[PDF][PDF] Characterization of cholesterol crystals in atherosclerotic plaques using stimulated Raman scattering and second-harmonic generation microscopy

JL Suhalim, CY Chung, MB Lilledahl, RS Lim, M Levi… - Biophysical journal, 2012 - cell.com
JL Suhalim, CY Chung, MB Lilledahl, RS Lim, M Levi, BJ Tromberg, EO Potma
Biophysical journal, 2012cell.com
Cholesterol crystals (ChCs) have been identified as a major factor of plaque vulnerability
and as a potential biomarker for atherosclerosis. Yet, due to the technical challenge of
selectively detecting cholesterol in its native tissue environment, the physiochemical role of
ChCs in atherosclerotic progression remains largely unknown. In this work, we demonstrate
the utility of hyperspectral stimulated Raman scattering (SRS) microscopy combined with
second-harmonic generation (SHG) microscopy to selectively detect ChC. We show that …
Abstract
Cholesterol crystals (ChCs) have been identified as a major factor of plaque vulnerability and as a potential biomarker for atherosclerosis. Yet, due to the technical challenge of selectively detecting cholesterol in its native tissue environment, the physiochemical role of ChCs in atherosclerotic progression remains largely unknown. In this work, we demonstrate the utility of hyperspectral stimulated Raman scattering (SRS) microscopy combined with second-harmonic generation (SHG) microscopy to selectively detect ChC. We show that despite the polarization sensitivity of the ChC Raman spectrum, cholesterol monohydrate crystals can be reliably discriminated from aliphatic lipids, from structural proteins of the tissue matrix and from other condensed structures, including cholesteryl esters. We also show that ChCs exhibit a nonvanishing SHG signal, corroborating the noncentrosymmetry of the crystal lattice composed of chiral cholesterol molecules. However, combined hyperspectral SRS and SHG imaging reveals that not all SHG-active structures with solidlike morphologies can be assigned to ChCs. This study exemplifies the merit of combining SRS and SHG microscopy for an enhanced label-free chemical analysis of crystallized structures in diseased tissue.
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