Myelin is the fatty substance protecting nerve endings, and is damaged and lost due to MS. A store of stem cells in the brain produces oligodendrocyte precursor cells (OPCs) which travel to areas of damage, become oligodendrocytes and produce new myelin.
When someone has MS, this repair process doesn’t work, and remyelination doesn’t take place. Scientists aren’t sure if this is because the fault is with the OPCs, or if the lesion environment prevents myelin regrowth, or both.
They investigated by making induced pluripotent stem cells (iPSCs) from the skin of three people with MS, and three healthy controls. The researchers then matured these cells to become OPCs and grafted them into the forebrain of mice which didn’t have myelin or a functional immune system.
The grafted cells spread through the mice’s brains, and matured into oligodendrocytes. This led them to conclude the inability of MS patients to regrown myelin was not down to the cells themselves, as these introduced cells would have had no effect on the mice.
No differences were observed in the behaviour of cells from MS patients and those from healthy people. Both produced myelin along the nerve fibres, including that of the brain and spinal cord. The mice’s brains became denser with myelinated axons, allowing electrical nerve impulses to travel at faster speeds than in those mice whose brains had not been grafted with cells.
Researchers say this means cells introduced this way may produce new myelin and remain stable over time, and that it is environmental factors, not OPCs, that are responsible for the lack of myelin regrowth seen in MS. They hope that further research may help them understand if iPSCs taken from the cells of people with MS might be a source of cells for myelin repair therapy in the future.
Source MS-UK 16 December 2020