AAV-mediated BDNF and GAS6 muscle delivery delays disease onset in SOD1G93A ALS mice

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease, with limited treatments. Gene therapy offers an alternative strategy for treating a large portion of ALS patients, however, the disparate genetic alterations in ALS complicate the development of gene therapies. Tyrosine receptor kinase B (TRKB) and Tyro3 receptors are highly expressed in mouse spinal cord motor neurons, suggesting that their ligands, brain-derived neurotrophic factor (BDNF) and growth arrest-specific 6 (GAS6), respectively, are crucial for neuronal survival. In this study, we tested whether genetically induced and muscle tissue-specific expression of such survival-enhancing ligands would ameliorate symptom development in the SOD1^G93A ALS mouse model. The therapeutic vectors (AAV-P_mus7-HuBDNF-teLuc or AAV-P_mus7-HuGAS6), or a control vector (AAV-P_mus7-teLuc) were injected intravenously via the retro-orbital route and intramuscularly into the hindlimb skeletal muscle of six-week-old mice. Treatment with the therapeutic vectors delayed disease onset and slowed progression in both male and female mice. Interestingly, a sex-specific response was observed, with female mice benefiting more from the treatments than males. Lumbar motor neuron survival was more sustained in the therapeutic vector-treated group compared to control vector group. No statistically significant extension of lifespan was observed in the treated groups.