Arterial mesenchyme and arteriosclerosis. Some aspects of the organization and interaction of connective tissue proteoglycans

Proteoglycans in human atherosclerotic lesions--a pilot qualitative and quantitative study by ruthenium red

A pilot study was carried out to test whether normal human aorta and aortic atherosclerotic lesions obtained at post-mortem examination were suitable for the demonstration of proteoglycans (PGs) by ruthenium red (RR) staining, and whether by this method qualitative and quantitative differences of PGs might be detectable in various types of lesions and between lesions and the normal aortic intima. The results indicate that the PGs of the above tissues obtained at post mortem were clearly visualized by electron microscopy using the RR-indicator and were thus suitable for quantitative and qualitative evaluation. Of the RR-positive granules only those 20 nm and larger were assessed. RR-granules measuring 20-50 nm were present in normal intima and media, in increased concentration in the innermost part of the mixed fatty-gelatinous lesion, and in a decreased concentration in the fibrous cap of an atherosclerotic plaque. The same RR-granules were observed in a fatty streak and in addition 50-100 nm granules were present in this type of lesion; the overall RR-granule-concentration was reduced here. Granules of both sizes were interconnected by filamentous network. The differential presence of the large (and hitherto unreported) as well as the smaller granules in the various lesions is briefly discussed in the light of the present-day knowledge of tissue-PGs, and the importance of an examination in situ of the compound PGs-complexes in their native form, is emphasized.

Dynamics of lipoprotein-glycosaminoglycan interactions in the atherosclerotic rabbit aorta in vivo

Dynamics of lipoprotein-glycosaminoglycan interactions in aortas were studied in vivo using the atherosclerotic rabbit model. Severe hypercholesterolemia and atherosclerosis were produced by relatively long-term feeding of a high cholesterol diet. [35S]Sulfate uptake by aorta was measured to assess the sulfated glycosaminoglycan metabolism while the plasma and aorta distribution of 125I-labeled LDL after intravascular injection was determined to monitor aortic LDL uptake and complex formation with glycosaminoglycans. The retention and distribution of LDL as lipoprotein-glycosaminoglycan complexes in different extracellular connective tissue elements were evaluated by extracting the tissues with saline, collagenase and elastase. Hypercholesterolemia with atherosclerosis resulted in a several-fold increase in the uptake of LDL by aorta despite a marked reduction of 125I-labeled LDL in the plasma compartment and in a significant increase in glycosaminoglycan content of aorta coupled with an increased 35S incorporation into glycosaminoglycans. Elastase-solubilized fractions from normal aortas and collagenase-solubilized fractions from atherosclerotic aortas contained maximum labeled and nonlabeled glycosaminoglycan, suggesting alterations in the make-up of fibrous structures of connective tissue matrix in atherosclerosis. Saline extraction and collagenase and elastase digestions solubilized varied proportions of lipoprotein-cholesterol and 125I-labeled LDL, thereby representing different pools of extracellular matrixbound lipoproteins. A tendency for 125I-labeled LDL to increase in collagenase- and elastase-solubilized fractions with time (4 h vs. 24 h) was noted. The occurrence of both lipoproteins and glycosaminoglycan (labeled and nonlabeled) in the ultracentrifugal floating fraction at solvent density 1.063 g/ml demonstrated that the lipoproteins solubilized by different extraction procedures occur in part as lipoprotein-glycosaminoglycan complexes. The specific activities of glycosaminoglycan in the complexes obtained by different extraction procedures differed markedly (elastase greater than collagenase greater than saline), emphasizing the presence of different pools of complexes. Thus, besides arterial cell-mediated processes, extracellular matrix components are important in affecting the retention and accumulation of LDL in atherosclerosis.

Connective tissue components in normal and atherosclerotic human coronary arteries

Human coronary arteries with various degrees of atherosclerosis were analyzed for the concentration of different types of glycosaminoglycans (GAGs). The changes in GAGs were considered against the background of macroscopic atherosclerosis, and the concentration of glycoprotein-bound hexosamines, collagen, calcium and cholesterol. The concentration of calcium was increased and that of hyaluronic acid decreased even in mildly atherosclerotic coronary arteries. The additional changes in advanced atherosclerosis included the increase of collagen and dermatan sulphate and the decrease of heparan sulphate. Cholesterol was increased in mild, and even further in advanced, atheroslcerosis. The concentrations of chondroitin sulphates and glycoprotein-bound hexosamines were not significantly affected by atherosclerosis.