Changes in the Expression of miR-34a and its Target Genes Following Spinal Cord Injury In Rats

BACKGROUND Results from DNA microarray experiments have shown that the expression of miR-34s undergoes significant changes following spinal cord injury (SCI). The present study was designed to detect changes in the expression of miR-34s and its target genes during the acute and sub-acute stages of SCI. MATERIAL AND METHODS Luxol fast blue (LFB) staining for myelin was used to observe the differences in the general morphology of the spinal cord after SCI in a contusion model in rats. qPCR was carried out to determine the expression variation of miR-34s and its target genes during the acute and sub-acute stages of SCI. The mimic technique was used to further confirm the regulatory effect of miR-34a on the potential target genes. RESULTS The expression level of miR-34a decreased immediately after SCI and persisted for 21 days after SCI. The expression level of miR-34c began decreasing at day 1 after SCI and persisted until day 14. The expression level of miR-34b did not undergo significant change after SCI. The results of double immunofluorescence and in-situ hybridization suggested that miR-34a was highly expressed in spinal cord neurons. Based on our bioinformatics analysis, we postulated that miR-34a might participate in post-SCI cell apoptosis by regulating the target gene Notch1, and likely participated in the inflammatory response and glial scar formation by regulating the candidate genes Csf1r and PDGFRa, respectively. The expression levels of the candidate genes Csf1r and PDGFRa were consistent with Notch1 after SCI. The mimic technique further confirmed the regulatory effect of miR-34a on the aforementioned target genes. CONCLUSIONS We postulate that miR-34a and miR-34c might participate in multiple aspects of cytobiological activities following SCI. MiR-34a in particular may participate in cell apoptosis, inflammatory response, and glial scar formation by regulating the target gene Notch1 and candidate target genes Csf1r and PDGFRa respectively.