title: Intravital bone imaging by two-photon excitation microscopy to identify osteocytic osteolysis in vivo.
abstract: Bone is a highly dynamic organ in which several cell types function cooperatively. Among these, osteocytes have recently emerged as an important regulator of bone homeostasis, although their mechanism of regulation is unclear. Here, intravital bone imaging by two-photon excitation microscopy allowed us to directly visualize 'osteocytic osteolysis', or resorption of bone in the lacuno-canalicular system. Osteocyte lacunae and the canalicular network in the cortex of murine tibiae were imaged by in vivo calcein staining, and local acidification in these structures was monitored using a topically applied pH sensor. We also demonstrated that sciatic neurectomy causes significant acidification around osteocytic lacunae and enlargement of lacuno-canalicular areas. These results provide strong evidence for osteocytic osteolysis, and demonstrate that two-photon intravital microscopy is useful for analysis of this phenomenon.
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Medicine and Frontier Biosciences, Osaka University, Osaka, Japan; Department of Orthopedic Surgery, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
authors.forename: Hiroshige
authors.initials: H
authors.lastname: Sano
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Medicine and Frontier Biosciences, Osaka University, Osaka, Japan; WPI-Immunology Frontier Research Center, Osaka University, Osaka, Japan; JST, CREST, Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Kikuta
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Medicine and Frontier Biosciences, Osaka University, Osaka, Japan; WPI-Immunology Frontier Research Center, Osaka University, Osaka, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Furuya
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Kondo
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Medicine and Frontier Biosciences, Osaka University, Osaka, Japan; WPI-Immunology Frontier Research Center, Osaka University, Osaka, Japan; JST, CREST, Tokyo, Japan. Electronic address: mishii@icb.med.osaka-u.ac.jp.
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
mesh_terms: D000818:Animals; D015519:Bone Density; D005260:Female; D005452:Fluoresceins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008810:Mice, Inbred C57BL; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D010011:Osteocytes / Q000473:pathology*; D010014:Osteolysis / Q000175:diagnosis* / Q000473:pathology* / Q000503:physiopathology; D012584:Sciatic Nerve / Q000601:surgery; D013977:Tibia / Q000473:pathology* / Q000503:physiopathology
chemical_list: D005452:Fluoresceins; C007740:fluorexon
keywords: Intravital imaging; Osteocyte; Osteocytic lacunae; Osteocytic osteolysis; Two-photon microscopy