Helena Domeij

Background:  Matrix metalloproteinase‐1 (MMP‐1) plays an important role in inflammatory diseases including periodontitis, which is characterized by tissue destruction and dense infiltration of mononuclear cells.Objectives:  The aim of this study was to investigate the effect of cell interactions between human gingival fibroblasts and human monocytes on the production of MMP‐1 in a coculture model.Methods:  The fibroblasts were cultured in either cell‐to‐cell contact with monocytes or in separated cocultures using a microporous membrane to prevent cell‐to‐cell contact. The mRNA expression of MMP‐1 was analyzed using reverse transcription–polymerase chain reaction (RT–PCR) and the protein levels of MMP‐1 in the cell medium were measured using enzyme‐linked immunosorbent assay (ELISA).Results:  Coculturing gingival fibroblasts with monocytes in cell‐to‐cell contact increased the mRNA expression of MMP‐1 in both fibroblasts and monocytes. The protein levels of MMP‐1 increased in the culture media of the cocultures and correlated to the number of fibroblasts as well as to the number of monocytes. When fibroblasts were cultured with monocytes in separated cocultures, the mRNA expression and protein level of MMP‐1 increased in the fibroblasts. In addition, treatment of fibroblasts with conditioned medium from monocytes also stimulated the production of MMP‐1 in the fibroblasts. Moreover, the levels of the MMP‐1 inhibitor, tissue inhibitor of metalloproteinase‐1 (TIMP‐1), increased in cocultures with cell‐to‐cell contact, but not in fibroblasts of separated cocultures. The glucocorticoid dexamethasone and the tetracycline doxycycline reduced the enhanced level of MMP‐1 in the cocultures with cell‐to‐cell contact.Conclusion:  The current study demonstrates that monocytes stimulate the production of MMP‐1 in gingival fibroblasts by cell interactions, which may contribute to the maintenance of MMP‐mediated tissue destruction in periodontitis.

Background:  Matrix metalloproteinase‐1 (MMP‐1) plays an important role in tissue remodelling and in the pathology of inflammatory diseases including periodontitis. The activity of MMP‐1 is firmly controlled by the endogenous tissue inhibitor of metalloproteinase‐1 (TIMP‐1).Objective:  The aim of the study was to investigate the production and regulation of MMP‐1 and TIMP‐1 with special regards to the enzyme protein kinase C (PKC) in human gingival fibroblasts.Methods:  Gingival fibroblasts were treated with substances related to PKC such as phorbol 12‐myristate 13‐acetate (PMA), interleukin‐1β, Ca²⁺‐ionophore A231817 and inhibitors of PKC, p38 mitogen‐activated protein kinase (p38 MAPK) and tyrosine kinase.Results:  The PKC activator PMA stimulated the production of MMP‐1 and TIMP‐1 at both the transcriptional and the translational level. The production of MMP‐1 and TIMP‐1 stimulated by PMA was abolished by the PKC inhibitor bisindolylmaleimide. Treatment of the cells with interleukin‐1β or A23187 synergistically increased the stimulatory effect of PMA on MMP‐1 production. In contrast, TIMP‐1 production was unaffected by interleukin‐1β and reduced by A23187. Tyrosine kinase inhibitor herbimycin A reduced MMP‐1 production induced by PMA, whereas the p38 MAPK‐inhibitor SB 203580 synergistically increased the stimulatory effect of PMA on both MMP‐1 and TIMP‐1 production.Conclusion:  The present study shows that MMP‐1 and TIMP‐1 production is regulated differently by interleukin‐1β and calcium in human gingival fibroblasts and that this difference is markedly amplified in the presence of the PKC‐activator PMA. Taken together, the discrepancy in the production of MMP‐1 and TIMP‐1 in gingival fibroblasts may contribute to tissue destruction in periodontal diseases.

Periodontitis is associated with enhanced production of cytokines, prostaglandins and matrix metalloproteinases (MMPs). The aim of this study was to investigate the production and regulation of MMP‐1 and MMP‐3 in human gingival fibroblasts challenged with the cytokines interleukin‐1β (IL‐1β), tumor necrosis factor α (TNFα) or epidermal growth factor (EGF). The results showed that gingival fibroblasts constitutively produce MMP‐1 and MMP‐3, and that the cytokines IL‐1β, TNFα and EGF increase both MMP‐1 and MMP‐3 production in gingival fibroblasts. The upregulation by the cytokines was apparent at 8 h of incubation and increased thereafter continuously during 48 h of incubation. The upregulation of MMPs, induced by IL‐1β or TNFα, was reduced by the cyxlooxygenase‐2 (COX‐2) inhibitor NS‐398, the p38 MAP‐kinase inhibitor SB 203580, and the tyrosine kinase inhibitor herbimycin A. In addition, MMP‐1 and MMP‐3 production, induced by IL‐1β, TNFα or EGF, was strongly reduced by the presence of the glucocorticoid dexamethasone. Our findings demonstrate that the cytokines IL‐1β, TNFα and EGF, respectively, enhance both MMP‐1 and MMP‐3 production in human gingival fibroblasts, and that the signal pathways COX‐2, MAP‐kinases and tyrosine kinases are partly involved in the production of MMPs.