Effects of interleukin-1β on matrix metalloproteinase-3 levels in human periodontal ligament cells

Matrix metalloproteinase-3 (MMP-3), or stromelysin-1, is an enzyme responsible for the degradation of a wide range of extracellular matrix proteins. Increases in MMP-3 activity have been found in several chronic inflammatory diseases, and this increased activity is thought to be mediated by interleukin-1β (IL-1β). Because IL-1β has been strongly associated with inflammatory periodontal disease, the purpose of this in vitro study was to investigate the role of IL-1β on the regulation of MMP-3 levels in cells derived from the human periodontal ligament (PDL). Human PDL cell cultures were treated with IL-1β at varying concentrations (0.01-1.0 ng/ml) for 24 hours prior to analysis at either transcript or protein levels. Following the isolation of total RNA, the relative levels of MMP-3 mRNA were determined using reverse transcription-polymerase chain reaction (RT-PCR) with ³²P- end-labeled primers. Immunocytochemical detection of MMP-3 protein was performed using polyclonal antibodies to human MMP-3. The results of RT-PCR analysis demonstrated a concentration-dependent increase in MMP-3 mRNA expression, with IL-1β treatments of 0.1 and 1.0 ng/ml significantly (P < 0.01) increased over those cells not treated with IL-1β. This increase in mRNA expression was paralleled by significant (P < 0.001) changes at the protein level, with an average of 27.6% of the cells stained positive for MMP-3 following IL-1β treatment (1.0 ng/ml), compared with control cells showing no positive staining for MMP-3. In conclusion, the results of this study demonstrate that IL-1β upregulates MMP-3 in human PDL cells on both an mRNA and a protein level. These findings suggest possibly important roles for IL-1β and MMP-3 in both normal turnover and maintenance of the PDL and in the connective tissue degradation associated with periodontal disease.