Acid mucopolysaccharides of fatty streaks in young, human male aortas

Distribution of glycosaminoglycans in the intima of human aortas: changes in atherosclerosis and diabetes mellitus

Arterial glycosaminoglycans are considered to be important in atherogenesis due to their ability to trap lipid inside the vessel wall and to influence cellular migration and proliferation. Atherosclerotic lesions have displayed an altered glycosaminoglycan content and distribution. Diabetes is a recognized risk factor for atherosclerosis, but no information is available on the arterial glycosaminoglycans in human diabetes. We examined glycosaminoglycans in normal and atherosclerotic intima of non-diabetic and Type 2 (non-insulin-dependent) diabetic patients. Intima was stripped from autopsy samples of thoracic aortas; normal and plaque areas were separated. Glycosaminoglycans were isolated by delipidation, proteolytic digestion, and precipitation and characterized by quantitation of total glycosaminoglycan and evaluation of glycosaminoglycan distribution by electrophoresis and densitometry. Results indicate a significant decrease in total glycosaminoglycan and significant changes in their distribution in atherosclerotic plaques: a relative decrease in heparan sulphate, a relative increase in dermatan sulphate and thus a decrease in the ratio of heparan sulphate to dermatan sulphate. A similar but less marked change in the ratio was found in normal intima of diabetic subjects, while in their plaques this change was more pronounced. This suggests that changes in arterial glycosaminoglycans (especially the ratio of heparan sulphate to dermatan sulphate) precede the development of lesions in diabetes and may be important in atherogenesis.

Composition of proteoglycans from human atherosclerotic lesions

Proteoglycans from human atherosclerotic lesions and from uninvolved aortic intima were isolated and their composition was studied. The tissues were sequentially extracted by guanidine hydrochloride followed by hydrolysis of the tissue by elastase. Chondroitin sulfate/dermatan sulfate proteoglycans were predominant in guanidine hydrochloride extracts of the tissue. Most of the heparan sulfate proteoglycans were released from the tissue by hydrolysis with elastase. The content of proteoglycan material, measured as uronate per unit weight of wet tissue, was lower in fatty streaks and fibrous plaques than in uninvolved tissue (0.58 and 0.48 mg vs. 0.7 mg/g wet tissue). The distribution of different glycosaminoglycans in guanidine hydrochloride-extracted proteoglycans was similar among the lesions and uninvolved tissue, but varied in the elastase-hydrolyzed extracts. Gel filtration studies suggested that the major proteoglycan material, chondroitin sulfate proteoglycans, from lesions had greater molecular weight than proteoglycans from uninvolved tissue. The studies indicate that alteration in intrinsic composition and molecular size of proteoglycans occurs in atherosclerotic lesions.

Proteoglycan composition of rabbit arterial wall under conditions of experimentally induced atherosclerosis

The concentration and composition of proteoglycans (PG) of the neointima developed following balloon catheter removal of aortic endothelium in rabbits, were assessed. PG were extracted from the aortic intimal-medial tissues with 4 M guanidinium chloride in the presence of protease inhibitors and purified subsequently by cesium chloride gradient ultracentrifugation and fractionation by high-performance liquid chromatography (HPLC). PG so obtained was analysed for its protein, cholesterol and glycosaminoglycan (GAG) content. For the characterization of the GAG moiety, an exhaustive proteolytic digestion was done. The GAG were then recovered by ethanolic precipitation and their relative distribution was determined after a selective enzymatic digestion using specific enzymes. Results show a significant increase in the amount of PG in the areas of the injured arterial wall covered by regenerated endothelium. In addition, changes in the composition of GAG were also found in the PG isolated from experimental animals when compared to PG isolated from normal aorta. A marked increase in the content of chondroitin sulfates and dermatan sulfate of injured tissue was seen. Hyaluronic acid content also changed in response to de-endothelialization and cholesterol feeding, but only moderately. The content of heparan sulfate remained unaffected in experimental tissues. Furthermore, cholesterol feeding aggravated the injury-induced increment of GAG. These findings are consistent with previously reported morphological observations, and correlate well with reports that arterial injury and cholesterol feeding act synergistically in the evolution of the atherosclerotic lesion and provide further evidence that the interaction of lipid and PG of the arterial wall may be of particular importance to our comprehension of the pathogenesis of atherosclerosis.

Aortic connective tissue in atherosclerotic aorta--a biochemical study

Biochemical analysis of the extracellular matrix of human aortas was performed on samples of ascending and descending aortas affected by atherosclerosis in comparison with a control group of nonatherosclerotic aortas. Ulcerated or heavily calcified atheromas were excised and excluded from the analysis in order to differentiate biochemical alterations leading to the formation of atheromas from those due to complications of already formed atheromas. Our results show that the development of atheromas brings about an extensive destruction of elastic fibers and muscular cells, and their place is occupied by other components of the extracellular matrix, most notably, collagen, non-uronic sugars, water, and lipids, which were found significantly increased.

The effect of haemodynamic stress on the glycosaminoglycan content of blood vessel walls of experimental aneurysms and arteriovenous fistulae

The glycosaminoglycan content of experimental saccular aneurysms and arteriovenous fistulae of sheep has been measured. In the experimental aneurysm hyaluronic acid, heparan sulphate, dermatan sulphate, chondroitin sulphate and total glycosaminoglycans were all elevated above control tissue levels with increases most striking for dermatan sulphate and chondroitin sulphate. In the anastomosed vein of the arteriovenous fistulae, total glycosaminoglycans were also significantly raised but which individual glycosaminoglycans were responsible was not clearly established. In the arteries feeding the fistulae, increased chondroitin sulphate in the proximal arterial segment was the only significant change observed. The changes were attributed to altered haemodynamic stresses and are similar to those reported for animal models of hypertension and early human atherosclerosis.

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.

Effect of low density lipoprotein on glycosaminoglycan secretion by cultured human smooth muscle cells and fibroblasts. Influence of serum concentration and cell proliferation rate

Glycosaminoglycan (GAG) secretion was studied in cultures of human fibroblasts and arterial smooth muscle cells. Supplementation of culture medium with whole human serum increased the secretion of GAG but this effect disappeared as cell density increased. Lipoprotein-free serum (LFS) supported cell growth but led to a decrease in GAG secretion and in cell cholesterol. Addition of human low density lipoprotein (LDL) to the medium containing 10% LFS produced increases in GAG secretion (200%) and cell cholesterol (300%) and a decrease (60%) in cell population. The effects of LDL were considerably smaller in medium containing 5% LFS; this was related to the lower rate of proliferation in this medium, since there was a close relationship between rate of proliferation and stimulation of GAG secretion by LDL independent of serum concentration. In addition, fetal smooth muscle cells showed a qualitatively different response to LDL in 5% LFS, with a biphasic dose-response of GAG secretion and cell number. It is concluded that: (1) whole human serum stimulates GAG secretion by sparse cell cultures, (2) LFS can support cell growth but not GAG secretion, (3) LDL stimulates GAG secretion but has a cytotoxic effect, (4) the degree of GAG stimulation by LDL is dependent on the proliferative state of cells, (5) at low serum concentrations fibroblasts and fetal smooth muscle cells show differences in response to LDL which are not evident at higher serum concentration.

Acidic glycosaminoglycan, lipid and water contents in human coronary arterial branches

The acidic glycosaminoglycans (AGAG) of the human coronary arterial tree (the main left and right branches and their distal portions) were analyzed by enzymatic methods employing chondroitinases, hyaluronidase and heparitinase. The AGAG content of human coronary arteries was highest in the left branch, intermediate in the right branch and lowest in the distal portions. Some compositional differences in AGAG were found in these three parts. The amount of AGAG in the coronary arterial tree decreased with increasing severity of atherosclerosis. The main AGAG were heparan sulfate (HS) and chondroitin 6-sulfate (C-6S), constituting 33-38% and 24-36% of the total AGAG, respectively. Dermatan sulfate (DS) and chondroitin 4-sulfate (C-4S) each comprised 1/5-1/10 of the total AGAG. Hyaluronic acid (HA) and oversulfated DS comprised smaller proportions of the total AGAG. A small amount of heparin was occasionally detected in the coronary arterial tree, particularly in the distal portions. The lipid content of the main branches was increased in mildly atherosclerotic parts but diminished in severely affected parts. The water content was relatively higher in the main branches and decreased with severity of atherosclerosis. A possible function of these AGAG in atherosclerosis is discussed with respect to the compositional changes.

Determination of mulecular-weight distribution of aorta glycosaminoglycans by automated gel filtration

This report describes an automated gel filtration procedure for estimation of molecular weights of glycosaminoglycans using Technicon sugar analyzer. A Sepharose CL-6B column was used for filtration. The method has been applied to determining the distribution of molecular weights of glycosaminoglycans from human aorta. The glycosaminoglycans were fractionated on a Dowex 1 (Cl-) column prior to gel filtration. On gel filtration, hyaluronic acid resolved into two components with estimated molecular weights of 38,000 and 8000. A molecular weight of 22,000 was estimated for heparan sulfate. Chondroitin 6-sulfate and dermatan sulfate eluted from the column in one peak, suggesting these two glycosaminoglycans have a similar molecular weight, 18,000. The procedure was found suitable for studying the gel filtration behavior of proteoglycans from bovine aorta and lung.

The effect of various dietary regimens and cholestyramine on aortic glycosaminoglycans during regression of atherosclerotic lesions in rhesus monkeys

The effect of various diets on the aortic glycosaminoglycan (GAG) composition was studied in rhesus monkeys. Aortas were obtained from monkeys fed diets containing cholesterol and comparative fats including coconut oil--butter and peanut oil and with and without cholestyramine. Additional groups in each experiment were placed on regression diets of low-fat, low-cholesterol with and without cholestyramine. Further, an atherogenic diet of coconut oil--butter was alternated every 2 months with a diet enriched with corn oil. GAG isolated from intima and media--adventitia indicated slight variations in the concentration of total GAG among different dietary groups but major differences in the concentration of individual GAG. The concentrations of hyaluronic acid and heparan sulfate were generally greater in aortas of monkeys fed corn oil diets than in those fed coconut oil--butter or peanut oil diets. The concentration of dermatan suulfate generally decreased during regression of lesions induced by the saturated fat--cholesterol diet. Furthermore, the aortas of monkeys with lesions from feeding peanut oil showed higher levels of dermatan sulfate and lower levels of chondroitin 4-sulfate than the saturated fat-fed groups. The addition of cholestyramine enhanced the effects of regression. These observations show that the composition of GAG of the arterial wall can be influenced by various dietary programs and that GAG play a role in induction and regression of experimental atherosclerotic lesions.

High density lipoproteinemia due to vigorous physical work inhibits the incorporation of [3H]thymidine and the synthesis of glycosaminoglycans by human aortic smooth muscle cells in culture

The effect of sera from normolipidemic men engaging in normal physical activity and from high density lipoproteinemic lumberjacks engaging in vigorous physical activity on the incorporation of [3H]thymidine and the synthesis of glycosaminoglycans by human aortic smooth muscle cells in culture was measured. At high concentration (15%) high density lipoproteinemic serum inhibited significantly (P less than 0.001) the incorporation of thymidine. The serum inhibited the synthesis of glycosaminoglycans at all concentrations tested (1--15%) with the most marked inhibition at 10 and 15%. At lower concentrations (1--5%) the inhibition was more pronounced for sulphated glycosaminoglycans than for hyaluronic acid. The inhibition was of the same magnitude for the subclasses (chondroitin, dermatan and heparan sulphates) of sulphated glycosaminoglycans studied. High density lipoproteinemia due to vigorous physical work is postulated as a protective factor against the early biochemical reactions of arterial smooth muscle cells in the development of atherosclerosis.

Glycosaminoglycan-lipoprotein complexes from aortas of hypercholesterolemic rabbits. Part 1. Isolation and characterization

Glycosaminoglycan-lipoprotein complexes were isolated from rabbit aortas exhibiting nearly confluent cholesterol-induced foam cell lesions by extraction with 0.15 M NaCl. Purification and characterization was achieved by gel chromatography, non-ionic differential flotation and by cellulose polyacetate electrophoresis. Analysis showed that these complexes consisted of very low density lipoproteins, heparan sulfate, chondroitin sulfate-C and hyaluronic acid. The demonstration that rabbit intimal foam cell lesions contain extractable glycosaminoglycan-lipoprotein complexes makes this animal model an excellent tool for further studies on the role of these complexes in the atherogenic process.

Heterogeneity in the composition and aggregation patterns of coronary intima acid mucopolysaccharides (glycosaminoglycans)

The thickened intima of human coronary arteries included acid mucopolysaccharides (glycosaminoglycans) with a large variety of patterns of composition and aggregation. This heterogeneity, detectable with histochemical methods, was related in our material to age, branching anatomical pattern, size of vessel, collateral or terminal character of the vessel, bifurcations, intimal histology, internal elastic membrane alterations, as well as to the onset of fatty streaks, gelatinous plaques and incorporated microthrombi.

Ultrastructure of proteoglycans in human renal arteries from end stage renal disease

Although glycosaminoglycans, particularly proteoglycans, have been characterized biochemically in normal and diseased arteries, little is known regarding their ultrastructural characteristics in human arteries. The observations reported here were made in renal arteries from nephrectomy specimens from patients with endstage kidney disease and hypertension. By light microscopy, the diffusely thick intima is characterized by small, slender smooth muscle cells embedded in a finely fibrillar, strongly alcian-blue positive, intercellular matrix. Ultrastructurally, there is a loose meshwork of collagen fibrils, elastic units and abundant fibrillogranular units staining strongly with ruthenium red and identified as proteoglycans. These consist of ovoid or diamond-shaped electron-dense granules about 300-500 A in diameter, having fine filamentous processes.

The effect of centrifugal force on glycosaminoglycan production by aortic smooth muscle cells in culture

Cultured smooth muscle cells from pig aorta subjected to centrifugation (48 h at 45 g over a 72-h period) increased their production of glycosaminoglycans by approximately 50%. The sulphated components, heparan sulphate, dermatan sulphate and chondroitin sulphate, showed a relatively greater increase than hyaluronic acid (66-34%). The results are consistent with the hypothesis that mechanical stress, such as hypertension, leads to increased accumulation of glycosaminoglycans in the aortic wall and that secondary trapping of lipoproteins by sulphated glycosaminoglycans produces atherosclerotic plaques.

Composition of acidic glycosaminoglycans in human cerebral arteries

(1) The composition of acidic glycosaminoglycans (AGAG) in the pooled human cerebral arteries was investigated by electrophoretic characterization before and after digestion with chondroitinases. Constitution of the chondroitin sulfate (CS) family was determined qualitatively on the basis of the disaccharide subunits of the CS chains after depolymerization with the enzymes. (2) The data obtained indicated that the AGAG in cerebral arteries consisted of, in order of amount, heparan sulfates, chondroitin-6-sulfate, dermatan sulfate, chondroitin-4-sulfate and hyaluronic acid. (3) The existence of oversulfated CS and undersulfated CS in the cerebral AGAG was supported by the detection of unsaturated di-sulfated and non-sulfated disaccharides on paper chromatography. In addition, the presence of hyaluronic acid was indicated by electrophoretic and enzymatic separation. (4) The distribution of the individual AGAG in cerebral arteries was also examined on the basis of molecular weight by gel filtration on a Sephadex G-100 column.

The ground substance of the arterial wall. Part 1. Extractability of glycosaminoglycans and the isolation of a proteoglycan from bovine aorta

Water and glycosaminoglycan contents were measured in upper and lower thoracic aortas of claves and steers. The ability of various molarities of guanidine hydrochloride to extract glycosaminoglycans from these tissues was assessed. Some glycosaminoglycans seem to be more resistant to extraction than others. A procedure is described for the isolation of a proteoglycan. The molecule appears to contain both dermatan sulfate and chondroitin sulfate. It also seems to be less dense than cartilage proteoglycans extracted by similar methods as assessed by its behavior in centrifugal fields. The properties, locus and biological activities of this molecule are currently being studied.

Lipoprotein-acid mucopolysaccharide complexes of human atherosclerotic lesions

Lipoprotein-acid mucopolysaccharide complexes occurring in different types of human atherosclerotic lesions were isolated and partially characterized. Complexes from fatty streaks and fibrous plaques were extracted from pooled tissues with 0.15 M NaCl, purified by gel filtration, and fractionated by ultracentrifugation. Both low and very low density lipoproteins were present; low density lipoprotein was predominant. The complexes were analyzed for uronic acid, cholesterol, phospholipid, and Ca-2+ contents; there was no significant difference in the relative molar ratios between complexes from fatty streaks and fibrous plaques. Acid mucopolysaccharides were isolated from the complexes and identified by electrophoresis and enzymatic studies. Chondroitin sulfate C and hyaluronic acid were found in complexes from fatty streaks and fibrous plaques. Heparin was detected only in fibrous plaques.