Molecular Imaging and Biology

, Volume 15, Issue 3, pp 250–261

Single-Chain VEGF/Cy5.5 Targeting VEGF Receptors to Indicate Atherosclerotic Plaque Instability

  • Ming Kai Lam
  • Sali Al-Ansari
  • Gooitzen M. van Dam
  • René A. Tio
  • Jan-Cees Breek
  • Riemer H. J. A. Slart
  • Jan-Luuk Hillebrands
  • Clark J. Zeebregts
Research Article

Abstract

Purpose

Unstable plaques may cause clinical events. Plaque destabilization results from the synergy between intraplaque angiogenesis and inflammation. Vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) are considered to be involved in these processes. We investigated the efficacy of the anti-VEGFR mimic single-chain VEGF (scVEGF) to map intra-plaque VEGFR expression and atherosclerotic plaque instability using near-infrared fluorescence (NIRF).

Procedures

Human carotid plaques were retrieved from 15 symptomatic and five asymptomatic patients. NIRF plaque imaging was performed pre-/post-incubation with scVEGF/Cy5.5. Biopsies taken from regions with high (hot spot) and low (cold spot) NIRF signals were examined for VEGF-A, VEGFR-1 and VEGFR-2 mRNA expression levels using real-time RT-PCR analysis. Immunohistochemistry for CD31 (endothelium), CD68 (macrophages) and αSMA (smooth muscle cells) was performed to evaluate plaque composition.

Results

NIRF imaging of 20 plaques revealed a heterogeneous distribution of scVEGF/Cy5.5 binding. After incubation NIRF activity increased from 3.9×10−5 ± 5.2×10−6 to 3.0×10−4 ± 2.2×10−5 and 5.8×10−5 ± 1.9×10−5 to 3.1×10−4 ± 1.9×10−5 photons/s/cm2/sr/illumination intensity on the intraluminal and extraluminal side, respectively (both p < 0.001). Real-time RT-PCR analysis showed a ~1.2- and ~16.4-fold increased mRNA expression of VEGFR-1 and VEGFR-2, respectively, in hot spots (vs. cold spots). Immunohistochemistry exhibited higher intraplaque capillary density in hot spots (vs. cold spots) (17.2 ± 3.7 vs. 5.4 ± 2.2 capillary/mm2; p = 0.037). Hot spots contained significantly reduced numbers of α-SMA-positive cells (vs. cold spots) (2.2 ± 0.7 % vs. 6.9 ± 1.5 %; p = 0.038). Finally, a ~2-fold increase of CD68+ infiltrating macrophages within hot spots (vs. cold spots) was observed (not significant, p = 0.17). Significant higher capillary density in hot spots (vs. cold spots) was observed in plaques from symptomatic patients but not in plaques from asymptomatic patients.

Conclusion

Our data support that scVEGF/Cy5.5 is a suitable indicator for plaque instability and a promising diagnostic tool for risk assessment in cardiovascular diseases.

Key words

Atherosclerosis VEGF Angiogenesis Near-infrared fluorescence imaging Molecular imaging probe 

Copyright information

© World Molecular Imaging Society 2012

Authors and Affiliations

  • Ming Kai Lam
    • 1
  • Sali Al-Ansari
    • 1
  • Gooitzen M. van Dam
    • 2
  • René A. Tio
    • 3
  • Jan-Cees Breek
    • 4
  • Riemer H. J. A. Slart
    • 5
  • Jan-Luuk Hillebrands
    • 6
  • Clark J. Zeebregts
    • 1
  1. 1.Division of Vascular Surgery, Department of SurgeryUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
  2. 2.Division of Abdominal Surgery, Department of SurgeryUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
  3. 3.Department of CardiologyUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
  4. 4.Department of SurgeryMartini HospitalGroningenThe Netherlands
  5. 5.Department of Nuclear Medicine and Molecular ImagingUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
  6. 6.Division of Pathology, Department of Pathology and Medical BiologyUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands

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