TNF and intervertebral disk degenerative disorder: Surprisingly, only mid‐stream and downstream inflammatory cytokines, for example, IL‐8, PGE2, and NO were detected, while the upstream cytokines TNF‐α and IL‐1β, which have been reported as the major inflammatory cytokines of (intact) disc degeneration and herniation, were absent.6, 15, 24 This finding may suggest that osmotic factors directly affect NP cells, and that the inflammation process within the degenerating disc is more complex than the classical inflammatory process induced by loss of tonicity.