Morphology, Function, and Differentiation of Bone Cells

Bone plays a pivotal role in storing calcium and phosphate in vertebrates. This tissue is maintained by the balance of bone formation and bone resorption. Osteoblast-lineage cells, consisting of osteoblasts, osteocytes and bone lining cells, are engaged in bone formation. Bone resorption is mediated by osteoclasts. Recent research revealed that receptor activator of NF-κB (RANK)-RANK ligand (RANKL) mechanism is essential for the differentiating and activating osteoclasts. Osteoblast-lineage cells regulate bone resorption via the expression of RANKL and osteoprotegerin (OPG), a decoy receptor for RANKL. Additionally, osteoblastlineage cells participate in degradation of bone matrix by secreting MMP-13. Thus, bone remodeling is achieved by the harmonized orchestration of osteoblast-lineage cells and osteoclast-lineage cells.