General Control Nonrepressed Protein 5 Modulates Odontogenic Differentiation Through NF-kappa B Pathway in Tumor Necrosis Factor-alpha-Mediated Impaired Human Dental Pulp Stem Cells

Dental pulp stem cells (DPSCs) from pulpitis patients showed defective osteogenic differentiation. However, as the most well-studied histone acetyltransferase, the impaired general control nonrepressed protein 5 (GCN5) plays essential roles in various developmental processes. The aim of this study was to investigate the effect of GCN5 on DPSCs odontogenic differentiation. The healthy dental pulp tissues were obtained from the extracted impacted third molar of patients with the informed consent. DPSCs were treated with a high concentration of tumor necrosis factor-alpha (TNF-alpha) (100 ng/mL) and odontogenic differentiation-related gene and GCN5 protein level by Western blot analysis. Proliferation of the DPSCs was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Immunofluorescence staining detected GCN5 and NF-kappa B signaling for p-p65. The mechanism of GCN5 regulating odontogenic differentiation of DPSCs was determined by small interfering RNA analysis. Our data suggested that TNF-alpha can significantly reduce mineralization and the expression of dentin matrix acidic phosphoprotein 1 and dentin sialophosphoprotein at higher concentration (100 ng/mL). Meanwhile, it showed that the inflammation in microenvironment resulted in a downregulation of GCN5 expression and GCN5 knockdown caused decreased odontogenic differentiation of DPSCs was also found. In addition, the knockdown of GCN5 increased the expression of phosphorylation of p65, thus activating NF-kappa B pathway of DPSCs. Meanwhile, NF-kappa B pathway inhibitor pyrrolidinedithiocarbamic acid reversed the siGCN5 decreased odontogenic differentiation of DPSCs. Altogether, our findings indicated that in inflammatory microenvironments GCN5 plays a protective role in pulpitis impaired odontogenic differentiation of DPSCs by activating NF-kappa B pathway, which may provide a potential approach to dentin regeneration.