Elsevier

Atherosclerosis

Volume 141, Issue 1, 5 October 1998, Pages 117-124
Atherosclerosis

Raman spectroscopy for quantifying cholesterol in intact coronary artery wall

https://doi.org/10.1016/S0021-9150(98)00155-5Get rights and content

Abstract

The chemical composition of vascular lesions, an important determinant of plaque progression and rupture, can not presently be determined in vivo. Prior studies have shown that Raman spectroscopy can accurately quantify the amounts of major lipid classes and calcium salts in homogenized coronary artery tissue. This study determines how the relative cholesterol content, which is calculated from Raman spectra collected at the luminal surface of an artery, is related to its depth in an intact arterial wall. Raman spectra of human atherosclerotic plaques were measured after thin tissue layers were successively placed on them. From these spectra, relative cholesterol contents were calculated and used to determine how cholesterol signal strength is attenuated by overlaying tissue. Then, intact artery samples (n=13) were examined spectroscopically, sectioned and stained specifically for cholesterol. Images of these sections were digitized, and image intensities were related to cholesterol content. These cholesterol amounts were weighed appropriately for depth into the tissue and area-integrated for comparison with spectroscopy results. A decaying exponential curve was fit to the layer study data (r2=0.97) and showed that ∼300 μm of tissue attenuates cholesterol signals by 50%. In intact plaques, the spectroscopically-determined cholesterol amounts correlated strongly and linearly with those determined by digital microscopy (r2=0.94). With Raman spectroscopy techniques, the cholesterol content of a lesion can be determined by properly accounting for its depth into an arterial wall. Our results suggest that chemical concentrations in an artery wall could be mapped throughout its thickness, possibly by combining Raman spectroscopy methods with other techniques.

Section snippets

Tissues

Human coronary arteries were dissected from hearts at autopsies conducted within 24 h after death. Patients (n=11) ranged in age from 44 to 81 years. The samples were rinsed with phosphate buffered saline (pH 7.4), frozen in liquid-nitrogen and stored at −80°C until use. After thawing, the artery segments were opened longitudinally, and specific locations, which appeared to be rich in cholesterol, were selected visually for the preparation of plaque models and for studies on intact plaques. No

Raman spectrum of atherosclerotic plaque

Fig. 2 shows a Raman spectrum (dots) obtained from an artery location that seemed to be rich in cholesterol by visual inspection, modeled to the set of spectra from the individual chemical components (line). As shown, this spectrum could be modeled accurately with this spectral model. The spectral model quantified the relative amounts of FC (9%), CE (7%), CS (9%), TG and PL (1%) and DA (74%). The luminal side of the spectroscopically examined location was marked with ink. The tissue was then

Discussion

We have determined that the cholesterol content of a lesion can be calculated from Raman spectra by properly accounting for the lesion’s depth into the arterial wall. We developed a plaque model and determined how the Raman spectral signature of cholesterol is attenuated by tissue. In intact plaques, the spectroscopically-determined cholesterol amounts correlated strongly and linearly with those determined by digital microscopy, indicating that this attenuation curve can model Raman signal

Acknowledgements

We wish to thank Nada Boustany from the M.I.T. George R. Harrison Spectroscopy Laboratory for helpful discussions and Professor H.J. Tanke and Willem Sloos for their collaboration and technical assistance. Financial support from the Netherlands Heart Foundation (95.134) is gratefully acknowledged.

References (23)

  • J.F. Toussaint et al.

    Magnetic resonance images lipid, fibrous, calcified, hemorrhagic, and thrombotic components of human atherosclerosis in vivo

    Circulation

    (1996)
  • Cited by (61)

    • Identification and characterization of Aspergillus species of fruit rot fungi using microscopy, FT-IR, Raman and UV–Vis spectroscopy

      2021, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
      Citation Excerpt :

      When we have been used Raman spectroscopic method, we did not need to add chemicals dyes to fungi samples for identify and classify them by that method. Raman spectroscopy is easy to use, its highly molecular specific and it gives wide information about chemical composition content of microorganisms such as fungi [17,18]. Raman spectra of biological molecules has been complex peaks because of fluorescence, therefore the fluorescence peaks has been removed from spectra by using first derivative spectra [19].

    • Investigation of lipid modifications in J774 macrophages by vibrational spectroscopies after eicosapentaenoic acid membrane incorporation in unloaded and cholesterol-loaded cells

      2019, Talanta
      Citation Excerpt :

      Components A1, A2, A3 and A4 express 93% of the information from the IR dataset. Atherosclerosis studies make a list of various in vivo imaging modalities used to better understand of the morphological changes accompanying the formation of atheromatous plaques, but do not give information about the chemical composition of these plaques. [1] Raman and infrared vibrational spectroscopies are suggested techniques for biochemical characterization of plaques in vitro. [13]

    • Raman spectroscopy of lipids: A review

      2015, Journal of Raman Spectroscopy
    View all citing articles on Scopus
    1

    Present address (JFB): 3M Austin Sector Laboratory, Austin, TX 78759, USA.

    View full text