Abstract
Aim: This study aimed to investigate the effect of valproic acid (VPA) exposure on pulp inflammation and regeneration.
Methods: The effects of VPA on pulp regeneration and reparative dentin formation were examined using cone-beam computed tomography (CBCT) and histological staining in vivo after 3 months of endodontic regenerative procedures (ERPs). In vitro, the effect of VPA on the odontogenic differentiation of human dental pulp stem cells (hDPSCs) was assessed using mineralization assays following lipopolysaccharide (LPS) exposure. Western blotting, quantitative real-time polymerase chain reaction, and reverse transcriptase polymerase chain reaction were performed to analyze changes in gene and transcript expression. Mineralization and transfection assays were conducted to evaluate the roles of histone deacetylase (HDAC)2 and HDAC5.
Results: Three months post-ERPs, CBCT imaging revealed well-sealed crowns and normal root apices with no apparent periapical lesions in all groups. The hDPSCs+VPA group exhibited a greater presence of neoformed connective tissues, dentin-like tissues and odontoblast-like cells compared to the hDPSCs group. Furthermore, mineralization assays demonstrated that VPA enhanced LPS-induced odontoblastic differentiation. In particular, during this process, VPA significantly downregulated the expression of HDAC2 and HDAC5 in hDPSCs treated with VPA and LPS, HDAC2 knockdown reduced odontoblastic protein production and the calcified nodules formation, while HDAC5 inhibition promoted odontoblastic differentiation in hDPSCs. Overexpression of HDAC2 or HDAC5 in the presence of VPA and LPS played the opposite role during the odontoblastic differentiation of hDPSCs.
Conclusions: This study demonstrated that VPA improved pulp regeneration by regulating LPS-induced odontogenic differentiation of hDPSCs, primarily through modulation of HDAC2 and HDAC5 activity.
Clinical relevance: These data demonstrate that VPA is a highly effective pharmacological candidate for dental pulp maintenance and regeneration, highlighting its clinical significance in restorative dentistry.