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KMID : 0848120080330010033
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International Journal of Oral Biology
2008 Volume.33 No. 1 p.33 ~ p.43
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High Extracellular Calcium Increased Expression of Ank, PC-1 and Osteopontin in Mouse Calvarial Cells
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Song Mi-Na
Ryoo Hyun-Mo
Woo Kyung-Mi
Kim Gwan-Shik
Baek Jeong-Hwa
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Abstract
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In the process of bone remodeling, mineral phase of bone is dissolved by osteoclasts, resulting in elevation of calcium concentration in micro-environment. This study was performed to explore the effect of high extracellular calcium (Ca²+e) on mineralized nodule formation and on the expression of progressive ankylosis (Ank), plasma cell membrane glycoprotein-1 (PC-1) and osteopontin by primary cultured mouse calvarial cells. Osteoblastic differentiation and mineralized nodule formation was induced by culture of mouse calvarial cells in osteoblast differentiation medium containing ascorbic acid and -glycerophosphate. Although Ank, PC-1 and osteopontin are well known inhibitors of mineralization, expression of these genes were induced at the later stage of osteoblast differentiation during when expression of osteocalcin, a late marker gene of osteoblast differentiation, was induced and mineralization was actively progressing. High Ca²+e(10 mM) treatment highly enhanced mRNA expression of Ank, PC-1 and osteopontin in the late stage of osteoblast differentiation but not in the early stage. Inhibition of p44/42 MAPK activation but not that of protein kinase C suppressed high Ca²+e-induced expression of Ank, PC-1 and osteopontin. When high Ca²+e(5 mM or 10 mM) was present in culture medium during when mineral deposition was actively progressing, matrix calcifiation was significantly increased by high Ca²+e. This stimulatory effect was abolished by pyrophosphate (5 mM) or levamisole (0.1-0.5 mM), an alkaline phosphatase inhibitor. In addition, probenecid (2mM), an inhibitor of Ank, suppressed matrix calcification in both control and high Ca²+e- treated group, suggesting the possible role of Ank in matrix calcification by osteoblasts. Taken together, these results showed that high Ca²+e stimulates expression of Ank, PC-1 and osteopontin as well as matrix calcification in late differentiation stage of osteoblasts and that p44/42 MAPK activation is involved in high Ca²+e- induced expression of Ank, PC-1 and osteopontin.
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KEYWORD
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high extracellular calcium, osteoblast, matrix calcification, Ank, PC-1, osteopontin
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