New research offers hope for new treatments for multiple sclerosis

Parliamentary Yearbook reports on the new research led by scientists at the University of Edinburgh and the University of Cambridge which may help to develop a treatment to repair nerve damage in multiple sclerosis. The research identifies the important role of immune cells, called macrophages, in the regeneration of the myelin sheath.

Nerve cells have extremely long thin nerve fibres which transmit impulses between distant parts of the body, enabling normal body function. A fatty layer called the myelin sheath insulates each nerve fibre in the brain and spinal cord.  This protective layer speeds up the transmission of electrical impulses as they pass along nerve fibres to and from the brain.  At certain intervals, the myelin layer is interrupted creating what is called “a node of Ranvier”.  These nodes in the myelin sheath have a vital function in speeding up the transmission of signals or impulses to and from the brain.  Rather than travelling the entire length of nerve fibres, electrical impulses travel from node to node. This enables nerve fibres to conduct signals at tremendous speeds in excess of 100 metres per second.

If the myelin sheath is inflamed, damaged or destroyed, nerve fibres are unable to transmit impulses efficiently. The transmission of impulses gets slower - as the impulse has no alternative but to travel the entire length of the nerve fibre - or stops.  In MS, the immune system attacks the myelin sheath causing it to becomes damaged.  At the same time, a natural process (called remyelination) in which cells called ‘oligodendrocytes’ repair myelin damage gradually fails.  Consequently, the transmission of nerve signals becomes disrupted in the way described which in turn causes impairment in sensation, movement, cognition or other functions depending on which nerves are involved. 

Currently, there are few treatments to suppress the immune system from causing further damage and no treatments which can repair the damage done.

Driven by the lack of therapies for progressive MS, the MS Society in the UK, the Wellcome Trust and the MS of Canada has funded this latest research.  Led by the University of Edinburgh and the University of Cambridge, the research investigated the regenerative process of remyelination in samples of brain tissue from humans with MS and in mice.

The researchers studied immune cells - called macrophages - known to be involved in remyelination.  They found that macrophages were found at higher levels when myelin regeneration was working well.  In addition, they identified that these important immune cells played a vital role in triggering remyelination. The macrophages released a protein called activin-A which stimulated oligdendrocytes to make myelin.

The study’s results suggest that studying macrophages and activin-A might lead to the development of regenerative therapies for multiple sclerosis.  Further research is planned which looks at how activin-A can be released artificially and whether its effects can be enhanced.

 A statement by the first author, Dr Veron Miron, from the Medical Council Centre for Regenrative Medicine at the University of Edinburgh, said:  “Approved therapies for multiple sclerosis work by reducing the initial myelin injury - they do not promote myelin regeneration. This study could help find new drugs to enhance myelin regeneration and help to restore lost functions in patients with multiple sclerosis.”

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