High extracellular calcium stimulates osteoclast-like cell formation and bone-resorbing activity in the presence of osteoblastic cells

✍ Scribed by Hiroshi Kaji; Toshitsugu Sugimoto; Masanori Kanatani; Kazuo Chihara

• Publisher: American Society for Bone and Mineral Research
• Year: 2009
• Tongue: English
• Weight: 827 KB
• Volume: 11
• Category: Article
• ISSN: 0884-0431
• DOI: 10.1002/jbmr.5650110707

✦ Synopsis

Abstract

The present study was performed to examine the effect of the high concentration of extracellular calcium ([Ca^2+^]~e~) on osteoclast‐like cell formation and bone‐resorbing activity in the presence or absence of osteoblasts. High [Ca^2+^]~e~ (3 and 5 mM) significantly stimulated osteoclast‐like cell formation in osteoblast‐containing mouse bone cell cultures, although high [Ca^2+^]~e~ did not affect the formation of osteoclast‐like cells from hemopoietic blast cells supported by granulocyte‐macrophage colony‐stimulating factor in mouse spleen cell cultures. The osteoclast‐like cells, newly formed by high [Ca^2+^]~e~ in the presence of osteoblasts, possessed the ability to form pits on the dentine slices. The conditioned medium from osteoblastic MC3T3‐E1 cells treated with high [Ca^2+^]~e~ (5 mM) significantly increased the formation of osteoclast‐like cells from hemopoietic blast cells, compared with the control medium. Dantrolene, an inhibitor of calcium mobilization from the intracellular calcium pool, and indomethacin significantly blocked high [Ca^2+^]~e~‐stimulated osteoclast‐like cell formation in the presence of osteoblasts, although voltage‐dependent calcium channel blockers and anti‐insulin‐like growth factor I antibody did not affect it. High [Ca^2+^]~e~, however, significantly stimulated the bone‐resorbing activity of mature osteoclasts in osteoblast‐containing mouse bone cell cultures, although high [Ca^2+^]~e~ inhibited bone‐resorbing activity in isolated rabbit osteoclasts. An increase in the extracellular magnesium concentration (5 mM) affected neither osteoclast‐like cell formation nor bone‐resorbing activity. In conclusion, high [Ca^2+^]~e~ stimulated osteoclast‐like cell formation and bone‐resorbing activity of mature osteoclasts, presumably via osteoblasts. (J Bone Miner Res 1996;11:912‐920)