Abstract
We examined the role of osteopontin (OPN) in the osteoclastogenesis of arthritis using collagen-induced arthritis (CIA). Cells from arthritic joints of wild-type (OPN +/+) mice spontaneously developed bone-resorbing osteoclast-like cells (OCLs). The cultured cells showed an enhanced expression of receptor activator of nuclear factor kappaB ligand (RANKL) and a decreased expression of osteoprotegerin (OPG). The addition of OPG reduced the number of OCLs, indicating that the osteoclastogenesis depends on the RANK/RANKL/OPG system. The cells also produced OPN abundantly and anti-OPN neutralizing antibodies suppressed the development of OCLs. Moreover, the addition of OPN increased the expression of RANKL and augmented differentiation of OCLs from OPN-deficient (OPN -/-) cells. OPN, like the combination of 1alpha,25-dihydroxyvitamin D(3) and dexamethasone, also enhanced the RANKL expression and decreased OPG expression in a stromal cell line, ST2. These results suggest that OPN acts as a positive regulator in the osteoclastogenesis of arthritis through the RANK/RANKL/OPG system.
MeSH terms
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Animals
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Arthritis / etiology
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Arthritis / metabolism*
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Calcitriol / metabolism
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Carrier Proteins / metabolism
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Cell Differentiation
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Cell Line
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Cells, Cultured
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Collagen / metabolism
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Dexamethasone / pharmacology
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Dose-Response Relationship, Drug
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Gene Expression Regulation*
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Glycoproteins / metabolism
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Membrane Glycoproteins / metabolism
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Mice
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Mice, Inbred DBA
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Mice, Transgenic
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Models, Genetic
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Osteoclasts / metabolism
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Osteopontin
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Osteoprotegerin
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RANK Ligand
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RNA, Messenger / metabolism
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Receptor Activator of Nuclear Factor-kappa B
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Receptors, Cytoplasmic and Nuclear / metabolism
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Receptors, Tumor Necrosis Factor
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Recombinant Proteins / chemistry
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Reverse Transcriptase Polymerase Chain Reaction
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Sialoglycoproteins / physiology*
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Stromal Cells / cytology
Substances
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Carrier Proteins
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Glycoproteins
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Membrane Glycoproteins
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Osteoprotegerin
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RANK Ligand
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RNA, Messenger
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Receptor Activator of Nuclear Factor-kappa B
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Receptors, Cytoplasmic and Nuclear
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Receptors, Tumor Necrosis Factor
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Recombinant Proteins
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Sialoglycoproteins
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Spp1 protein, mouse
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Tnfrsf11a protein, mouse
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Tnfrsf11b protein, mouse
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Tnfsf11 protein, mouse
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Osteopontin
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Dexamethasone
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Collagen
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Calcitriol