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Crosstalk Between Human Monocytic U937 Cells and Gingival Fibroblasts in Coculturally Enhanced Matrix Metalloproteinase-2 Expression.

BACKGROUND
Matrix metalloproteinases (MMPs) play a key role in inflammatory periodontal disease. Synergistically enhanced MMP-2 expression in a coculture of human gingival fibroblasts (HGFs) and human monocytic U937 cells was observed. Crosstalk between these two cells via the extracellular matrix metalloproteinase inducer (EMMPRIN) was demonstrated.


METHODS
Enzyme levels of MMP-2 in HGFs and direct coculture with U937 were examined by zymography. MMP-2 and EMMPRIN expressions of HGFs and U937 were determined in coculture and conditioned cultures (using supernatants from HGF- or U937-conditioned medium). The crosstalk was evaluated by EMMPRIN extrasupplement and EMMPRIN inhibition, through pretreatment of U937 with cyclosporine-A.


RESULTS
Direct coculturing of HGFs and U937 enhanced MMP-2 enzyme level and mRNA expression. Coculturing also increased membranous EMMPRIN expression of U937, but not from HGFs. In conditioned cultures, mRNA expression of MMP-2 increased in HGFs which received U937-conditioned medium. Increased MMP-2 was not observed in U937 with HGF-conditioned medium, although mRNA expression of EMMPRIN increased. Enhanced MMP-2 was observed after administration of exogenous EMMPRIN in HGFs; however, reduced MMP-2 enzyme level was noted if EMMPRIN of cocultured U937 was inhibited.


CONCLUSIONS
In the coculture of HGFs and U937, upregulated EMMPRIN expression in U937, which may be triggered by HGFs, can enhance MMP-2 expression in HGFs. Crosstalk between HGFs and U937 involving MMP-2 from HGFs was proposed; EMMPRIN from U937 may play a particular role.