title: TNAP stimulates vascular smooth muscle cell trans-differentiation into chondrocytes through calcium deposition and BMP-2 activation: Possible implication in atherosclerotic plaque stability.
abstract: Atherosclerotic plaque calcification varies from early, diffuse microcalcifications to a bone-like tissue formed by endochondral ossification. Recently, a paradigm has emerged suggesting that if the bone metaplasia stabilizes the plaques, microcalcifications are harmful. Tissue-nonspecific alkaline phosphatase (TNAP), an ectoenzyme necessary for mineralization by its ability to hydrolyze inorganic pyrophosphate (PPi), is stimulated by inflammation in vascular smooth muscle cells (VSMCs). Our objective was to determine the role of TNAP in trans-differentiation of VSMCs and calcification. In rodent MOVAS and A7R5 VSMCs, addition of exogenous alkaline phosphatase (AP) or TNAP overexpression was sufficient to stimulate the expression of several chondrocyte markers and induce mineralization. Addition of exogenous AP to human mesenchymal stem cells cultured in pellets also stimulated chondrogenesis. Moreover, TNAP inhibition with levamisole in mouse primary chondrocytes dropped mineralization as well as the expression of chondrocyte markers. VSMCs trans-differentiated into chondrocyte-like cells, as well as primary chondrocytes, used TNAP to hydrolyze PPi, and PPiprovoked the same effects as TNAP inhibition in primary chondrocytes. Interestingly, apatite crystals, associated or not to collagen, mimicked the effects of TNAP on VSMC trans-differentiation. AP and apatite crystals increased the expression of BMP-2 in VSMCs, and TNAP inhibition reduced BMP-2 levels in chondrocytes. Finally, the BMP-2 inhibitor noggin blocked the rise in aggrecan induced by AP in VSMCs, suggesting that TNAP induction in VSMCs triggers calcification, which stimulates chondrogenesis through BMP-2. Endochondral ossification in atherosclerotic plaques may therefore be induced by crystals, probably to confer stability to plaques with microcalcifications.
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France; Lebanese University, Laboratory of Cancer Biology and Molecular Immunology, EDST-PRASE, Hadath-Beirut, Lebanon.
authors.forename: Maya
authors.initials: M
authors.lastname: Fakhry
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France; Laboratory of Biochemistry of Lipids, Department of Biochemistry, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Roszkowska
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Briolay
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Bougault
authors.affiliation: Univ Lyon, Université Jean Monnet Saint-Etienne, LBTO, UMR INSERM 1059, F-42023 Saint-Etienne, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Guignandon
authors.affiliation: Universidad Complutense de Madrid, Facultad de Veterinaria, Dpt. Bioquimica y Biologia Molecular IV, Madrid, Spain.
authors.forename: Juan Ignacio
authors.initials: JI
authors.lastname: Diaz-Hernandez
authors.affiliation: Universidad Complutense de Madrid, Facultad de Veterinaria, Dpt. Bioquimica y Biologia Molecular IV, Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Diaz-Hernandez
authors.affiliation: Laboratory of Biochemistry of Lipids, Department of Biochemistry, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Slawomir
authors.initials: S
authors.lastname: Pikula
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France.
authors.forename: René
authors.initials: R
authors.lastname: Buchet
authors.affiliation: Lebanese University, Laboratory of Cancer Biology and Molecular Immunology, EDST-PRASE, Hadath-Beirut, Lebanon.
authors.forename: Eva
authors.initials: E
authors.lastname: Hamade
authors.affiliation: Lebanese University, Laboratory of Cancer Biology and Molecular Immunology, EDST-PRASE, Hadath-Beirut, Lebanon.
authors.forename: Bassam
authors.initials: B
authors.lastname: Badran
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Bessueille
authors.affiliation: Univ Lyon, University Lyon 1, ICBMS, UMR CNRS 5246, F-69622 Lyon, France. Electronic address: david.magne@univ-lyon1.fr.
authors.forename: David
authors.initials: D
authors.lastname: Magne
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D054338:Cell Transdifferentiation; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism; D020219:Chondrogenesis; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D058226:Plaque, Atherosclerotic / Q000378:metabolism
chemical_list: D055396:Bone Morphogenetic Protein 2; C510878:ALPL protein, mouse; D000469:Alkaline Phosphatase; D002118:Calcium
keywords: Chondrocytes; Inorganic pyrophosphate; Microcalcification; Tissue-nonspecific alkaline phosphatase; VSMCs; Vascular calcification