miRNA-221 Regulates Spinal Cord Injury-Induced Inflammatory Response through Targeting TNF-α Expression

Objectives To investigate the roles of miR-221 in spinal cord injury (SCI) as well as the underlying mechanism.Methods A mouse model of SCI was generated and used to examine dynamic changes in grip strength of the mouse upper and lower limbs. The expression of miR-221 and tumor necrosis factor- α (TNF- α ) was detected by RT-qPCR and Western blot. Levels of inflammation and oxidative stress in microglia cells of the injured mice overexpressing miR-221 were then measured by ELISA. Bioinformatics analysis and dual-luciferase reporter assay were conducted to identify the miR-221 target.Results We successfully constructed SCI mouse model. The results of qRT-PCR showed that miR-221 was gradually upregulated in the spinal cord tissue of mice in the SCI group with the prolonged injury time. At the same time, the mRNA and protein of TNF- α gradually decreased. We further confirmed through cell experiments that the inflammatory factors TNF- α and IL-6, as well as iNOS and eROS, were upregulated in spinal cord microglia cells of SCI mice, and upregulation of miR-122 can inhibit their expression. Finally, the luciferase reporter experiment confirmed that miR-122 targeted TNF- α .Conclusions We present evidence that miR-221 promotes functional recovery of the injured spinal cord through targeting TNF- α , while alleviating inflammatory response and oxidative stress.