Lyophilized Small Extracellular Vesicles (sEVs) Derived from Human Adipose Stem Cells Maintain Efficacy to Promote Healing in Neuronal Injuries.

Background: Traumatic brain injury (TBI) occurs in individuals of all ages, predominantly during sports, accidents, and in active military service members. Chronic consequences of TBI include declined cognitive and motor function, dementia, and emotional distress. Small extracellular vesicles (sEVs), previously referred to as exosomes, are nano-sized lipid vesicles that play a role in intercellular communication. Our prior research established the efficacy of sEVs derived from human adipose stem cells (hASC sEVs) in accelerating the healing of brain injuries. The hASC sEVs are a biologic therapeutic and need to be stored at -20 °C or -80 °C. This limits their use in translating to everyday use in clinics or their inclusion in first-aid kits for application immediately after injury. To address this, here we demonstrate that hASC sEVs can be stored at room temperature (RT) for two months post lyophilization. Methods: A transmission electron microscope (TEM) and nanoparticle tracking analysis (NTA) were used to validate the morphology of lyophilized RT sEVs. Using in vitro models of neuronal injury mimicking physical injury, inflammation, and oxidative stress, we demonstrate that lyophilized RT hASC sEVs are viable and promote the healing of neuronal injuries. Results: The lyophilized sEVs maintain their purity, size, and morphology upon rehydration. Lyophilized, RT stored sEVs showed better efficacy after two months compared with -80 °C stored sEVs. Conclusions: RT storage of lyophilized hASC sEVs maintains their efficacy to accelerate the healing of injuries in neuronal cells. This will advance the use of hASC sEVs, bringing them closer to use in clinics, home first-aid kits, and on battlefields by active service members.