[Bone and calcium update; bone research update. Trafficking of osteoclast precursors visualized by intravital imaging technology]

Osteoclasts are 'bone-resorbing' giant polykaryons that differentiate from mononuclear macrophage/monocyte-lineage hematopoietic precursors. However, it has remained unclear how osteoclast precursors migrate into the bone surface and what controls their migratory behaviors in vivo . To investigate these questions, we utilized an advanced imaging system for visualizing live bone tissues with intravital multiphoton microscopy that we have recently established. By means of the system we have recently succeeded in visualization of osteoclast precursors in live bones and revealed that sphingosine-1-phosphate (S1P) , a lipid mediator, dynamically regulates migration and localization of osteoclasts and their precursors in vivo . Here we show the latest data and the detailed methodology of intravital imaging of bone tissues, and also discuss its further application.