| Collagen and elastin of the extracellular matrix (ECM) play an important role in tissue mechanics. They are key contributors in tissue remodeling during maturation and disease, including atherosclerosis, the focus of this research. Atherosclerosis is a complex disease mediated by inflammatory processes. Lesion encroachment on the arterial lumen can impede blood flow, or become unstable and shed fragments with the risk for myocardial infarction or stroke. The instability of these lesions is important clinically and improved diagnostic tools are needed to discriminate between the stable and unstable plaque. The primary method of the research was fluorescent spectroscopy of the matrix proteins with corroborating data from histology. Studies were completed on three different tissues (i) rat tail tendon (RTT), (ii) atherosclerosis in cholesterol fed rabbits and (iii) human carotid surgical specimens. The rat tail tendon study tested fluorescence spectroscopy on a maturing collagen tissue. Tendon and skin from 27 male Wistar rats of young age were evaluated by fluorescence spectroscopy, birefringence microscopy and histology, with a positive correlation (R2=0.60) between birefringence and maximum fluorescence intensity. The rabbit study was on in vivo fluorescence spectroscopy of accelerated plaque growth, setting the stage for future endovascular applications. Spectra (53 animals) were obtained from the aorta, including experimental subgroups of cholesterol fed, angioplasty injury, vascular stented animals, and anti-inflammatory treatments. Wavelength segments were correlated with immunohistology, extracted protein assays, and measurements of plaque geometry. Fluorescence data correlated strongly with measures of collagen and elastin, demonstrating the power of fluorescence spectroscopy for evaluating tissue responses to injury and different therapies. The endarterectomy study involved surgical specimens from 25 patients with significant occlusion of the carotid bifurcation. Tissue from a few specimens was snap frozen and assessed for ECM gene expression. Fluorescence spectra of the luminal lesion surfaces showed marked increases in collagen I in the region of the internal carotid artery (CA) in comparison to the common CA. These results were supported by measurements from immunohistology and polarizing microscopy. The study helps to validate fluorescence spectroscopy as an approach for vascular tissue. Together these studies advance our understanding of atherosclerosis and show potential for clinical applications of fluorescence spectroscopy.;Keywords. atherosclerosis, auto fluorescence, birefringence, collagen, cross linking, elastin, extracellular matrix, fluorescence spectroscopy, plaque, tissue remodeling... |
