title: Osteocyte specific responses to soluble and mechanical stimuli in a stem cell derived culture model.
abstract: Studying osteocyte behavior in culture has proven difficult because these embedded cells require spatially coordinated interactions with the matrix and surrounding cells to achieve the osteocyte phenotype. Using an easily attainable source of bone marrow mesenchymal stem cells, we generated cells with the osteocyte phenotype within two weeks. These "stem cell derived-osteocytes" (SCD-O) displayed stellate morphology and lacunocanalicular ultrastructure. Osteocytic genes Sost, Dmp1, E11, and Fgf23 were maximally expressed at 15 days and responded to PTH and 1,25(OH)2D3. Production of sclerostin mRNA and protein, within 15 days of culture makes the SCD-O model ideal for elucidating regulatory mechanisms. We found sclerostin to be regulated by mechanical factors, where low intensity vibration significantly reduced Sost expression. Additionally, this model recapitulates sclerostin production in response to osteoactive hormones, as PTH or LIV repressed secretion of sclerostin, significantly impacting Wnt-mediated Axin2 expression, via β-catenin signaling. In summary, SCD-O cells produce abundant matrix, rapidly attain the osteocyte phenotype, and secrete functional factors including sclerostin under non-immortalized conditions. This culture model enables ex vivo observations of osteocyte behavior while preserving an organ-like environment. Furthermore, as marrow-derived mesenchymal stem cells can be obtained from transgenic animals; our model enables study of genetic control of osteocyte behaviors.
authors.affiliation: Department of Physical Therapy, School of Health and Rehabilitation Sciences, Indiana University, Indianapolis, IN 46202.
authors.forename: William R
authors.initials: WR
authors.lastname: Thompson
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Gunes
authors.initials: G
authors.lastname: Uzer
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Kaitlyn E
authors.initials: KE
authors.lastname: Brobst
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Buer
authors.initials: B
authors.lastname: Sen
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Sherwin S
authors.initials: SS
authors.lastname: Yen
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Maya
authors.initials: M
authors.lastname: Styner
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Janet
authors.initials: J
authors.lastname: Rubin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D060466:Axin Protein / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D000089703:Fibroblast Growth Factor-23; D006023:Glycoproteins / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010011:Osteocytes / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D051176:beta Catenin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D060466:Axin Protein; C111729:Axin2 protein, mouse; D004268:DNA-Binding Proteins; C000717427:FGF23 protein, human; C000717428:Fgf23 protein, mouse; D006023:Glycoproteins; C543506:INIP protein, human; D036341:Intercellular Signaling Peptides and Proteins; C486030:Sost protein, mouse; D051176:beta Catenin; D000089703:Fibroblast Growth Factor-23