Abstract: Objective To study the molecular biology mechanisms of Wistar rats after spinal cord injury, and find out key microRNAs. Methods A total of 15 Wistar rats were divided into control group (n = 3) and spinal cord injury group (n = 12). The latter group was divided into four hours, three days, seven days and 14 days subgroups, with three rats in each subgroup. Microarray 3.0 was used to investigate microRNA expression profiles of Wistar rats with spinal cord injury. Bioinformatics was used to predict microRNAs playing key regulatory roles, and to predict target genes. Reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) was applied to detect the expression of miR-20a-3p. Western blotting was employed to detect the signal transducer and activator of transcription (STAT) 3 level. The correlation between target protein and microRNA expression trend in each group was analyzed. The key microRNA was inhibited in the neurons. The relationship between target protein expression and axon growth was observed with immunofluorescence. Results In the rats with spinal cord injury, totally 658 microRNAs had changed at least once. In all the altered microRNAs, miR-20a-3p was upregulated obviously. It predicted that the target gene of miR-20a-3p was STAT3 via application of bioinformatics analysis. The expression trend of STAT 3 and miR-20a-3p in spinal cord was opposite. After the inhibition of miR-20a-3p, the expression of STAT3 in neurons was unregulated and axonal growth was extended. Conclusion The upregulation of miR-20a-3p leads to downregulation of STAT3, and miR-20a-3p is one of the key targets in the treatment of spinal cord injury.

Key words: spinal cord injury, neuron, microRNA, therapeutic target, rats