title: Low extracellular sodium promotes adipogenic commitment of human mesenchymal stromal cells: a novel mechanism for chronic hyponatremia-induced bone loss.
abstract: Hyponatremia represents an independent risk factor for osteoporosis and fractures, affecting both bone density and quality. A direct stimulation of bone resorption in the presence of reduced extracellular sodium concentrations ([Na(+)]) has been shown, but the effects of low [Na(+)] on osteoblasts have not been elucidated. We investigated the effects of a chronic reduction of extracellular [Na(+)], independently of osmotic stress, on human mesenchymal stromal cells (hMSC) from bone marrow, the common progenitor for osteoblasts and adipocytes. hMSC adhesion and viability were significantly inhibited by reduced [Na(+)], but their surface antigen profile and immuno-modulatory properties were not altered. In low [Na(+)], hMSC were able to commit toward both the osteogenic and the adipogenic phenotypes, as demonstrated by differentiation markers analysis. However, the dose-dependent increase in the number of adipocytes as a function of reduced [Na(+)] suggested a preferential commitment toward the adipogenic phenotype at the expense of osteogenesis. The amplified inhibitory effect on the expression of osteoblastic markers exerted by adipocytes-derived conditioned media in low [Na(+)] further supported this observation. The analysis of cytoskeleton showed that low [Na(+)] were associated with disruption of tubulin organization in hMSC-derived osteoblasts, thus suggesting a negative effect on bone quality. Finally, hMSC-derived osteoblasts increased their expression of factors stimulating osteoclast recruitment and activity. These findings confirm that hyponatremia should be carefully taken into account because of its negative effects on bone, in addition to the known neurological effects, and indicate for the first time that impaired osteogenesis may be involved.
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Fibbi
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Benvenuti
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Giuliani
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Deledda
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Luciani
authors.affiliation: ASAcampus Joint Laboratory, ASA Research Division, "Center for Research, Transfer and High Education on Chronic, Inflammatory, Degenerative and Neoplastic Disorders for the Development of Novel Therapies" (DENOThe), Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Monici
authors.affiliation: Haematology Unit, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Mazzanti
authors.affiliation: Department of NEUROFARBA, University of Florence, Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Ballerini
authors.affiliation: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy. alessandro.peri@unifi.it.
authors.forename: A
authors.initials: A
authors.lastname: Peri
mesh_terms: D050156:Adipogenesis; D001854:Bone Marrow Cells / Q000378:metabolism; D001862:Bone Resorption / Q000209:etiology* / Q000378:metabolism*; D002448:Cell Adhesion; D002470:Cell Survival; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D007010:Hyponatremia / Q000150:complications* / Q000378:metabolism*; D007959:Lymphocyte Culture Test, Mixed; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D009997:Osmotic Pressure; D010012:Osteogenesis; D010641:Phenotype; D012964:Sodium / Q000172:deficiency*; D014404:Tubulin / Q000378:metabolism
chemical_list: D014404:Tubulin; D012964:Sodium
keywords: Bone marrow adipogenetic/osteogenetic balance; Chronic hyponatremia; Mesenchymal stromal cells; Osteoporosis