“…Osteoblasts are highly specialized cells that are responsible for the development of bone, production of bone matrix proteins, maintenance of bone density, and formation of hydroxyapatite mineral (Marks and Hermey, 1996). Osteoblasts employ intracellular Ca 2+ as a second messenger modulating fluid shear stress or hormonal responses and also a cofactor for bone mineralization (Lieberherr et al, 1993;Heaney, 1996;Hung et al, 1996;Chen et al, 2000;Nesti et al, 2002). When sufficient amounts of calcium and phosphate are supplied, osteoblasts synthesize and secret a collagenous extracellular matrix that nucleates the formation of hydroxyapatite crystal, in response to diverse extracellular stimuli such as steroid hormones, growth factors, cytokines, biochemical signals and extracellular Ca 2+ concentration (Yamaguchi et al, 1998;McAllister and Frangos, 1999;De Jong et al, 2002).…”