Changes of CD90 expression and immunoreactive cell localisation in rat dental pulp after cavity preparation.

CD90 expression and immunoreactive cell localisation in rat dental pulp cells after cavity preparation was investigated. Cavity preparation was performed on the maxillary first molar of 8-week-old Wistar rats (n = 36), and immunohistochemistry and quantitative real-time PCR were performed. CD90-immunoreactivity was observed among subodontoblastic cells in the control group. One day after cavity preparation, the CD90-immunoreactivity disappeared under the cavity area. While CD90-immunoreactivity was faint after 3 days, the re-arrangement of odontoblasts was detected in contact with dentine. After 5 days, the odontoblasts were observed beneath the dentine, and CD90-immunoreactive cells were localised under the odontoblast layer. Immunofluorescence showed co-localisation of CD90 and nestin was detected after 3 days. After 5 days, CD90-immunoreactivity increased at the subodontoblastic layer. mRNA expression of CD90 and DSPP decreased after cavity preparation, and gradually recovered (P < 0.01). These results suggest that CD90-immunoreactive cells in the subodontoblastic layer contribute to regeneration of odontoblast and subodontoblastic layers following cavity preparation.

Human Dental Pulp Cells Express Cellular Markers for Inflammation and Hard Tissue Formation in Response to Bacterial Information.

INTRODUCTION: Lipopolysaccharide (LPS) is a major component of the outer membranes of gram-negative bacteria associated with deep dental caries and pulpitis. When bacteria invade dentinal tubes and dentin is continually destroyed, tertiary dentin is formed by preexisting odontoblasts. However, the relationship between LPS and tertiary dentin formation remains unclear. We investigated whether LPS stimulation induces the formation of hard tissue in human dental pulp cells (hDPCs). METHODS: Immortalized hDPCs were cultured, and Escherichia coli-derived LPS (1 µg/mL) was incorporated into the culture medium. Samples were obtained after 0, 1, 3, 7, 14, and 21 days, and messenger RNA expression of IL-1ß, IL-6, Wnt5a, Runx2, ALP, and alkaline phosphatase (ALP) activity was investigated. RESULTS: Quantitative real-time polymerase chain reaction revealed higher messenger RNA expression levels of IL-1ß and IL-6 in the LPS group on 1 day (P < .05). The expression levels of dentinogenesis-related markers including Wnt5a, Runx2, and ALP were higher in the LPS group (2.0-, 4.7- and 10.0-fold, respectively) than that in the control group at 14 days (P < .01). ALP activity was significantly stronger in the LPS group than in the control group at 21 days (P < .01). Treatment of Box5, an antagonist of Wnt5a, showed a decreased expression of Runx2 and ALP (P < .05). CONCLUSIONS: These results indicate that LPS stimulation induces the gene expression of inflammatory cytokines and hard tissue formation through Wnt5a signaling pathways in hDPCs.