Background
Roughly 50% of people living with multiple sclerosis (MS) experience MS-related pain. The pain is thought to arise from damage and inflammation to the central nervous system (CNS), leading to abnormal processing and/or transmission of pain-related messages from the body to the CNS. The pain can manifest in a variety of forms, such as appearing with no provocation or from a simple touch and causing hot, painful prickling sensations or muscle spasms. No matter the manifestation, MS-related pain reduces quality of life and represents an important need for people living with MS.
One promising therapeutic option that is being studied is exercise, as it has already been shown to be capable of alleviating other MS symptoms such as depression, fatigue and anxiety. A team of MS Society-funded researchers at the University of Alberta – including doctoral student Curtis Benson and Donald Paty Career Development Award recipient Dr. Bradley Kerr – set out to determine whether running exercise could mitigate both disease progression as well as pain sensitization in mice with an MS-like disorder. Their work was published in the journal Experimental Neurology.
The Study
An MS-like disorder was experimentally induced in mice. Each mouse was allowed to run for an hour every day on a running wheel, both before and after the onset of symptoms (measured as tail and limb disability). Mice were only given an hour of wheel access in order to simulate a realistic amount of exercise in the average person. How running affected the disorder’s progress, as well as pain sensitivity, was recorded over time. To measure pain sensitivity in the mice, the researchers used a standard test where they applied fibres of varying thicknesses to the rear paw and observed changes in behaviour to determine a pain “threshold”.
In the final phase of the study, researchers explored how running affected the MS-like disease on a cellular level. Using a combination of microscopy and advanced screening techniques, the authors studied the animals’ spinal cords, which are affected by MS-like lesions and are home to a pain-processing centre. The researchers assessed infiltration of immune cells into the spinal cord, nerve cell activity (higher activity suggests elevated pain processing and, therefore, elevated pain) as well as a number of factors indicating overall health of the spinal cord.
Results
Running one hour a day delayed the onset of symptoms and reduced pain sensitivity in mice with an MS-like disorder compared to mice without running access. However, running did not reduce symptom severity (tail and limb disability) once the symptoms began.
At the cellular level, running reduced the number of infiltrating immune cells throughout the spinal cord and dampened nerve cell activity in the spinal cord’s pain processing centre. Overall, running appeared to promote a healthier cellular environment in the spinal cords of mice with an MS-like disorder.
Comment
This study demonstrates that an hour of daily running can delay onset of MS-like symptoms and reduce pain sensitivity in mice. While it is difficult to make a definitive conclusion about how these results would benefit people living with MS, that the improvements were achieved with relatively moderate amounts of running make the findings extremely promising. Not only is moderate exercise generally regarded as a healthy lifestyle factor, but recent experimental evidence strongly suggests that it can offer an effective non-drug based therapeutic strategy for the treatment of various MS symptoms alongside disease-modifying therapies (read our recent update on the benefits of certain types of exercise on cognitive performance in people living with relapsing-remitting MS). Future work in the field could focus on understanding what types of exercise, including duration and intensity, should be incorporated into ongoing therapeutic regimens to best benefit people living with MS.
Source
Benson C et al. (2015). Voluntary wheel running delays disease onset and reduces pain hypersensitivity in early experimental autoimmune encephalomyelitis (EAE). Experimental Neurology. Epub ahead of print DOI:10.1016/jexpneurol.2015.05.017.