Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s disease, is a progressive neurodegenerative disorder that affects the nerve cells (neurons) that transmit electrical impulses from the brain to the muscles in the body. When the muscles don’t receive messages from the brain, they lose strength and die, leading to weakness and paralysis.
ALS progresses rapidly – people with ALS usually die within two to five years of receiving a diagnosis. Every day, two to three Canadians die of ALS.
Voluntary muscles in the body can be divided in two categories: slow and fast. Slow muscle fibres support long, sustained movements while fast muscle fibres support more spontaneous motion. Studies in humans and mice have shown that fast muscles are more vulnerable in ALS. Based on this information, researchers used a form of gene therapy to convert fast muscles in the legs of a mouse with ALS to the slow type, thereby making them less affected by the disease. Mice that received this procedure scored better on a test of motor function than mice that received a placebo-like procedure.
In addition, mice that received the procedure had 66 per cent more motor neurons in a section of their spinal cord compared with the placebo-treated mice, suggesting that the treatment helped preserve these critical neurons. Using another form of gene therapy to switch muscle in the opposite direction (from slow to fast) had the reverse effect causing mice to become impaired faster, lose more neurons, and to have increased mortality.
“While we carried out our study in mice, this study has relevance to human treatments for ALS” says Dr. Blair Leavitt, the senior investigator of the study.
“Potential treatments for ALS based on a similar gene therapy approach targeting another gene are already in human clinical trials. A major pharmaceutical company is currently developing novel gene therapy agents based on our findings that could eventually be used in human clinical trials for ALS. A similar gene therapy approach could potentially be beneficial in other disorders such as Muscular Dystrophy and Spinal Muscular Atrophy, two major causes of childhood neuromuscular disease.
“Unfortunately, this approach is still several years away, and more basic research needs to be done before of this approach can be translated into treatments for people suffering from ALS.”
This research was supported by grants from the Canadian Institutes of Health Research in collaboration with the Muscular Dystrophy Association of Canada and the ALS Society of Canada.