of animal model studies sometimes do not translate to humans and may be years away from being a marketable treatment. However, the researchers are now studying how the segment patterns are affected by the targeted stimulation of nerve cell activity and by the neurotransmitters released as a result.