LAUSR

Mesenchymal stem/stromal cells (MSC)-derived small extracellular vesicles (sEVs) possess therapeutic potential for treatment of traumatic brain injury (TBI). The essential role of miRNAs underlying the beneficial effects of MSC-derived sEVs for treatment of TBI remains elusive. The present study was designed to investigate the role of microRNAs in sEVs from MSCs with argonaut 2 (Ago2) knockdown in neurological recovery, neuroinflammation, and neurovascular remodeling in TBI rats. Therapeutic effects of sEVs derived from naïve MSCs (naïve-sEV), MSCs transfected with a vector carrying scramble control shRNA (Vector-sEV), MSCs transfected with a lentiviral vector based shRNA against Ago2 to knock down Ago2 (Ago2-KD-sEV) were determined in adult male rats subjected to a moderate TBI induced by controlled cortical impact. sEVs (naïve-sEV, Vector-sEV, and Ago2-KD-sEV) or Vehicle (phosphate-buffered solution) were given intravenously one day post injury (PI). Multiple neurological functional tests were performed weekly PI for 5 weeks. The Morris water maze test was performed for spatial learning and memory 31-35 days PI. All animals were euthanized 5 weeks PI and the brains were collected for analyses of lesion volume, cell loss, neurovascular remodeling, and neuroinflammation. Ago2 knockdown reduced global sEV miRNA levels. Compared to the Vehicle treatment, both naïve-sEV and Vector-sEV treatments significantly improved functional recovery, reduced hippocampal neuronal cell loss, inhibited neuroinflammation, and promoted neurovascular remodeling (angiogenesis and neurogenesis). However, Ago2-KD-sEV treatment had a significantly less therapeutic effect on all the parameters measured above than did naïve-sEV and Vector-sEV treatments. The therapeutic effects of Ago2-KD-sEV were comparable to that of Vehicle treatment. Our findings demonstrate that attenuation of Ago2 protein in MSCs reduces miRNAs in MSC-derived sEVs and abolishes exosome treatment-induced beneficial effects in TBI recovery, suggesting that miRNAs in MSC-derived sEVs play an essential role in reducing neuronal cell loss, inhibiting neuroinflammation, augmenting angiogenesis and neurogenesis as well as improving functional recovery in TBI. The findings underscore the important role of miRNAs in MSC-derived sEVs in the treatment of TBI.