TNF and intervertebral disk degenerative disorder: Considering that the elevated expression of TNF-α and IL-1β is a hallmark trait during NPC degeneration (Risbud and Shapiro, 2014; Fontana et al., 2015; Oichi et al., 2020; Wang et al., 2020), many researchers used them to simulate the microenvironment of IDD in vitro (Cheng et al., 2018; Wang et al., 2018, 2020).