title: Characterisation of calcium phosphate crystals on calcified human aortic vascular smooth muscle cells and potential role of magnesium.
abstract: BACKGROUND
  Cardiovascular disease including vascular calcification (VC) remains the leading cause of death in patients suffering from chronic kidney disease (CKD). The process of VC seems likely to be a tightly regulated process where vascular smooth muscle cells are playing a key role rather than just a mere passive precipitation of calcium phosphate. Characterisation of the chemical and crystalline structure of VC was mainly led in patients or animal models with CKD. Likewise, Mg2+ was found to be protective in living cells although a potential role for Mg2+ could not be excluded on crystal formation and precipitation. In this study, the crystal formation and the role of Mg2+ were investigated in an in vitro model of primary human aortic vascular smooth muscle cells (HAVSMC) with physical techniques.
  
  
  RESULTS
  In HAVSMC incubated with increased Ca x Pi medium, only calcium phosphate apatite crystals (CPA) were detected by Micro-Fourier Transform InfraRed spectroscopy (µFTIR) and Field Effect Scanning Electron Microscope (FE-SEM) and Energy Dispersive X-ray spectrometry (EDX) at the cell layer level. Supplementation with Mg2+ did not alter the crystal composition or structure. The crystal deposition was preferentially positioned near or directly on cells as pictured by FE-SEM observations and EDX measurements. Large µFTIR maps revealed spots of CPA crystals that were associated to the cellular layout. This qualitative analysis suggests a potential beneficial effect of Mg2+ at 5 mM in noticeably reducing the number and intensities of CPA µFTIR spots.
  
  
  CONCLUSIONS
  For the first time in a model of HAVSMC, induced calcification led to the formation of the sole CPA crystals. Our data seems to exclude a physicochemical role of Mg2+ in altering the CPA crystal growth, composition or structure. Furthermore, Mg2+ beneficial role in attenuating VC should be linked to an active cellular role.
authors.affiliation: INSERM U-1088, Amiens, France; University of Picardie Jules Verne, Amiens, France.
authors.forename: Loïc
authors.initials: L
authors.lastname: Louvet
authors.affiliation: Université Pierre et Marie Curie, Collège de France, Paris, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Bazin
authors.affiliation: Fresenius Medical Care Deutschland GmbH, Bad Homburg, Germany.
authors.forename: Janine
authors.initials: J
authors.lastname: Büchel
authors.affiliation: Fresenius Medical Care Deutschland GmbH, Bad Homburg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Steppan
authors.affiliation: Fresenius Medical Care Deutschland GmbH, Bad Homburg, Germany; Department of Nephrology, University of Dusseldorf, Dusseldorf, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Passlick-Deetjen
authors.affiliation: INSERM U-1088, Amiens, France; University of Picardie Jules Verne, Amiens, France; Paris Ile de France Ouest (UVSQ) University, Paris, France.
authors.forename: Ziad A
authors.initials: ZA
authors.lastname: Massy
mesh_terms: D001011:Aorta / Q000378:metabolism* / Q000473:pathology; D002130:Calcium Phosphates / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D051436:Renal Insufficiency, Chronic / Q000378:metabolism / Q000473:pathology; D061205:Vascular Calcification / Q000378:metabolism* / Q000473:pathology
chemical_list: D002130:Calcium Phosphates; C020243:calcium phosphate; D008274:Magnesium