LPS Pre-Conditioned Olfactory Ensheathing Cells Derived Extracellular Vesicle Regulate Microglia Polarization Through mir-1224/CD44/SLC7A11 Axis Following Spinal Cord Injury.

Olfactory ensheathing cell (OEC) is one of the most promising cell candidates for the treatment of spinal cord injury (SCI). In recent years, the exosomes of OECs have shown neuroprotective properties in SCI. The aim of the present study was to examine whether exosomes derived from LPS preconditioned OEC could exhibit superior anti-inflammatory effect and also to investigate the underlying mechanisms. The extracellular vesicles derived from OECs under normal condition (N-EVs) and LPS preconditioned (L-EVs) were characterized with electron microscope, nanoparticle tracking analysis (NTA), and western blot. Metabolomics analysis was performed to analyze the metabolites in L-EVs treated microglia. Next, miRNA microarray analysis was used to compare the differential miRNAs in N-EVs and L-EVs. And gain and loss function experiments were performed to ascertain the efficacy of the anti-inflammatory mechanisms of L-EVs. Our results indicated that L-EVs could regulate microglia polarization from M1 phenotype to M2 phenotype. The metabolomics analysis showed that L-EVs treatment altered amino metabolism, and decreased the expression of Solute carrier family 7 member 11 (SLC7A11) in microglia. miRNA microarray analysis showed higher expression level of mir-1224 in L-EVs compared with N-EVs. The in vitro gain and loss function experiments demonstrated that mir-1224 promotes the degradation of CD44, and further decreases the expression of SLC7A11 in microglia which might involve in the cellular process of modulation microglial polarization. The extracellular vesicle derived from LPS preconditioned OECs exhibit a promising therapeutic paradigm for the treatment of SCI. And L-EVs alleviated neuroinflammation via modulating microglia polarization through mir-1224/CD44/SLC7A11 axis.