title: Calcium-containing crystals enhance receptor activator of nuclear factor κB ligand/macrophage colony-stimulating factor-mediated osteoclastogenesis via extracellular-signal-regulated kinase and p38 pathways.
abstract: OBJECTIVE
  Diseases associated with calcium-containing crystal deposition can lead to local bone erosion. We aimed to determine whether calcium-containing crystal-hydroxyapatite, β-tricalcium phosphate and CPPD enhanced osteoclastogenesis and to define underlying mechanisms of action.
  
  
  METHODS
  Osteoclastogenesis was studied by culturing murine RAW 264.7 osteoclast precursor cells with RANK ligand (RANKL)/ M-CSF and/or calcium-containing crystals, and observing the tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and TRAP activity. Resorption pit formation was used to evaluate osteoclast activity. Real-time RT-PCR analysis revealed osteoclast marker genes, including TRAP, cathepsin K and calcitonin receptor (CTR). Western blotting was used to analyse the phosphorylation levels of signal transduction molecules.
  
  
  RESULTS
  Three kinds of calcium-containing crystal significantly enhanced RANKL/M-CSF-induced osteoclastogenesis in RAW 264.7 cells, as evidenced by the increased number of TRAP-positive multinucleated cells, TRAP activity and resorption pit formation in a dose-dependent manner. Hydroxyapatite, β-tricalcium phosphate and CPPD treatments significantly enhanced RANKL/M-CSF-induced mRNA expression of TRAP, cathepsin K and CTR. Moreover, the three kinds of calcium-containing crystal enhanced the phosphorylation of extracellular-signal-regulated kinase and p38 in RANKL/M-CSF-treated cells.
  
  
  CONCLUSIONS
  We concluded that calcium-containing crystals can promote osteoclastogenesis and bone resorption through the extracellular-signal-regulated kinase and p38 pathways. Together with synovial activation, this mechanism may be important in the pathogenesis of destructive arthropathies triggered by calcium-containing crystals.
authors.affiliation: Division of Rheumatology, Immunology and Allergy, Taipei Medical University Hospital, Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University.
authors.forename: Chi-Ching
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Department of Physical Medicine and Rehabilitation, Center for Nano-tissue Engineering and Imaging.
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Tsai
authors.affiliation: Division of Rheumatology, Immunology and Allergy, Taipei Medical University Hospital.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Department of Primary Care Medicine, Taipei Medical University Hospital, Department of General Medicine, School of Medicine, College of Medicine.
authors.forename: Shyr-Yi
authors.initials: SY
authors.lastname: Lin
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University and ycliang@tmu.edu.tw.
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Liang
mesh_terms: D000135:Acid Phosphatase / Q000502:physiology; D000818:Animals; D001862:Bone Resorption / Q000503:physiopathology; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology*; D002130:Calcium Phosphates / Q000494:pharmacology; D056657:Cathepsin K / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D003460:Crystallization; D017886:Durapatite / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology*; D051379:Mice; D023421:Models, Animal; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D010012:Osteogenesis / Q000187:drug effects* / Q000502:physiology; D053245:RANK Ligand / Q000502:physiology*; D018003:Receptors, Calcitonin / Q000502:physiology; D000071681:Tartrate-Resistant Acid Phosphatase
chemical_list: D002130:Calcium Phosphates; D007527:Isoenzymes; D053245:RANK Ligand; D018003:Receptors, Calcitonin; C505689:Tnfsf11 protein, mouse; C485817:beta-tricalcium phosphate; D016173:Macrophage Colony-Stimulating Factor; D017886:Durapatite; D048049:Extracellular Signal-Regulated MAP Kinases; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase; D056657:Cathepsin K; D002118:Calcium
keywords: calcium-containing crystals; extracellular-signal-regulated kinase; osteoclastogenesis; p38; receptor activator of nuclear factor kB ligand