Transcranial Focused Ultrasound Modifies Disease Progression in SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressively worsening neurodegenerative condition with very few treatment options available. Ultrasound neuromodulation offers promising benefits for treating neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. However, the effects and underlying mechanisms of ultrasound neuromodulation on ALS remain unclear. A head-mounted ultrasound neuromodulation system was developed to noninvasively stimulate the motor cortex of symptomatic mice carrying the G93A human SOD1 mutation (SOD $1^{\text {G93A}}$ ) for four weeks. Motor performance was assessed through the rotarod locomotor test, grip strength test, and open field test. In addition, the effect of ultrasound stimulation on the elastic modulus of gastrocnemius muscle atrophy was measured using real-time shear wave elastography (SWE). Subsequently, the brain tissues of the mice were harvested. Gastrocnemius morphology was examined using hematoxylin-eosin and Gomori aldehyde-fuchsin (GAF) staining. The number of neurons and the phenotype of microglia in the motor cortex were observed by immunohistochemical analysis. Ultrasound therapy delayed disease onset by 10.7% and increased the lifespan by 6.7% in SOD $1^{\text {G93A}}$ mice by reduction of neuronal loss and enhancement of M2 microglia in the motor cortex. Furthermore, we found significant improvements in motor function for ultrasound-treated mice. More importantly, ultrasound stimulation ameliorated gastrocnemius muscle atrophy in the SOD $1^{\text {G93A}}$ mice. These results revealed the neuroprotective effects of ultrasound against the disease pathogenesis of SOD $1^{\text {G93A}}$ mice. Transcranial ultrasound neuromodulation provides an innovative tool for the intervention and treatment of neurodegenerative diseases.