If you or someone you love has multiple sclerosis, you probably know a bit about myelin.
The human body needs to protect its crucial nerve cells, so it surrounds them in a material called myelin. Disease like multiple sclerosis strip away this myelin sheath, reducing the effectiveness of nerve cells. Scientists have known that for a while, but there was still information missing. Researchers at Technical University of Munich observed, for the first time ever, the formation of the myelin sheath in real time. Keep reading to learn more, or follow the original story here.
Scientists refer to nerve fibers as axons. The body naturally coats these axons in myelin. Myelin acts similarly to the insulating layer of an electrical wire. Removing insulation, such as what occurs in cases of multiple sclerosis, severely hinders the transmission of signals.
Unlike electrical insulation, myelin does not form a seamless layer over axons. Myelin forms in segments across the nerve cell. The segments exist in various lengths, and gaps called nodes of Ranvier exist between them.
The nervous system functions properly as a result of both the myelin itself and the spacing of these gaps.
When myelin is destroyed, the human body has some ability to repair it. Dr. Tim Czopka, a neuroscientist at Technical University of Munich (TUM), led the first real time tracking of the myelin rebuilding process. Dr. Czopka’s team used newly developed indicators to follow the formation of myelin in the spinal cord of zebrafish.
The team reached the following conclusion: the identifiable pattern of myelin segments are outlined within a few days of when myelin begins to form. The segments grow as the zebrafish does. The patterns segments follow, however, remain fixed.
Next, the research team erased certain segments of myelin.
“What happened next surprised us,” says Dr. Czopka. “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 myelin rebuilds in a predictable pattern. Nearby segments first extend themselves to bridge the gap. Once a new segment has been created between them, the original segments shrink back to recreate necessary gaps.
The next question demanding to be answered is what controls the restoration process– what kicks it off? Dr. Czopka does not believe oligodendrocytes – myelin forming cells – are responsible. More likely, it seems axons themselves are in control of the process. “You could say that they know best which pattern is needed for the signals to be transmitted at optimal speed,” says Dr. Czopka.
Now, Dr. Czopka’s team studies how the myelin segment formation is influenced by the targeted stimulation of nerve cell activity and by the neurotransmitters released as a result.
“If we can understand the role of the axons in myelin generation and remodelling, it may yield new approaches to controlling it,” Dr. Czopka explains, “That would be relevant for the treatment of illnesses such as multiple sclerosis.”