Clinical evidence links arterial calcification and cardiovascular risk. Finite-element modelling of the stress distribution within atherosclerotic plaques has suggested that subcellular microcalcifications in the fibrous cap may promote material failure of the plaque, but that large calcifications can stabilize it. Yet the physicochemical mechanisms underlying such mineral formation and growth in atheromata remain unknown. Here, by using three-dimensional collagen hydrogels that mimic structural features of the atherosclerotic fibrous cap, and high-resolution microscopic and spectroscopic analyses of both the hydrogels and of calcified human plaques, we demonstrate that calcific mineral formation and maturation results from a series of events involving the aggregation of calcifying extracellular vesicles, and the formation of microcalcifications and ultimately large calcification areas. We also show that calcification morphology and the plaque’s collagen content—two determinants of atherosclerotic plaque stability—are interlinked.

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This work was supported by a research grant from Kowa Company to M.A. E.A. is supported by grants from the National Institutes of Health (R01HL114805; R01HL109506) and a Harvard Catalyst Advanced Microscopy Pilot Award. Harvard Catalyst support is provided by The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award UL1 TR001102) and financial contributions from Harvard University and its affiliated academic healthcare centres. The content is solely the responsibility of the authors and does not necessarily represent the official views of Harvard Catalyst, Harvard University and its affiliated academic healthcare centres, or the National Institutes of Health. P.L. is supported by R01HL80472. The authors thank T. Pham, J. Choi and B. Pieper for technical assistance and C. Swallom for editorial expertise. T. Holmes and M. Siciliano from the Brigham and Women’s Hospital Anatomic Pathology Laboratory graciously provided human autopsy tissue. G. Sukhova provided surgically resected carotid artery tissue from endarterectomy patients at Brigham and Women’s Hospital. S. Singh contributed valuable insight into data interpretation and presentation. Two-photon microscopy and structured illumination imaging were performed at the Harvard Center for Biological Imaging. S.B. was supported by the Junior Research Fellowship scheme from Imperial College London.

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  1. Center for Interdisciplinary Cardiovascular Sciences, Cardiovascular Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA

    • Joshua D. Hutcheson
    • , Claudia Goettsch
    • , Natalia Maldonado
    • , Jessica L. Ruiz
    • , Wilson Goh
    • , Katsumi Yabusaki
    • , Tyler Faits
    • , Masanori Aikawa
    •  & Elena Aikawa
  2. Department of Medical Physics & Biomedical Engineering, University College London, London WC1E 6BT, UK

    • Sergio Bertazzo
  3. Department of Biomedical Engineering & Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands

    • Carlijn Bouten
  4. Center for Excellence in Vascular Biology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA

    • Gregory Franck
    • , Thibaut Quillard
    • , Peter Libby
    • , Masanori Aikawa
    •  & Elena Aikawa
  5. Department of Biomedical Engineering, City College of New York, New York, New York 10031, USA

    • Sheldon Weinbaum


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J.D.H. designed the study, performed sample preparation, conducted experimental work, carried out data interpretation and drafted the manuscript. C.G. aided with study design and data interpretation. S.B. performed DDC-SEM and EDS experiments. N.M. performed microCT analysis. J.L.R. aided with super-resolution microscopy and FTIR spectroscopy. W.G. aided with analysis of FTIR spectroscopy. K.Y. performed image segmentation analysis of histological images. T.F. performed histological tissue assessment. C.B. provided a custom collagen probe. G.F. and T.Q. helped obtain and analyse tissue from the MMP-13-deficient mice. P.L. directed the generation of the MMP-13-deficient mice and provided the human carotid specimens. C.B., M.A., P.L. and S.W. provided critical review of the manuscript. E.A. provided the study concept, participated in study design and data interpretation, and aided in manuscript development.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Elena Aikawa.

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