title: Collagen production of osteoblasts revealed by ultra-high voltage electron microscopy.
abstract: In the bone, collagen fibrils form a lamellar structure called the "twisted plywood-like model." Because of this unique structure, bone can withstand various mechanical stresses. However, the formation of this structure has not been elucidated because of the difficulty of observing the collagen fibril production of the osteoblasts via currently available methods. This is because the formation occurs in the very limited space between the osteoblast layer and bone matrix. In this study, we used ultra-high-voltage electron microscopy (UHVEM) to observe collagen fibril production three-dimensionally. UHVEM has 3-MV acceleration voltage and enables us to use thicker sections. We observed collagen fibrils that were beneath the cell membrane of osteoblasts elongated to the outside of the cell. We also observed that osteoblasts produced collagen fibrils with polarity. By using AVIZO software, we observed collagen fibrils produced by osteoblasts along the contour of the osteoblasts toward the bone matrix area. Immediately after being released from the cell, the fibrils run randomly and sparsely. But as they recede from the osteoblast, the fibrils began to run parallel to the definite direction and became thick, and we observed a periodical stripe at that area. Furthermore, we also observed membrane structures wrapped around filamentous structures inside the osteoblasts. The filamentous structures had densities similar to the collagen fibrils and a columnar form and diameter. Our results suggested that collagen fibrils run parallel and thickly, which may be related to the lateral movement of the osteoblasts. UHVEM is a powerful tool for observing collagen fibril production.
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan.
authors.forename: Rumiko
authors.initials: R
authors.lastname: Hosaki-Takamiya
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan.
authors.forename: Mana
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Imai
authors.affiliation: Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nishida
authors.affiliation: Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
authors.forename: Hirotaro
authors.initials: H
authors.lastname: Mori
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan.
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kawanabe
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Dentistry, Osaka University, 1-8 Yamada-Oka, Suita, Osaka, 565-0871, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamashiro
authors.affiliation: Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata, Kita-ku, Okayama, Okayama, 700-8525, Japan. kamioka@md.okayama-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kamioka
mesh_terms: D000818:Animals; D000071556:Cancellous Bone / Q000648:ultrastructure; D002642:Chick Embryo; D003094:Collagen / Q000096:biosynthesis; D024022:Fibrillar Collagens / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008857:Microscopy, Interference; D010006:Osteoblasts / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D024022:Fibrillar Collagens; D003094:Collagen
keywords: Bone; Collagen fibril; Osteoblast; Three-dimensional reconstruction; Ultra-high voltage electron microscopy