Effects of MicroRNA-494 on Astrocyte Proliferation and Synaptic Remodeling in the Spinal Cord of a Rat Model of Chronic Compressive Spinal Cord Injury by Regulating the Nogo/Ngr Signaling Pathway

Abstract

Background/Aims: Chronic compression of the spinal cord causes the loss of motor neurons in the anterior horn, but the precise and extensive mechanism for the loss is not completely determined. Therefore, this study aims to explore the role of microRNA-494 (miR-494) in the proliferation of astrocytes and in the synaptic remodeling in the spinal cord of a rat model of chronic spinal cord injury (SCI) by regulating the Nogo/NgR signaling pathway. Methods: A rat model of chronic, compressive SCI was established, and the spinal cord state, blood supply changes, and astrocyte apoptosis were observed. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting were used to detect expression of miR-494 and the Nogo/NgR signaling pathway-related genes. Fluorescence in situ hybridization (FISH) was used for detecting miR-494 expression and distribution. Results: Higher miR-494 expression was accompanied by the inhibition of astrocyte proliferation and synaptic remodeling. In addition, CDK6 could be regulated by miR-494 and was shown to be one of the target genes of miR-494. Positive expression of miR-494 detected by FISH was consistent with the results from RT-qPCR that miR-494 could downregulate CDK6 gene expression. Moreover, the direct miR-494 target CDK6 plays important inhibitory roles in chronic SCI by suppressing the Nogo/ NgR signaling pathway. Conclusions: The results demonstrated that miR-494 inhibition can promote astrocyte proliferation and synaptic remodeling by suppressing the Nogo/NgR signaling pathway in a rat model of chronic SCI.