Effects of histone deacetylase inhibitors on regenerative cell responses in human dental pulp cells.

AIM

To investigate the growth, migratory and adhesive effects of trichostatin A (TSA) and valproic acid (VPA), two histone deacetylase inhibitors (HDACis), on human dental pulp stem cells (hDPSCs).

METHODOLOGY

To verify that TSA or VPA functions as an HDAC inhibitor, the expressions of histones H3 and H4 were examined using Western blotting analysis. hDPSC growth and metabolic activity was evaluated by MTT viability analysis at different time-points and by cell count experiments. The expression of cell cycle regulatory proteins and apoptosis-associated proteins was examined by Western blot analysis. Migration effects were investigated using wound healing and transwell migration assays. An adhesion assay was also performed in the presence and absence of HDACis. The levels of chemokines and adhesion molecules relevant to repair in hDPSCs were also assessed by qRT-PCR and Western blot analysis. The data were analysed, where appropriate, using Student's t-test or one-way anova followed by the Student-Newman-Keuls test using SPSS software.

RESULTS

Trichostatin A and VPA enhanced acetylation of histones H3 and H4 (P < 0.05). Significant increases (P < 0.05) in MTT levels in hDPSCs were observed after treatment with TSA (2 and 20 nmol L ) or VPA (1 and 10 mmol L ). Cell numbers were not significantly affected at the concentration of TSA (0.2-10 nmol L ) or VPA (0.01-100 mmol L ) applied compared with the control at 3, 5 or 7 days (P > 0.05). At the same time, the expression of Cdx2 and cyclin A was upregulated by 2 nmol L TSA and 1 mmol L VPA (P < 0.05). Higher TSA or VPA concentrations induced apoptosis in hDPSCs in the cell count and apoptosis experiments (P < 0.05). Moreover, TSA and VPA significantly depressed the expression of Cdx2 and cyclin A (P < 0.05), whilst it significantly improved the level of p21 (P < 0.05). TSA and VPA promoted migration and adhesion of hDPSCs (P < 0.05). The levels of chemokines and adhesion molecules were significantly upregulated after exposure of hDPSCs to 20 nmol L TSA or 1 mmol L VPA (P < 0.05).

CONCLUSIONS

Histone deacetylase inhibitors at specific concentrations promoted proliferation, migration and adhesion of hDPSCs, which may contribute to novel regenerative therapies for pulpal disease treatment.