Circulating microRNAs as biomarkers for evaluating the severity of acute spinal cord injury

Study design: An in vivo study in mouse models of spinal cord contusion. Objectives: To develop a novel indicator to anticipate the severity of spinal cord injury (SCI) during the acute phase and for the assessment of the efficacy of novel therapies. MicroRNAs (miRNAs) circulating in the peripheral blood are reported to modulate signaling between cells, and to be diagnostic markers for cancers. The purpose of this study was to identify circulating miRNAs for predicting the severity of SCI in the acute phase. Setting: Department of Orthopaedic Surgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan. Methods: Mouse SCI models were made using Infinite Horizon impactor with 50 or 70 kdyn compressing power following thoracic laminectomy. The mice were then divided into four groups: normal (without surgery), sham (laminectomy only), mild (50 kdyn), and severe (70 kdyn). TaqMan low-density array analysis and real-time PCR were performed to identify candidate miRNAs that were increased in the serum relative to the severity of SCI. Results: The expression levels of miR-9*, miR-219 and miR-384-5p in the serum were significantly increased relative to the severity of SCI 12h after injury. The expression of miR-9* was also significantly increased relative to injury severity at 3 and 24h after injury. Conclusion: Serum miR-9*, miR-219 and miR-384-5p might be promising biomarkers for predicting the severity of SCI.