| [ Summary ] |
Osteoclasts are multinucleated cells responsible for bone resorption. Although the mechanisms by which monocyte / macrophage lineage cells differentiate into osteoclasts under the control of osteoblasts are well known, osteoclast precursors in vivo have not been clearly characterized. It has previously been shown that cell cycle progression and subsequent cell cycle withdrawal in osteoclast precursors are required for their differentiation into osteoclasts in vivo. Those osteoclast precursors were then termed “cell cycle arrested-quiescent osteoclast precursors (QuOPs)”. In vivo studies have revealed that osreoblasts prepare the osteoclast niche, in which QuOPs are maintained for long periods in an undifferentiated state. Furthermore, the maintenance of QuOPs was dispensable for M-CSF, RANKL, and OPG. QuOPs in the osreoclast niche differentiated into osteoclasts without cell cycle progression in response to bone resorption-inducing stimuli. The osteoclast niche may make it possible for osreoclasts to be promptly formed at the correct location in all situations. |