title: Elevation of fibrinogen due to loss of ovarian function enhances actin ring formation and leads to increased bone resorption.
abstract: The aim of the present study was to evaluate the effect of fibrinogen on number and function of osteoclasts (OC) consequently resulting in bone loss. It was hypothesized that the enhanced level of released fibrinogen due to loss of ovarian function caused bone loss by acting on OCs. Bone loss was induced by ovariectomy (OVX) in mice and analyzed by micro-CT. The effect of fibrinogen on OCs was evaluated by tartrate-resistant acid phosphatase, annexin V, actin staining, pit formation observed on dentine slices, and Western blotting. Exogenous fibrinogen increased OC survival, actin ring formation, and bone resorption in vitro. The effect of fibrinogen was dependent on β(3)-integrin, which is a marker for mature OCs. Fibrinogen induced the activation of transforming oncogene from Ak strain (Akt), Ras-related C3 botulinum toxin substrate 1 (Rac1), and Rho family of GTPase (Rho) and the degradation of the Bcl-2 interacting mediator of cell death (Bim) in a manner similar to macrophage colony-stimulating factor (M-CSF). OVX increased plasma fibrinogen and serum M-CSF together with elevated actin ring formation and bone loss. The increased fibrinogen level due to loss of ovarian function may contribute, at least partly, to bone loss through the enhanced number and activity of OCs.
authors.affiliation: Dept. of Biological Sciences (BK21 Program) and the Immunomodulation Research Center, Univ. of Ulsan, Ulsan, Korea.
authors.forename: Ke
authors.initials: K
authors.lastname: Ke
authors.forename: Woon-Ki
authors.initials: WK
authors.lastname: Kim
authors.forename: Ok-Joo
authors.initials: OJ
authors.lastname: Sul
authors.forename: Van Tien
authors.initials: VT
authors.lastname: Phan
authors.forename: Mi-Hyun
authors.initials: MH
authors.lastname: Lee
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Kim
authors.forename: Shin-Yoon
authors.initials: SY
authors.lastname: Kim
authors.forename: Hye-Seon
authors.initials: HS
authors.lastname: Choi
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001854:Bone Marrow Cells / Q000502:physiology; D001862:Bone Resorption / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism*; D002454:Cell Differentiation; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D005340:Fibrinogen / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000502:physiology*; D010024:Osteoporosis / Q000150:complications / Q000378:metabolism*; D010052:Ovariectomy; D017698:Postmenopause / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D018709:Statistics, Nonparametric; D055114:X-Ray Microtomography
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D019030:Receptors, Vitronectin; C094340:integrin alphavbeta1; D016173:Macrophage Colony-Stimulating Factor; D005340:Fibrinogen