Regular Exercise Prolongs Survival in a Type 2 Spinal Muscular Atrophy Model Mouse

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Abstract
Several studies indicate that physical exercise is likely to be neuroprotective, even in the case of neuromuscular disease. In the present work, we evaluated the efficiency of running-based training on type 2 spinal muscular atrophy (SMA)-like mice. The model used in this study is an SMN (survival motor neuron)-null mouse carrying one copy of a transgene of human SMN2. The running-induced benefits sustained the motor function and the life span of the type 2 SMA-like mice by 57.3%. We showed that the extent of neuronal death is reduced in the lumbar anterior horn of the spinal cord of running-trained mice in comparison with untrained animals. Notably, exercise enhanced motoneuron survival. We showed that the running-mediated neuroprotection is related to a change of the alternative splicing pattern of exon 7 in the SMN2 gene, leading to increased amounts of exon 7-containing transcripts in the spinal cord of trained mice. In addition, analysis at the level of two muscles from the calf, the slow-twitch soleus and the fast-twitch plantaris, showed an overall conserved muscle phenotype in running-trained animals. These data provide the first evidence for the beneficial effect of exercise in SMA and might lead to important therapeutic developments for human SMA patients.