Increased IL-17 expression in degenerated human discs and increased production in cultured annulus cells exposed to IL-1ß and TNF-α

IL-17 is expressed in a number of tissues including the intervertebral disc, where it exerts strong inflammatory properties. We evaluated IL-17 using immunolocalization in herniated and non-herniated human discs, IL-17 gene expression, and the production of IL-17 by annulus cells cultured in three dimensions in the presence of IL-1ß or TNF-α. There was no difference in the percentage of IL-17 positive cells in annulus or nucleus in herniated vs. non-herniated disc specimens. Molecular studies confirmed expression of IL-17 in disc tissue, with significantly increased expression in more degenerated discs; there was no difference in expression between herniated vs. non-herniated discs. Exposure to IL-1ß or TNF-α resulted in significantly greater production of IL-17. Our findings expand understanding of IL-17 production by disc cells and reveal the importance of non-canonical IL-17 production in the disc. Significantly greater expression of IL-17 in more degenerated discs adds to our understanding of the changes in disc cell function with advancing stages of disc degeneration.