Matrix metalloproteinases (MMPs) are known to be involved in IVD degeneration by hydrolyzing the extracellular matrix (ECM), especially the collagens. The degradation of proteoglycans, which is another main ECM component in the IVD, however, has not been extensively investigated. This study aimed to determine the expression of ADAMTS-5 in human herniated intervertebral disc (IVD) tissues and to investigate whether interleukin-1β (IL-1β)-induced expression of ADAMTS-5 is mediated by nitric oxide (NO). Forty-five herniated IVDs were harvested and immunostained to determine the distribution and type of ADAMTS-5 expressing cells. Rat NP cells maintained in alginate beads were treated with IL-1β, accumulation of NO was detected by Griess reaction, the expression of ADAMTS-5 and inducible nitric oxide synthase (iNOS) was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), the content of proteoglycans in alginate beads was visualized by alcian blue staining, and the effect of aminoguanidine on the changes in alginate beads induced by IL-1β treatment were also examined. Immunohistochemical results from 45 herniated discs showed that ADAMTS-5-positive cells are commonly seen in cell clusters, that the percentage of ADAMTS-5-positive cells was higher in uncontained herniated discs than in contained ones, and that the percentage of ADAMTS-5-positive cells correlated with the age of the patients. IL-1β treatment resulted in increased accumulation of NO, increased expression of ADAMTS-5 and iNOS, whereas the accumulation of proteoglycan in alginate beads decreased. Aminoguanidine significantly reversed the changes in alginate beads induced by IL-1β treatment. We thus suggested that ADAMTS-5 is probably involved in the process of IVD degeneration, and that IL-1β-induced expression of ADAMTS-5 is mediated by NO.
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