Expression of versican V3 by arterial smooth muscle cells alters tumor growth factor β (TGFβ)-, epidermal growth factor (EGF)-, and nuclear factor κB (NFκB)-dependent signaling pathways, creating a microenvironment that resists monocyte adhesion

V3: an enigmatic isoform of the proteoglycan versican

V3 is an isoform of the extracellular matrix (ECM) proteoglycan (PG) versican generated through alternative splicing of the versican gene such that the two major exons coding for sequences in the protein core that support chondroitin sulfate (CS) glycosaminoglycan (GAG) chain attachment are excluded. Thus, versican V3 isoform carries no GAGs. A survey of PubMed reveals only 50 publications specifically on V3 versican, so it is a very understudied member of the versican family, partly because to date there are no antibodies that can distinguish V3 from the CS-carrying isoforms of versican, that is, to facilitate functional and mechanistic studies. However, a number of in vitro and in vivo studies have identified the expression of the V3 transcript during different phases of development and in disease, and selective overexpression of V3 has shown dramatic phenotypic effects in "gain and loss of function" studies in experimental models. Thus, we thought it would be useful and instructive to discuss the discovery, characterization, and the putative biological importance of the enigmatic V3 isoform of versican.

The Contribution of Vascular Proteoglycans to Atherothrombosis: Clinical Implications

The vascular extracellular matrix (ECM) produced by endothelial and smooth muscle cells is composed of collagens and glycoproteins and plays an integral role in regulating the structure and function of the vascular wall. Alteration in the expression of these proteins is associated with endothelial dysfunction and has been implicated in the development and progression of atherosclerosis. The ECM composition of atherosclerotic plaques varies depending on plaque phenotype and vulnerability, with distinct differences observed between ruptured and erodes plaques. Moreover, the thrombi on the exposed ECM are diverse in structure and composition, suggesting that the best antithrombotic approach may differ depending on plaque phenotype. This review provides a comprehensive overview of the role of proteoglycans in atherogenesis and thrombosis. It discusses the differential expression of the proteoglycans in different plaque phenotypes and the potential impact on platelet function and thrombosis. Finally, the review highlights the importance of this concept in developing a targeted approach to antithrombotic treatments to improve clinical outcomes in cardiovascular disease.

The inflammatory oxidant peroxynitrous acid modulates the structure and function of the recombinant human V3 isoform of the extracellular matrix proteoglycan versican

Continued oxidant production during chronic inflammation generates host tissue damage, with this being associated with pathologies including atherosclerosis. Atherosclerotic plaques contain modified proteins that may contribute to disease development, including plaque rupture, the major cause of heart attacks and strokes. Versican, a large extracellular matrix (ECM) chondroitin-sulfate proteoglycan, accumulates during atherogenesis, where it interacts with other ECM proteins, receptors and hyaluronan, and promotes inflammation. As activated leukocytes produce oxidants including peroxynitrite/peroxynitrous acid (ONOO^-/ONOOH) at sites of inflammation, we hypothesized that versican is an oxidant target, with this resulting in structural and functional changes that may exacerbate plaque development. The recombinant human V3 isoform of versican becomes aggregated on exposure to ONOO^-/ONOOH. Both reagent ONOO^-/ONOOH and SIN-1 (a thermal source of ONOO^-/ONOOH) modified Tyr, Trp and Met residues. ONOO^-/ONOOH mainly favors nitration of Tyr, whereas SIN-1 mostly induced hydroxylation of Tyr, and oxidation of Trp and Met. Peptide mass mapping indicated 26 sites with modifications (15 Tyr, 5 Trp, 6 Met), with the extent of modification quantified at 16. Multiple modifications, including the most extensively nitrated residue (Tyr¹⁶¹), are within the hyaluronan-binding region, and associated with decreased hyaluronan binding. ONOO^-/ONOOH modification also resulted in decreased cell adhesion and increased proliferation of human coronary artery smooth muscle cells. Evidence is also presented for colocalization of versican and 3-nitrotyrosine epitopes in advanced (type II-III) human atherosclerotic plaques. In conclusion, versican is readily modified by ONOO^-/ONOOH, resulting in chemical and structural modifications that affect protein function, including hyaluronan binding and cell interactions.

TGF-β1 and TGFβR2 Gene Polymorphisms in Patients with Unstable Angina

Acute coronary syndromes result from a sudden reduction in the lumen of a coronary artery as a result of atherosclerotic plaque rupture, its swelling or the formation of thrombotic lesions. Many mediators with inflammatory, prothrombotic and proatherogenic effects have been shown to be involved, including numerous cytokines, chemokines, adhesion molecules and growth factors. TGF-β1 is a pleiotropic cytokine found in various cells that regulates cell growth, differentiation and matrix production. The aim of our study was to assess the association between polymorphisms in the TGF-β1 gene (rs1800469, rs1800470) and polymorphisms in the TGFBR2 receptor gene (rs6785358, rs9838682) and the risk of unstable angina, as well as selected clinical parameters affecting the risk of ischemic heart disease. The study included 232 patients with unstable angina. The diagnosis of unstable angina was made by typical clinical presentation and confirmation of significant coronary artery lumen stenosis (>70%) during coronary angiography. There were no statistically significant differences in the distribution of TGFBR2 rs6785358 and rs9838682 genotypes and haplotypes between patients with unstable angina and control subjects. We observed increased values of plasma total and LDL cholesterol levels, as well as triglycerides, in patients with the TGFBR2 rs9838682 AA genotype. In patients with the TGFBR2 rs6785358 AA genotype, we noted increased BMI values. There were no statistically significant associations between other studied polymorphisms and clinical parameters. Polymorphisms in the TGF-β1 gene (rs1800469, rs1800470) and polymorphisms in the TGFBR2 receptor gene (rs6785358, rs9838682) are not significant risk factors for unstable angina in our population. The TGFBR2 gene rs9838682 polymorphism may influence the lipid parameters in patients with coronary artery disease.

Targeting Versican as a Potential Immunotherapeutic Strategy in the Treatment of Cancer

A growing body of literature links events associated with the progression and severity of immunity and inflammatory disease with the composition of the tissue extracellular matrix as defined by the matrisome. One protein in the matrisome that is common to many inflammatory diseases is the large proteoglycan versican, whose varied function is achieved through multiple isoforms and post-translational modifications of glycosaminoglycan structures. In cancer, increased levels of versican are associated with immune cell phenotype, disease prognosis and failure to respond to treatment. Whether these associations between versican expression and tumour immunity are the result of a direct role in the pathogenesis of tumours is not clear. In this review, we have focused on the role of versican in the immune response as it relates to tumour progression, with the aim of determining whether our current understanding of the immunobiology of versican warrants further study as a cancer immunotherapy target.

The synthesis and secretion of versican isoform V3 by mammalian cells: A role for N-linked glycosylation

Versican is a large extracellular matrix (ECM) chondroitin sulfate (CS) proteoglycan found in most soft tissues, which is encoded by the VCAN gene. At least four major isoforms (V0, V1, V2, and V3) are generated via alternative splicing. The isoforms of versican are expressed and accumulate in various tissues during development and disease, where they contribute to ECM structure, cell growth and migration, and immune regulation, among their many functions. While several studies have identified the mRNA transcript for the V3 isoform in a number of tissues, little is known about the synthesis, secretion, and targeting of the V3 protein. In this study, we used lentiviral generation of doxycycline-inducible rat V3 with a C-terminal tag in stable NIH 3T3 cell lines and demonstrated that V3 is processed through the classical secretory pathway. We further show that N-linked glycosylation is required for efficient secretion and solubility of the protein. By site-directed mutagenesis, we identified amino acids 57 and 330 as the active N-linked glycosylation sites on V3 when expressed in this cell type. Furthermore, exon deletion constructs of V3 revealed that exons 11-13, which code for portions of the carboxy region of the protein (G3 domain), are essential for V3 processing and secretion. Once secreted, the V3 protein associates with hyaluronan along the cell surface and within the surrounding ECM. These results establish critical parameters for the processing, solubility, and targeting of the V3 isoform by mammalian cells and establishes a role for V3 in the organization of hyaluronan.

Versican-A Critical Extracellular Matrix Regulator of Immunity and Inflammation

The extracellular matrix (ECM) proteoglycan, versican increases along with other ECM versican binding molecules such as hyaluronan, tumor necrosis factor stimulated gene-6 (TSG-6), and inter alpha trypsin inhibitor (IαI) during inflammation in a number of different diseases such as cardiovascular and lung disease, autoimmune diseases, and several different cancers. These interactions form stable scaffolds which can act as "landing strips" for inflammatory cells as they invade tissue from the circulation. The increase in versican is often coincident with the invasion of leukocytes early in the inflammatory process. Versican interacts with inflammatory cells either indirectly via hyaluronan or directly via receptors such as CD44, P-selectin glycoprotein ligand-1 (PSGL-1), and toll-like receptors (TLRs) present on the surface of immune and non-immune cells. These interactions activate signaling pathways that promote the synthesis and secretion of inflammatory cytokines such as TNFα, IL-6, and NFκB. Versican also influences inflammation by interacting with a variety of growth factors and cytokines involved in regulating inflammation thereby influencing their bioavailability and bioactivity. Versican is produced by multiple cell types involved in the inflammatory process. Conditional total knockout of versican in a mouse model of lung inflammation demonstrated significant reduction in leukocyte invasion into the lung and reduced inflammatory cytokine expression. While versican produced by stromal cells tends to be pro-inflammatory, versican expressed by myeloid cells can create anti-inflammatory and immunosuppressive microenvironments. Inflammation in the tumor microenvironment often contains elevated levels of versican. Perturbing the accumulation of versican in tumors can inhibit inflammation and tumor progression in some cancers. Thus versican, as a component of the ECM impacts immunity and inflammation through regulating immune cell trafficking and activation. Versican is emerging as a potential target in the control of inflammation in a number of different diseases.

A role for proteoglycans in vascular disease

The content of proteoglycans (PGs) is low in the extracellular matrix (ECM) of vascular tissue, but increases dramatically in all phases of vascular disease. Early studies demonstrated that glycosaminoglycans (GAGs) including chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS) and heparan sulfate (HS) accumulate in vascular lesions in both humans and in animal models in areas of the vasculature that are susceptible to disease initiation (such as at branch points) and are frequently coincident with lipid deposits. Later studies showed the GAGs were covalently attached to specific types of core proteins that accumulate in vascular lesions. These molecules include versican (CSPG), biglycan and decorin (DS/CSPGs), lumican and fibromodulin (KSPGs) and perlecan (HSPG), although other types of PGs are present, but in lesser quantities. While the overall molecular design of these macromolecules is similar, there is tremendous structural diversity among the different PG families creating multiple forms that have selective roles in critical events that form the basis of vascular disease. PGs interact with a variety of different molecules involved in disease pathogenesis. For example, PGs bind and trap serum components that accumulate in vascular lesions such as lipoproteins, amyloid, calcium, and clotting factors. PGs interact with other ECM components and regulate, in part, ECM assembly and turnover. PGs interact with cells within the lesion and alter the phenotypes of both resident cells and cells that invade the lesion from the circulation. A number of therapeutic strategies have been developed to target specific PGs involved in key pathways that promote vascular disease. This review will provide a historical perspective of this field of research and then highlight some of the evidence that defines the involvement of PGs and their roles in the pathogenesis of vascular disease.

Sheep-Specific Immunohistochemical Panel for the Evaluation of Regenerative and Inflammatory Processes in Tissue-Engineered Heart Valves

The creation of living heart valve replacements via tissue engineering is actively being pursued by many research groups. Numerous strategies have been described, aimed either at culturing autologous living valves in a bioreactor (in vitro) or inducing endogenous regeneration by the host via resorbable scaffolds (in situ). Whereas a lot of effort is being invested in the optimization of heart valve scaffold parameters and culturing conditions, the pathophysiological in vivo remodeling processes to which tissue-engineered heart valves are subjected upon implantation have been largely under-investigated. This is partly due to the unavailability of suitable immunohistochemical tools specific to sheep, which serves as the gold standard animal model in translational research on heart valve replacements. Therefore, the goal of this study was to comprise and validate a comprehensive sheep-specific panel of antibodies for the immunohistochemical analysis of tissue-engineered heart valve explants. For the selection of our panel we took inspiration from previous histopathological studies describing the morphology, extracellular matrix composition and cellular composition of native human heart valves throughout development and adult stages. Moreover, we included a range of immunological markers, which are particularly relevant to assess the host inflammatory response evoked by the implanted heart valve. The markers specifically identifying extracellular matrix components and cell phenotypes were tested on formalin-fixed paraffin-embedded sections of native sheep aortic valves. Markers for inflammation and apoptosis were tested on ovine spleen and kidney tissues. Taken together, this panel of antibodies could serve as a tool to study the spatiotemporal expression of proteins in remodeling tissue-engineered heart valves after implantation in a sheep model, thereby contributing to our understanding of the in vivo processes which ultimately determine long-term success or failure of tissue-engineered heart valves.

Hepatic expression profiling identifies steatosis-independent and steatosis-driven advanced fibrosis genes

Chronic liver disease (CLD) is associated with tissue-destructive fibrosis. Considering that common mechanisms drive fibrosis across etiologies, and that steatosis is an important cofactor for pathology, we performed RNA sequencing on liver biopsies of patients with different fibrosis stages, resulting from infection with hepatitis C virus (HCV) (with or without steatosis) or fatty liver disease. In combination with enhanced liver fibrosis score correlation analysis, we reveal a common set of genes associated with advanced fibrosis, as exemplified by those encoding the transcription factor ETS-homologous factor (EHF) and the extracellular matrix protein versican (VCAN). We identified 17 fibrosis-associated genes as candidate EHF targets and demonstrated that EHF regulates multiple fibrosis-associated genes, including VCAN, in hepatic stellate cells. Serum VCAN levels were also elevated in advanced fibrosis patients. Comparing biopsies from patients with HCV with or without steatosis, we identified a steatosis-enriched gene set associated with advanced fibrosis, validating follistatin-like protein 1 (FSTL1) as an exemplar of this profile. In patients with advanced fibrosis, serum FSTL1 levels were elevated in those with steatosis (versus those without). Liver Fstl1 mRNA levels were also elevated in murine CLD models. We thus reveal a common gene signature for CLD-associated liver fibrosis and potential biomarkers and/or targets for steatosis-associated liver fibrosis.

Proteoglycans as Immunomodulators of the Innate Immune Response to Lung Infection

Proteoglycans (PGs) are complex, multifaceted molecules that participate in diverse interactions vital for physiological and pathological processes. As structural components, they provide a scaffold for cells and structural organization that helps define tissue architecture. Through interactions with water, PGs enable molecular and cellular movement through tissues. Through selective ionic interactions with growth factors, chemokines, cytokines, and proteases, PGs facilitate the ability of these soluble ligands to regulate intracellular signaling events and to influence the inflammatory response. In addition, recent findings now demonstrate that PGs can activate danger-associated molecular patterns (DAMPs) and other signaling pathways to influence production of many of these soluble ligands, indicating a more direct role for PGs in influencing the immune response and tissue inflammation. This review will focus on PGs that are selectively expressed during lung inflammation and will examine the novel emerging concept of PGs as immunomodulatory regulators of the innate immune responses in lungs.

Gefitinib and pyrrolidine dithiocarbamate decrease viral replication and cytokine production in dengue virus infected human monocyte cultures

AIMS

The epidermal growth factor receptor (EGFR) and nucleotide-binding and oligomerization-domain containing 2 (NOD2) are important in cancer and in microbial recognition, respectively. These molecules trigger intracellular signaling pathways inducing the expression of inflammatory genes by NF-kB translocation. Gefitinib (GBTC) and pyrrolidine dithiocarbamate (PDTC) are capable of inhibiting EGFR/NOD2 and NF-kB, respectively. In earlier stages of dengue virus (DENV) infection, monocytes are capable of sustaining viral replication and increasing cytokine production, suggesting that monocyte/macrophages play an important role in early DENV replication. GBTC and PDTC have not been used to modify the pathogenesis of DENV in infected cells. This study was aimed to determine the effect of GBTC and PDTC on viral replication and cytokine production in DENV serotype 2 (DENV2)-infected human monocyte cultures.

MAIN METHODS

GBTC and PDTC were used to inhibit EGFR/NOD2 and NF-kB, respectively. Cytokine production was measured by ELISA and viral replication by plaque forming unit assay.

KEY FINDINGS

Increased DENV2 replication and anti-viral cytokine production (IFN-α/β, TNF-α, IL-12 and IL-18) in infected cultures were found. These parameters were decreased after EGFR/NOD2 or NF-kB inhibitions.

SIGNIFICANCE

The inhibitory effects of GBTC and PDTC on viral replication and cytokine production can be beneficial in the treatment of patients infected by dengue and suggest a possible role of EGFR/NOD2 receptors and NF-kB in dengue pathogenesis.

Interplay of extracellular matrix and leukocytes in lung inflammation

During inflammation, leukocytes influx into lung compartments and interact with extracellular matrix (ECM). Two ECM components, versican and hyaluronan, increase in a range of lung diseases. The interaction of leukocytes with these ECM components controls leukocyte retention and accumulation, proliferation, migration, differentiation, and activation as part of the inflammatory phase of lung disease. In addition, bronchial epithelial cells from asthmatic children co-cultured with human lung fibroblasts generate an ECM that is adherent for monocytes/macrophages. Macrophages are present in both early and late lung inflammation. Matrix metalloproteinase 10 (MMP10) is induced in alveolar macrophages with injury and infection and modulates macrophage phenotype and their ability to degrade collagenous ECM components. Collectively, studies outlined in this review highlight the importance of specific ECM components in the regulation of inflammatory events in lung disease. The widespread involvement of these ECM components in the pathogenesis of lung inflammation make them attractive candidates for therapeutic intervention.

Provisional matrix: A role for versican and hyaluronan

Hyaluronan and versican are extracellular matrix (ECM) components that are enriched in the provisional matrices that form during the early stages of development and disease. These two molecules interact to create pericellular "coats" and "open space" that facilitate cell sorting, proliferation, migration, and survival. Such complexes also impact the recruitment of leukocytes during development and in the early stages of disease. Once thought to be inert components of the ECM that help hold cells together, it is now quite clear that they play important roles in controlling cell phenotype, shaping tissue response to injury and maintaining tissue homeostasis. Conversion of hyaluronan-/versican-enriched provisional matrix to collagen-rich matrix is a "hallmark" of tissue fibrosis. Targeting the hyaluronan and versican content of provisional matrices in a variety of diseases including, cardiovascular disease and cancer, is becoming an attractive strategy for intervention.

Versican Deficiency Significantly Reduces Lung Inflammatory Response Induced by Polyinosine-Polycytidylic Acid Stimulation

Viral infection is an exacerbating factor contributing to chronic airway diseases, such as asthma, via mechanisms that are still unclear. Polyinosine-polycytidylic acid (poly(I:C)), a Toll-like receptor 3 (TLR3) agonist used as a mimetic to study viral infection, has been shown to elicit inflammatory responses in lungs and to exacerbate pulmonary allergic reactions in animal models. Previously, we have shown that poly(I:C) stimulates lung fibroblasts to accumulate an extracellular matrix (ECM), enriched in hyaluronan (HA) and its binding partner versican, which promotes monocyte adhesion. In the current study, we aimed to determine the in vivo role of versican in mediating inflammatory responses in poly(I:C)-induced lung inflammation using a tamoxifen-inducible versican-deficient mouse model (Vcan^-/- mice). In C57Bl/6 mice, poly(I:C) instillation significantly increased accumulation of versican and HA, especially in the perivascular and peribronchial regions, which were enriched in infiltrating leukocytes. In contrast, versican-deficient (Vcan^-/-) lungs did not exhibit increases in versican or HA in these regions and had strikingly reduced numbers of leukocytes in the bronchoalveolar lavage fluid and lower expression of inflammatory chemokines and cytokines. Poly(I:C) stimulation of lung fibroblasts isolated from control mice generated HA-enriched cable structures in the ECM, providing a substrate for monocytic cells in vitro, whereas lung fibroblasts from Vcan^-/- mice did not. Moreover, increases in proinflammatory cytokine expression were also greatly attenuated in the Vcan^-/- lung fibroblasts. These findings provide strong evidence that versican is a critical inflammatory mediator during poly(I:C)-induced acute lung injury and, in association with HA, generates an ECM that promotes leukocyte infiltration and adhesion.

Polymorphisms of TGFβ-1 and TGFBR2 in relation to coronary artery disease in a Chinese population

BACKGROUND AND AIM

TGF-β1 has been previously reported to be involved in the pathogenesis of atherosclerosis. The aim of the present study was to assess whether functional gene polymorphisms of TGF-β1 and its key receptor TGF-β receptor type II (TGFBR2) contribute as risk factors to the onset and severity of atherosclerotic coronary artery disease (CAD).

DESIGN AND METHODS

A total of 605 patients who underwent angiography for suspected CAD were prospectively recruited to this study. Coronary stenosis severity was assessed by the number of narrowed coronary vessels and the Gensini score. Among them, 502 patients had documented CAD, and 103 patients without documented CAD served as non-CAD controls. All patients were genotyped for one TGF-β1 polymorphism (rs1800470 (+T29C)) and two TGFBR2 polymorphisms (rs6785385 (-3779A/G), rs764522 (-1444C/G)) by polymerase chain reaction-restriction fragment length polymorphism and confirmed by direct sequencing.

RESULTS

No significant difference in the frequency for either polymorphism was found between CAD and control patients. Neither TGFBR2 rs6785385 (-3779A/G) nor rs764522 (-1444C/G) gene polymorphisms were associated with the severity of CAD (P>0.05). In male CAD patients, polymorphisms at TGF-β1 rs1800470 (+T29C) were, however, associated with the severity of CAD. The T allele frequency was significantly and positively correlated with the number of narrowed coronary arteries (three or more vessels: 49.3%, two vessels: 44.1%, one vessel: 36.9%) (P=0.039). Gensini scores in patients with the TT, CT, and CC genotype were 34.33±2.23, 32.06±4.79, and 26.90±3.83, respectively (P<0.05). In multiple linear regression analysis, the T allele of TGF-β1 polymorphism was independently correlated with the Gensini score (β=0.131).

CONCLUSION

TGF-β1 T29C gene polymorphism may be associated with severity of CAD in male patients. TGFBR2 polymorphisms may not determine the genetic susceptibility to CAD.

Cancer Cell-derived Exosomes Induce Mitogen-activated Protein Kinase-dependent Monocyte Survival by Transport of Functional Receptor Tyrosine Kinases

Tumor-associated macrophages (TAM) play pivotal roles in cancer initiation and progression. Monocytes, the precursors of TAMs, normally undergo spontaneous apoptosis within 2 days, but can subsist in the inflammatory tumor microenvironment for continuous survival and generation of sufficient TAMs. The mechanisms underlying tumor-driving monocyte survival remain obscure. Here we report that cancer cell-derived exosomes were crucial mediators for monocyte survival in the inflammatory niche. Analysis of the survival-promoting molecules in monocytes revealed that cancer cell-derived exosomes activated Ras and extracellular signal-regulated kinases in the mitogen-activated protein kinase (MAPK) pathway, resulting in the prevention of caspase cleavage. Phosphorylated receptor tyrosine kinases (RTKs), such as phosphorylated epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), were abundantly expressed in cancer cell-derived exosomes. Knock-out of EGFR or/and HER-2, or alternatively, inhibitors against their phosphorylation significantly disturbed the exosome-mediated activation of the MAPK pathway, inhibition of caspase cleavage, and increase in survival rate in monocytes. Moreover, the deprived survival-stimulating activity of exosomes due to null expression of EGFR and HER-2 could be restored by activation of another RTK, insulin receptor. Overall, our study uncovered a mechanism of tumor-associated monocyte survival and demonstrated that cancer cell-derived exosomes can stimulate the MAPK pathway in monocytes through transport of functional RTKs, leading to inactivation of apoptosis-related caspases. This work provides insights into the long sought question on monocyte survival prior to formation of plentiful TAMs in the tumor microenvironment.

Inhibition of versican expression by siRNA facilitates tropoelastin synthesis and elastic fiber formation by human SK-LMS-1 leiomyosarcoma smooth muscle cells in vitro and in vivo

Versican is an extracellular matrix (ECM) molecule that interacts with other ECM components to influence ECM organization, stability, composition, and cell behavior. Versican is known to increase in a number of cancers, but little is known about how versican influences the amount and organization of the ECM components in the tumor microenvironment. In the present study, we modulated versican expression using siRNAs in the human leiomyosarcoma (LMS) smooth muscle cell line SK-LMS-1, and observed the formation of elastin and elastic fibers in vitro and also in vivo in a nude mouse tumor model. Constitutive siRNA-directed knockdown of versican in LMS cells resulted in increased levels of elastin, as shown by immunohistochemical staining of the cells in vitro, and by mRNA and protein analyses. Moreover, versican siRNA LMS cells, when injected into nude mice, generated smaller tumors that had significantly greater immunohistochemical and histochemical staining for elastin when compared to control tumors. Additionally, microarray analyses were used to determine the influence of versican isoform modulation on gene expression profiles, and to identify genes that influence and relate to the process of elastogenesis. cDNA microarray analysis and TaqMan low density array validation identified previously unreported genes associated with downregulation of versican and increased elastogenesis. These results highlight an important role for the proteoglycan versican in regulating the expression and assembly of elastin and the phenotype of LMS cells.

Versican localizes to the nucleus in proliferating mesenchymal cells

OBJECTIVE

Versican is a versatile and highly interactive chondroitin sulfate proteoglycan that is found in the extracellular matrix (ECM) of many tissues and is a major component of developing and developed lesions in atherosclerotic vascular disease. In this paper, we present data to indicate that versican may have important intracellular functions in addition to its better known roles in the ECM.

METHODS AND RESULTS

Rat aortic smooth muscle cells were fixed and immunostained for versican and images of fluorescently labeled cells were obtained by confocal microscopy. Intracellular versican was detected in the nucleus and cytosol of vascular smooth muscle cells. The use of a synthetic neutralizing peptide eliminated versican immunostaining, demonstrating the specificity of the antibody used in this study. Western blot of pure nuclear extracts confirmed the presence of versican in the nucleus, and multifluorescent immunostaining showed strong colocalization of versican and nucleolin, suggesting a nucleolar localization of versican in nondividing cells. In dividing valve interstitial cells, a strong signal for versican was observed in and around the condensed chromosomes during the various stages of mitosis. Multifluorescent immunostaining for versican and tubulin revealed versican aggregated at opposing poles of the mitotic spindle during metaphase. Knockdown of versican expression using siRNA disrupted the organization of the mitotic spindle and led to the formation of multipolar spindles during metaphase.

CONCLUSIONS

Collectively, these data suggest an intracellular function for versican in vascular cells where it appears to play a role in mitotic spindle organization during cell division. These observations open a new avenue for studies of versican, suggesting even more diverse roles in vascular health and disease.

Expression of V3 Versican by Rat Arterial Smooth Muscle Cells Promotes Differentiated and Anti-inflammatory Phenotypes

Arterial smooth muscle cells (ASMCs) undergo phenotypic changes during development and pathological processes in vivo and during cell culture in vitro. Our previous studies demonstrated that retrovirally mediated expression of the versican V3 splice variant (V3) by ASMCs retards cell proliferation and migration in vitro and reduces neointimal thickening and macrophage and lipid accumulation in animal models of vascular injury and atherosclerosis. However, the molecular pathways induced by V3 expression that are responsible for these changes are not yet clear. In this study, we employed a microarray approach to examine how expression of V3 induced changes in gene expression and the molecular pathways in rat ASMCs. We found that forced expression of V3 by ASMCs affected expression of 521 genes by more than 1.5-fold. Gene ontology analysis showed that components of the extracellular matrix were the most significantly affected by V3 expression. In addition, genes regulating the formation of the cytoskeleton, which also serve as markers of contractile smooth muscle cells (SMCs), were significantly up-regulated. In contrast, components of the complement system, chemokines, chemokine receptors, and transcription factors crucial for regulating inflammatory processes were among the genes most down-regulated. Consistently, we found that the level of myocardin, a key transcription factor promoting contractile SMC phenotype, was greatly increased, and the proinflammatory transcription factors NFκB1 and CCAAT/enhancer-binding protein β were significantly attenuated in V3-expressing SMCs. Overall, these findings demonstrate that V3 expression reprograms ASMCs promoting differentiated and anti-inflammatory phenotypes.

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

We provide a comprehensive classification of the proteoglycan gene families and respective protein cores. This updated nomenclature is based on three criteria: Cellular and subcellular location, overall gene/protein homology, and the utilization of specific protein modules within their respective protein cores. These three signatures were utilized to design four major classes of proteoglycans with distinct forms and functions: the intracellular, cell-surface, pericellular and extracellular proteoglycans. The proposed nomenclature encompasses forty-three distinct proteoglycan-encoding genes and many alternatively-spliced variants. The biological functions of these four proteoglycan families are critically assessed in development, cancer and angiogenesis, and in various acquired and genetic diseases where their expression is aberrant.

FACE analysis as a fast and reliable methodology to monitor the sulfation and total amount of chondroitin sulfate in biological samples of clinical importance

Glycosaminoglycans (GAGs) due to their hydrophilic character and high anionic charge densities play important roles in various (patho)physiological processes. The identification and quantification of GAGs in biological samples and tissues could be useful prognostic and diagnostic tools in pathological conditions. Despite the noteworthy progress in the development of sensitive and accurate methodologies for the determination of GAGs, there is a significant lack in methodologies regarding sample preparation and reliable fast analysis methods enabling the simultaneous analysis of several biological samples. In this report, developed protocols for the isolation of GAGs in biological samples were applied to analyze various sulfated chondroitin sulfate- and hyaluronan-derived disaccharides using fluorophore-assisted carbohydrate electrophoresis (FACE). Applications to biologic samples of clinical importance include blood serum, lens capsule tissue and urine. The sample preparation protocol followed by FACE analysis allows quantification with an optimal linearity over the concentration range 1.0–220.0 µg/mL, affording a limit of quantitation of 50 ng of disaccharides. Validation of FACE results was performed by capillary electrophoresis and high performance liquid chromatography techniques.