Abstract
The osteoclast is the unique type of cell that resorbs bone in vivo and it is required for normal skeletal development and postnatal homeostasis. Osteoclast deficiency impairs skeletal development during embryogenesis and results in osteopetrosis and impaired tooth eruption. In contrast, excessive osteoclast formation in adults results in bone loss in a number of conditions, including osteoporosis, rheumatoid arthritis, and metastatic bone disease. Osteoclasts are derived from monocytes/macrophages; they can be generated in vitro by treatment of these precursor cells with macrophage colony stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL). This chapter describes procedures for generating osteoclasts from mouse bone marrow cells in vitro using M-CSF and RANKL and assessing their ability to form resorption lacunae on thin bone slices.