title: The alteration of a mechanical property of bone cells during the process of changing from osteoblasts to osteocytes.
abstract: Osteocytes acquire their stellate shape during the process of changing from osteoblasts in bone. Throughout this process, dynamic cytoskeletal changes occur. In general, changes of the cytoskeleton affect cellular mechanical properties. Mechanical properties of living cells are connected with their biological functions and physiological processes. In this study, we for the first time analyzed elastic modulus, a mechanical property of bone cells. Bone cells in embryonic chick calvariae and in isolated culture were identified using fluorescently labeled phalloidin and OB7.3, a chick osteocyte-specific monoclonal antibody, and then observed by confocal laser scanning microscopy. The elastic modulus of living cells was analyzed with atomic force microscopy. To examine the consequences of focal adhesion formation on the elastic modulus, cells were pretreated with GRGDS and GRGES, and then the elastic modulus of the cells was analyzed. Focal adhesions in the cells were visualized by immunofluorescence of vinculin. From fluorescence images, we could distinguish osteoblasts, osteoid osteocytes and mature osteocytes both in vivo and in vitro. The elastic modulus of peripheral regions of cells in all three populations was significantly higher than in their nuclear regions. The elastic modulus of the peripheral region of osteoblasts was 12053+/-934 Pa, that of osteoid osteocytes was 7971+/-422 Pa and that of mature osteocytes was 4471+/-198 Pa. These results suggest that the level of elastic modulus of bone cells was proportional to the stage of changing from osteoblasts to osteocytes. The focal adhesion area of osteoblasts was significantly higher than that of osteocytes. The focal adhesion area of osteoblasts was decreased after treatment with GRGDS, however, that of osteocytes was not. The elastic modulus of osteoblasts and osteoid osteocytes were decreased after treatment with GRGDS. However, that of mature osteocytes was not changed. There were dynamic changes in the mechanical property of elastic modulus and in focal adhesions of bone cells.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Okayama-City, Okayama, 700-8525, Japan.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Sugawara
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Okayama-City, Okayama, 700-8525, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Ando
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Okayama-City, Okayama, 700-8525, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kamioka
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Okayama-City, Okayama, 700-8525, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Ishihara
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai-City, Miyagi, 980-8574, Japan.
authors.forename: Sakhr A
authors.initials: SA
authors.lastname: Murshid
authors.affiliation: Department of Physiology, Kawasaki Medical School, Matushima 57, Kurashiki-city, Okayama, 701-0192, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: Department of Medical Engineering, Kawasaki Medical School, Matushima 57, Kurashiki-city, Okayama, 701-0192, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kataoka
authors.affiliation: Department of Physiology, Kawasaki Medical School, Matushima 57, Kurashiki-city, Okayama, 701-0192, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Tsujioka
authors.affiliation: Department of Medical Engineering, Kawasaki Medical School, Matushima 57, Kurashiki-city, Okayama, 701-0192, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Kajiya
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Okayama-City, Okayama, 700-8525, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamashiro
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai-City, Miyagi, 980-8574, Japan. Electronic address: t-yamamo@mail.tains.tohoku.ac.jp.
authors.forename: Teruko
authors.initials: T
authors.lastname: Takano-Yamamoto
mesh_terms: D000818:Animals; D019070:Cell Lineage; D002642:Chick Embryo; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology*; D010011:Osteocytes / Q000166:cytology*
chemical_list: D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid