The myelin layer (concentric) surrounds the axon of a neuron: Wikimedia CommonsMultiple sclerosis is an inflammatory (auto)immune-mediated disease in which the patient’s immune system destroys the protective sheath (called myelin) that envelops and protects the nerves. As a result, the flow of information in the brain and spinal cord is interrupted. Ultimately, the actual nerve cells are affected and die. Patients with multiple sclerosis show a variety of symptoms involving the central nervous system, including spasms, difficulty walking, bladder and bowel problems and fatigue.

This BBC news clip explains what happens in MS, and outlines one stem-cell-based approach to developing a treatment for the disease.

There are two concurrent components to any successful therapeutic approach to multiple sclerosis:

1. to prevent damage to the central nervous system by interfering with inflammation caused by the immune system’s attack on the nerves;
2. to repair the existing damage.

Stem cells are potentially useful in both components. Clinical trials have been carried out in which patients have received intensive immunosuppressive treatments followed by transplants of blood stem cells from their own bone marrow or blood. These trials aimed to block the autoimmune reaction that causes myelin and nerve damage, and they have shown some benefits: a proportion of patients did not progress in the disease, although some showed no improvement and others regressed.

Research using animal models has shown that it is possible to promote repair of the myelin (remyelination) surrounding damaged nerves by transplanting very young ensheathing cells (so-called precursor cells), made from embryonic stem cellsⁱ or adult neural (brain) stem cells. This myelin repair can be either direct or indirect. Direct myelin repair involves differentiation of stem/precursor cells into myelin forming cells. Indirect remyelination is mainly due to a ‘bystander’ effect of the stem/precursor cells, in which the cells release molecules capable of suppressing inflammation, providing support for the development and growth of nerves, promoting the formation of new blood vessels, and/or reducing nitric oxide-mediated nerve damage.

Apart from stem cell transplantation, scientists know that in the early stages of multiple sclerosis the existing myelinating cells are able to offer some spontaneous remyelination. An important area of research is focused on finding ways to enhance remyelination from these cells.

Relevant links:
The European Multiple Sclerosis Platform
The Multiple Sclerosis Society
Multiple Sclerosis Trust
The National Insitute of Neurological Disorders and Stroke