Regulation of MicroRNAs After Spinal Cord Injury in Adult Zebrafish

Spinal cord injury (SCI) is a central nerve injury that often leads to loss of motor and sensory functions at or below the level of the injury. Zebrafish have a strong ability to repair after SCI, but the role of microRNAs (miRNAs) after SCI remains unclear. Locomotor behavior analysis showed that adult zebrafish recovered about 30% of their motor ability at 2 weeks and 55% at 3 weeks after SCI, reflecting their strong ability to repair SCI. Through miRNA sequencing, mRNA sequencing, RT-qPCR experiment verification, and bioinformatics predictive analysis, the key miRNAs and related genes in the repair of SCI were screened. A total of 38 miRNAs were significantly different, the top ten miRNAs were verified by RT-qPCR. The prediction target genes were verified by the mRNAs sequencing results at the same time point. Finally, 182 target genes were identified as likely to be networked regulated by the 38 different miRNAs. GO and KEGG enrichment analysis found that miRNAs targeted gene regulation of many key pathways, such as membrane tissue transport, ribosome function, lipid binding, and peroxidase activity. The PPI network analysis showed that miRNAs were involved in SCI repair through complex network regulation, among which dre-miR-21 may enhance cell reversibility through nop56, and that dre-miR-125c regulates axon growth through kpnb1 to repair SCI.

Graphical Abstract

miRNAs promote neuronal survival and axon growth after SCI. The expression of dre-miR-21 was increased after SCI. Dre-miR-21 targets nop56 mRNA, which causes the Nop56 expression level to reduce, thus reducing the nuclei of ribosomal RNA methylation level, increasing the resistance of neurons, and promoting neuronal cell survival. The level of dre-miR-125c is increased after SCI, and dre-miR-125c targets kpnb1 mRNA and reduces the concentration of Kpnb1 at the axon site, thereby promoting axon outgrowth. At the same time, Kpnb1 is a retrograde signal protein of nerve injury, and reducing the expression level of Kpnb1 can inhibit cell death caused by excessive stress response.