Raman Spectroscopic Evaluation of the Effects of Diet and Lipid-Lowering Therapy on Atherosclerotic Plaque Development in Mice

Abstract

Abstract-Quantitative characterization of atherosclerotic plaque composition with standard histopathological methods remains limited to sectioned plaques. Raman spectroscopy enables nondestructive quantification of atherosclerotic plaque composition. We used Raman spectroscopy to study the effects of diet and lipid-lowering therapy on plaque development in apolipoprotein (APO) E*3-Leiden transgenic mice. Raman spectra were obtained over the full width and entire length of the ascending aorta and aortic arch. Spectra were modeled to calculate the relative dry weights of cholesterol and calcium salts, and quantitative maps of their distribution were created. In male mice (nϭ20) that received a high-fat/high-cholesterol (HFC) diet for 0, 2, 4, or 6 months, Raman spectroscopy showed good correlation between cholesterol accumulation and total serum cholesterol exposure (rϷ0.87, PϽ0.001). In female mice (nϭ10) that were assigned to an HFC diet, with or without 0.01% atorvastatin, a strong reduction in cholesterol accumulation (57%) and calcium salts (97%) (PϽ0.01) was demonstrated in the atorvastatin-treated group. In conclusion, Raman spectroscopy can be used to quantitatively study the size and distribution of depositions of cholesterol and calcification in APOE*3-Leiden transgenic mice. This study encourages Raman spectroscopy for the quantitative investigation of atherosclerosis and lipid-lowering therapy in larger animals or humans in vivo. Key Words: atherosclerosis Ⅲ Raman spectroscopy Ⅲ cholesterol Ⅲ calcification Ⅲ lipid-lowering treatment P rogression of atherosclerosis is dependent on the amount of lipids that accumulate in the intima of arteries. 1,2 Several drugs have been developed that successfully lower the plasma cholesterol concentration, thereby reducing the rate of progression of atherosclerosis. 3,4 However, despite the success of these drugs, a considerable number of treated patients will still encounter an ischemic event. To improve management of patients with atherosclerosis, a more thorough understanding of plaque progression and regression in vivo, at the chemical level, is required.Raman spectroscopy is a technique that can provide this kind of information. It provides quantitative information about the molecular composition of a sample and enables the nondestructive examination of small volumes of tissue. 5 A Raman method to quantify the relative amounts of protein, cholesterol, adventitial fat, and calcium salts (CS) in the human coronary artery wall has been developed by Brennan et al. 6 Recently, it was demonstrated that high signal-to-noise Raman spectra can be obtained from the aortic arch and arteries of sheep in vivo, in the presence of blood flow, by using specially designed Raman fiber-optic catheters and a transluminal approach. 7,8 We studied atherosclerotic plaque formation in transgenic mice that were fed a high cholesterol-containing diet. These mice, carrying the dysfunctional apoE variant from patients with a dominantly inherited form of familial dysbetalipoproteinemia (APOE...

Multiplex Coherent Anti-Stokes Raman Spectroscopy Images Intact Atheromatous Lesions and Concomitantly Identifies Distinct Chemical Profiles of Atherosclerotic Lipids

“…31,32 The plaque composition changes seen following statin therapy have been studied by Raman microscopy, showing a decrease in atherosclerotic plaque size. 33 These studies, however, have not demonstrated how statins directly alter lipid crystals, thereby stabilizing adverse components of stable plaques. We demonstrated that the chemical profiles of lipid crystals were changed by statin therapy using multiplex CARS.…”

Inflammation as a Cardiovascular Risk Factor

“…It can potentially quantify cholesterol in plaque and can monitor the effects of atheroma-modifying therapy. 23,31 Raman spectroscopy is limited by the fact that blood absorbs laser light and that it is 1-dimensional. 23 It can, however, be combined with other imaging techniques to provide important information about plaque composition.…”

Surface enhanced Raman spectroscopy (SERS): Potential applications for disease detection and treatment

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