microRNAs (miRNAs) play an important regulatory role in the self-renewal and differentiation of stem cells. In this study, we examined the effects of miRNA-124 (miR-124) overexpression in bone marrow-derived mesenchymal stem cells. In particular, we focused on the effect of overexpression on the differentiation of bone marrow-derived mesenchymal stem cells into neurons. First, we used GeneChip technology to analyze the expression of miRNAs inbone marrow-derived mesen-chymal stem cells, neural stem cells and neurons. miR-124 expression was substantially reduced inbone marrow-derived mesenchymal stem cells compared with the other cell types. We con-structed a lentiviral vector overexpressing miR-124 and transfected it intobone marrow-derived mesenchymal stem cells. Intracellular expression levels of the neuronal early markersβ-III tu-bulin and microtubule-associated protein-2 were signiifcantly increased, and apoptosis induced by oxygen and glucose deprivation was reduced in transfected cells. After miR-124-transfected bone marrow-derived mesenchymal stem cells were transplanted into the injured rat spinal cord, a large number of cells positive for the neuronal marker neurofilament-200 were observed in the transplanted region. The Basso-Beattie-Bresnahan locomotion scores showed that the motor function of the hind limb of rats with spinal cord injury was substantially improved. These re-sults suggest that miR-124 plays an important role in the differentiation ofbone marrow-derived mesenchymal stem cells into neurons. Our ifndings should facilitate the development of novel strategies for enhancing the therapeutic efifcacy ofbone marrow-derived mesenchymal stem cell transplantation for spinal cord injury.