Find offers hope for treating MS

A discovery that ageing nerve fibres can be rejuvenated by young cells may have important implications for treating multiple sclerosis (MS), scientists have said.

MS occurs when the immune system destroys myelin, the fatty insulating layer that protects nerve fibres in the brain and spinal cord. Symptoms can range from mild numbness and tingling to vision loss and crippling paralysis.

Early in the disease, the myelin can repair itself to some extent and maintain normal nerve function. However as the patient ages, this ability - known as remyelination - is increasingly lost, making treatment much more difficult. Less myelin is restored until nerve fibres are permanently destroyed.

The new study on mice shows that the age-associated decline of remyelination can be reversed. When old mice were exposed to immune cells taken from the blood of young mice, the myelin covering their spinal cord nerve fibres began to regenerate.

The discovery could pave the way to new therapies for MS, according to the British and US scientists whose work is reported online in the journal Cell Stem Cell.

Professor Robin Franklin, director of the MS Society's Cambridge Centre for Myelin Repair at Cambridge University, said: "What we have shown in our study... is that the age-associated decline in remyelination is reversible.

"We found that remyelination in old adult mice can be made to work as efficiently as it does in young adult mice. For individuals with MS, this means that in theory regenerative therapies will work throughout the duration of the disease."

In the study, small patches of spinal cord myelin were artificially destroyed in old mice, mimicking the effects of MS. Those areas were then exposed to "macrophage" immune cells taken from the blood of young mice.

The immune cells helped resident stem cells to manufacture new myelin and repair the damage. This was partly the result of the macrophages clearing away myelin debris caused by the original injury. Previous studies have shown that such debris impedes the regeneration process.

US author Dr Amy Wagers, from Harvard University in Boston, said: "Ageing impairs regenerative potential in the central nervous system. This impairment can be reversed, however, suggesting that the eventual development of cell-based or drug-based interventions that mimic the rejuvenation signals found in our study could be used therapeutically."