Growth-related production of proteoglycans and hyaluronic acid in synchronous arterial smooth muscle cells

Hyaluronan stimulates ex vivo B lymphocyte chemotaxis and cytokine production in a murine model of fungal allergic asthma

Allergic asthma is a chronic inflammatory disease of the airways characterized by excessive eosinophilic and lymphocytic inflammation with associated changes in the extracellular matrix (ECM) resulting in airway wall remodeling. Hyaluronan (HA) is a nonsulfated glycosaminoglycan ECM component that functions as a structural cushion in its high molecular mass (HMM) but has been implicated in metastasis and other disease processes when it is degraded to smaller fragments. However, relatively little is known about the role HA in mediating inflammatory responses in allergy and asthma. In the present study, we used a murine Aspergillus fumigatus inhalational model to mimic human disease. After observing in vivo that a robust B cell recruitment followed a massive eosinophilic egress to the lumen of the allergic lung and corresponded with the detection of low molecular mass HA (LMM HA), we examined the effect of HA on B cell chemotaxis and cytokine production in the ex vivo studies. We found that LMM HA functioned through a CD44-mediated mechanism to elicit chemotaxis of B lymphocytes, while high molecular mass HA (HMM HA) had little effect. LMM HA, but not HMM HA, also elicited the production of IL-10 and TGF-β1 in these cells. Taken together, these findings demonstrate a critical role for ECM components in mediating leukocyte migration and function which are critical to the maintenance of allergic inflammatory responses.

Hyaluronan deposition and co-localization with inflammatory cells and collagen in a murine model of fungal allergic asthma

OBJECTIVE

Allergic asthma is a chronic inflammatory disease of the airways characterized by excessive inflammation and remodeling of the extracellular matrix (ECM) and associated cells of the airway wall. Under inflammatory conditions, hyaluronan (HA), a major component of the ECM, undergoes dynamic changes, which may in turn affect the recruitment and activation of inflammatory cells leading to acute and chronic immunopathology of allergic asthma.

METHODS

In the present study, we measured the changes in HA levels generated at sites of inflammation, and examined its effect on inflammatory responses and collagen deposition in an Aspergillus fumigatus murine inhalational model of allergic asthma.

RESULTS

We found that HA levels are elevated in allergic animals and that the increase correlated with the influx of inflammatory cells 5 days after the second allergen challenge. This increase in HA levels appeared largely due to upregulation of hyaluronidase-1 (HYAL1) and hyaluronidase-2 (HYAL2). Furthermore, HA co-localizes with areas of new collagen synthesis and deposition.

CONCLUSIONS

Overall, our findings contribute to the growing literature that focuses on the components of ECM as inflammatory mediators rather than mere structural support products. The evidence of HA localization in fungal allergic asthma provides the impetus to study HA more closely with allergic leukocytes in murine models. Further studies examining HA's role in mediating cellular responses may help to develop targets for treatment in patients with severe asthma due to fungal sensitization.

Adenosine A2B receptor and hyaluronan modulate pulmonary hypertension associated with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. The development of pulmonary hypertension (PH) in patients with COPD is strongly associated with increased mortality. Chronic inflammation and changes to the lung extracellular matrix (ECM) have been implicated in the pathogenesis of COPD, yet the mechanisms that lead to PH secondary to COPD remain unknown. Our experiments using human lung tissue show increased expression levels of the adenosine A2B receptor (ADORA2B) and a heightened deposition of hyaluronan (HA; a component of the ECM) in remodeled vessels of patients with PH associated with COPD. We also demonstrate that the expression of HA synthase 2 correlates with mean pulmonary arterial pressures in patients with COPD, with and without a secondary diagnosis of PH. Using an animal model of airspace enlargement and PH, we show that the blockade of ADORA2B is able to attenuate the development of a PH phenotype that correlates with reduced levels of HA deposition in the vessels and the down-regulation of genes involved in the synthesis of HA.

High levels of hyaluronan in idiopathic pulmonary arterial hypertension

Hyaluronan (HA), a large glycosaminoglycan found in the ECM, has major roles in lung and vascular biology and disease. However, its role in idiopathic pulmonary arterial hypertension (IPAH) is unknown. We hypothesized that HA metabolism is abnormal in IPAH. We measured the plasma levels of HA in IPAH and healthy individuals. We also evaluated HA synthesis and the expression of HA synthases and hyaluronidases in pulmonary artery smooth muscle cells (PASMCs) from explanted lungs. Plasma HA levels were markedly elevated in IPAH compared with controls [HA (ng/ml, mean +/- SD): IPAH 325 +/- 80, control 28 +/- 9; P = 0.02]. In vitro, unstimulated IPAH PASMCs produced high levels of HA compared with control cells [HA in supernatant (microg/ml, mean +/- SD): IPAH 12 +/- 2, controls 6 +/- 0.9; P = 0.04]. HA levels were also higher in IPAH PASMC lysates. The increased HA was biologically relevant as shown by tissue staining and increased HA-specific binding of mononuclear cells to IPAH compared with control PASMCs [number of bound cells x 10(4) (mean +/- SD): IPAH 9.5 +/- 3, control 3.0 +/- 1; P = 0.01]. This binding was abrogated by the addition of hyaluronidase. HA synthase-2 and hyaluronidase-2 were predominant in control and IPAH PASMCs. Interestingly, the expressions of HA synthase-2 and hyaluronidase-2 were approximately 2-fold lower in IPAH compared with controls [HA synthase-2 (relative expression mean +/- SE): IPAH 4.3 +/- 0.02, control 7.8 +/- 0.1; P = 0.0004; hyaluronidase-2 (relative expression mean +/- SE): IPAH 4.2 +/- 0.06, control 7.6 +/- 0.07; P = 0.008]. Thus patients with IPAH have higher circulating levels of HA, and PASMCs derived from IPAH lungs produce more HA compared with controls. This is associated with increased tissue levels and increased binding of inflammatory cells suggesting a role for HA in remodeling and inflammation in IPAH.

Hyaluronan-dependent pericellular matrix

Hyaluronan is a multifunctional glycosaminoglycan that forms the structural basis of the pericellular matrix. Hyaluronan is extruded directly through the plasma membrane by one of three hyaluronan synthases and anchored to the cell surface by the synthase or cell surface receptors such as CD44 or RHAMM. Aggregating proteoglycans and other hyaluronan-binding proteins, contribute to the material and biological properties of the matrix and regulate cell and tissue function. The pericellular matrix plays multiple complex roles in cell adhesion/de-adhesion, and cell shape changes associated with proliferation and locomotion. Time-lapse studies show that pericellular matrix formation facilitates cell detachment and mitotic cell rounding. Hyaluronan crosslinking occurs through various proteins, such as tenascin, TSG-6, inter-alpha-trypsin inhibitor, pentraxin and TSP-1. This creates higher order levels of structured hyaluronan that may regulate inflammation and other biological processes. Microvillous or filopodial membrane protrusions are created by active hyaluronan synthesis, and form the scaffold of hyaluronan coats in certain cells. The importance of the pericellular matrix in cellular mechanotransduction and the response to mechanical strain are also discussed.

Intracellular localization of hyaluronan in proliferating cells

Hyaluronan is a high molecular weight glycosaminoglycan found in the extracellular matrix of many tissues, where it is believed to promote cell migration and proliferation. It was recently shown that hyaluronan-dependent pericellular matrix formation is a rapid process that occurs as cells detach during mitosis. Growing evidence for intracellular hyaluronan in tissues in vivo, together with evidence of intracellular hyaluronan binding molecules, prompted us to examine hyaluronan distribution and uptake as well as hyaluronan binding sites in cells and their relationship to cell proliferation in vitro, using a biotinylated hyaluronan binding protein and fluorescein-labeled hyaluronan. In permeabilized smooth muscle cells and fibroblasts, hyaluronan staining was seen in the cytoplasm in a diffuse, network-like pattern and in vesicles. Nuclear hyaluronan staining was observed and confirmed by confocal microscopy and was often associated with nucleoli and nuclear clefts. After serum stimulation of 3T3 cells, there was a dramatic increase in cytoplasmic hyaluronan staining, especially during late prophase/early prometaphase of mitosis. In contrast, unstimulated cells were negative. There was a pronounced alteration in the amount and distribution of hyaluronan binding sites, from a mostly nucleolar distribution in unstimulated cells to one throughout the cytoplasm and nucleus after stimulation. Exogenous fluorescein-labeled hyaluronan was taken up avidly into vesicles in growing cells but was localized distinctly compared to endogenous hyaluronan, suggesting that hyaluronan in cells may be derived from an intracellular source. These data indicate that intracellular hyaluronan may be involved in nucleolar function, chromosomal rearrangement, or other events in proliferating cells. (J Histochem Cytochem 47:1331-1341, 1999)

Growth factors increase pericellular proteoglycans independently of their mitogenic effects on A10 rat vascular smooth muscle cells

Proliferation of vascular smooth muscle cells with the accumulation of proteoglycans in the extracellular matrix is one of the significant changes found in atherosclerotic lesions. In order to clarify the relationship between pericellular proteoglycan and cell growth, we established a simple method for quantitatively estimating the amount of pericellular proteoglycans and investigated the effects of various growth factors on the synthesis of pericellular proteoglycans by cultured A10 rat smooth muscle cells. Analysis of trypsin accessible [35SO4]-labeled material in the pericellular area of the A10 cell culture by Q-sepharose anion-exchange chromatography showed two peaks. One peak, eluted at 0.55 M NaCl, disappeared after treatment with 2 mU/ml of heparitinase, indicating that heparan sulfates (HS) were present. The other peak, which eluted at 0.65 M NaCl, disappeared with 20 mU/ml of chondroitinase ABC, indicating the presence of chondroitin sulfates and dermatan sulfates (CS/DS). We estimated the effects of several growth factors on the synthesis of the pericellular proteoglycans by measuring heparitinase- and chondroitinase-ABC-sensitive radioactivities. Although PDGF-AB significantly stimulated cell proliferation and the synthesis of pericellular CS/DS, its dose-dependent effect on the cell growth did not coincide with that on the proteoglycan synthesis. IGF-I (1 nM) increased pericellular CS/DS but not the cell number, while basic FGF (1 nM) and EGF (1 nM) increased the cell number but not pericellular CS/DS. All the growth factors we examined had no effect on the synthesis of pericellular HS. These results indicate that growth factors increase pericellular proteoglycans independently of their mitogenic effects.

Hyaluronan and hyaluronectin production in injured rat thoracic aorta

The aim of our study was to investigate the production of hyaluronan (HA) by the intima-media during the sclerotic response to aortic injury with a catheter balloon in the rat. In addition we analyzed, for the first time in this model, the production of a glycoprotein (hyaluronectin, HN) which binds specifically to HA. HA and HN were analyzed in control (D0), 14 (D14) and 28 (D28) days after injury using biochemical and immunohistochemical techniques. Intima-media DNA content and wet weight increased significantly on D14 and declined on D28 (but remained significantly increased in comparison to controls). HA content (median in D0 = 448 ng) increased significantly on D14 (2P < 0.04) and on D28 (2P < 0.02). HN content (median in D0 = 920 ng) increased significantly on D14 (2P < 0.05) but decreased on D28 to return to the control level. On D0 the amount of HN was about 3 times higher than that of HA (median ratio HA/HN = 0.34). The ratio remained unchanged on D14 but significantly increased on D28 (2P < 0.02). HPLC and Western blotting showed no difference between HN extracted from normal aorta and HN extracted from injured aorta at D14. Different isoforms of HN were present in both cases, ranging from 400 to 45 kDa. The HA increase on D14 and D28 was not related to a change in hyaluronidase activity of aortic tissue. Immunohistochemical analysis showed at D0 a small amount of HA around arterial smooth muscle cells (ASMC) in media, at D14 more HA was localized around and between ASMC in media and neointima but at D28 it was localized mainly near the vessel lumen. HN formed all the time (D0, D14 and D28) a continuous layer localized near the vessel lumen. In vitro studies showed that production of HA and HN was stimulated when ASMC proliferate and HA at high concentrations (1-100 micrograms/ml) reduced, in a dose dependent manner, ASMC growth. In conclusion our results show that both neointima formation in vivo and ASMC proliferation in vitro correlated with increased HA and HN production. This suggests that HA and HN are probably involved in the formation of neointima. On the other hand, the finding that HA continued to increase in the aorta when neointima decreased and that high concentrations of HA reduce ASMC proliferation in culture suggest that HA might be involved in the regression of neointima.

Distribution of hyaluronan during extracellular matrix remodeling in human restenotic arteries and balloon-injured rat carotid arteries

BACKGROUND

The glycosaminoglycan hyaluronan (HA) is present in developing tissues and healing wounds and forms a loose, hydrated extracellular matrix (ECM) that promotes processes such as cell migration. To investigate the potential contribution of HA to the pathogenesis of restenosis, we studied (1) human lesions obtained by directional atherectomy and (2) experimentally induced neointima formation in balloon-injured rat carotid arteries.

METHODS AND RESULTS

A biotinylated proteoglycan fragment that binds specifically to HA was used to stain atherectomy specimens from 29 human restenotic lesions (mean restenosis interval, 6.0+/-4.4 months) and 8 human primary lesions. The loose myxoid ECM typical of human restenotic arteries demonstrated intense, diffuse staining for HA. The intensity was inversely related to the density of immunostaining for collagen types I and III and was lowest in hypocellular primary atherosclerotic plaque. Among 24 rat carotid arteries retrieved 3, 7, 14, 28, 42, or 56 days after balloon injury and immunostained as well for proliferating cell nuclear antigen, staining for HA in the neointima reached a maximum 7 days after balloon injury and was associated with the presence of proliferating, PCNA-positive smooth muscle cells.

CONCLUSIONS

Hyaluronan is a characteristic constituent of the loose myxoid ECM in human restenotic arteries and of the neointima in experimentally injured arteries. The presence of hyaluronan may be a marker for an initial phase of the extracellular matrix remodeling that occurs during the development of a fibroproliferative lesion and could facilitate biological processes such as cell migration.

Differentiated properties and proliferation of arterial smooth muscle cells in culture

The smooth muscle cell is the sole cell type normally found in the media of mammalian arteries. In the adult, it is a terminally differentiated cell that expresses cytoskeletal marker proteins like smooth muscle alpha-actin and smooth muscle myosin heavy chains, and contracts in response to chemical and mechanical stimuli. However, it is able to revert to a proliferative and secretory active state equivalent to that seen during vasculogenesis in the fetus, and this is a prerequisite for the involvement of the smooth muscle cell in the formation of atherosclerotic and restenotic lesions. A similar transition from a contractile to a synthetic phenotype occurs when smooth muscle cells are established in culture. Accordingly, an in vitro system has been used extensively to study the regulation of differentiated properties and proliferation of these cells. During the first few days after seeding, the cells are reorganized structurally with a loss of myofilaments and formation of a widespread endoplasmic reticulum and a prominent Golgi complex. In parallel, they lose their contractility and instead become competent to divide in response to a large variety of mitogens, including platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). After entering the cell cycle, they start to produce these and other mitogens on their own, and continue to replicate in the absence of exogenous stimuli for a restricted number of generations. Furthermore, they start to secrete extracellular matrix components such as collagen, elastin, and proteoglycans. The mechanisms that control this change in morphology and function of the smooth muscle cells are still poorly understood. Adhesive proteins such as fibronectin and laminin apparently have an important role in determining the basic phenotypic state of the cells and exert their effects via integrin receptors. The proliferative and secretory activities of the cells are influenced by a multitude of growth factors, cytokines, and other molecules. Although much work remains before an integrated view of this regulatory machinery can be achieved, there is no doubt that the cell culture technique has contributed substantially to our knowledge of smooth muscle differentiation and growth. At the same time, it has been crucial in exploring the role of these cells in vascular disease and developing new therapeutic strategies to cope with major causes of human death and disability.

A case of pretibial myxedema associated with Graves' disease: an immunohistochemical study of serum-derived hyaluronan-associated protein

The myxomatous materials in cutis from a patient with pretibial myxedema (PTM) with Graves' disease were found to be mainly hyaluronic acid (HA), which had accumulated extensively in the upper dermis. Fibroblasts were increased in number in the mid to lower dermis. To clarify the mechanism of the deposition of HA in the dermis, we employed an antibody against serum-derived hyaluronan-associated protein (SHAP). This immunohistochemical study disclosed that the greater part of the fibroblasts in the mid to lower dermis stained positively, while the fibroblasts surrounded by fairly large amounts of HA in the upper dermis stained faintly or not at all. From these results, we suspect that the accumulation of HA progresses from the upper to the low dermis and that the interaction of fibroblasts and SHAP leads to development of the physiophathological cutaneous changes seen in our case.

Transforming growth factor-beta 1 increases internalization of basic fibroblast growth factor by smooth muscle cells: implication of cell-surface heparan sulphate proteoglycan endocytosis

Basic fibroblast growth factor (bFGF) was internalized by smooth muscle cells (SMC) from pig aorta. Correlation between heparin inhibition of binding and late internalization (8 h) implicated low-affinity sites in bFGF internalization. Transforming growth factor-beta 1 (TGF-beta 1) induced a 38% increase in bFGF internalized between 4 and 8 h. While bFGF and/or TGF-beta 1 enhanced cell-surface proteoglycan synthesis, 35S-labelled proteoglycans of the extracellular matrix (ECM) were not affected. This might be explained by the different turnover rates displayed by the two populations of proteoglycans. Although bFGF and/or TGF-beta 1 induced a similar stimulation in cell-surface chondroitin sulphate/dermatan sulphate and heparan sulphate (HS) proteoglycan synthesis, only the turnover of HS proteoglycans was increased. Twice as much HS proteoglycan was internalized in the presence of TGF-beta 1 or bFGF. Furthermore, TGF-beta 1 induced a 43 +/- 12% increase in HS proteoglycan internalized in the presence of bFGF with a parallel 38% increase in bFGF internalization. Overall, the results indicated that bFGF bound to two HS proteoglycan populations. bFGF storage (70% of bFGF bound to SMC) was not affected by TGF-beta 1 under our conditions and involved ECM proteoglycans characterized by a low turnover. bFGF internalization up-regulated by TGF-beta 1 involved cell-surface HS proteoglycan characterized by a high turnover.

Glycosaminoglycans in the human aorta in diabetes mellitus: a study of tunica media from areas with and without atherosclerotic plaque

Alterations in the connective tissue of the arterial wall have been suggested to play a role in the development of macrovascular disease in diabetes mellitus. The present study deals with changes in the content of GAG in aortic tunica media in human diabetes by separately analysing normal areas and areas with fibrous plaques. The thoracic aorta from 15 diabetic patients (7 with IDDM, 8 with NIDDM), and 30 sex- and age-matched non-diabetic subjects were collected at autopsy. Tunica intima was removed and GAG were isolated from the dried defatted and pulverized tunica media. GAG were quantified by uronic acid analysis and characterized by electrophoresis on cellulose acetate. Results showed that IDDM patients had a relative and absolute increase in hyaluronic acid in normal tunica media compared to non-diabetic subjects. There was a significant positive correlation between hyaluronic acid content of normal tunica media and duration of diabetes, but not between hyaluronic acid content and age. When tunica media from plaque areas was compared to normal areas the same pattern was evident in diabetic patients as in non-diabetic patients--significantly increased proportion of dermatan sulphate and reduced hyaluronic acid. The data agree with the notion that the arterial wall is subject to different pathological processes in diabetes, one of classical atherosclerosis with changes in GAG similar to non-diabetic subjects, and the other seen in areas without plaques with dissimilar alterations in GAG. These data therefore support the concept of the presence of a macrovascular disease in diabetes different from atherosclerosis.