Osteocytes, the most abundant cells in bone, are believed to play a key role in skeletal mechanosensing whereby they modulate bone modeling and remodeling in response to changes in shear or strain forces. Although it is well-established that bone responds to its mechanical environment, the mechanisms underlying the mechano- transduction pathway are poorly understood. Moreover, recent findings have documented a role of osteocytes in the regulation of phosphate homeostasis. Using a mechanically active or static culture condition to culture osteocytes, we will test the hypothesis that SOST and FGF-23 are important regulators of mechano-sensation. Initial studies will be devoted to establish conditionally immortalized osteocytic cell lines derived from transgenic mice expressing the fluorescent green protein (GFP) under the control of DMP-1 (known to be expressed exclusively in osteocytes) and carrying the temperature-sensitive immortalizing SV40 antigen. Cells will be grown on 3D scaffold and subjected to 1g, microgravity (NASA horizontal bioreactor) or increase mechanical stimulation (NASA vertical Bioreactor). We will then investigate the role of SOST and FGF23 signaling in osteocytes (under static and dynamic condition) by selectively silencing these transcripts using small interfering RNAs (siRNA). Analysis of gene expression patterns under these conditions and measuring secretion of sclerostin and FGF23 will provide insights into mechano-transduction pathways and mineral ion regulation (UH2). Lastly utilizing the microgravity environment and minimal fluid shear culture conditions available only onboard of the International Space Station (ISS) we propose to investigate osteocytes responses to unloading conditions (UH3). The eOSTEO flight hardware will be modified accordingly to the aims of this ISS mission. Implementation Partner for this proposal are Calm Technologies and the Canadian Space Agency (CSA). Results derived from the studies proposed could have significant implications for therapy of bone disorders related to disuse or immobilization.

Public Health Relevance

If successful this proposal will significantly advance our knowledge of the role of mechanical forces on osteocytes biology and further enhance our understanding of these cells. Results derived from the studies proposed could have significant implications for therapy of bone disorders related to disuse or immobilization. Thus, its relevance is high for skeletal biology.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Exploratory/Developmental Cooperative Agreement Phase II (UH3)
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Special Emphasis Panel (ZEB1-OSR-E (M1))
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Chen, Faye H
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Massachusetts General Hospital
United States
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Fulzele, Keertik; Dedic, Christopher; Lai, Forest et al. (2018) Loss of Gs? in osteocytes leads to osteopenia due to sclerostin induced suppression of osteoblast activity. Bone 117:138-148
Shi, Chao; Uda, Yuhei; Dedic, Christopher et al. (2018) Carbonic anhydrase III protects osteocytes from oxidative stress. FASEB J 32:440-452
Fulzele, Keertik; Lai, Forest; Dedic, Christopher et al. (2017) Osteocyte-Secreted Wnt Signaling Inhibitor Sclerostin Contributes to Beige Adipogenesis in Peripheral Fat Depots. J Bone Miner Res 32:373-384
Qin, Yiwen; Peng, Yuanzhen; Zhao, Wei et al. (2017) Myostatin inhibits osteoblastic differentiation by suppressing osteocyte-derived exosomal microRNA-218: A novel mechanism in muscle-bone communication. J Biol Chem 292:11021-11033
Spatz, Jordan M; Wein, Marc N; Gooi, Jonathan H et al. (2015) The Wnt Inhibitor Sclerostin Is Up-regulated by Mechanical Unloading in Osteocytes in Vitro. J Biol Chem 290:16744-58
Wein, Marc N; Spatz, Jordan; Nishimori, Shigeki et al. (2015) HDAC5 controls MEF2C-driven sclerostin expression in osteocytes. J Bone Miner Res 30:400-11
Pajevic, Paola Divieti; Spatz, Jordan M; Garr, Jenna et al. (2013) Osteocyte biology and space flight. Curr Biotechnol 2:179-183