[Development of methodology for living bone imaging.]

Bone tissue consist of a wide variety of cells such as osteoclasts, osteoblasts and osteocytes which are involved in bone metabolism, hematopoietic cells which can differentiate and mature in the bone marrow, other mesenchymal cells and nerve cells. Recent advances in "fluorescent imaging technology" have made it possible to observe bone tissue alive. And intravital imaging enable us not only to examine the "morphology" but also to analyze the "dynamics" of the cells. We have improved "two-photon microscope" which can observe deep tissue with minimally invasive manner and have established an imaging method to observe the movement of cells in living bone tissue in real time. In this review, we summarize the methodology of intravital imaging, such as the principle of two-photon excitation microscope, method of in vivo imaging of bone, and analysis of acquired imaging data.