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Old cells repair damage in the brains of MS patients

Jonas Frisén

A new study shows that there is a very limited regeneration of cells in the brain of patients diagnosed with multiple sclerosis (MS).

The disease progression in MS usually fluctuates between periods of deterioration and periods of remission. Studies in mice have shown that damaged myelin can be reformed, and that this requires generation of new oligodendrocytes that make the myelin. It has been assumed that periods of remission in MS patients are caused by newly formed oligodendrocytes replacing the lost myelin. But in this study, a research group from Karolinska Institutet has been able to show that there is no regeneration of oligodendrocytes in MS patients in those areas where the myelin seems to have been reformed. Instead, it appears as if old oligodendrocytes that have survived the attack from the immune defence are able to form new myelin.

“We were highly surprised that humans proved to be so different from the animals that have been studied. In humans, there is very limited regeneration of oligodendrocytes, but they seem to have a greater capacity to contribute to repair,” says Jonas Frisén, Professor at the Department of Cell and Molecular Biology at Karolinska Institutet, who led the study.

The importance of treating MS aggressively at an early stage

These new findings indicate the importance of treating MS aggressively at an early stage of the disease progression, in order to prevent the loss of oligodendrocytes.

“Since few oligodendrocytes are formed, it is important to save the ones you have as they can repair the damage caused by the disease,” says Jonas Frisén.

To determine the age of the oligodendrocytes in the MS patients, the researchers measured the amount of the isotope carbon-14 from nuclear detonations during the cold war, which was stored in the cells’ genome, i.e. the DNA. Since the detonations ceased, there has been a gradual decrease of carbon-14, which acts as a type of date mark for when the cells were formed. This method of determining the age of a cell was developed by Jonas Frisén’s team in the early 2000s.

The results are published in the journal NatureAnother paper is also published simultaneously in Nature, from Associate Professor Gonçalo Castelo-Branco’s group also at Karolinska Institutet, arriving at overlapping conclusions, with a different methodology.

 

Photo of Jonas Frisén, Professor The Department of Cell and Molecular Biology, Karolinska Institutet: Stefan Zimmerman