In multiple sclerosis, misdirected immune cells damage the sheaths of the nerve cells in the brain. Researchers claim they have discovered a naturally occurring mechanism that can be used to improve the repair of the myelin sheaths.

MS is an inflammatory autoimmune disease of the central nervous system. In most cases, MS progresses in relapses, which occur irregularly as excessive inflammatory reactions in the spinal cord and brain. In the process, misdirected immune cells destroy the protective myelin sheaths of the nerve fibers and thus damage the nerves.

It is true that the nerve fiber sheaths can be partially restored by the body's own repair processes. But this spontaneous remyelination usually proceeds incompletely in MS patients or fails to occur at all. To date, there is no drug that promotes this repair. 

Sugar compound activates immune cells of the brain

In addition to their work as "trash collectors" for the removal of damaged cells and foreign bodies, the microglia cells of the brain also take on tasks for the immune response and constantly look for signs of injury or infection. If there is a problem, the microglial cells are activated and release cytokines and other signaling molecules. This attracts other immune cells such as T and B cells, which normally reside outside the brain. 

The body's own sugar compound polysialic acid plays a crucial role in the activation of microglia. Researchers from the Department of Neurology with Clinical Neurophysiology and the Institute of Clinical Biochemistry at the Hannover Medical School, in Hannover, Germany, said the microglia has an immune receptor called Siglec-E that recognizes polysialic acid. If the sugar molecule binds to the receptor, the microglia cells switch from the state "proinflammatory" to "anti-inflammatory." This regulatory mechanism can apparently also be controlled from outside. 

By externally adding polysialic acid to cultures with living tissue sections, the researchers were able to show that previously destroyed myelin sheaths were almost completely renewed as a result of an anti-inflammatory effect of polysialic acid on the microglia. 

Programming key cells for healing

The destruction of the myelin sheaths and nerve cells has serious consequences that can affect all brain and spinal cord functions – mainly the ability to move and coordinate, the sense of touch, and the ability to see. Activating the self-healing powers in the brain would be a promising support in MS therapy, which currently focuses exclusively on the immune system outside,

Researchers admit, however, the studies on the tissue section cultures have only limited significance. They are optimistic based on the results that myelin regulation also works in the living organism. Researchers said the advantage is that the Siglec-E receptor in the brain actually only sits on the microglia cells and the polysialic acid can therefore intervene there in a very targeted way. Next, the research team would like to test the results in the animal model of MS.

The results are published in the journal Frontiers in Cellular Neuroscience.