Identification of Sclerostin as a Putative New Myokine Involved in the Muscle-to-Bone Crosstalk
Maria Sara Magarò,
Jessika Bertacchini,
Francesca Florio,
Manuela Zavatti,
Francesco Potì,
Francesco Cavani,
Emanuela Amore,
Ilaria De Santis,
Alessandro Bevilacqua,
Luca Reggiani Bonetti,
Pietro Torricelli,
Delphine B. Maurel,
Stefano Biressi,
Carla Palumbo
Affiliations
Maria Sara Magarò
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Jessika Bertacchini
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Francesca Florio
Department of Cellular, Computational and Integrative Biology (CIBIO) and Dulbecco Telethon Institute, University of Trento, 38123 Povo, Trento, Italy
Manuela Zavatti
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Francesco Potì
Department of Medicine and Surgery—Unit of Neurosciences, University of Parma, 43126 Parma, Italy
Francesco Cavani
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Emanuela Amore
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Ilaria De Santis
Department of Medical and Surgical Sciences (DIMEC), Alma Mater Studiorum, University of Bologna, 40138 Bologna, Italy
Alessandro Bevilacqua
Advanced Research Center for Electronic Systems (ARCES), University of Bologna, 40126 Bologna, Italy
Luca Reggiani Bonetti
Department of Medical and Surgical Sciences for Children and Adults, AOU Policlinico of Modena, University of Modena and Reggio Emilia, 41124 Modena, Italy
Pietro Torricelli
Department of Radiology, University Hospital of Modena, 41124 Modena, Italy
Delphine B. Maurel
Pharmaceutical Sciences Department, University of Bordeaux, BioTis, INSERM Unit 1026, 33076 Bordeaux, France
Stefano Biressi
Department of Cellular, Computational and Integrative Biology (CIBIO) and Dulbecco Telethon Institute, University of Trento, 38123 Povo, Trento, Italy
Carla Palumbo
Department of Biomedical, Metabolic and Neural Sciences, Section of Human Morphology, University of Modena and Reggio Emilia, 41124 Modena, Italy
Bone and muscle have been recognized as endocrine organs since they produce and secrete “hormone-like factors” that can mutually influence each other and other tissues, giving rise to a “bone–muscle crosstalk”. In our study, we made use of myogenic (C2C12 cells) and osteogenic (2T3 cells) cell lines to investigate the effects of muscle cell-produced factors on the maturation process of osteoblasts. We found that the myogenic medium has inhibitory effects on bone cell differentiation and we identified sclerostin as one of the myokines produced by muscle cells. Sclerostin is a secreted glycoprotein reportedly expressed by bone/cartilage cells and is considered a negative regulator of bone growth due to its role as an antagonist of the Wnt/β-catenin pathway. Given the inhibitory role of sclerostin in bone, we analyzed its expression by muscle cells and how it affects bone formation and homeostasis. Firstly, we characterized and quantified sclerostin synthesis by a myoblast cell line (C2C12) and by murine primary muscle cells by Western blotting, real-time PCR, immunofluorescence, and ELISA assay. Next, we investigated in vivo production of sclerostin in distinct muscle groups with different metabolic and mechanical loading characteristics. This analysis was done in mice of different ages (6 weeks, 5 and 18 months after birth) and revealed that sclerostin expression is dynamically modulated in a muscle-specific way during the lifespan. Finally, we transiently expressed sclerostin in the hind limb muscles of young mice (2 weeks of age) via in vivo electro-transfer of a plasmid containing the SOST gene in order to investigate the effects of muscle-specific overproduction of the protein. Our data disclosed an inhibitory role of the muscular sclerostin on the bones adjacent to the electroporated muscles. This observation suggests that sclerostin released by skeletal muscle might synergistically interact with osseous sclerostin and potentiate negative regulation of osteogenesis possibly by acting in a paracrine/local fashion. Our data point out a role for muscle as a new source of sclerostin.
