Hyaluronate binding properties of versican

Regulation of versican expression in macrophages is mediated by canonical type I interferon signaling via ISGF3

Growing evidence supports a role for versican as an important component of the inflammatory response, with both pro- and anti-inflammatory roles depending on the specific context of the system or disease under investigation. Our goal is to understand the regulation of macrophage-derived versican and the role it plays in innate immunity. In previous work, we showed that LPS triggers a signaling cascade involving Toll-like receptor (TLR)4, the Trif adaptor, type I interferons, and the type I interferon receptor, leading to increased versican expression by macrophages. In the present study, we used a combination of chromatin immunoprecipitation, siRNA, chemical inhibitors, and mouse model approaches to investigate the regulatory events downstream of the type I interferon receptor to better define the mechanism controlling versican expression. Results indicate that transcriptional regulation by canonical type I interferon signaling via interferon-stimulated gene factor 3 (ISGF3), the heterotrimeric transcription factor complex of Irf9, Stat1, and Stat2, controls versican expression in macrophages exposed to LPS. This pathway is not dependent on MAPK signaling, which has been shown to regulate versican expression in other cell types. The stability of versican mRNA may also contribute to prolonged versican expression in macrophages. These findings strongly support a role for macrophage-derived versican as a type I interferon-stimulated gene and further our understanding of versican's role in regulating inflammation.NEW & NOTEWORTHY We report the novel finding that versican expression is regulated by the interferon-stimulated gene factor 3 (ISGF3) arm of canonical type I Ifn signaling in LPS-stimulated macrophages. This pathway is distinct from mechanisms that control versican expression in other cell types. This suggests that macrophage-derived versican may play a role in limiting a potentially excessive inflammatory response. The detailed understanding of how versican expression is regulated in different cells could lead to unique approaches for enhancing its anti-inflammatory properties.

Biomimetic strategies for the deputization of proteoglycan functions

Proteoglycans (PGs), which have glycosaminoglycan chains attached to their protein cores, are essential for maintaining the morphology and function of healthy body tissues. Extracellular PGs perform various functions, classified into the following four categories: i) the modulation of tissue mechanical properties; ii) the regulation and protection of the extracellular matrix; iii) protein sequestration; and iv) the regulation of cell signaling. The depletion of PGs may significantly impair tissue function, encompassing compromised mechanical characteristics and unregulated inflammatory responses. Since PGs play critical roles in the function of healthy tissues and their synthesis is complex, the development of PG mimetic molecules that recapitulate PG functions for tissue engineering and therapeutic applications has attracted the interest of researchers for more than 20 years. These approaches have ranged from semisynthetic graft copolymers to recombinant PG domains produced by cells that have undergone genetic modifications. This review discusses some essential extracellular PG functions and approaches to mimicking these functions.

Versican controlled by Lmx1b regulates hyaluronate density and hydration for semicircular canal morphogenesis

During inner ear semicircular canal morphogenesis in zebrafish, patterned canal-genesis zones express genes for extracellular matrix component synthesis. These include hyaluronan and the hyaluronan-binding chondroitin sulfate proteoglycan Versican, which are abundant in the matrices of many developing organs. Charged hyaluronate polymers play a key role in canal morphogenesis through osmotic swelling. However, the developmental factor(s) that control the synthesis of the matrix components and regulation of hyaluronate density and swelling are unknown. Here, we identify the transcription factor, Lmx1b, as a positive transcriptional regulator of hyaluronan, Versican, and chondroitin synthesis genes crucial for canal morphogenesis. We show that Versican regulates hyaluronan density through its protein core, whereas the charged chondroitin side chains contribute to the osmotic swelling of hyaluronate. Versican-tuned properties of hyaluronate matrices may be a broadly used mechanism in morphogenesis with important implications for understanding diseases where these matrices are impaired, and for hydrogel engineering for tissue regeneration.

Hyaluronan degradation by HYAL2 is essential for odontoblastic differentiation and migration of mouse dental papilla cells

The coordination between odontoblastic differentiation and directed cell migration of mesenchymal progenitors is necessary for regular dentin formation. The synthesis and degradation of hyaluronan (HA) in the extracellular matrix create a permissive niche that directly regulates cell behaviors. However, the role and mechanisms of HA degradation in dentin formation remain unknown. In this work, we present that HA digestion promotes odontoblastic differentiation and cell migration of mouse dental papilla cells (mDPCs). Hyaluronidase 2 (HYAL2) is responsible for promoting odontoblastic differentiation through degrading HA, while hyaluronidase 1 (HYAL1) exhibits negligible effect. Silencing Hyal2 generates an extracellular environment rich in HA, which attenuates F-actin and filopodium formation and in turn inhibits cell migration of mDPCs. In addition, activating PI3K/Akt signaling significantly rescues the effects of HA accumulation on cytodifferentiation. Taken together, the results confirm the contribution of HYAL2 to HA degradation in dentinogenesis and uncover the mechanism of the HYAL2-mediated HA degradation in regulating the odontoblastic differentiation and migration of mDPCs.

Regulation of Versican Expression in Macrophages is Mediated by Canonical Type I Interferon Signaling via ISGF3

Growing evidence supports a role for versican as an important component of the inflammatory response, with both pro- and anti-inflammatory roles depending on the specific context of the system or disease under investigation. Our goal is to understand the regulation of macrophage-derived versican and the role it plays in innate immunity. In previous work, we showed that LPS triggers a signaling cascade involving TLR4, the Trif adaptor, type I interferons, and the type I interferon receptor, leading to increased versican expression by macrophages. In the present study, we used a combination of chromatin immunoprecipitation, siRNA, chemical inhibitors, and mouse model approaches to investigate the regulatory events downstream of the type I interferon receptor to better define the mechanism controlling versican expression. Results indicate that transcriptional regulation by canonical type I interferon signaling via the heterotrimeric transcription factor, ISGF3, controls versican expression in macrophages exposed to LPS. This pathway is not dependent on MAPK signaling, which has been shown to regulate versican expression in other cell types. The stability of versican mRNA may also contribute to prolonged versican expression in macrophages. These findings strongly support a role for macrophage-derived versican as a type I interferon-stimulated gene and further our understanding of versican's role in regulating inflammation.

High-Fat Diet Has a Protective Sex-Dependent Effect on Aortic Aneurysm Severity in a Marfan Syndrome Mouse Model

BACKGROUND

Marfan syndrome (MFS) is a genetic disorder caused by mutations in fibrillin-1 and is characterized by thoracic aortic aneurysms and other complications. Previous studies revealed sexual dimorphisms in formation of aortic aneurysm in patients with MFS. The current study aimed to investigate the combined role of a high-fat diet (HFD) and biological sex in aortic disease using the mgR/mgR MFS mouse model.

METHODS

Male and female mgR/mgR mice, as well as wild-type (WT) littermate mice, were fed a control diet (CD [10% fat]) or HFD (60% fat) from 4 to 12 weeks of age. Key aortic disease parameters analyzed included the diameter of the aortic wall; elastic fibre fragmentation; proteoglycan content; mRNA levels of Mmp12, Col1a1, Col3a1, and Fbn1; and fibrillin-1 deposition in the aortic wall.

RESULTS

HFD-fed female mgR/mgR mice had significantly reduced aortic diameters (35%), elastic fibre fragmentation (56%), pathologically enhanced proteoglycans (45%), and expression of Mmp12 (64%), Col1a1 (41%), and Col3a1 (43%) compared with male mgR/mgR mice on HFD. Fibrillin-1 deposition and Fbn1 mRNA levels were unaffected. The data reveal a protective effect of HFD in female mice. In contrast, CD did not exert any protective effects.

CONCLUSIONS

This study demonstrates a specific sexual dimorphism in MFS mice, with HFD exerting an explicit protective effect on severity of aortic disease in female mice. These preclinical data may be useful for developing nutritional recommendations for individuals with MFS in the longer term.

An immunohistochemical study of matrix components in primary and secondary cartilages of embryonic chick skull

OBJECTIVES

This study aimed to compare the extracellular matrix of primary cartilage with the secondary cartilage of chicks using immunohistochemical analyses in order to understand the features of chick secondary chondrogenesis.

METHODS

Immunohistochemical analysis was performed on the extracellular matrix of quadrate (primary), squamosal, surangular, and anterior pterygoid secondary cartilages using various antibodies targeting the extracellular matrix of cartilage and bone.

RESULTS

The localization of collagen types I, II, and X, versican, aggrecan, hyaluronan, link protein, and tenascin-C was identified in the quadrate cartilage, with variations within and between the regions. Newly formed squamosal and surangular secondary cartilages showed simultaneous immunoreactivity for all molecules investigated. However, collagen type X immunoreactivity was not observed, and there was weak immunoreactivity for versican and aggrecan in the anterior pterygoid secondary cartilage.

CONCLUSIONS

The immunohistochemical localization of extracellular matrix in the quadrate (primary) cartilage was comparable to that of long bone (primary) cartilage in mammals. The fibrocartilaginous nature and rapid differentiation into hypertrophic chondrocytes, which are known structural features of secondary cartilage, were confirmed in the extracellular matrix of squamosal and surangular secondary cartilages. Furthermore, these tissues appear to undergo developmental processes similar to those in mammals. However, the anterior pterygoid secondary cartilage exhibited unique features that differed from primary and other secondary cartilages, suggesting it is formed through a distinct developmental process.

Molecular mechanisms regulating extracellular matrix-mediated remodeling in the ductus arteriosus

Progressive remodeling throughout the fetal and postnatal period is essential for anatomical closure of the ductus arteriosus (DA). Internal elastic lamina interruption and subendothelial region widening, elastic fiber formation impairment in the tunica media, and intimal thickening are distinctive features of the fetal DA. After birth, the DA undergoes further extracellular matrix-mediated remodeling. Based on the knowledge obtained from mouse models and human disease, recent studies revealed a molecular mechanism of DA remodeling. In this review, we focus on matrix remodeling and regulation of cell migration/proliferation associated with DA anatomical closure and discuss the role of prostaglandin E receptor 4 (EP4) signaling and jagged1-Notch signaling as well as myocardin, vimentin, and secretory components including tissue plasminogen activator, versican, lysyl oxidase, and bone morphogenetic proteins 9 and 10.

Histochemical and Immunohistochemical Methods for the Identification of Proteoglycans

Proteoglycans (PGs) are non-fibrillar extracellular matrix (ECM) molecules composed by a protein core and glycosaminoglycan (GAG) chains. These molecules are present in all tissues playing essential structural, biomechanical, and biological roles. In addition, PGs can regulate cell behavior due to their versatility and ability to interact with other ECM molecules, growth factors, and cells. The distribution of PGs can be evaluated by histochemical and immunohistochemical methods. Histochemical methods aimed to provide a useful overview of the presence and distribution pattern of certain groups of PGs. In contrast, immunohistochemical procedures aimed the identification of highly specific target molecules. In this chapter we described Alcian Blue, Safranin O, and Toluidine Blue histochemical methods for the screening of PGs in tissue sections. Finally, we describe the immunohistochemical procedures for specific identification of PGs (decorin, biglycan, and versican) in formaldehyde-fixed and paraffin-embedded tissues.

CD44 In Sarcomas: A Comprehensive Review and Future Perspectives

It is widely accepted that the tumor microenvironment, particularly the extracellular matrix, plays an essential role in the development of tumors through the interaction with specific protein-membrane receptors. One of the most relevant proteins in this context is the transmembrane protein CD44. The role of CD44 in tumor progression, invasion, and metastasis has been well established in many cancers, although a comprehensive review concerning its role in sarcomas has not been published. CD44 is overexpressed in most sarcomas and several in vitro and in vivo experiments have shown a direct effect on tumor progression, dissemination, and drug resistance. Moreover, CD44 has been revealed as a useful marker for prognostic and diagnostic (CD44v6 isoform) in osteosarcoma. Besides, some innovative treatments such as HA-functionalized liposomes therapy have become an excellent CD44-mediated intracellular delivery system for osteosarcoma. Unfortunately, the reduced number of studies deciphering the prognostic/diagnostic value of CD44 in other sarcoma subgroups, neither than osteosarcoma, in addition to the low number of patients involved in those studies, have produced inconclusive results. In this review, we have gone through the information available on the role of CD44 in the development, maintenance, and progression of sarcomas, analyzing their implications at the prognostic, therapeutic, and mechanistic levels. Moreover, we illustrate how research involving the specific role of CD44 in the different sarcoma subgroups could suppose a chance to advance towards a more innovative perspective for novel therapies and future clinical trials.

Fluid transport in the brain

The brain harbors a unique ability to, figuratively speaking, shift its gears. During wakefulness, the brain is geared fully toward processing information and behaving, while homeostatic functions predominate during sleep. The blood-brain barrier establishes a stable environment that is optimal for neuronal function, yet the barrier imposes a physiological problem; transcapillary filtration that forms extracellular fluid in other organs is reduced to a minimum in brain. Consequently, the brain depends on a special fluid [the cerebrospinal fluid (CSF)] that is flushed into brain along the unique perivascular spaces created by astrocytic vascular endfeet. We describe this pathway, coined the term glymphatic system, based on its dependency on astrocytic vascular endfeet and their adluminal expression of aquaporin-4 water channels facing toward CSF-filled perivascular spaces. Glymphatic clearance of potentially harmful metabolic or protein waste products, such as amyloid-β, is primarily active during sleep, when its physiological drivers, the cardiac cycle, respiration, and slow vasomotion, together efficiently propel CSF inflow along periarterial spaces. The brain's extracellular space contains an abundance of proteoglycans and hyaluronan, which provide a low-resistance hydraulic conduit that rapidly can expand and shrink during the sleep-wake cycle. We describe this unique fluid system of the brain, which meets the brain's requisites to maintain homeostasis similar to peripheral organs, considering the blood-brain-barrier and the paths for formation and egress of the CSF.

E-cigarette and food flavoring diacetyl alters airway cell morphology, inflammatory and antiviral response, and susceptibility to SARS-CoV-2

Diacetyl (DA) is an α-diketone that is used to flavor microwave popcorn, coffee, and e-cigarettes. Occupational exposure to high levels of DA causes impaired lung function and obstructive airway disease. Additionally, lower levels of DA exposure dampen host defenses in vitro. Understanding DA’s impact on lung epithelium is important for delineating exposure risk on lung health. In this study, we assessed the impact of DA on normal human bronchial epithelial cell (NHBEC) morphology, transcriptional profiles, and susceptibility to SARS-CoV-2 infection. Transcriptomic analysis demonstrated cilia dysregulation, an increase in hypoxia and sterile inflammation associated pathways, and decreased expression of interferon-stimulated genes after DA exposure. Additionally, DA exposure resulted in cilia loss and increased hyaluronan production. After SARS-CoV-2 infection, both genomic and subgenomic SARS-CoV-2 RNA were increased in DA vapor- compared to vehicle-exposed NHBECs. This work suggests that transcriptomic and physiologic changes induced by DA vapor exposure damage cilia and increase host susceptibility to SARS-CoV-2.

[A new therapeutic target for patent ductus arteriosus]

The ductus arteriosus (DA) maintains the fetal circulation by connecting the aorta and pulmonary arteries. Patent ductus arteriosus (PDA) occurs in >70% extremely-low-birth-weight infants. Patients with PDA exhibit circulatory failure, which is caused by left-to-right shunt. The DA immediately contracts after birth in response to the elevation of blood oxygen tension and to the decline in circulating prostaglandin E₂ (PGE₂). Cyclooxygenase inhibitors targeting smooth muscle cell (SMC) contraction represent only pharmacological treatment for PDA. However, it is important for DA anatomical closure that intimal thickening (IT) is appropriately formed between SMC layer and endothelial cells (EC). IT begins to form before the second-trimester and becomes prominent toward the end of third-trimester as an increase in placenta-derived PGE₂. Immature DAs frequently fail to be close due to poorly formed IT. IT consists of extracellular matrices (ECM) and migrated DA-SMCs from the tunica media. A glycoprotein fibulin-1 is expressed in developing cardiovascular system and binds to multiple ECMs. We found that PGE₂ increased fibulin-1 via EP4 in DA-SMCs, and Fbln1-deficient mice exhibited PDA with poor IT formation. Although EP4 is a Gs-coupled GPCR, fibulin-1 was secreted from DA-SMCs through the phospholipase C-protein kinase C-non-canonical NFκB signaling pathway. Fibulin-1 bound to DA-EC-derived versican which is a binding partner of hyaluronan, which promoted directional DA-SMC migration toward ECs and contributed to IT formation in the DA. Fibulin-1 upregulation by the activation of specific downstream pathway of EP4 may serve a new pharmacological strategy for PDA.

Isolation and Purification of Versican and Analysis of Versican Proteolysis

Versican is a widely distributed chondroitin sulfate proteoglycan that forms large complexes with the glycosaminoglycan hyaluronan (HA). As a consequence of HA binding to its receptor CD44 and interactions of the versican C-terminal globular (G3) domain with a variety of extracellular matrix proteins, versican is a key component of well-defined networks in pericellular matrix and extracellular matrix. Versican is crucial for several developmental processes in the embryo ranging from cardiac development to digit separation, and there is an increasing interest in its roles in cancer and inflammation. Versican proteolysis by ADAMTS proteases is highly regulated, occurs at specific peptide bonds, and is relevant to several physiological and disease mechanisms. In this chapter, methods are described for the isolation and detection of intact and cleaved versican in tissues using morphologic and biochemical techniques. These, together with the methodologies for purification and analysis of recombinant versican and an N-terminal versican fragment named versikine that are provided here, are likely to facilitate further progress on the biology of versican and its proteolysis.

Identification of VCAN as Hub Gene for Diabetic Kidney Disease Immune Injury Using Integrated Bioinformatics Analysis

Background: Diabetic kidney disease (DKD) is a leading cause of chronic kidney disease in China. Tubular injury contributes to the progression of DKD. Our study was conducted to explore the differential gene expression profiles between kidneys from patients with DKD and kidney living donors (LDs). Methods: In total, seven DKD and eighteen LD gene expression profiles from the GSE104954 dataset were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were analyzed in R with the limma package. DEGs were uploaded to the g:Profiler online database to explore the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Ingenuity pathway analysis (IPA) was carried out using online IPA software. Weighted gene co-expression network analysis (WGCNA) was performed using the WGCNA R package. By integrating DEGs and genes from the top 1 phenotype-gene associated module, we determined the hub gene. We next tested the hub gene, VCAN, in the GSE30122 dataset. We also validated the versican levels in human kidney tissues, explored immune cell type enrichment using an online database xCell, and investigated the correlation between cell types and VCAN expression. Results: A total of 563 DEGs was identified. A large number of pathways were involved in the immune response process according to the results of GO, KEGG, and IPA. Using WGCNA, we selected the lightcyan module in which genes showed the strongest correlation with the phenotype and smallest P-value. We also identified VCAN as a hub gene by integrating DEG analysis and WGCNA. Versican expression was upregulated in human diabetic kidney tissue. Moreover, versican was speculated to play a role in immune injury according to the enrichment of functions and signaling pathways. VCAN transcript levels correlate with the assembly of immune cells in the kidney. Conclusion: Immune processes played an essential role in DKD tubulointerstitium injury. The hub gene VCAN contributed to this process.

Extracellular matrix-mediated remodeling and mechanotransduction in large vessels during development and disease

The vascular extracellular matrix (ECM) is synthesized and secreted during embryogenesis and facilitates the growth and remodeling of large vessels. Proper interactions between the ECM and vascular cells are pivotal for building the vasculature required for postnatal dynamic circulation. The ECM serves as a structural component by maintaining the integrity of the vessel wall while also regulating intercellular signaling, which involves cytokines and growth factors. The major ECM component in large vessels is elastic fibers, which include elastin and microfibrils. Elastin is predominantly synthesized by vascular smooth muscle cells (SMCs) and uses microfibrils as a scaffold to lay down and assemble cross-linked elastin. The absence of elastin causes developmental defects that result in the subendothelial proliferation of SMCs and inward remodeling of the vessel wall. Notably, elastic fiber formation is attenuated in the ductus arteriosus and umbilical arteries. These two vessels function during embryogenesis and close after birth via cellular proliferation, migration, and matrix accumulation. In dynamic postnatal mechano-environments, the elastic fibers in large vessels also serve an essential role in proper signal transduction as a component of elastin-contractile units. Disrupted mechanotransduction in SMCs leads to pathological conditions such as aortic aneurysms that exhibit outward remodeling. This review discusses the importance of the ECM-mainly the elastic fiber matrix-in large vessels during developmental remodeling and under pathological conditions. By dissecting the role of the ECM in large vessels, we aim to provide insights into the role of ECM-mediated signal transduction that can provide a basis for seeking new targets for intervention in vascular diseases.

Human Lectins, Their Carbohydrate Affinities and Where to Find Them

Lectins are a class of proteins responsible for several biological roles such as cell-cell interactions, signaling pathways, and several innate immune responses against pathogens. Since lectins are able to bind to carbohydrates, they can be a viable target for targeted drug delivery systems. In fact, several lectins were approved by Food and Drug Administration for that purpose. Information about specific carbohydrate recognition by lectin receptors was gathered herein, plus the specific organs where those lectins can be found within the human body.

Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications

Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.

Essential hyaluronan structure for binding with hyaluronan-binding protein (HABP) determined by glycotechnological approach

Hyaluronan specifically binds to aggrecan globular domain 1, which is often referred to as just hyaluronan binding protein (HABP), however, the hyaluronan carbohydrate structure recognized by HABP had not been studied in detail. The aim of the present study was to investigate the important structure of hyaluronan for binding to HABP. We prepared hybrid oligosaccharides from hyaluronan and chondroitin, with or without modification of the reducing or non-reducing terminus, as tools to determine the preferred structure of hyaluronan for binding to the HABP by a competitive ELISA-like method. The non-reducing terminal structure was critical, especially, the glucuronic acid (GlcUA) and N-acetylglucosamine (GlcNAc) of the hyaluronan-unit are essential for complete HABP binding activity, and for any HABP binding activity, respectively. It is possible to replace GlcUAβ-1-3GlcNAc of the internal disaccharide units with GlcUAβ-1-3N-acetylgalactosamine (GalNAc), if the chain length is decasaccharide or larger.

A Role for HAPLN1 During Phenotypic Modulation of Human Lung Fibroblasts In Vitro

Hyaluronan and proteoglycan link protein 1 (HAPLN1) stabilizes interactions between two important extracellular matrix (ECM) macromolecules, versican and hyaluronan, which facilitate proliferation of fibroblasts and their conversion to myofibroblasts. However, the role of HAPLN1 in these events has not been studied. Using immunocytochemistry, cellular and ECM locations of HAPLN1 were evaluated in cultured human lung fibroblasts during proliferation and conversion to myofibroblasts. HAPLN1 localized to pericellular matrices, associating with both versican and hyaluronan in the ECM and on the cell surface. Nuclear and total HAPLN1 immunostaining increased after myofibroblast induction. Confocal microscopy showed HAPLN1 predominant in the ECM under cells while versican predominated above cells. Versican and HAPLN1 were also juxtaposed in columnar inclusions in the cytoplasm and nucleus. Nuclear HAPLN1 staining in interphase cells redistributed to the cytosol during mitosis. In the absence of TGF-β1, addition of exogenous bovine HAPLN1 (together with aggrecan G1) facilitated myofibroblast formation, as seen by significant upregulation of α-smooth muscle actin (SMA) staining, while adding full-length bovine versican had no effect. Increased compaction of hyaluronan-rich ECM suggests that HAPLN1 plus G1 addition affects hyaluronan networks and myofibroblast formation. These observations demonstrate changes in both extracellular and intracellular localization of HAPLN1 during fibroblast proliferation and myofibroblast conversion suggesting a possible role in fibrotic remodeling.

Fibulin-1 Integrates Subendothelial Extracellular Matrices and Contributes to Anatomical Closure of the Ductus Arteriosus

OBJECTIVE

The ductus arteriosus (DA) is a fetal artery connecting the aorta and pulmonary arteries. Progressive matrix remodeling, that is, intimal thickening (IT), occurs in the subendothelial region of DA to bring anatomic DA closure. IT is comprised of multiple ECMs (extracellular matrices) and migrated smooth muscle cells (SMCs). Because glycoprotein fibulin-1 binds to multiple ECMs and regulates morphogenesis during development, we investigated the role of fibulin-1 in DA closure. Approach and Results: Fibulin-1-deficient (Fbln1^-/-) mice exhibited patent DA with hypoplastic IT. An unbiased transcriptome analysis revealed that EP4 (prostaglandin E receptor 4) stimulation markedly increased fibulin-1 in DA-SMCs via phospholipase C-NFκB (nuclear factor κB) signaling pathways. Fluorescence-activated cell sorting (FACS) analysis demonstrated that fibulin-1 binding protein versican was derived from DA-endothelial cells (ECs). We examined the effect of fibulin-1 on directional migration toward ECs in association with versican by using cocultured DA-SMCs and ECs. EP4 stimulation promoted directional DA-SMC migration toward ECs, which was attenuated by either silencing fibulin-1 or versican. Immunofluorescence demonstrated that fibulin-1 and versican V0/V1 were coexpressed at the IT of wild-type DA, whereas 30% of versican-deleted mice lacking a hyaluronan binding site displayed patent DA. Fibulin-1 expression was attenuated in the EP4-deficient mouse (Ptger4^-/-) DA, which exhibits patent DA with hypoplastic IT, and fibulin-1 protein administration restored IT formation. In human DA, fibulin-1 and versican were abundantly expressed in SMCs and ECs, respectively.

CONCLUSIONS

Fibulin-1 contributes to DA closure by forming an environment favoring directional SMC migration toward the subendothelial region, at least, in part, in combination with EC-derived versican and its binding partner hyaluronan.

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.

Aortic Aneurysms and Dissections Series

The aortic wall is composed of highly dynamic cell populations and extracellular matrix. In response to changes in the biomechanical environment, aortic cells and extracellular matrix modulate their structure and functions to increase aortic wall strength and meet the hemodynamic demand. Compromise in the structural and functional integrity of aortic components leads to aortic degeneration, biomechanical failure, and the development of aortic aneurysms and dissections (AAD). A better understanding of the molecular pathogenesis of AAD will facilitate the development of effective medications to treat these conditions. Here, we summarize recent findings on AAD published in ATVB. In this issue, we focus on the dynamics of aortic cells and extracellular matrix in AAD; in the next issue, we will focus on the role of signaling pathways in AAD.

Visualization and Quantification of Pericellular Matrix

The pericellular matrix (PCM), also known as the pericellular coat or glycocalyx, lies between the plasma membrane and the interstitial extracellular matrix (ECM). It can have a dramatic influence on cell function because of its presence at the interface between the cell and its microenvironment. A common tool used to demonstrate the PCM is the particle exclusion assay in which fixed red blood cells are utilized to outline the boundary of the cell together with its PCM. PCM visualization and quantification provide opportunities to uncover the roles of ADAMTS proteases in PCM remodeling in many cell types and processes.

The biology and role of CD44 in cancer progression: therapeutic implications

CD44, a non-kinase transmembrane glycoprotein, is overexpressed in several cell types including cancer stem cells and frequently shows alternative spliced variants that are thought to play a role in cancer development and progression. Hyaluronan, the main ligand for CD44, binds to and activates CD44 resulting in activation of cell signaling pathways that induces cell proliferation, increases cell survival, modulates cytoskeletal changes, and enhances cellular motility. The different functional roles of CD44 standard (CD44s) and specific CD44 variant (CD44v) isoforms are not fully understood. CD44v contain additional peptide motifs that can interact with and sequester growth factors and cytokines at the cell surface thereby functioning as coreceptors to facilitate cell signaling. Moreover, CD44v were expressed in metastasized tumors, whereas switching between CD44v and CD44s may play a role in regulating epithelial to mesenchymal transition (EMT) and in the adaptive plasticity of cancer cells. Here, we review current data on the structural and functional properties of CD44, the known roles for CD44 in tumorigencity, the regulation of CD44 expression, and the potential for targeting CD44 for cancer therapy.

Harnessing chondroitin sulphate in composite scaffolds to direct progenitor and stem cell function for tissue repair

This review details the inclusion of chondroitin sulphate in bioscaffolds for superior functional properties in tissue regenerative applications.

The Therapeutic Potential of Hyaluronan in COPD

Insights into the clinical course of COPD indicate the need for new therapies for this condition. The discovery of alpha-1 antitrypsin deficiency (AATD) led to the protease-antiprotease imbalance hypothesis, which was applied to COPD related to AATD as well as COPD not related to AATD. The discovery of AATD brought recognition to the importance of elastin fibers in maintaining lung matrix structure. Two cross-linking amino acids, desmosine and isodesmosine (DI), are unique to mature elastin and can serve as biomarkers of the degradation of elastin. The intravenous augmentation treatment and lung density in severe alpha-1 antitrypsin deficiency (RAPID) study shows a correlation of an anatomic index of COPD (on CT imaging) correlating with a chemical indicator of matrix injury in COPD, DI. The results suggest that preservation of lung elastin structure may slow the progression of COPD. Hyaluronan aerosol decreases the severity of elastase-induced emphysema in animals and has induced reductions in DI levels in preliminary human studies. Hyaluronan deserves further development as a therapy for COPD.

The biochemistry and immunohistochemistry of versican

Versican is a chondroitin sulfate proteoglycan found in the extracellular matrix that is important for changes in cell phenotype associated with development and disease. Versican has been shown to be involved in cardiovascular disorders, as well as lung disease and fibrosis, inflammatory bowel disease, cancer, and several other diseases that have an inflammatory component. Versican was first identified as a fibroblast proteoglycan and forms large multimolecular complexes with hyaluronan and other components of the provisional matrix during wound healing and inflammation. The biology of versican has been well studied. Versican plays a major role in embryogenesis, particularly heart formation, where versican deletion proves lethal. The ability to purify versican to characterize and to use in experimental systems is vital to defining its role in development and disease. Protein expression systems have proven challenging to obtain milligram quantities of full-length versican. Here, we describe proteoglycan biochemical purification techniques that have been developed by others, but which we have adapted to use with our source tissues and cells. We also include methods for immunohistochemical localization and quantitation of versican in tissue sections.

A Functional Variant of SMAD4 Enhances Thoracic Aortic Aneurysm and Dissection Risk through Promoting Smooth Muscle Cell Apoptosis and Proteoglycan Degradation

Recent studies indicate important roles for SMAD4 in SMCs proliferation, extracellular matrix maintenance, and blood vessel remodeling. However, the genetic effects of SMAD4 in the pathogenesis of thoracic aortic aneurysm and dissection (TAAD) are still largely unknown. Here we identified a functional variant of SMAD4 which might be involved in the pathological progression of TAAD. Five tagging SNPs of SMAD4 were genotyped in 202 TAAD cases and 400 controls using MALDI-TOF. rs12455792 CT or TT variant genotypes was associated with an significantly elevated TAAD risk (adjusted OR = 1.58, 95%CI = 1.09–2.30) under a dominant genetic model. It was located in the 5’UTR and predicted to influence transcription activity and RNA folding of SMAD4. In luciferase reporter assay, rs12455792 T allele markedly decreased luciferase activities. Accordingly, SMAD4 expression in tissues was lower in patients with CT or TT genotypes, compared with CC. Movat's pentachrome showed that rs12455792 T allele enhanced SMCs loss and fibers accumulation. With angiotensin II induction, rate of Apoptotic SMCs was significantly higher while SMAD4 silenced. Moreover, rs12455792 T allele also increased Versican degradation via ADAMTS-4. In conclusion, this variant might promote SMCs apoptosis and proteoglycans degradation, and further facilitate the progress of TAAD. Our findings identified rs12455792 as a predictor for progression of vascular media pathological changes related thoracic aortic disorders.

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The variant on 5'UTR of SMAD4 gene significantly increased thoracic aortic aneurysm and dissection risk.

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The variant rs12455792 reduced SMAD4 expression and influenced its effects on proteoglycans degradation, SMCs apoptosis and fiber accumulation.

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rs1rs12455792 might be a potential therapeutic marker in vascular media pathological changes related thoracic aortic disorders.

Understanding the genetic features of thoracic aortic aneurysm and dissection can lead to precision surgery strategy. In this study, we demonstrated that SMAD4 rs12455792 is located in the transcription factor binding site and the allele change influences transcription activity and SMAD4 expression. Decrease of SMAD4 expression promotes proteoglycans degradation, vascular SMCs apoptosis and fiber accumulation, which are involved in pathological progression of TAAD. rs12455792 might be a potential therapeutic marker in vascular media pathological changes related thoracic aortic disorders.

Lumican and versican protein expression are associated with colorectal adenoma-to-carcinoma progression

Background

One prominent event associated with colorectal adenoma-to-carcinoma progression is genomic instability. Approximately 85% of colorectal cancer cases exhibit chromosomal instability characterized by accumulation of chromosome copy number aberrations (CNAs). Adenomas with gain of chromosome 8q, 13q, and/or 20q are at high risk of progression to cancer. Tumor progression is also associated with expansion of the extracellular matrix (ECM) and the activation of non-malignant cells within the tumor stroma. The glycoproteins versican and lumican are overexpressed at the mRNA level in colon carcinomas compared to adenomas, and are associated with the formation of tumor stroma.

Purpose

The aim of this study was to characterize versican and lumican protein expression in tumor progression and investigate their association with CNAs commonly associated with adenoma-to-carcinoma progression.

Methods

Tissue microarrays were constructed with colon adenomas and carcinomas that were characterized for MSI-status and DNA copy number gains of chromosomes 8q, 13q and 20q. Sections were immunohistochemically stained for lumican and versican. Protein expression levels were evaluated using digitized slides, and scores were finally dichotomized into a positive or negative score per sample.

Results

Lumican and versican expression were both observed in neoplastic cells and in the tumor stroma of colon adenomas and carcinomas. Lumican expression was more frequently present in epithelial cells of carcinomas than adenomas (49% versus 18%; P = 0.0001) and in high-risk adenomas and carcinomas combined compared to low-risk adenomas (43% versus 16%; P = 0.005). Versican staining in the tumor stroma was more often present in high-risk adenomas combined with carcinomas compared to low-risk adenomas (57% versus 36%; P = 0.03) and was associated with the presence of gain of 13q (71% versus 44%; P = 0.04).

Conclusion

Epithelial lumican and stromal versican protein expression are increased during colorectal adenoma-to-carcinoma progression.

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.

The extracellular matrix in cancer progression: Role of hyalectan proteoglycans and ADAMTS enzymes

Remodelling of the extracellular matrix (ECM) has emerged as a key factor in cancer progression. Proteoglycans, including versican and other hyalectans, represent major structural elements of the ECM where they interact with other important molecules, including the glycosaminoglycan hyaluronan and the CD44 cell surface receptor. The hyalectan proteoglycans are regulated through cleavage by the proteolytic actions of A Disintegrin-like And Metalloproteinase domain with Thrombospondin-1 motif (ADAMTS) family members. Alteration in the balance between hyalectan proteoglycans and ADAMTS enzymes has been proposed to be a crucial factor in cancer progression either in a positive or negative manner depending on the context. Further complexity arises due to the formation of bioactive cleavage products, such as versikine, which may also play a role, and non-enzymatic functions for ADAMTS proteins. This research is providing fresh insights into cancer biology and opportunities for the development of new diagnostic and treatment strategies.

Hyaluronan as a therapeutic target in human diseases

Accumulation and turnover of extracellular matrix is a hallmark of tissue injury, repair and remodeling in human diseases. Hyaluronan is a major component of the extracellular matrix and plays an important role in regulating tissue injury and repair, and controlling disease outcomes. The function of hyaluronan depends on its size, location, and interactions with binding partners. While fragmented hyaluronan stimulates the expression of an array of genes by a variety of cell types regulating inflammatory responses and tissue repair, cell surface hyaluronan provides protection against tissue damage from the environment and promotes regeneration and repair. The interactions of hyaluronan and its binding proteins participate in the pathogenesis of many human diseases. Thus, targeting hyaluronan and its interactions with cells and proteins may provide new approaches to developing therapeutics for inflammatory and fibrosing diseases. This review focuses on the role of hyaluronan in biological and pathological processes, and as a potential therapeutic target in human diseases.

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.

Differences in the distribution of versican, decorin, and biglycan in atherosclerotic human coronary arteries

The distributions of versican, biglycan, and decorin have been examined in segments of normal and atherosclerotic human coronary arteries using antibodies directed against the core proteins of these macromolecules. Versican immunostaining was prominent throughout the extracellular matrix (ECM) in regions of the vessels that contained abundant smooth-muscle cells, such as in diffuse intimal thickenings, fibrous caps, and in zones of loose, myxoid connective tissue. Versican also was present in smooth-muscle-rich thrombi and at borders of the lipid-rich cores of advanced atherosclerotic lesions. Biglycan immunostaining was observed in diffuse intimal thickenings, fibrous caps, and myxoid areas, but, unlike versican, it was abundant in the lipid-rich core of advanced plaques. However, biglycan immunostaining was absent in smooth-muscle cell-enriched thrombi. Decorin immunostaining paralleled biglycan immunostaining except that it was conspicuously absent in the myxoid areas of the plaque and markedly reduced in diffuse intimal thickenings. Both biglycan and decorin immunostaining were consistently associated with some of the microvessels in the thrombi and in advanced atherosclerotic plaques. Taken together, these results indicate that specific proteoglycans distribute to topographically defined regions of normal and atherosclerotic human coronary arteries and that these different distributions may indicate a diversity of functions in normal and pathologic processes of the arterial wall.

Neuronally produced versican V2 renders C-fiber nociceptors IB4 -positive

A subpopulation of nociceptors, the glial cell line-derived neurotrophic factor (GDNF)-dependent, non-peptidergic C-fibers, expresses a cell-surface glycoconjugate that can be selectively labeled with isolectin B4 (IB4 ), a homotetrameric plant lectin from Griffonia simplicifolia. We show that versican is an IB4 -binding molecule in rat dorsal root ganglion neurons. Using reverse transcriptase polymerase chain reaction (RT-PCR), in situ hybridization and immunofluorescence experiments on rat lumbar dorsal root ganglion, we provide the first demonstration that versican is produced by neurons. In addition, by probing Western blots with splice variant-specific antibodies we show that the IB4 -binding versican contains only the glycosaminoglycan alpha domain. Our data support V2 as the versican isoform that renders this subpopulation of nociceptors IB4 -positive (+). A subset of nociceptors, the GDNF-dependent non-peptidergic C-fibers can be characterized by its reactivity for isolectin B4 (IB4), a plant lectin from Griffonia simplicifolia. We have previously demonstrated that versican V2 binds IB4 in a Ca2 + -dependent manner. However, given that versican is thought to be the product of glial cells, it was questionable whether versican V2 can be accountable for the IB4-reactivity of this subset of nociceptors. The results presented here prove - for the first time - a neuronal origin of versican and suggest that versican V2 is the molecule that renders GDNF-dependent non-peptidergic C-fibers IB4-positive.

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.

Isolation and purification of versican and analysis of versican proteolysis

Versican is a widely distributed chondroitin sulfate proteoglycan that forms large complexes with the glycosaminoglycan hyaluronan (HA). As a consequence of HA binding to its receptor CD44 and interactions of the versican C-terminal globular (G3) domain with a variety of extracellular matrix proteins, versican is a key component of well-defined networks in pericellular matrix and extracellular matrix. It is crucial for several developmental processes in the embryo and there is increasing interest in its roles in cancer and inflammation. Versican proteolysis by ADAMTS proteases is highly regulated, occurs at specific peptide bonds, and is relevant to several physiological and disease mechanisms. In this chapter, methods are described for the isolation and detection of intact and cleaved versican in tissues using morphologic and biochemical techniques. These, together with the methodologies for purification and analysis of recombinant versican and a versican fragment provided here, are likely to facilitate further progress on the biology of versican and its proteolysis.

More than just a filler - the role of hyaluronan for skin homeostasis

In recent years, hyaluronan (HA) has become an increasingly attractive substance as a non-immunogenic filler and scaffolding material in cosmetic dermatology. Despite its wide use for skin augmentation and rejuvenation, relatively little is known about the molecular structures and interacting proteins of HA in normal and diseased skin. However, a comprehensive understanding of cutaneous HA homeostasis is required for future the development of HA-based applications for skin regeneration. This review provides an update on HA-based structures, expression, metabolism and its regulation, function and pharmacological targeting of HA in skin.

Glioma-derived versican promotes tumor expansion via glioma-associated microglial/macrophages Toll-like receptor 2 signaling

BACKGROUND

Accumulation and infiltration of microglia/brain macrophages around and into glioma tissue promote tumor invasion and expansion. One tumor-promoting mechanism of microglia/brain macrophages is upregulation of membrane type 1 matrix metalloprotease (MT1-MMP), which promotes the degradation of extracellular matrix. MT1-MMP upregulation is induced by soluble factors released by glioma cells activating microglial Toll-like receptor 2 (TLR2).

METHODS

Versican identified by proteomics was silenced in glioma cells by short interference RNA and short hairpin RNA approaches and studied in vitro and after injection into mouse brains or organotypic brain slices.

RESULTS

The splice variants V0/V1 of the endogenous TLR2 ligand versican are highly expressed in mouse and human glioma tissue. Versican-silenced gliomas induced less MT1-MMP expression in microglia both in vitro and in vivo, which resulted in smaller tumors and longer survival rates as compared with controls. Recombinant versican V1 induced significantly higher levels of MT1-MMP in wild-type microglia compared with untreated and treated TLR2 knockout microglial cells. Using glioma-injected organotypic brain slices, we found that the impact of versican signaling on glioma growth depended on the presence of microglia. Moreover, we found that TLR2 expression is upregulated in glioma-associated microglia but not in astrocytes. Additionally, an established TLR2 neutralizing antibody reduced glioma-induced microglial MT1-MMP expression as well as glioma growth ex vivo.

CONCLUSIONS

Our results show that versican released from glioma promotes tumor expansion through glioma-associated microglial/macrophage TLR2 signaling and subsequent expression of MT1-MMP. This signaling cascade might be a novel target for glioma therapies.

Determinants of versican-V1 proteoglycan processing by the metalloproteinase ADAMTS5

Proteolysis of the Glu(441)-Ala(442) bond in the glycosaminoglycan (GAG) β domain of the versican-V1 variant by a disintegrin-like and metalloproteinase domain with thrombospondin type 1 motif (ADAMTS) proteases is required for proper embryo morphogenesis. However, the processing mechanism and the possibility of additional ADAMTS-cleaved processing sites are unknown. We demonstrate here that if Glu(441) is mutated, ADAMTS5 cleaves inefficiently at a proximate upstream site but normally does not cleave elsewhere within the GAGβ domain. Chondroitin sulfate (CS) modification of versican is a prerequisite for cleavage at the Glu(441)-Ala(442) site, as demonstrated by reduced processing of CS-deficient or chondroitinase ABC-treated versican-V1. Site-directed mutagenesis identified the N-terminal CS attachment sites Ser(507) and Ser(525) as essential for processing of the Glu(441)-Ala(442) bond by ADAMTS5. A construct including only these two GAG chains, but not downstream GAG attachment sites, was cleaved efficiently. Therefore, CS chain attachment to Ser(507) and Ser(525) is necessary and sufficient for versican proteolysis by ADAMTS5. Mutagenesis of Glu(441) and an antibody to a peptide spanning Thr(432)-Gly(445) (i.e. containing the scissile bond) reduced versican-V1 processing. ADAMTS5 lacking the C-terminal ancillary domain did not cleave versican, and an ADAMTS5 ancillary domain construct bound versican-V1 via the CS chains. We conclude that docking of ADAMTS5 with two N-terminal GAG chains of versican-V1 via its ancillary domain is required for versican processing at Glu(441)-Ala(442). V1 proteolysis by ADAMTS1 demonstrated a similar requirement for the N-terminal GAG chains and Glu(441). Therefore, versican cleavage can be inhibited substantially by mutation of Glu(441), Ser(507), and Ser(525) or by an antibody to the region of the scissile bond.

The functional diversity of essential genes required for mammalian cardiac development

Genes required for an organism to develop to maturity (for which no other gene can compensate) are considered essential. The continuing functional annotation of the mouse genome has enabled the identification of many essential genes required for specific developmental processes including cardiac development. Patterns are now emerging regarding the functional nature of genes required at specific points throughout gestation. Essential genes required for development beyond cardiac progenitor cell migration and induction include a small and functionally homogenous group encoding transcription factors, ligands and receptors. Actions of core cardiogenic transcription factors from the Gata, Nkx, Mef, Hand, and Tbx families trigger a marked expansion in the functional diversity of essential genes from midgestation onwards. As the embryo grows in size and complexity, genes required to maintain a functional heartbeat and to provide muscular strength and regulate blood flow are well represented. These essential genes regulate further specialization and polarization of cell types along with proliferative, migratory, adhesive, contractile, and structural processes. The identification of patterns regarding the functional nature of essential genes across numerous developmental systems may aid prediction of further essential genes and those important to development and/or progression of disease. genesis 52:713–737, 2014.