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Chromatographically isolated CD63+CD81+ extracellular vesicles from mesenchymal stromal cells rescue cognitive impairments after TBI

Significance It has gradually been recognized that the vesicles secreted by cells are a major means by which cells communicate with each other. This recognition has stimulated interest in using vesicles to deliver therapeutic agents. The results presented here address several limitations to progress in the field by developing protocols to produce and isolate large numbers of extracellular vesicles (EVs) from stem-like cells found in the bone marrow. The isolated EVs were found to reduce the adverse effects of traumatic injury to the brain in mice. Extracellular vesicles (EVs) secreted by cells present an attractive strategy for developing new therapies, but progress in the field is limited by several issues: The quality of the EVs varies with the type and physiological status of the producer cells; protocols used to isolate the EVs are difficult to scale up; and assays for efficacy are difficult to develop. In the present report, we have addressed these issues by using human mesenchymal stem/stromal cells (MSCs) that produce EVs when incubated in a protein-free medium, preselecting the preparations of MSCs with a biomarker for their potency in modulating inflammation, incubating the cells in a chemically defined protein-free medium that provided a stable environment, isolating the EVs with a scalable chromatographic procedure, and developing an in vivo assay for efficacy of the cells in suppressing neuroinflammation after traumatic brain injury (TBI) in mice. In addition, we demonstrate that i.v. infusion of the isolated EVs shortly after induction of TBI rescued pattern separation and spatial learning impairments 1 mo later.