The effects of tumor necrosis factor-α on mineralization of human dental apical papilla cells

Abstract

Introduction: Human dental apical papilla cells (APCs) have mineralization potential, which plays a key role in the root development of young permanent teeth. Limited literature is available about APC mineralization in the presence of inflammatory cytokines. The purpose of this study was to investigate the effects of tumor necrosis factor-α (TNF-α) on APC mineralization.

Methods: APC cultures were established with the enzymatic dissociation method in vitro. The viability of APCs treated with TNF-α was investigated using methyl-thiazol-tetrazolium assays. Cells were then cultured in osteo-/dentinogenic medium with TNF-α, and mineralization was assessed by alizarin red S staining. Bone sialoprotein (BSP) and dentin sialoprotein (DSP) were analyzed using immunocytochemistry. Mineralization genes such as BSP, dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and dentin matrix acidicphosphoprotein-1 (DMP1) were determined with real-time polymerase chain reaction analyses.

Results: The viability of cultured cells was higher with TNF-α concentrations of 10 ng/mL and 50 ng/mL than with 5 ng/mL or in the control group. Alizarin red S staining showed that APCs had a higher mineralization activity when the osteo-/dentinogenic culture medium contained 10 ng/mL TNF-α. Immunocytochemical detection showed that the expression of BSP and DSP was positive in APCs after they were induced in osteo-/dentinogenic medium. The expression of mineralization genes differed when treated with 10 ng/mL TNF-α (ie, the expression of DSPP mRNA increased on days 7 and 14, whereas the expression of DSPP mRNA decreased on day 21).

Conclusions: TNF-α may promote APC mineralization in short-term cultures and inhibit the mineralization in long-term cultures.