In Amyotrophic lateral sclerosis, muscle denervation and degeneration of motoneurons result in progressive muscle weakness and atrophy. For preserving neuromuscular function in the SOD1G93A mouse model, we synergically influenced on motoneuron terminals and muscles by boosting the secretion of α-Klotho in skeletal muscles. α-Klotho is a pleiotropic chronokine with an excellent profile as a neuroprotective and myoregenerative agent. 

To overexpress α-Klotho in the muscles of SOD1G93A mice, AAV8 vectors were systemically administered at 3x10¹⁴vg/kg at an early stage of the disease. Secretion of α-Klotho enhanced motor function and strength of the animals and delayed the onset of the disease. Neuromuscular functional improvement was reflected as increased amplitudes of the compound muscle action potentials (CMAP) and the motor evoked potentials (MEPs). α-Klotho-treated SOD1G93A mice showed more surviving motoneurons and a significant reduction in glial reactivity in the spinal cord. All this correlating to a higher number of occupied neuromuscular junctions and a preserved mass of the muscles.

In view of the high doses of AAV8 vectors needed to reach therapeutic efficacy, we moved to a myotropic AAV vector. With a 20-fold decrease in the dose, we achieved higher preservation of neuromuscular connectivity, motor performance and strength in SOD1G93A mice. More importantly, when mice were treated at a symptomatic stage, α-Klotho slowed down the progressive decline characteristic of SOD1G93A mice.

Overall, our results provide evidence that the secretion of α-Klotho by muscles can promote functional improvement in ALS and may open a new avenue for the treatment of this devastating disorder.