MicroRNA-135a-5p Promotes the Functional Recovery of Spinal Cord Injury by Targeting SP1 and ROCK

Abstract Emerging evidence indicates that microRNAs play a pivotal role in neural remodeling after spinal cord injury (SCI). This study aimed to investigate the mechanisms of miR-135a-5p in regulating the functional recovery of SCI by impacting its target genes and downstream signalings. The gene transfection assay and luciferase reporter assay confirmed the target relationship between miR-135a-5p and its target genes (SP1 and ROCK1/2). By establishing the H2O2-induced injury model, miR-135a-5p transfection was found to inhibit the apoptosis of PC12 cells by downregulating SP1 gene, which subsequently induced downregulation of pro-apoptotic proteins (Bax, cleaved caspase-3) and upregulation of anti-apoptotic protein Bcl-2. By measuring the neurites length of PC12 cells, miR-135a-5p transfection was found to promote the axon outgrowth by downregulating ROCK1/2 gene, which subsequently caused upregulation of phosphate protein kinase B (AKT) and phosphate glycogen synthase kinase 3β (GSK3β). The employment of the rat SCI models showed that miR-135a-5p could increase the Basso, Beattie and Bresnahan (BBB) scores, indicating neurological function recovery. In conclusion, miR-135a-5p-SP1-Bax/Bcl2/caspase-3 and miR-135a-5p-ROCK-AKT/GSK3β axes are involved in functional recovery of SCI by regulating neural apoptosis and axon regeneration respectively and thus, can be promising effective therapeutic strategies in SCI.