Characterisation of calcium phosphate crystals on calcified human aortic vascular smooth muscle cells and potential role of magnesium

PLoS One. 2015 Jan 21;10(1):e0115342. doi: 10.1371/journal.pone.0115342. eCollection 2015.


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.

Methodology/principal findings: 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/significance: 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Aorta / metabolism*
  • Aorta / pathology
  • Calcium Phosphates / metabolism*
  • Cells, Cultured
  • Female
  • Humans
  • Magnesium / metabolism*
  • Male
  • Myocytes, Smooth Muscle / metabolism*
  • Myocytes, Smooth Muscle / pathology
  • Renal Insufficiency, Chronic / metabolism
  • Renal Insufficiency, Chronic / pathology
  • Vascular Calcification / metabolism*
  • Vascular Calcification / pathology


  • Calcium Phosphates
  • calcium phosphate
  • Magnesium

Grant support

The funders (Fresenius Medical Care Deutschland GmbH) participated in part of the study design and revision of the final version of manuscript. They had no role in data collection, analysis, preparation of manuscript and decision to publish.