[Bone and bone related biochemical examinations. Bone and collagen related metabolites. Regulatory mechanisms of osteoclast differentiation and function].

Osteoclast differentiation is tightly regulated by osteoblasts. Osteoblasts express two cytokines, macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-kappaB ligand (RANKL), essential for osteoclast differentiation. Osteoclast precursors firstly differentiate into mononuclear osteoclasts in response to M-CSF and RANKL. Nuclear factor of activated T cells 1 (NFATc1) is a transcription factor, which is involved in the determination of osteoclast differentiation. The mononuclear osteoclast then fuses each other to form the multinucleated cell. Dendritic cell-specific transmembrane protein (DC-STAMP) plays an important role in the fusion of mononuclear osteoclasts. Osteoclasts recognize bone and form ruffled borders and clear zones on the bone surface (polarization). Polarizing osteoclasts construct active vascular transportation systems to resorb bone efficiently. RANK-TRAF6 (TNF receptor-associated factor 6) -mediated signals key roles in both osteoclast differentiation and function. In this article, I will review the recent findings on osteoclast differentiation and function.