Stem Cell therapy at stem cells 21

Status of Stem Cell Therapy for Multiple Sclerosis

About Multiple Sclerosis (MS)

Multiple Sclerosis, with an incidence of 100 in 100000 in the US and Europe, is by far the most frequent neurodegenerative disease (1). MS is a chronic, demyelinating disease of the brain and spinal cord - collectively the central nervous system (CNS). Demyelination is a process of gradual destruction of the myelin sheath, that surrounds many of the axons of nerve cells (neurons), leading to axonal injury or loss and consequently severely impaired nerve signals. The disease is named for the multiple scleroses (scars or plaques) that are created on the myelinated axons. A repair mechanism - remyelination of the axons by cells known as oligodendrocytes - takes place in the early phases of disease but the reformed myelin sheaths are thinner and less effective. Repeated attacks lead to fewer effective remyelinations until a scar is built up on the damaged axon. The central nervous system should be able to recruit oligodendrocyte stem cells but something would seem to inhibit stem cells in the affected areas.

Electron micrograph showing branched oligodendrocytes with processes extending to several underlying axons

One oligodendrocyte wraps myelin around axons of several neurons

It is generally accepted that MS is an inflammatory autoimmune disease - whereby an individual's own immune response attacks the nervous system. Certain viruses, bacteria, stress and genetics have been implicated in disease manifestations. MS causes a variety of symptoms depending on where in the CNS the multiple lesions occur. Also, neurological deficits are progressively accumulated. In any individual there may be several complicating factors affecting the unpredictable course of the disease - there may be times of dormancy or times when there is steady progression.

The disease is categorised by several subtypes:
Relapsing remitting MS: unpredictable relapses (attacks) followed by months to years of remission. Effects of attacks may either resolve or may be permanent.
Secondary progressive MS: characterised by neurologic decline between attacks without periods of remission. Most common type of MS and causes most disability.
Primary progressive MS: decline occurs continuously without clear attacks, no remission.
Progressive relapsing MS: steady neurologic decline from onset, patients suffer superimposed attacks. Least common.

While MS does not currently have a cure, there are several treatments available for moderating the symptoms and for managing the various consequences of attacks. The currently approved treatments are aimed at returning function after an attack and preventing disability.

MS Treatment Objectives - the way forward: A Role for Stem Cells

During multiple relapses in the course of MS, oligodendrocytes and their progenitors are lost(2) and the nervous system has only limited capacity to recover from this extensive neuronal or glial damage. This is partly due to the formation of barriers, known as "glial" scars, which are triggered by the body to protect the injured nerve tissue from further injury. This dense scar tissue throws up a blockade to foreign cells, including transplants meant to heal and regenerate (group at Harvard medical school). There is evidence, however, that the adult CNS retains populations of cells with stem cell-like properties that have extensive proliferative capacity (3).