Dual effects of 1α,25-dihydroxyvitamin D3 on inflammation and osteogenic differentiation in lipopolysaccharide-stimulated dental pulp stem cells.

BACKGROUND/PURPOSE: Vitamin D is traditionally known for bone metabolism and also exerts immunomodulatory effects. Dental pulp stem cells (DPSCs) are essential for pulp repair but are impaired under lipopolysaccharide (LPS)-induced inflammation. Therefore, we examined the dual effects of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) on inflammation and osteogenic differentiation in DPSCs. MATERIALS AND METHODS: Human DPSCs were pretreated with 1α,25(OH)2D3 (0.001-1 μM) and stimulated with LPS (1 μg/mL). Thereafter, cell viability was assessed using the 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide assay. Expression of interleukin (IL)-1β, IL-8, and cyclooxygenase-2 (COX-2) was measured using real-time quantitative PCR and Western blot. Moreover, osteogenic activity was evaluated via alkaline phosphatase (ALP) staining. Mitogen-activated protein kinase signaling was analyzed via Western blot, and extracellular signal-regulated kinase (ERK)/c-Jun N-terminal kinase (JNK) inhibitors were applied to confirm mechanistic involvement. RESULTS: The 1α,25(OH)2D3 did not affect DPSC viability under inflammatory conditions. However, the compound markedly suppressed LPS-induced IL-8 and COX-2 expression, with modest effects on IL-1β. LPS markedly reduced ALP activity, which was dose-dependently restored by 1α,25(OH)2D3. Mechanistically, 1α,25(OH)2D3 induced transient phosphorylation of ERK and JNK but not that of p38. Furthermore, Inhibition of ERK or JNK abrogated the osteogenic rescue, thereby confirming their essential roles. CONCLUSION: The 1α,25(OH)2D3 exerts dual actions in LPS-stimulated DPSCs by attenuating inflammatory mediators and promoting osteogenic differentiation through ERK/JNK signaling. These findings suggest its promising potential as a therapeutic adjunct in regenerative endodontics under inflamed conditions.