Effects of Calcium Hydroxide on Osteoblast Differentiation and Mineralization
Objectives: Calcium hydroxide has been broadly used for endodontic treatments since it exhibits antibacterial effects due to the strong alkalinity. In addition, as frequently utilized for apexification, Ca(OH)2 is effective to promote mineralization. However, the detailed mechanism of Ca(OH)2 to induce mineralization remains unclear. The purpose of this study is to examine the effects of Ca(OH)2 on differentiation and mineralization of osteoblasts, focusing on the role of calcium ion and alkalinity. Methods: Murine primary osteoblasts were cultured in α-MEM containing 10% FCS with different concentrations of Ca(OH)2 and pH : 1) 0 mg/ml Ca(OH)2, pH 7.4, 2) 0.25 mg/ml Ca(OH)2, pH 8.5, 3) 0.25 mg/ml Ca(OH)2, pH 7.4. The expression levels of osteoblast differentiation markers were determined using quantitative RT-PCR, and the activation of ERK, p38 and JNK were examined by western blotting analysis. Mineralization of osteoblasts cultured with MAPK inhibitor was evaluated by alizarin red staining. Results: Osteoblasts cultured with 0.25 mg/ml Ca(OH)2 showed mineralization. Mineralization level of osteoblsats cultured with 0.25 mg/ml Ca(OH)2 at pH 7.4 is greater than at pH 8.5. Expression levels of osteopontin, osteocalcin and alkaline phosphatase mRNA in osteoblasts cultured with 0.25 mg/ml Ca(OH)2 were up-regulated, and especially, strong enhancement of osteopontin expression was observed at pH 7.4 (Student t-test, p<0.05). The phosphorylation duration time of p38 and JNK in osteoblasts stimulated with Ca(OH)2 at pH 7.4 was longer than at pH 8.5. Inhibitor treatment for p38 and JNK dose-dependently suppressed mineralization induced by Ca(OH)2. Conclusions: Calcium hydroxide induces osteoblast differentiation and mineralization, and its effects are pronounced in the neutral condition based on the activation of p38 and JNK. These results suggest the importance of calcium ion on osteoblastic differentiation. (This study was supported by a Grant-in-Aid for Scientific Research No. 22791832 from the Japan Society for the Promotion of Science.)
Division: Japanese Division Meeting
Meeting:2010 Japanese Division Meeting (Kitakyushi City, Japan) Location: Kitakyushi City, Japan
Year: 2010 Final Presentation ID: Abstract Category|Abstract Category(s):Scientific Groups
Authors
Nasa, Hiroko
( Osaka University, Suita, N/A, Japan
)
Itoh, Shousaku
( Osaka University, Suita, N/A, Japan
)
Imazato, Satoshi
( Osaka University, Suita, N/A, Japan
)
Ebisu, Shigeyuki
( Osaka University, Suita, N/A, Japan
)