Extracellular calcium increases fibroblast growth factor 2 gene expression via extracellular signal-regulated kinase 1/2 and protein kinase A signaling in mouse dental papilla cells

We previously reported that elevated extracellular calcium (Ca²⁺) levels increase bone morphogenetic protein 2 expression in human dental pulp (hDP) cells. However, it is unknown whether extracellular Ca²⁺ affects the expression of other growth factors such as fibroblast growth factor 2 (FGF2). Objective: The present study aimed to examine the effect of extracellular Ca²⁺ on FGF2 gene expression in hDP and immortalized mouse dental papilla (mDP) cells. Materials and Methods: Cells were stimulated with 10 mM CaCl₂ in the presence or absence of cell signaling inhibitors. FGF2 gene expression was assessed using real-time polymerase chain reaction. The phosphorylation status of signaling molecules was examined by Western blotting. Results: Extracellular Ca²⁺ increased FGF2 gene expression in mDP and hDP cells. Gene expression of the calcium-sensing receptor and G protein-coupled receptor family C group 6 member A, both of which are extracellular Ca²⁺ sensors, was not detected. Ca²⁺-mediated Fgf2 expression was reduced by pretreatment with the protein kinase A (PKA) inhibitor H-89 or extracellular signal-regulated kinase (ERK) 1/2 inhibitor PD98059 but not by pretreatment with the protein kinase C inhibitor GF-109203X or p38 inhibitor SB203580. Extracellular Ca²⁺ increased PKA activity and ERK1/2 phosphorylation. Ca²⁺-induced PKA activity decreased by pretreatment with PD98059. Conclusions: These findings indicate that elevated extracellular Ca²⁺ levels led to increased Fgf2 expression through ERK1/2 and PKA in mDP cells and that this mechanism may be useful for designing regenerative therapies for dentin.