MMP9 and intervertebral disk degenerative disorder: Notably, the enrichment score analysis (gene term ratio) for the KEGG pathway showed that a large proportion (~15–20%) of IDD-related genes are involved in the IL-17 and TNF signaling pathways, suggesting that signaling genes involved in these pathways such as CCL2, IL-17A, CCL5, CSF1, CSF2, CX3CL1, IL18R1, IL1B, IL6, LIF, MMP14, MMP3, MMP9, PTGS2, SELE, SOCS3, TNF may play important roles in IDD development (Figure 2).