Comparative studies of aortic acid mucopolysaccharides in fifteen species

Cardiac functional and histopathologic findings in humans and mice with mucopolysaccharidosis type I: implications for assessment of therapeutic interventions in hurler syndrome

Hurler syndrome (mucopolysaccharidosis type I [MPS I]) is a uniformly lethal autosomal recessive storage disease caused by absence of the enzyme alpha-l-iduronidase (IDUA), which is involved in lysosomal degradation of sulfated glycosaminoglycans (GAGs). Cardiomyopathy and valvar insufficiency occur as GAGs accumulate in the myocardium, spongiosa of cardiac valves, and myointima of coronary arteries. Here we report the functional, biochemical, and morphologic cardiac findings in the MPS I mouse. We compare the cardiac functional and histopathological findings in the mouse to human MPS I. In MPS I mice, we have noted aortic insufficiency, increased left ventricular size, and decreased ventricular function. Aortic and mitral valves are thickened and the aortic root is dilated. However, murine MPS I is not identical to human MPS I. Myointimal proliferation of epicardial coronary arteries is unique to human MPS I, whereas dilation of aortic root appears unique to murine MPS I. Despite the differences between murine and human MPS I, the murine model provides reliable in vivo outcome parameters, such as thickened and insufficient aortic valves and depressed cardiac function that can be followed to assess the impact of therapeutic interventions in preclinical studies in Hurler syndrome.

Proteoglycans in Atherosclerosis and Restenosis

The proteoglycan versican is one of several extracellular matrix (ECM) molecules that accumulate in lesions of atherosclerosis and restenosis. Its unique structural features create a highly interactive molecule that binds growth factors, enzymes, lipoproteins, and a variety of other ECM components to influence fundamental events involved in vascular disease. Versican is one of the principal genes that is upregulated after vascular injury and is a prominent component in stented and nonstented restenotic lesions. The synthesis of versican is highly regulated by specific growth factors and cytokines and the principal source of versican is the smooth muscle cell. Versican interacts with hyaluronan, a long chain glycosaminoglycan, to create expanded viscoelastic pericellular matrices that are required for arterial smooth muscle cell (ASMC) proliferation and migration. Versican is also prominent in advanced lesions of atherosclerosis, at the borders of lipid-filled necrotic cores as well as at the plaque-thrombus interface, suggesting roles in lipid accumulation, inflammation, and thrombosis. Versican influences the assembly of ECM and controls elastic fiber fibrillogenesis, which is of fundamental importance in ECM remodeling during vascular disease. Collectively, these studies highlight the critical importance of this specific ECM component in atherosclerosis and restenosis.

Immunolocalization of collagen types I and III in the arterial wall of the rat

Collagen types I and III were located by immunofluorescence procedures in the aorta and coronary arteries of the rat. Type I collagen was most prevalent in the adventitia of the aorta with only small amounts present in the intima and media. Type III collagen appeared to be a significant component in the media of the aorta and also in the adventitia of both blood vessels. The intima and media of the coronary arteries did not stain strongly for either type I or III collagen. Neither staining procedure was altered with preincubation of the sections with hyaluronidase or chondroitinase ABC. These studies indicate that type III collagen is a major component of the adventitia which has previously not been recognized by immunohistochemical techniques, possibly due to masking of collagen staining with glycosaminoglycans.

Proteoglycans and hypertension. I. A biochemical and ultrastructural study of aorta glycosaminoglycans in spontaneously hypertensive rats

The extracellular matrix of blood vessel walls contains elastin, collagen, and proteoglycans, all of which can affect vascular resistance and, hence, blood pressure by virtue of their biomechanical properties. In the present study, we have begun to explore the possibility that proteoglycans may play a role in the pathophysiology of hypertension by analyzing, qualitatively and quantitatively, the polysaccharide components of proteoglycans from aorta of two normotensive rat strains, Wistar Kyoto (WKY) and Wistar rats, and from spontaneously hypertensive (SH) rats of the Okamoto strain. The total concentration of aorta glycosaminoglycans in the SH rat was 33% higher than in the WKY rat, due to a 164% increase in chondroitin 4- and 6-sulfate. The content of dermatan sulfate (DS), hyaluronic acid (HA), and heparan sulfate (HS) was similar in the two strains. The 4-wk-old SH rat also had an increase in chondroitin sulfate (CS) compared to the 4-wk-old WKY rat, without any change in DS, HA, or HS. The Wistar rat had approximately the same concentration of CS und DS in the aorta as the WKY rat, but HS und HA were reduced by 62 and 37%, respectively. The galactosaminoglycans (CS and DS) were heterogeneous on cellulose acetate electrophoresis and exhibited a different pattern for each of the three strains. Undersulfated CS accounted for 15% of the total CS in WKY aorta but was present in only trace amounts in the SH aorta; 2% of the CS from the Wistar aorta was undersulfated. In all three strains, DS was exclusively 4-sulfated, and the CS contained approximately equal amounts of 4- and 6-sulfated galactosamine residues. Ultrastructural studies demonstrated that the HS was localized in the subendothelial matrix and the pericellular region surrounding the medial smooth muscle cells. CS and DS were primarily associated with collagen in the media. In the SH rat aorta the subendothelial matrix was thicker, and there was a relative increase in the CS/DS in the smooth muscle cell pericellular matrix. We suggest that, if similar alterations in CS proteoglycans are present in the resistance vessels, these changes may contribute to the increased peripheral vascular resistance in the hypertensive animal.

Proteoglycans in primate arteries. III. Characterization of the proteoglycans synthesized by arterial smooth muscle cells in culture

Near confluent monolayers of arterial smooth muscle cells derived from Macaca nemestrina were labeled with Na2[35S]O4 and the newly synthesized proteoglycans present in the culture medium and cell layer were extracted with either 4 M guanidine HCl (dissociative solvent) or 0.5 M guanidine HCl (associative solvent) in the presence of protease inhibitors. The proteoglycans in both compartments were further purified by cesium chloride density gradient ultracentrifugation. Two size classes of proteoglycans were observed in the medium as determined by chromatography on Sepharose CL-2B. The large population (Kav = 0.31) contained predominantly chondroitin sulfate chains with Mr = approximately 40,000. The smaller population (Kav = 0.61) contained dermatan sulfate chains of similar Mr (approximately 40,000). When tested for their ability to aggregate, only proteoglycans in the large-sized population were able to aggregate. A chondroitin sulfate containing proteoglycan with identical properties was isolated from the cell layer. In addition, the cell layer contained a dermatan sulfate component which eluted later on Sepharose CL-2B (Kav = 0.78) than the dermatan sulfate proteoglycan present in the medium. Electron microscopy of the purified proteoglycans revealed a bottlebrush structure containing a central core averaging 140 nm in length with an average of 8 to 10 side projections. The length of the side projections varied but averaged between 70 and 75 nm. Similar bottlebrush structures were observed in the intercellular matrix of the smooth muscle cell cultures after staining with Safranin 0. This culture system provides a model to investigate parameters involved in the regulation of synthesis and degradation of arterial proteoglycans.

Proteoglycans, DNA, and RNA in rat granulation tissue, skin, and aorta. Biochemical and histological studies

Proteoglycans in skin and aorta and nucleic acids in skin were studied in rats with subcutaneous sponge implants and in unoperated rats and compared with the sponge induced granulation tissue during a 42 day period. In rat aorta there was a predominance of the sulphated glycosaminoglycans, in particular heparan sulphate, while in skin there was a predominance of hyaluronic acid and dermatan sulphate. The subcutaneous sponge implantation caused a decrease in the dry weights of skin and aorta but did not influence the concentrations of the measured variables. In aorta the concentrations of chondroitin sulphate and dermatan sulphate decreased with age while in skin there was a slight fall in the concentrations of hyaluronic acid and heparan sulphate with age. The rate of biosynthesis of proteoglycans as estimated from the 35S-sulphate uptake was higher in skin than in aorta. A sequential development was noticed in granulation tissue with an initial high content of hyaluronic acid followed by increasing amounts of chondroitin sulphate and dermatan sulphate in older granulation tissue. The RNA/DNA ratio reached a maximum in 14 day old granulation tissue, but was unchanged in skin throughout the 42 day period. It is concluded that the distribution of proteoglycans and nucleic acids differs from tissue to tissue. This may be of relevance for tissue differences in susceptibility to diseases and to the effects - and side-effects - of drugs. The morphological and biochemical development of sponge induced granulation tissue from rats was similar to other types of granulation tissue during the first 4 weeks.

Effects of androgen treatment on the male rat aorta

Androgen was given to male rats to determine if it exerted effects on the aortic wall distinct from those of estrogen deficit. Although a general anabolic effect was avoided, significant vascular effects were observed. The amounts of mural fibrous proteins, elastin and collagen, were significantly increased in treated animals; noncollagenous, alkali-soluble protein, thought to reflect the cellular component, was unchanged with treatment. These effects were not detectable on microscopic examination and measurement of the vessel wall despite attempts to duplicate closely in vivo wall dimensions before study. These findings of distinct and marked effects of androgen on vascular metabolism extend the growing evidence for an important role of sex hormones in vessel wall structure and function.