Objective: To uncover the role of microRNA-127-5p (miRNA-127-5p) in aggravating motor dysfunction following spinal cord injury (SCI) by regulating the mitogen-activated protein kinase 1 (MAPK1) level.
Materials and methods: In vivo SCI model in mice was established by constructing spinal cord hitting injury. Mice were classified into sham group, SCI group, SCI+miRNA-127-5p mimics group, and SCI+miRNA-127-5p mimics+MAPK1 group, respectively. Grip strengths of mouse pair forepaws, right forepaw, and left forepaw at different time points were determined. Expression levels of miRNA-127-5p and MAPK1 in mice of each group at post-SCI were detected. Potential binding sites in promoter regions of miRNA-127-5p and MAPK1 were predicted by bioinformatics and further confirmed by Dual-Luciferase reporter gene assay and Western blot.
Results: Grip strengths of SCI mice were much lower than those in sham group at different time points after SCI procedures. MiRNA-127-5p was markedly downregulated on the postoperative 3rd day in SCI group, and its level time-dependently decreased since after. In vivo overexpression of miRNA-127-5p in SCI mice improved their grip strengths from the postoperative 7th day. MAPK1 was the direct target of miRNA-127-5p. Transfection of miRNA-127-5p mimics downregulated protein level of MAPK1 in 293T cells. Overexpression of MAPK1 abolished the protective effect of miRNA-127-5p on motor function recovery following SCI.
Conclusions: Downregulation of miRNA-127-5p aggravates SCI-induced motor dysfunction through negatively regulating MAPK1 level.