ABSTRACT
Bone is made up of seven hierarchical structures and consists of hydroxyapatite and collagen as major constituents (Venkatesan and Kim 2010a, 2010b; Venkatesan et al. 2011a, 2011b). Defects in bone can occur due to many reasons such as motor accidents, birth defects, osteoporosis, arthritis, bone gangrene, and low calcium levels. The mass and function of bones depend on the maintenance of a complicated balance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Calcium and phosphate are the two minerals that are essential for normal bone formation. Osteoblasts secrete a calciable matrix that contains minerals; collagen; and a small amount of noncollagenous proteins including osteopontin, osteonectin, bone sialoprotein, and osteocalcin (Gay, Gilman, and Sugiyama 2000). The function of osteoclasts is to remove bone tissue by removing its mineralized matrix and breaking up the organic bone (90% collagen). An increase in the number of osteoclast cells and their function normally induces bone osteoporosis, indicating that osteoclasts play a pivotal role in bone homeostasis (Manolagas 2000; Miyamoto and Suda 2003).
