title: Lnk Deficiency Leads to TPO-Mediated Osteoclastogenesis and Increased Bone Mass Phenotype.
abstract: The Lnk adapter protein negatively regulates the signaling of thrombopoietin (TPO), the main megakaryocyte (MK) growth factor. Lnk-deficient (-/-) mice have increased TPO signaling and increased MK number. Interestingly, several mouse models exist in which increased MK number leads to a high bone mass phenotype. Here we report the bone phenotype of these mice. MicroCT and static histomorphometric analyses at 20 weeks showed the distal femur of Lnk-/-mice to have significantly higher bone volume fraction and trabecular number compared to wild-type (WT) mice. Notably, despite a significant increase in the number of osteoclasts (OC), and decreased bone formation rate in Lnk-/-mice compared to WT mice, Lnk-/-mice demonstrated a 2.5-fold greater BV/TV suggesting impaired OC function in vivo. Additionally, Lnk-/-mouse femurs exhibited non-significant increases in mid-shaft cross-sectional area, yet increased periosteal BFR compared to WT femurs was observed. Lnk-/-femurs also had non-significant increases in polar moment of inertia and decreased cortical bone area and thickness, resulting in reduced bone stiffness, modulus, and strength compared to WT femurs. Of note, Lnk is expressed by OC lineage cells and when Lnk-/-OC progenitors are cultured in the presence of TPO, significantly more OC are observed than in WT cultures. Lnk is also expressed in osteoblast (OB) cells and in vitro reduced alkaline phosphatase activity was observed in Lnk-/-cultures. These data suggest that both direct effects on OB and OC as well as indirect effects of MK in regulating OB contributes to the observed high bone mass. J. Cell. Biochem. 118: 2231-2240, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.|Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: David J
authors.initials: DJ
authors.lastname: Olivos
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Marta
authors.initials: M
authors.lastname: Alvarez
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Ying-Hua
authors.initials: YH
authors.lastname: Cheng
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Richard Adam
authors.initials: RA
authors.lastname: Hooker
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.|Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Ciovacco
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Monique
authors.initials: M
authors.lastname: Bethel
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Haley
authors.initials: H
authors.lastname: McGough
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Christopher
authors.initials: C
authors.lastname: Yim
authors.affiliation: Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Brahmananda R
authors.initials: BR
authors.lastname: Chitteti
authors.affiliation: Department of Biomedical and Applied Sciences, Indiana University School of Dentistry, Indianapolis, Indiana.
authors.forename: Pierre P
authors.initials: PP
authors.lastname: Eleniste
authors.affiliation: Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Horowitz
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana.|Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.|Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Edward F
authors.initials: EF
authors.lastname: Srour
authors.affiliation: Department of Biomedical and Applied Sciences, Indiana University School of Dentistry, Indianapolis, Indiana.
authors.forename: Angela
authors.initials: A
authors.lastname: Bruzzaniti
authors.affiliation: Department of Physical Therapy, Indiana University School of Health and Rehabilitation Sciences, Indianapolis, Indiana.
authors.forename: Robyn K
authors.initials: RK
authors.lastname: Fuchs
authors.affiliation: Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.|Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Kacena
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D049109:Cell Proliferation / Q000235:genetics / Q000502:physiology; D005260:Female; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism*; D010012:Osteogenesis / Q000235:genetics / Q000502:physiology; D000067996:RAW 264.7 Cells; D013926:Thrombopoietin / Q000235:genetics / Q000378:metabolism*; D055114:X-Ray Microtomography
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; C490777:Lnk protein, mouse; D008565:Membrane Proteins; D013926:Thrombopoietin; D000469:Alkaline Phosphatase
keywords: BONE MASS; BONE PHENOTYPE; LNK; MEGAKARYOCYTES; OSTEOBLASTS; OSTEOCLASTS