Transcriptomic analyses reveal cell cycle and complement inhibitors may be specific for treatment of spinal cord injury in aged and young mice *

Previous studies have indicated age-specific pathological and function outcomes in young and aged patients suffering spinal cord injury (SCI). The goal of this study was to explain these differences using gene expression profiles from the Gene Expression Omnibus database under accession number GSE93561, including spinal cord samples from 3 young injured and 3 control mice (2-3-month old), 2 aged injury and control mice (15-18-month old). Differentially expressed genes (DEGs) between SCI and control mice were identified using the LIMMA method according to the threshold of adjusted p < 0.05 and |log (fold change)| > 1.5. Protein-protein interaction (PPI) network was constructed using data from STRING database, followed by module analysis by Cytoscape software to screen crucial genes. KEGG pathway and GO enrichment analyses were performed to investigate the underlying functions of DEGs using DAVID tool. As a result, 1604 and1153 were respectively identified between SCI and normal control in aged and young mice. Further, a Venn diagram was built, resulting in 960 common, 644 aged and 193 young specific DEGs. Function enrichment indicated the common DEGs were involved in Osteoclast differentiation, ECM-receptor interaction, NF-kappa B signaling pathway and Focal adhesion, while unique genes for aged and young group were cell cycle and complement-related, respectively (FDR < 0.05). This conclusion has also been demonstrated in the function analysis of genes in modules (common, 4; aged, 2; young, 1) screened from PPI. Accordingly, cell cycle and complement inhibitors may be specific for treatment of SCI in aged and young mice.