Fluorescence reflectance imaging of macrophage-rich atherosclerotic plaques using an alphavbeta3 integrin-targeted
Jens Waldeck1, Florian Häger, Carsten Höltke
1Department of Clinical Radiology, University Hospital Muenster, University of Muenster, Muenster, Germany. waldeck@uni-muenster.de
Unlabelled:
Macrophages play an important role during the development and progression of atherosclerotic plaques. alphavbeta3 integrins are highly expressed by macrophages; thus, targeting alphavbeta3 may allow targeting of culprit macrophage-loaded atherosclerotic lesions in vivo.
Methods:
An alphavbeta3-targeted Arg-Gly-Asp (RGD) peptide was labeled with the cyanine 5.5 (Cy 5.5) dye and applied to image atherosclerotic plaques in apolipoprotein E-deficient mice.
Results:
The peptide-dye conjugate binds to alphavbeta3 integrin-positive RAW264.7 macrophages with high affinity. Competition experiments confirmed binding specificity of the probe. A significant fluorochrome accumulation in atherosclerotic plaques was demonstrated 24 h after injection by fluorescence reflectance imaging, which was blocked with high efficiency by competition with the unlabeled peptide. Conversely, the nonconjugated dye revealed only a minor fluorescence signal in the plaques. Fluorescence microscopy revealed colocalization of the probe with macrophages in the plaque of a mouse model for accelerated atherosclerosis, which was corroborated in human carotid artery specimens. In addition to macrophage-associated signals, binding of the probe to the neointima or elastica of the arteries was observed.
Conclusion:
RGD-Cy 5.5, combined with near-infrared optical imaging methods, allows the specific imaging of alphavbeta3-integrin expression on macrophages recruited to vascular lesions and may serve to estimate macrophage-bound inflammatory activity of atherosclerotic lesions.
Insights
A novel imaging probe targets alphaVbeta3 integrins on macrophages within atherosclerotic plaques. This method allows specific visualization of macrophage-loaded lesions, aiding in the assessment of vascular inflammation.
Area of Science:
- Cardiovascular Research
- Molecular Imaging
- Immunology
Background:
- Macrophages are key players in atherosclerosis development and progression.
- AlphaVbeta3 integrins are highly expressed on macrophages within atherosclerotic lesions.
- Targeting alphaVbeta3 integrins offers a potential strategy for in vivo imaging of these macrophage-rich plaques.
Purpose of the Study:
- To develop and evaluate an imaging probe for specifically targeting alphaVbeta3 integrin-expressing macrophages in atherosclerotic plaques.
- To assess the feasibility of using this probe with near-infrared optical imaging for visualizing atherosclerotic lesions.
Main Methods:
- An alphaVbeta3-targeted Arg-Gly-Asp (RGD) peptide was conjugated with the cyanine 5.5 (Cy 5.5) dye.
- The RGD-Cy 5.5 probe was used to image atherosclerotic plaques in apolipoprotein E-deficient mice.
- Binding specificity was confirmed through competition experiments and fluorescence microscopy.
Main Results:
- The RGD-Cy 5.5 probe demonstrated high-affinity binding to alphaVbeta3 integrin-positive macrophages.
- Significant probe accumulation was observed in atherosclerotic plaques 24 hours post-injection, with specificity confirmed by blocking studies.
- Fluorescence microscopy confirmed probe colocalization with macrophages in both mouse models and human carotid artery specimens.
Conclusions:
- RGD-Cy 5.5, coupled with near-infrared optical imaging, enables specific visualization of alphaVbeta3 integrin expression on macrophages in vascular lesions.
- This approach holds promise for estimating macrophage-associated inflammatory activity in atherosclerotic lesions.
- The study validates a targeted imaging strategy for macrophage-rich atherosclerotic plaques.
