TNF and intervertebral disk degenerative disorder: Tumor necrosis factor-α (TNF-α) is the key inflammatory factor that accelerates senescence of NP cells and induces the expression of other inflammatory mediators (Postal and Appenzeller, 2011; Johnson et al., 2015; Khan et al., 2017); as a result, matrix metalloproteinase (MMP) increases and, ultimately, loss of ECM occurs and IDD develops (Sun et al., 2015).