Distribution of Matrix Metalloproteinases in Human Atherosclerotic Carotid Plaques and Their Production by Smooth Muscle Cells and Macrophage Subsets
Distribution of Matrix Metalloproteinases in Human Atherosclerotic Carotid Plaques and Their Production by Smooth Muscle Cells and Macrophage Subsets
Nynke A. Jager 2
Bastiaan M. Wallis de Vries 1
Jan-Luuk Hillebrands 0
Niels J. Harlaar 1
René A. Tio 5
Riemer H. J. A. Slart 4
Gooitzen M. van Dam 1
Hendrikus H. Boersma 3 4
Clark J. Zeebregts 1
Johanna Westra 2
0 Departments of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen , PB 30.0019700 RB, Groningen , The Netherlands
1 Department of Surgery, Division of Vascular Surgery, University Medical Center Groningen, University of Groningen , Groningen, PB 30.0019700 RB, Groningen , The Netherlands
2 Departments of Rheumatology and Clinical Immunology, University Medical Center Groningen, University of Groningen , PB 30.0019700 RB, Groningen , The Netherlands
3 Departments of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen , PB 30.0019700 RB, Groningen , The Netherlands
4 Departments of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen , PB 30.0019700 RB, Groningen , The Netherlands
5 Department of Cardiology, University Medical Center Groningen, University of Groningen , PB 30.0019700 RB, Groningen , The Netherlands
Purpose: In this study, the potential of matrix metalloproteinase (MMP) sense for detection of atherosclerotic plaque instability was explored. Secondly, expression of MMPs by macrophage subtypes and smooth muscle cells (SMCs) was investigated. Procedures: Twenty-three consecutive plaques removed during carotid endarterectomy were incubated in MMPSense™ 680 and imaged with IVIS® Spectrum. mRNA levels of MMPs, macrophage markers, and SMCs were determined in plaque specimens, and in in vitro differentiated M1 and M2 macrophages. Results: There was a significant difference between autofluorescence signals and MMPSense signals, both on the intraluminal and extraluminal sides of plaques. MMP-9 and CD68 messenger RNA (mRNA) expression was higher in hot spots, whereas MMP-2 and αSMA expression was higher in cold spots. In vitro M2 macrophages had higher mRNA expression of MMP-1, MMP-9, MMP-12, and TIMP-1 compared to M1 macrophages. Conclusion: MMP-9 is most dominantly MMP present in atherosclerotic plaques and is produced by M2 rather than M1 macrophages.
Matrix metalloproteinase; Macrophage; Atherosclerotic plaque; Smooth muscle cell; MMPSense
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Abbreviations: BMI, Body mass index; CCD, Charged-coupled device; CEA, Carotid
endarterectomy; Ct, Threshold cycle; CVA, Cerebrovascular accident; CXCL4, Chemokine ligand 4;
ECM, Extracellular matrix; ELISA, Enzyme-linked immunosorbent assay; FCS, Fetal calf serum;
GAPDH, Glyceraldehyde-3-phosphate dehydrogenase; HRP, Horseradish peroxidase; IFN-γ,
Interferon-gamma; IL, Interleukin; IRB, International Review Board; LPS, Lipopolysacharride;
MCSF, Macrophage colony-stimulating factor; MMP, Matrix metalloproteinases; mRNA,
Messenger ribonucleic acid; PBMCs, Peripheral blood mononuclear cells; SMCs, Smooth muscle cells;
TBR, Target to background; TIA, Transient ischemic attack; TIMP, Tissue inhibitors of
metalloproteinases
Atherosclerosis is a progressive inflammatory disease
characterized by the accumulation of lipid-filled
macrophages within the arterial intima. Continued inflammation
may promote rupture of the atherosclerotic plaque’s
protective fibrous cap causing subsequent clinical
ischemic events [1, 2]. The fibrous cap covering an advanced
atherosclerotic plaque is typically composed of smooth
muscle cells (SMCs) and extracellular matrix (ECM) [3].
Activated monocyte-derived macrophages and SMCs are
critically involved in the development of high-risk
vulnerable plaques by producing matrix
metalloproteinases (MMPs) [1, 4, 5].
A heterogeneous population of macrophages exists
including a classically activated macrophage type (M1) as
well as an alternatively activated macrophage population
(M2) [6]. The M1 macrophage is thought to have
proinflammatory properties, and polarization in vitro is driven
by low concentration lipopolysacharride (LPS) and
interferon-gamma (IFN-γ). Defined as classically, however,
M2 macrophages are anti-inflammatory and immune
regulatory. Upon cytokine stimulation, they modify development
of atherosclerotic plaques. The M2 macrophage population
can be divided in M2a, M2b, and M2c subtypes, depending
on the cytokine environment (IL-4, immune complexes, and
IL-10, respectively)[7]. In contrast to its classical M2
properties, the function of M2a macrophages is type II
inflammation, and the function of type M2c is matrix
deposition and tissue remodeling; this last mentioned type
might be most important in atherosclerosis [8]. Recently,
Wolfs et al. suggested that additional circumstances in the
local microenvironment makes macrophage polarization in
the atherosclerotic tissue even more complex than the
typically described M1 and M2 macrophage d (...truncated)