Generating Human Osteoclasts In Vitro from Bone Marrow and Peripheral Blood

Osteoclasts derive from macrophage colony-stimulating factor (M-CSF)-dependent hemopoietic precursors that develop into cells that express the α_v β₃ subunit of the vitronectin receptor (VNR) and the calcitonin receptor (CTR). The extracellular degradative process, known as bone resorption, is the hallmark of the osteoclast, and includes removal of both the hydroxyapatite and organic components of the skeleton. For bone resorption to occur, osteoclasts form a subcellular space, referred to as an extracellular lysosome, into which they secrete acid and enzymes when they come into contact with either calcified bone or dentine but not with plastic or uncalcified collagen-based matrices. This subcellular space is dependent upon the formation of a “tight seal” by the osteoclast, a process involving rearrangement of the cytoskeleton into a characteristic F-actin ring structure (see the chapter by Nesbitt and Horton, this volume , for details).