Osteoclast (OC) are bone resorbing cells whose development and activity are under the influence of osteoblast (OB). The potential association between those two cell lineages is an area of significant interest. It was not until 1998 that osteoclast differentiation factor (ODF) and osteoprotegerin (OPG) was cloned. The two novel TNF superfamily members have been recently demonstrate to be the key extracellular regulators of osteoclasteogenesis and bone resorption both in vivo and in vitro, and they play important roles in osteoporosis development, diagnosis and treatment.
