Cellular functional character of extracellular matrix on dental pulpitis

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The extracellular matrix (ECM) plays an important role in the growth and degeneration of cells As a result of infection and host immunoreaction, ECM is damaged by matrix metalloproteases (MMPs). Plasmin, which is produced from limited degradation of plasminogen by plasminogen activator (PA), activated latent MMPs and stimulates the synthesis of kinin. The inflammatory cytokines such as IL-1beta, IL-6 and TNF-alpha are synthesized by invasion of bacteria or virus. The effect of various inflammatory cytokines on the PA/plasmin system in human dental pulp cells was examined and compared with the effect on human gingival cells in order to characterize dental pulp cells in pulpitis. Dental pulp and gingival cells which were obtained from same donor were cultured in alpha-MEM with 10 % fetal calf serum and under 5 % CO_2 in air at 37 ℃. Both cells in a con fluent-stage were incubated for 24 h in medium containing 2 % PCS and treated with various cytokines (IL-1beta, IL-6 and TNF-alpha). The PA activity in conditioned medium was measured using fluorescent substrate. The expression of tPA mRNA was analyzed by RT-PCR. The PA activity of dental pulp cells was higher and the expression of tPA mRNA was stronger than that of gingival cells when both cells were incubated with IL-6 and TNF-alpha. The inflammatory cytokines (IL-1beta, IL-6 and TNF-alpha) stimulated PA activity via an enhancement of tPA gene expression and MMP-2 activity, and tPA activated by these cytokines stimulated MMP-9, Thus the inflammatory cytokines may be involved in extracellular matrix degradation through a stimulation of the PA/plasmin system of human dental pulp cells. Dental pulp cells were different from gingival cells in the response of the IL-6 and TNF-alpha to PA-plasmin system and MMP-9. The extracellular matrix of dental pulp is more strongly damaged through IL-6 and TNF-alpha produced in progress of inflammation.