title: Autocrine stimulation of osteoblast activity by Wnt5a in response to TNF-α in human mesenchymal stem cells.
abstract: Although anti-tumor necrosis factor (TNF)-α treatments efficiently block inflammation in ankylosing spondylitis (AS), they are inefficient to prevent excessive bone formation. In AS, ossification seems more prone to develop in sites where inflammation has resolved following anti-TNF therapy, suggesting that TNF-α indirectly stimulates ossification. In this context, our objectives were to determine and compare the involvement of Wnt proteins, which are potent growth factors of bone formation, in the effects of TNF-α on osteoblast function. In human mesenchymal stem cells (MSCs), TNF-α significantly increased the levels of Wnt10b and Wnt5a. Associated with this effect, TNF-α stimulated tissue-non specific alkaline phosphatase (TNAP) and mineralization. This effect was mimicked by activation of the canonical β-catenin pathway with either anti-Dkk1 antibodies, lithium chloride (LiCl) or SB216763. TNF-α reduced, and activation of β-catenin had little effect on expression of osteocalcin, a late marker of osteoblast differentiation. Surprisingly, TNF-α failed to stabilize β-catenin and Dkk1 did not inhibit TNF-α effects. In fact, Dkk1 expression was also enhanced in response to TNF-α, perhaps explaining why canonical signaling by Wnt10b was not activated by TNF-α. However, we found that Wnt5a also stimulated TNAP in MSCs cultured in osteogenic conditions, and increased the levels of inflammatory markers such as COX-2. Interestingly, treatment with anti-Wnt5a antibodies reduced endogenous TNAP expression and activity. Collectively, these data suggest that increased levels of Dkk1 may blunt the autocrine effects of Wnt10b, but not that of Wnt5a, acting through non-canonical signaling. Thus, Wnt5a may be potentially involved in the effects of inflammation on bone formation.
authors.affiliation: ICBMS, UMR CNRS 5246, University of Lyon 1, Bâtiment Raulin, 43 Bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Briolay
authors.forename: P
authors.initials: P
authors.lastname: Lencel
authors.forename: L
authors.initials: L
authors.lastname: Bessueille
authors.forename: J
authors.initials: J
authors.lastname: Caverzasio
authors.forename: R
authors.initials: R
authors.lastname: Buchet
authors.forename: D
authors.initials: D
authors.lastname: Magne
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000378:metabolism; D002113:Calcification, Physiologic / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D013167:Spondylitis, Ankylosing / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*; D051153:Wnt Proteins / Q000378:metabolism*; D000071818:Wnt-5a Protein; D051176:beta Catenin / Q000378:metabolism
chemical_list: C501126:DKK1 protein, human; D007211:Indoles; D036341:Intercellular Signaling Peptides and Proteins; D008301:Maleimides; D011518:Proto-Oncogene Proteins; C417521:SB 216763; D014409:Tumor Necrosis Factor-alpha; C491119:WNT10B protein, human; C085389:WNT5A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D051176:beta Catenin; C548267:ALPL protein, human; D000469:Alkaline Phosphatase; D018021:Lithium Chloride