Selective Imaging of Vascular Endothelial Growth Factor Receptor-1 and Receptor-2 in Atherosclerotic Lesions in Diabetic and Non-diabetic ApoE-/- Mice

Mol Imaging Biol. 2018 Feb;20(1):85-93. doi: 10.1007/s11307-017-1045-2.

Abstract

Purpose: Plaque vulnerability is associated with inflammation and angiogenesis, processes that rely on vascular endothelial growth factor (VEGF) signaling via two receptors, VEGFR-1 and VEGFR-2. We have recently reported that enhanced uptake of scVEGF-PEG-DOTA/Tc-99m (scV/Tc) single photon emission computed tomography (SPECT) tracer that targets both VEGFR-1 and VEGFR-2, identifies accelerated atherosclerosis in diabetic relative to non-diabetic ApoE-/- mice. Since VEGFR-1 and VEGFR-2 may play different roles in atherosclerotic plaques, we reasoned that selective imaging of each receptor can provide more detailed information on plaque biology.

Procedures: Recently described VEGFR-1 and VEGFR-2 selective mutants of scVEGF, named scVR1 and scVR2, were site-specifically derivatized with Tc-99m chelator DOTA via 3.4 kDa PEG linker, and their selectivity to the cognate receptors was confirmed in vitro. scVR1 and scVR2 conjugates were radiolabeled with Tc-99m to specific activity of 110 ± 11 MBq/nmol, yielding tracers named scVR1/Tc and scVR2/Tc. 34-40 week old diabetic and age-matched non-diabetic ApoE-/- mice were injected with tracers, 2-3 h later injected with x-ray computed tomography (CT) contrast agent and underwent hybrid SPECT/CT imaging. Tracer uptake, localized to proximal aorta and brachiocephalic vessels, was quantified as %ID from. Tracer uptake was also quantified as %ID/g from gamma counting of harvested plaques. Harvested atherosclerotic arterial tissue was used for immunofluorescent analyses of VEGFR-1 and VEGFR-2 and various lineage-specific markers.

Results: Focal, receptor-mediated uptake in proximal aorta and brachiocephalic vessels was detected for both scVR1/Tc and scVR2/Tc tracers. Uptake of scVR1/Tc and scVR2/Tc was efficiently inhibited only by "cold" proteins of the same receptor selectivity. Tracer uptake in this area, expressed as %ID, was higher in diabetic vs. non- diabetic mice for scVR1/Tc (p = 0.01) but not for scVR2/Tc. Immunofluorescent analysis revealed enhanced VEGFR-1 prevalence in and around plaque area in diabetic mice.

Conclusions: Selective VEGFR-1 and VEGFR-2 imaging of atherosclerotic lesions may be useful to explore plaque biology and identify vulnerability.

Keywords: Atherosclerosis; Diabetes; Molecular imaging; Vascular endothelial growth factor receptor (VEGFR).

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apolipoproteins E / deficiency*
  • Apolipoproteins E / metabolism
  • Atherosclerosis / complications
  • Atherosclerosis / diagnosis*
  • Atherosclerosis / metabolism*
  • Atherosclerosis / pathology
  • Blood Glucose / metabolism
  • Diabetes Mellitus, Experimental / blood
  • Diabetes Mellitus, Experimental / complications
  • Diabetes Mellitus, Experimental / diagnosis*
  • Diabetes Mellitus, Experimental / metabolism*
  • Male
  • Mice
  • Molecular Imaging / methods*
  • Polyethylene Glycols / chemistry
  • Single-Chain Antibodies
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon
  • Vascular Endothelial Growth Factor Receptor-1 / metabolism*
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism*

Substances

  • Apolipoproteins E
  • Blood Glucose
  • Single-Chain Antibodies
  • Polyethylene Glycols
  • Vascular Endothelial Growth Factor Receptor-1
  • Vascular Endothelial Growth Factor Receptor-2