Study on the role of chemokines in the infiltration of inflammatory cells in dental pulp tissue destruction

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Severe pulpitis resulted from dental caries is characterized by a marked inflammatory infiltrate such as lymphocytes. Little is known about the recruitment of these cells into the lesion of dental plup in carious teeth. Macrophage inflammatory protein-3α (MIP-3α), one of the CC chemokines, is known to attract CC chemokine receptor 6 (CCR6)-expressing T cells, and CCR6 is typically expressed on memory T cells.Then, we ezamined the expression of MIP-3α Mrna by RT-PCR and the distribution of MIP-3α-positive and CCR6-positive cells by immunohistochemistry in human dental pulp. MIP-3α expression was observed in all of the inflamed pulp samples, and microvascular endothelial cells. Moreover, CCR6 expression was also observed in the infiltrating lymphocytes, predominantly memory phenotype T cells. In contrast, MIP-3α and CCR6 was scarcely detected in normal pulps.We also examined the pattern of MIP-3α expression in endothelial cells stimulated by Streptococcus mutans or cytokine (IL-1 β or TNF α) in vitro. The level of MIP-3α increased in time- and dose-dependent manner, and that both cytokines strongly induced MIP-3α secretion compared with S. mutans.These findings suggest that MIP-3α plays an important role in the advancement of pulpal inflammation via the recruitment of CCR6-expressing lymphocytes. Furthermore, this study indicate that endothelial cells may modulate the accumulation of lymphocytes through the MIP-3α production.