title: Regulatory effects of fibroblast growth factor-8 and tumor necrosis factor-α on osteoblast marker expression induced by bone morphogenetic protein-2.
abstract: BMP induces osteoblast differentiation, whereas a key proinflammatory cytokine, TNF-α, causes inflammatory bone damage shown in rheumatoid arthritis. FGF molecules are known to be involved in bone homeostasis. However, the effects of FGF-8 on osteoblast differentiation and the interaction between FGF-8, BMPs and TNF-α have yet to be clarified. Here we investigated the effects of FGF-8 in relation to TNF-α actions on BMP-2-induced osteoblast marker expression using myoblast cell line C2C12, osteoblast precursor cell line MC3T3-E1 and rat calvarial osteoblasts. It was revealed that FGF-8 inhibited BMP-2-induced expression of osteoblast differentiation markers, including Runx2, osteocalcin, alkaline phosphatase, type-1 collagen and osterix, in a concentration-dependent manner. The inhibitory effects of FGF-8 on BMP-induced osteoblast differentiation and Smad1/5/8 activation were enhanced in the presence of TNF-α action. FGF-8 also inhibited BMP-2-induced expression of Wnt5a, which activates a non-canonical Wnt signaling pathway. FGF-8 had no significant influence on the expression levels of TNF receptors, while FGF-8 suppressed the expression of inhibitory Smad6 and Smad7, suggesting a possible feedback activity through FGF to BMP receptor (BMPR) signaling. Of note, inhibition of ERK activity and FGF receptor (FGFR)-dependent protein kinase, but not JNK or NFκB pathway, suppressed the FGF-8 actions on BMP-induced osteoblast differentiation. FGF-8 was revealed to suppress BMP-induced osteoblast differentiation through the ERK pathway and the effects were enhanced by TNF-α. Given the finding that FGF-8 expression was increased in synovial tissues of rheumatoid arthritis, the functional interaction between FGFR and BMPR signaling may be involved in the development process of inflammatory bone damage.
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Katsuyama
authors.affiliation: Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan. Electronic address: fumiotsu@md.okayama-u.ac.jp.
authors.forename: Fumio
authors.initials: F
authors.lastname: Otsuka
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Terasaka
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Inagaki
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Takano-Narazaki
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Ken-Ei
authors.initials: KE
authors.lastname: Sada
authors.affiliation: Okayama University Hospital, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Makino
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis*; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D051524:Fibroblast Growth Factor 8 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D051785:Smad Proteins / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D000943:Antigens, Differentiation; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; C496457:Fgf8 protein, mouse; D016328:NF-kappa B; D051785:Smad Proteins; D014409:Tumor Necrosis Factor-alpha; D051524:Fibroblast Growth Factor 8; D048670:MAP Kinase Kinase 4
keywords: Bone morphogenetic protein (BMP); Fibroblast growth factor (FGF)-8; Osteoblast; Osteogenesis; Tumor necrosis factor (TNF)-α