Overexpression of miR-133B in reactive astrocytes enhances their released exosomes which contribute to neurite remodeling and functional recovery after stroke
Liu Z, Chopp M, Li Y, Gan X, Wang F, Shang X, Zhang Z, and Xin H. Overexpression of miR-133B in reactive astrocytes enhances their released exosomes which contribute to neurite remodeling and functional recovery after stroke. Stroke 2019; 50(Suppl 1):TP122.
Introduction: Astrocyte exosomes participate in the maintenance of axons and plasticity of neuronal networks. Overexpression of miR-133B in reactive astrocytes increases the release of exosomes which contribute to neurite outgrowth in vitro. Here, we investigate whether in vivo overexpression of miR-133B in reactive astrocytes enhances exosome release and subsequently promote the neurite remodeling and functional recovery after stroke. Methods: Mice (n=8) subjected to permanent middle cerebral artery occlusion were intranasally infused with the lentivirus generated from pLVX-GFAP-CherryPicker1 (Control) and pLVX-GFAP-CherryPicker1~miR-133b (miR-133b overexpression) at 24h post stroke. Functional tests including pellet reaching were performed and mice were sacrificed at 28 days post stroke. Neurite remodeling was determined with immunohistochemistry and reactive astrocyte released exosomes were isolated based on the CherryPicker tag and quantified. In vitro studies were performed to verify the effects of miR-133B modified astrocyte exosomes on neurite outgrowth. Level of a miR-133B targeted protein, PIKFYVE, a phosphoinositide kinase which facilitates lysosomal maturation and degradation was measured by Western blot. Results: Compared with control lentivirus treatment, miR-133B overexpressing lentivirus treatment significantly improved functional recovery after stroke (p<0.05). Numbers of reactive astrocyte exosomes from miR-133B lentivirus treated mice were significantly increased and their miR-133B cargo was upregulated. Neurite outgrowth (branches and length) of in vitro cultured mouse cortical neurons was significantly enhanced in miR-133B overexpression astrocyte exosome treated group compared to control astrocyte exosome treated group (p<0.05, respectively). Western blot data showed that stroke increased PIKFYVE expression was downregulated by the miR-133B overexpression. Conclusions: Overexpression of miR-133B in reactive astrocytes increases their exosome release and increases the miR-133B content within these exosomes possibly via downregulation of PIKFYVE, and the enhanced reactive astrocyte exosomes subsequently promote neurite remodeling and functional recovery after stroke.