title: Relaxin augments BMP-2-induced osteoblast differentiation and bone formation.
abstract: Relaxin (Rln), a polypeptide hormone of the insulin superfamily, is an ovarian peptide hormone that is involved in a diverse range of physiological and pathological reactions. In this study, we investigated the effect of Rln on bone morphogenetic protein 2 (BMP-2)-induced osteoblast differentiation and bone formation. Expression of Rln receptors was examined in the primary mouse bone marrow stem cells (BMSCs) and mouse embryonic fibroblast cell line C3H/10T1/2 cells by RT-PCR and Western blot during BMP-2-induced osteoblast differentiation. The effect of Rln on osteoblast differentiation and mineralization was evaluated by measuring the alkaline phosphatase activity, osteocalcin production, and Alizarin red S staining. For the in vivo evaluation, BMP-2 and/or Rln were administered with type I collagen into the back of mice, and after 3 weeks, bone formation was analyzed by micro-computed tomography (µCT). Western blot was performed to determine the effect of Rln on osteoblast differentiation-related signaling pathway. Expression of Rxfp 1 in BMSCs and C3H/10T1/2 cells was significantly increased by BMP-2. In vitro, Rln augmented BMP-2-induced alkaline phosphatase expression, osteocalcin production, and matrix mineralization in BMSCs and C3H/10T1/2 cells. In addition, in vivo administration of Rln enhanced BMP-2-induced bone formation in a dose-dependent manner. Interestingly, Rln synergistically increased and sustained BMP-2-induced Smad, p38, and transforming growth factor-β activated kinase (TAK) 1 phosphorylation. BMP-2-induced Runx 2 expression and activity were also significantly augmented by Rln. These results show that Rln enhanced synergistically BMP-2-induced osteoblast differentiation and bone formation through its receptor, Rxfp 1, by augmenting and sustaining BMP-2-induced Smad and p38 phosphorylation, which upregulate Runx 2 expression and activity. These results suggest that Rln might be useful for therapeutic application in destructive bone diseases.
authors.affiliation: Dental Science Research Institute, Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, Korea.
authors.forename: Jung-Sun
authors.initials: JS
authors.lastname: Moon
authors.forename: Sun-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Sin-Hye
authors.initials: SH
authors.lastname: Oh
authors.forename: Yong-Wook
authors.initials: YW
authors.lastname: Jeong
authors.forename: Jee-Hae
authors.initials: JH
authors.lastname: Kang
authors.forename: Jong-Chun
authors.initials: JC
authors.lastname: Park
authors.forename: Hye-Ju
authors.initials: HJ
authors.lastname: Son
authors.forename: Suk
authors.initials: S
authors.lastname: Bae
authors.forename: Byung-Il
authors.initials: BI
authors.lastname: Park
authors.forename: Min-Seok
authors.initials: MS
authors.lastname: Kim
authors.forename: Jeong-Tae
authors.initials: JT
authors.lastname: Koh
authors.forename: Hyun-Mi
authors.initials: HM
authors.lastname: Ko
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D010012:Osteogenesis / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D012065:Relaxin / Q000494:pharmacology*; D051785:Smad Proteins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D055396:Bone Morphogenetic Protein 2; D050659:Core Binding Factor Alpha 1 Subunit; D020930:MAP Kinase Kinase Kinases; D043562:Receptors, G-Protein-Coupled; D012065:Relaxin; D051785:Smad Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C478103:RXFP1 protein, mouse; C493716:Runx2 protein, mouse
keywords: BMP; BONE; RELAXIN; RXFP