Secondary Release of Exosomes from Astrocytes Contributes to the Increase in Neural Plasticity and Improvement of Functional Recovery after Stroke in Rats Treated with Exosomes Harvested from MicroRNA 133b Overexpressing Multipotent Mesenchymal Stromal Cells
We previously demonstrated that multipotent mesenchymal stromal cells (MSCs) that overexpress microRNA 133b (miR 133b) significantly improve functional recovery in rats subjected to middle cerebral artery occlusion (MCAO) compared with naive MSCs and that exosomes generated from naive MSCs mediate the therapeutic benefits of MSC therapy for stroke. Here we investigated whether exosomes isolated from miR 133b overexpressing MSCs (Ex miR 133b+ exert amplified therapeutic effects. Rats subjected to 2 h of MCAO were intra arterially injected with Ex miR 133b+ exosomes from MSCs infected by blank vector (Ex Con) or phosphate buffered saline (PBS) and were sacrificed 28 days after MCAO. Compared with the PBS treatment, both exosome treatment groups exhibited significant improvement of functional recovery. Ex miR 133b+ treatment significantly increased functional improvement and neurite remodeling/brain plasticity in the ischemic boundary area compared with the Ex Con treatment. Treatment with Ex miR 133b+ also significantly increased brain exosome content compared with Ex Con treatment. To elucidate mechanisms underlying the enhanced therapeutic effects of Ex miR 133b+ astrocytes cultured under oxygen and glucose deprived (OGD) conditions were incubated with exosomes harvested from naive MSCs (Ex Naive) miR 133b downregulated MSCs (Ex miR 133b and Ex miR 133b+ Compared with the Ex Naive treatment, Ex miR 133b+ significantly increased exosomes released by OGD astrocytes, whereas Ex miR 133b significantly decreased the release. Also, exosomes harvested from OGD astrocytes treated with Ex miR 133b+ significantly increased neurite branching and elongation of cultured cortical embryonic rat neurons compared with the exosomes from OGD astrocytes subjected to Ex Con. Our data suggest that exosomes harvested from miR 133b overexpressing MSCs improve neural plasticity and functional recovery after stroke with a contribution from a stimulated secondary release of neurite promoting exosomes from astrocytes.
Cell transplantation