New roles of osteoblasts involved in osteoclast differentiation

Figure 2 In vivo dynamics of osteoclast precursors. Cells expressing both receptor activator of nuclear factor-κB (RANK) and c-Fms are cell cycle-arrested quiescent osteoclast precursors (QOPs) in vivo. QOPs are detected in hematopoietic organs such as the spleen and bone. macrophage colony-stimulating factor (M-CSF) and/or interleukin 34 (IL-34) appear to be involved in the differentiation of hematopoietic progenitor cells into QOPs. Some QOPs circulate to find bone. Osteoblasts play a role in the homing of QOPs to bone. QOPs in bone differentiate into osteoclasts without cell cycle progression in response to M-CSF/IL-34 and RANK ligand.