Intranasal administration of human mesenchymal stromal cell-derived small extracellular vesicles delays disease progression in the SOD1(G93A) mouse model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron loss, with no established disease-modifying therapy. Mesenchymal stem/stromal cells (MSCs) have been reported to exert neuroprotective effects in models of injury and disease, acting primarily through release of small extracellular vesicles (sEVs). MSC-derived sEVs (MSC-sEVs) have therefore attracted attention as a potential cell-free therapeutic approach for treating neurological conditions such as ALS. Because MSC-sEVs can cross both the nasal epithelial barrier and blood-brain barrier to reach the central nervous system (CNS), intranasal administration represents an attractive approach for repeated delivery of MSC-sEVs for long-term administration. In this study, we administered bone marrow-derived MSC-sEVs or vehicle intranasally to a SOD1(G93A) transgenic mouse model of ALS; the large majority of the sEVs had surface markers for exosomes. Dosing was for three consecutive days per week beginning one day after onset of neurological symptoms and continuing until a moribund state. Neurological score and body weight were recorded daily. Although total survival time and post-onset survival duration were not significantly prolonged by MSC-sEV treatment, MSC-sEV treatment significantly delayed progression from a mild symptom phase (NeuroScore 1) to more severe symptoms (NeuroScore 2) compared with vehicle-treated controls and showed a trend toward slower weight loss. These findings indicate that intranasal administration of MSC-sEVs can delay functional deterioration and prolong the mild impairment stage in an ALS mouse model. If translatable to human patients, such preservation of neurological function could represent a clinically meaningful outcome.