Raman microspectroscopy of human coronary atherosclerosis: Biochemical assessment of cellular and extracellular morphologic structures in situ

Background. We have previously shown that Raman spectroscopy can be used fo r chemical analysis of intact human coronary artery atherosclerotic lesions ex vivo without tissue homogenization or extraction. Here, we report the c hemical analysis of individual cellular and extracellular components of ath erosclerotic lesions in different stages of disease progression in situ usi ng Raman microspectroscopy. Methods: Thirty-five coronary artery samples we re taken from 16 explanted transplant recipient hearts, and thin sections w ere prepared. Using a high-resolution confocal Raman microspectrometer syst em with an 830-nm laser light, high signal-to-noise Raman spectra were obta ined from the following morphologic structures: internal and external elast ic lamina, collagen fibers, fat, foam cells, smooth muscle cells, necrotic core, beta -carotene, cholesterol crystals, and calcium mineralizations. Th eir Raman spectra were modeled by using a linear combination of basis Raman spectra from the major biochemicals present in arterial tissue, including collagen, elastin, actin, myosin, tropomyosin, cholesterol monohydrate, cho lesterol linoleate, phosphatidyl choline, triolein, calcium hydroxyapatite, calcium carbonate, and ii-carotene. Results. The results show that the var ious morphologic structures have characteristic Raman spectra, which vary l ittle from structure to structure and from artery to artery. The biochemica l model described the spectrum of each morphologic structure quite well, in dicating that the most essential biochemical components were included in th e model. Furthermore, the biochemical composition of each structure, indica ted by the fit contributions of the biochemical basis spectra of the morpho logic structure spectrum, was very consistent. Conclusion. The Raman spectr a of various morphologic structures in normal and atherosclerotic coronary artery may be used as basis spectra in a linear combination model to analyz e the morphologic composition of atherosclerotic coronary artery lesions. ( C) 2001 Elsevier Science inc. All rights reserved.