title: Static and dynamic hypergravity responses of osteoblasts and osteoclasts in medaka scales.
abstract: Fish scales are a form of calcified tissue similar to that found in human bone. In medaka scales, we detected both osteoblasts and osteoclasts and subsequently developed a new scale assay system. Using this system, we analyzed the osteoblastic and osteoclastic responses under 2-, 3-, and 4-gravity (G) loading by both centrifugation and vibration. After loading for 10 min, the scales from centrifugal and vibration loading were incubated for 6 and 24 hrs, respectively, after which the osteoblastic and osteoclastic activities were measured. Osteoblastic activity significantly increased under 2- to 4-G loading by both centrifugation and vibration. In contrast, we found that osteoclastic activity significantly decreased under 2- and 3-G loading in response to both centrifugation and vibration. Under 4-G loading, osteoclastic activity also decreased on centrifugation, but significantly increased under 4-G loading by vibration, concomitant with markedly increased osteoblastic activity. Expression of the receptor activator of the NF-κB ligand (RANKL), an activation factor of osteoclasts expressed in osteoblasts, increased significantly under 4-G loading by vibration but was unchanged by centrifugal loading. A protein sequence similar to osteoprotegerin (OPG), which is known as an osteoclastogenesis inhibitory factor, was found in medaka using our sequence analysis. The ratio of RANKL/OPG-like mRNAs in the vibration-loaded scales was significantly higher than that in the control scales, although there was no difference between centrifugal loaded scales and the control scales. Accordingly, medaka scales provide a useful model by which to analyze bone metabolism in response to physical strain.
authors.affiliation: Japan Aerospace Exploration Agency, Tsukuba, Ibaraki 305-8505, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Yano
authors.forename: Kei-Ichiro
authors.initials: K
authors.lastname: Kitamura
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Satoh
authors.forename: Masaki
authors.initials: M
authors.lastname: Nakano
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Hattori
authors.forename: Toshio
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Mika
authors.initials: M
authors.lastname: Ikegame
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakashima
authors.forename: Katsunori
authors.initials: K
authors.lastname: Omori
authors.forename: Kazuichi
authors.initials: K
authors.lastname: Hayakawa
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Chiba
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sasayama
authors.forename: Sadakazu
authors.initials: S
authors.lastname: Ejiri
authors.forename: Yuko
authors.initials: Y
authors.lastname: Mikuni-Takagaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mishima
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Funahashi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Nobuo
authors.initials: N
authors.lastname: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001696:Biomechanical Phenomena; D005786:Gene Expression Regulation / Q000502:physiology; D018471:Hypergravity; D009990:Oryzias / Q000033:anatomy & histology*; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology*; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism
chemical_list: D053244:Osteoprotegerin