Interaction between collagens and glycosaminoglycans investigated using a surface plasmon resonance biosensor

Unveiling Charge-Pair Salt-Bridge Interaction Between GAGs and Collagen Protein in Cartilage: Atomic Evidence from DNP-Enhanced ssNMR at Natural Isotopic Abundance

The interactions between glycosaminoglycans (GAGs) and proteins are essential in numerous biochemical processes that involve ion-pair interactions. However, there is no evidence of direct and specific interactions between GAGs and collagen proteins in native cartilage. The resolution of solid-state NMR (ssNMR) can offer such information but the detection of GAG interactions in cartilage is limited by the sensitivity of the experiments when 13C and 15N isotopes are at natural abundance. In this communication, this limitation is overcome by taking advantage of dynamic nuclear polarization (DNP)-enhanced magic-angle spinning (MAS) experiments to obtain two-dimensional (2D) 15N-13C and 13C-13C correlations on native samples at natural abundance. These experiments unveiled inter-residue correlations in the aliphatic regions of the collagen protein previously unobserved. Additionally, our findings provide direct evidence of charge-pair salt-bridge interactions between negatively charged GAGs and positively charged arginine (Arg) residues of collagen protein. We also identified potential hydrogen bonding interactions between hydroxyproline (Hyp) and GAGs, offering atomic insights into the biochemical interactions within the extracellular matrix of native cartilage. Our approach may provide a new avenue for the structural characterization of other native systems.

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

Biomaterial choice is an essential step during the development tissue engineering and regenerative medicine (TERM) applications. The selected biomaterial must present properties allowing the physiological-like recapitulation of several processes that lead to the reestablishment of homeostatic tissue or organ function. Biomaterials derived from the extracellular matrix (ECM) present many such properties and their use in the field has been steadily increasing. Considering this growing importance, it becomes imperative to provide a comprehensive overview of ECM biomaterials, encompassing their sourcing, processing, and integration into TERM applications. This review compiles the main strategies used to isolate and process ECM-derived biomaterials as well as different techniques used for its characterization, namely biochemical and chemical, physical, morphological, and biological. Lastly, some of their applications in the TERM field are explored and discussed.

Hyaluronic acid turnover controls the severity of cerebral cavernous malformations in bioengineered human micro-vessels

Cerebral cavernous malformations (CCMs) are vascular lesions that predominantly form in blood vessels of the central nervous system upon loss of the CCM multimeric protein complex. The endothelial cells within CCM lesions are characterized by overactive MEKK3 kinase and KLF2/4 transcription factor signaling, leading to pathological changes such as increased endothelial cell spreading and reduced junctional integrity. Concomitant to aberrant endothelial cell signaling, non-autonomous signals from the extracellular matrix (ECM) have also been implicated in CCM lesion growth and these factors might explain why CCM lesions mainly develop in the central nervous system. Here, we adapted a three-dimensional microfluidic system to examine CCM1 deficient human micro-vessels in distinctive extracellular matrices. We validate that pathological hallmarks are maintained in this model. We further show that key genes responsible for homeostasis of hyaluronic acid, a major extracellular matrix component of the central nervous system, are dysregulated in CCM. Supplementing the matrix in our model with distinct forms of hyaluronic acid inhibits pathological cell spreading and rescues barrier function. Hyaluronic acid acts by dampening cell-matrix adhesion signaling in CCM, either downstream or in parallel of KLF2/4. This study provides a proof-of-principle that ECM embedded 3D microfluidic models are ideally suited to identify how changes in ECM structure and signaling impact vascular malformations.

Chondroitin sulfate, dermatan sulfate, and hyaluronic acid differentially modify the biophysical properties of collagen-based hydrogels

Fibrillar collagens and glycosaminoglycans (GAGs) are structural biomolecules that are natively abundant to the extracellular matrix (ECM). Prior studies have quantified the effects of GAGs on the bulk mechanical properties of the ECM. However, there remains a lack of experimental studies on how GAGs alter other biophysical properties of the ECM, including ones that operate at the length scales of individual cells such as mass transport efficiency and matrix microstructure. This study focuses on the GAG molecules chondroitin sulfate (CS), dermatan sulfate (DS), and hyaluronic acid (HA). CS and DS are stereoisomers while HA is the only non-sulfated GAG. We characterized and decoupled the effects of these GAG molecules on the stiffness, transport, and matrix microarchitecture properties of type I collagen hydrogels using mechanical indentation testing, microfluidics, and confocal reflectance imaging, respectively. We complement these biophysical measurements with turbidity assays to profile collagen aggregate formation. Surprisingly, only HA enhanced the ECM indentation modulus, while all three GAGs had no effect on hydraulic permeability. Strikingly, we show that CS, DS, and HA differentially regulate the matrix microarchitecture of hydrogels due to their alterations to the kinetics of collagen self-assembly. In addition to providing information on how GAGs define key physical properties of the ECM, this work shows new ways in which stiffness measurements, microfluidics, microscopy, and turbidity kinetics can be used complementarily to reveal details of collagen self-assembly and structure. STATEMENT OF SIGNIFICANCE: Collagen and glycosaminoglycans (GAGs) are integral to the structure, function, and bioactivity of the extracellular matrix (ECM). Despite widespread interest in collagen-GAG composite hydrogels, there is a lack of quantitative understanding of how different GAGs alter the biophysical properties of the ECM across tissue, cellular, and subcellular length scales. Here we show using mechanical, microfluidic, microscopy, and analytical methods and measurements that the GAG molecules chondroitin sulfate, dermatan sulfate, and hyaluronic acid differentially regulate the mechanical, transport, and microstructural properties of hydrogels due to their alterations to the kinetics of collagen self-assembly. As such, these results will inform improved design and utilization of collagen-based scaffolds of tailored composition, mechanical properties, molecular availability due to mass transport, and microarchitecture.

Extension of the SUGRES-1P Coarse-Grained Model of Polysaccharides to Heparin

Heparin is an unbranched periodic polysaccharide composed of negatively charged monomers and involved in key biological processes, including anticoagulation, angiogenesis, and inflammation. Its structure and dynamics have been studied extensively using experimental as well as theoretical approaches. The conventional approach of computational chemistry applied to the analysis of biomolecules is all-atom molecular dynamics, which captures the interactions of individual atoms by solving Newton's equation of motion. An alternative is molecular dynamics simulations using coarse-grained models of biomacromolecules, which offer a reduction of the representation and consequently enable us to extend the time and size scale of simulations by orders of magnitude. In this work, we extend the UNIfied COarse-gRaiNed (UNICORN) model of biological macromolecules developed in our laboratory to heparin. We carried out extensive tests to estimate the optimal weights of energy terms of the effective energy function as well as the optimal Debye-Hückel screening factor for electrostatic interactions. We applied the model to study unbound heparin molecules of polymerization degree ranging from 6 to 68 residues. We compare the obtained coarse-grained heparin conformations with models obtained from X-ray diffraction studies of heparin. The SUGRES-1P force field was able to accurately predict the general shape and global characteristics of heparin molecules.

Development of a novel air-liquid interface airway tissue equivalent model for in vitro respiratory modeling studies

The human airways are complex structures with important interactions between cells, extracellular matrix (ECM) proteins and the biomechanical microenvironment. A robust, well-differentiated in vitro culture system that accurately models these interactions would provide a useful tool for studying normal and pathological airway biology. Here, we report the development and characterization of a physiologically relevant air-liquid interface (ALI) 3D airway 'organ tissue equivalent' (OTE) model with three novel features: native pulmonary fibroblasts, solubilized lung ECM, and hydrogel substrate with tunable stiffness and porosity. We demonstrate the versatility of the OTE model by evaluating the impact of these features on human bronchial epithelial (HBE) cell phenotype. Variations of this model were analyzed during 28 days of ALI culture by evaluating epithelial confluence, trans-epithelial electrical resistance, and epithelial phenotype via multispectral immuno-histochemistry and next-generation sequencing. Cultures that included both solubilized lung ECM and native pulmonary fibroblasts within the hydrogel substrate formed well-differentiated ALI cultures that maintained a barrier function and expressed mature epithelial markers relating to goblet, club, and ciliated cells. Modulation of hydrogel stiffness did not negatively impact HBE differentiation and could be a valuable variable to alter epithelial phenotype. This study highlights the feasibility and versatility of a 3D airway OTE model to model the multiple components of the human airway 3D microenvironment.

Bioactive composite hydrogels as 3D mesenchymal stem cell encapsulation environment for bone tissue engineering: in vitro and in vivo studies

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

Functions of chondroitin/dermatan sulfate containing GalNAc4,6-disulfate

Chondroitin sulfate (CS) and dermatan sulfate (DS) containing GalNAc4,6-disulfate (GalNAc4S6S) were initially discovered in marine animals. Following the discovery, these glycosaminoglycans have been found in various animals including human. In the biosynthesis of CS/DS containing GalNAc4S6S, three groups of sulfotransferases are involved; chondroitin 4-sulfotransferases (C4STs), dermatan 4-sulfotransferase-1 (D4ST-1) and GalNAc 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST). GalNAc4S-6ST and its products have been shown to play important roles in the abnormal pathological conditions such as central nervous system injury, cancer development, abnormal tissue fibrosis, development of osteoporosis, and infection with viruses or nematodes. CS/DS containing GalNAc4S6S has been shown to increase with the functional differentiation of mast cells, macrophages and neutrophils. Genetic approaches using knockout or knockdown of GalNAc4S-6ST, blocking of the epitopes containing GalNAc4S6S by specific antibodies and chemical technology that enabled the synthesis of oligosaccharides with defined sulfation patterns have been applied successfully to these investigations. These studies contributed significantly to the basic understanding of the functional roles of CS/DS containing GalNAc4S6S in various abnormal conditions, and appear to provide promising clues to the development of possible measures to treat them.

Glycosaminoglycans modulate long-range mechanical communication between cells in collagen networks

Glycosaminoglycans (GAGs) are carbohydrates that are expressed ubiquitously in the human body and are among the key macromolecules that influence the development, homeostasis, and pathology of native tissues. Abnormal accumulation of GAGs has been observed in metabolic disorders, solid tumors, and fibrotic tissues. Here we theoretically and experimentally show that tissue swelling caused by the highly polar nature of GAGs significantly affects the mechanical interactions between resident cells by altering the organization and alignment of the collagenous extracellular matrix. The role of GAGs in modulating cellular force transmission revealed here can guide the design of biomaterial scaffolds in regenerative medicine and provides insights on the role of cell–cell communication in tumor progression and fibrosis.

Cells can sense and respond to mechanical forces in fibrous extracellular matrices (ECMs) over distances much greater than their size. This phenomenon, termed long-range force transmission, is enabled by the realignment (buckling) of collagen fibers along directions where the forces are tensile (compressive). However, whether other key structural components of the ECM, in particular glycosaminoglycans (GAGs), can affect the efficiency of cellular force transmission remains unclear. Here we developed a theoretical model of force transmission in collagen networks with interpenetrating GAGs, capturing the competition between tension-driven collagen fiber alignment and the swelling pressure induced by GAGs. Using this model, we show that the swelling pressure provided by GAGs increases the stiffness of the collagen network by stretching the fibers in an isotropic manner. We found that the GAG-induced swelling pressure can help collagen fibers resist buckling as the cells exert contractile forces. This mechanism impedes the alignment of collagen fibers and decreases long-range cellular mechanical communication. We experimentally validated the theoretical predictions by comparing the intensity of collagen fiber alignment between cellular spheroids cultured on collagen gels versus collagen–GAG cogels. We found significantly lower intensities of aligned collagen in collagen–GAG cogels, consistent with the prediction that GAGs can prevent collagen fiber alignment. The role of GAGs in modulating force transmission uncovered in this work can be extended to understand pathological processes such as the formation of fibrotic scars and cancer metastasis, where cells communicate in the presence of abnormally high concentrations of GAGs.

The leptospiral LipL21 and LipL41 proteins exhibit a broad spectrum of interactions with host cell components

Leptospirosis is a globally prevalent zoonotic disease, and is caused by pathogenic spirochetes from the genus Leptospira. LipL21 and LipL41 are lipoproteins expressed strongly on the outer membrane of pathogenic Leptospira spp. Many studies have shown that both proteins are interesting targets for vaccines and diagnosis. However, their role in host-pathogen interactions remains underexplored. Therefore, we evaluated the capacity of LipL21 and LipL41 to bind with glycosaminoglycans (GAGs), the cell receptors and extracellular matrix, and plasma components by ELISA. Both proteins interacted with collagen IV, laminin, E-cadherin, and elastin dose-dependently. A broad-spectrum binding to plasma components was also observed. Only LipL21 interacted with all the GAG components tested, whereas LipL41 presented a concentration-dependent binding only for chondroitin 4 sulfate. Although, both proteins have the ability to interact with fibrinogen, only LipL21 inhibited fibrin clot formation partially. Both proteins exhibited a decrease in plasminogen binding in the presence of amino caproic acid (ACA), a competitive inhibitor of lysine residues, suggesting that their binding occurs via the kringle domains of plasminogen. LipL41, but not LipL21, was able to convert plasminogen to plasmin, and recruit plasminogen from normal human serum, suggesting that the interaction of this protein with plasminogen may occur in physiological conditions. This work provides the first report demonstrating the capacity of LipL21 and LipL41 to interact with a broad range of host components, highlighting their importance in host-Leptospira interactions.

Fabrication of porous chitosan particles using a novel two-step porogen leaching and lyophilization method with the label-free multivariate spectral assessment of live adhered cells

Porous chitosan (CS) particles were fabricated using a novel two-step technique that employed a porogen leaching phase followed by lyophilization or freeze-drying. Poly(ethylene glycol) (PEG) was mixed as a porogen in two different quantities with the CS solution before particle synthesis via coacervation. After the PEG leached out into deionized (DI) water at an elevated constant temperature, the final freeze-dried CS particles revealed surface features that resembled pore pockets. A three-dimensional (3D) culture of murine osteoblast cell line (OB-6) was seeded on these particles to analyze the effect of the porous structure on the cell activity, as compared to a control group with no added porogen. The results highlighted an enhancement in cell adhesion and proliferation on the two porous sample groups. A Raman spectroscopy-based label-free technique for live cell biomarker analysis was applied using multivariate spectral analysis. Results of the spectral analysis in the molecular fingerprint region corresponding to the Raman shift between 900 cm^-1 and 1700 cm^-1inferred inter-group variations. The bands at 1005 cm^-1 and 1375 cm^-1 were assigned to the live cell biomarkers phenylalanine and glycosaminoglycan, respectively, and were assessed during the multivariate spectral analysis. The corresponding score plot and loading information generated from the Principal Component Analysis (PCA) of the Raman spectrum at day 7 and day 14, pointed at inter-group spectral variations related to cell adhesion and proliferation between the two porous CS particle groups and the control.

Exploring the transcriptomic network of multi-ligand scavenger receptor Stabilin-1- and Stabilin-2-deficient liver sinusoidal endothelial cells

The Class H scavenger receptors Stabilin-1 (Stab1) and Stabilin-2 (Stab2) are two of the most highly expressed genes in liver sinusoidal endothelial cells (LSECs). While Stab1-deficient (Stab1KO) and Stab2-deficient (Stab2KO) mice are phenotypically unremarkable, Stab1/2-double-deficient (StabDKO) mice exhibit perisinusoidal liver fibrosis, glomerulofibrotic nephropathy and a reduced life expectancy. These conditions are caused by insufficiently scavenged circulating noxious blood factors. The effects of either Stab-single- or double-deficiency on LSEC differentiation and function, however, have not yet been thoroughly investigated. Therefore, we performed comprehensive transcriptomic analyses of primary LSECs from Stab1KO, Stab2KO and StabDKO mice. Microarray analysis revealed dysregulation of pathways and genes involved in established LSEC functions while sinusoidal endothelial marker gene expression was grossly unchanged. 82 genes were significantly altered in Stab1KO, 96 genes in Stab2KO and 238 genes in StabDKO compared with controls; 42 genes were found to be commonly dysregulated in all three groups and all of these genes were downregulated. These commonly downregulated genes (CDGs) were categorized as "potential scavengers," "cell adhesion molecules," "TGF-β/BMP-signaling" or "collagen and extracellular matrix (ECM) components". Among CDGs, Colec10, Lumican and Decorin, were the most strongly down-regulated genes and the corresponding proteins impact on the interaction of LSECs with chemokines, ECM components and carbohydrate structures. Similarly, "chemokine signaling," "cytokine-cytokine receptor interaction" and "ECM-receptor interaction," were the GSEA categories which represented most of the downregulated genes in Stab1KO and Stab2KO LSECs. In summary, our data show that loss of a single Stabilin scavenger receptor - and to a greater extent of both receptors - profoundly alters the transcriptomic repertoire of LSECs. These alterations may affect LSEC-specific functions, especially interactions of LSECs with the ECM and during inflammation as well as clearance of the peripheral blood.

Oncofetal Chondroitin Sulfate: A Putative Therapeutic Target in Adult and Pediatric Solid Tumors

Solid tumors remain a major challenge for targeted therapeutic intervention strategies such as antibody-drug conjugates and immunotherapy. At a minimum, clear and actionable solid tumor targets have to comply with the key biological requirement of being differentially over-expressed in solid tumors and metastasis, in contrast to healthy organs. Oncofetal chondroitin sulfate is a cancer-specific secondary glycosaminoglycan modification to proteoglycans expressed in a variety of solid tumors and metastasis. Normally, this modification is found to be exclusively expressed in the placenta, where it is thought to facilitate normal placental implantation during pregnancy. Informed by this biology, oncofetal chondroitin sulfate is currently under investigation as a broad and specific target in solid tumors. Here, we discuss oncofetal chondroitin sulfate as a potential therapeutic target in childhood solid tumors in the context of current knowhow obtained over the past five years in adult cancers.

Glycosaminoglycan-Inspired Biomaterials for the Development of Bioactive Hydrogel Networks

Glycosaminoglycans (GAG) are long, linear polysaccharides that display a wide range of relevant biological roles. Particularly, in the extracellular matrix (ECM) GAG specifically interact with other biological molecules, such as growth factors, protecting them from proteolysis or inhibiting factors. Additionally, ECM GAG are partially responsible for the mechanical stability of tissues due to their capacity to retain high amounts of water, enabling hydration of the ECM and rendering it resistant to compressive forces. In this review, the use of GAG for developing hydrogel networks with improved biological activity and/or mechanical properties is discussed. Greater focus is given to strategies involving the production of hydrogels that are composed of GAG alone or in combination with other materials. Additionally, approaches used to introduce GAG-inspired features in biomaterials of different sources will also be presented.

Implication of the Whitefly, Bemisia tabaci, Collagen Protein in Begomoviruses Acquisition and Transmission

Begomoviruses are the largest group of plant viruses transmitted exclusively by the whitefly, Bemisia tabaci (Gennadius), in a persistent, circulative, and nonpropagative manner. Begomoviruses in association with B. tabaci cause enormous loss to world agricultural crops. Transmission, retention, and circulation of begomovirus in B. tabaci are facilitated by its interaction with several proteins of the insect and its endosymbionts. However, very few such proteins have been identified from B. tabaci that are involved in this specific interaction. Here, we have performed yeast two-hybrid assay between B. tabaci complementary DNA expression library and the coat protein (CP) of tomato leaf curl New Delhi virus (ToLCNDV) and cotton leaf curl Rajasthan virus (CLCuV). Collagen was the common protein found to be interacting with both of the viruses. The collagen protein was found to be localized in gut layers of B. tabaci. Additionally, pull-down and dot-blot assays confirmed the association of endogenous collagen with ToLCNDV CP. Immunolocalization analysis also showed colocalization of ToLCNDV particles and collagen within insect gut. Finally, B. tabaci fed on anticollagen antibody and exhibited ∼46% reduction in ToLCNDV transmission, suggesting a supportive role for collagen in virus transmission.

The concentration-dependent effect of anethole on collagen, MMP-2 and GAG in human skin fibroblast cultures

PURPOSE

In aging skin and some skin disorders, components of skin extracellular matrix (ECM) are disturbed and therefore research to find skin drugs is important. Evaluation of anethole impact on collagen, GAGs and MMP-2 in human skin fibroblasts was the aim of this study.

MATERIALS AND METHODS

For collagen assay the Sircol dye, 5-[³H]proline and real time-PCR were used. MMP-2 activity was detected by zymography. GAG concentration was determined using 1,9-dimethylmethylene blue (DMMB). Cell viability was assayed with MTT.

RESULTS

In cells treated with 1 and 10 μM anethole, a significant increase in collagen synthesis was demonstrated. In contrast, collagen synthesis was significantly decreased in cells exposed to 100 μM anethole. Similar alterations were found in collagen type I expression. The concentration of collagen secreted into the medium was higher only in cells exposed to 1 μM anethole, while it was lower under the influence of higher compound concentrations. It may be due to the lack of pro-MMP-2 activation at 1 μM and a significant increase in the level of MMP-2 at 10 and 100 μM anethole. GAG concentration was reduced under the influence of 100 μM anethole, whereas anethole at lower concentrations revealed the ability to prevent H₂O₂-induced GAG increase. No significant cytotoxicity of anethole to fibroblasts was noted.

CONCLUSIONS

Our findings demonstrate the concentration-dependent action of anethole on the crucial components of ECM in cultured skin fibroblasts, which may be somewhat beneficial and may possibly be developed towards a therapeutic use in some skin disorders.

Optimization of cell growth on palmitoyl-hyaluronan knitted scaffolds developed for tissue engineering applications

Polysaccharides meet several criteria for a suitable biomaterial for tissue engineering, which include biocompatibility and ability to support the delivery and growth of cells. Nevertheless, most of these polysaccharides, for example dextran, alginate, and glycosaminoglycans, are highly soluble in aqueous solutions. Hyaluronic acid hydrophobized by palmitic acid and processed to the form of wet-spun fibers and the warp-knitted textile scaffold is water non-soluble, but biodegradable material, which could be used for the tissue engineering purpose. However, its surface quality does not allow cell attachment. To enhance the biocompatibility the surface of palmitoyl-hyaluronan was roughened by freeze drying and treated by different cell adhesive proteins (fibronectin, fibrinogen, laminin, methacrylated gelatin and collagen IV). Except for collagen IV, these proteins covered the fibers uniformly for an extended period of time and supported the adhesion and cultivation of dermal fibroblasts and mesenchymal stem cells. Interestingly, adipose stem cells cultivated on the fibronectin-modified scaffold secreted increasing amount of HGF, SDF-1, and VEGF, three key growth factors involved in cardiac regeneration. These results suggested that palmitoyl-hyaluronan scaffold may be a promising material for various applications in tissue regeneration, including cardiac tissue repair. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1488-1499, 2018.

Glycosaminoglycans from bovine eye vitreous humour and interaction with collagen type II

Glycosaminoglycans (GAGs) play an important role in stabilizing the gel state of eye vitreous humour. In this study, the composition of GAGs present in bovine eye vitreous was characterized through disaccharide analysis by liquid chromatography-mass spectrometry. The interaction of GAGs with collagen type II was assessed using surface plasmon resonance (SPR). The percentage of hyaluronic acid (HA), chondroitin sulfate (CS) and heparan sulfate (HS), of total GAG, were 96.2%, 3.5% and 0.3%, respectively. The disaccharide composition of CS consisted of 4S (49%), 0S (38%) 6S (12%), 2S6S (1.5%) and 2S4S (0.3%). The disaccharide composition of HS consisted of 0S (80%), NS2S (7%), NS (7%), 6S (4%), NS6S (2%), and TriS, 2S and 4S6S (each at 0.1%). The average molecular weights of CS and HS were 148 kDa and 204 kDa, respectively. SPR reveals that collagen type II binds to heparin (primarily composed of TriS) with a binding affinity (K _D) of 755 nM and interacts with other GAGs, including CSB and CSE. Both bovine vitreous CS and HS interact with collagen type II, with vitreous HS showing a higher binding affinity.

Extracellular matrix-inspired assembly of glycosaminoglycan–collagen fibers

We report on the fabrication of fibers exclusively from the extracellular matrix components by interfacial complexation without using any crosslinking agent.

Chondroitin sulfate cluster of epiphycan from salmon nasal cartilage defines binding specificity to collagens

Epiphycan (EPY) from salmon nasal cartilage has a glycosaminoglycan (GAG) domain that is heavily modified by chondroitin 4-sulfate and chondroitin 6-sulfate. The functional role of the GAG domain has not been investigated. The interaction of EPY with collagen was examined in vitro using surface plasmon resonance analysis. EPY was found to bind to type I collagen via clustered chondroitin sulfate (CS), while a single chain of CS was unable to bind. Types I, III, VII, VIII and X collagen showed high binding affinity with EPY, whereas types II, IV, V, VI and IX showed low binding affinities. Chemical modification of lysine residues in collagen decreased the affinity with the clustered CS. These results suggest that lysine residues of collagen are involved in the interaction with the clustered CS, and the difference in lysine modification defines the binding affinity to EPY. The clustered CS was also involved in an inter-saccharide interaction, and formed self-associated EPY. CS of EPY promoted fibril formation of type I collagen.

Synthesis and characterization of water soluble biomimetic chitosans for bone and cartilage tissue regeneration

Sulfated chitosan-arginine was synthesized to replicate growth factor-binding glycosaminoglycans. This material promoted cartilage formation from human progenitor cells while chitosan-arginine promoted bone.

Fibrinogen, riboflavin, and UVA to immobilize a corneal flap--molecular mechanisms

PURPOSE

Tissue glue containing fibrinogen (FIB) and riboflavin (RF), upon exposure to long wavelength ultraviolet light (UVA, 365 nM) has been proposed potentially to solve long-standing problems presented by corneal wound and epithelial ingrowth side-effects from laser-assisted in situ keratomileuis (LASIK). Data presented in a previous study demonstrated an ability of FIB + RF + UVA to adhere two stromal surfaces; however, to our knowledge no molecular mechanisms have been proposed to account for interactions occurring between corneal extracellular matrix (ECM) and tissue glue molecules. Here, we document several covalent and noncovalent interactions between these classes of macromolecules.

METHODS

SDS-PAGE and Western blot techniques were used to identify covalent interactions between tissue glue molecules and corneal ECM molecules in either the presence or absence of RF and UVA, in vitro and ex vivo. Surface plasmon resonance (SPR) was used to characterize noncovalent interactions, and obtain k(a), k(d), and K(D) binding affinity values.

RESULTS

SDS-PAGE and Western blot analyses indicated that covalent interactions occurred between neighboring FIB molecules, as well as between FIB and collagen type I (Coll-I) proteins (in vitro and ex vivo). These interactions occurred only in the presence of RF and UVA. SPR data demonstrated the ability of FIB to bind noncovalently to corneal stroma molecules, Coll-I, decorin, dermatan sulfate, and corneal basement membrane molecules, laminin and heparan sulfate--only in the presence of Zn(2+).

CONCLUSIONS

Covalent and (zinc-mediated) noncovalent mechanisms involving FIB and stromal ECM molecules contribute to the adhesion created by FIB + RF + UVA.

Anti-inflammatory effect of proteoglycan and progesterone on human uterine cervical fibroblasts

AIMS

The aim of this study was to compare the anti-inflammatory effect of proteoglycan (PG) with that of progesterone (P) in the cultured fibroblasts from human uterine cervix.

MAIN METHODS

After obtaining informed consent, the cervix was collected from normal women undergoing total hysterectomy. The cervix was cultured until fibroblasts proliferated and had grown to confluence, then, the fibroblasts were stimulated by lipopolysaccharide (LPS) with or without PG, P and a combination of both; they were cultured for 24-48 h. The anti-inflammatory effects of PG and P were evaluated by the suppression of IL-6 or IL-8 secretion. The expression of the IL-6 or IL-8 gene and the expression of their protein were determined by real-time PCR, and ELISA, respectively. Activation of Toll-like receptor (TLR) 4 was evaluated by Western blotting.

KEY FINDINGS

LPS markedly enhanced gene and protein expression of IL-6 and IL-8 in human uterine cervical fibroblasts. The up-regulation of the IL-6 or IL-8 gene and protein expression by LPS was significantly suppressed with PG, P and a combination of both. Western blotting revealed that combination of PG and P showed more potent inhibition on LPS-stimulated TLR4 induction than that seen by each.

SIGNIFICANCE

This study showed that both PG and P have an inhibitory effect on LPS-induced inflammation. This anti-inflammatory effect of PG and P was augmented by co-administration of both, suggesting for the first time that PG has an anti-inflammatory effect on human uterine cervical fibroblasts.

Synthesis of neoproteoglycans using the transglycosylation reaction as a reverse reaction of endo-glycosidases

A method for the synthesis of carbohydrate chains (glycosaminoglycans) and their coupling to peptides was investigated using proteoglycans. Glycosidases generally catalyze a hydrolytic reaction, but can also mediate the reverse reaction, which in this case is a transglycosylation. In the transglycosylation reaction of bovine testicular hyaluronidase, which is an endoglycosidase, glycosaminoglycans (hyaluronan and chondroitin sulfates) release disaccharide (uronic acid-N-acetylhexosamine) moieties from non-reducing terminal sites, and then the liberated disaccharides are transferred immediately to the non-reducing termini of other glycosaminoglycan chains. Using such continuous reactions, it is possible to synthesize glycosaminoglycan chains according to a specific design. It then becomes possible to transfer glycosaminoglycan chains synthesized on a peptide to other peptides using the transglycosylation reaction of endo-β-xylosidase acting on the linkage region between a peptide and glycosaminoglycan chains of proteoglycans. We believe this approach will open a new field for the synthesis of homogeneous proteoglycans or their corresponding analogues.

Type IX collagen interacts with fibronectin providing an important molecular bridge in articular cartilage

Type IX collagen is covalently bound to the surface of type II collagen fibrils within the cartilage extracellular matrix. The N-terminal, globular noncollagenous domain (NC4) of the α1(IX) chain protrudes away from the surface of the fibrils into the surrounding matrix and is available for molecular interactions. To define these interactions, we used the NC4 domain in a yeast two-hybrid screen of a human chondrocyte cDNA library. 73% of the interacting clones encoded fibronectin. The interaction was confirmed using in vitro immunoprecipitation and was further characterized by surface plasmon resonance. Using whole and pepsin-derived preparations of type IX collagen, the interaction was shown to be specific for the NC4 domain with no interaction with the triple helical collagenous domains. The interaction was shown to be of high affinity with nanomolar K(d) values. Analysis of the fibronectin-interacting clones indicates that the constant domain is the likely site of interaction. Type IX collagen and fibronectin were shown to co-localize in cartilage. This novel interaction between the NC4 domain of type IX collagen and fibronectin may represent an in vivo interaction in cartilage that could contribute to the matrix integrity of the tissue.

Glycosaminoglycans as polyelectrolytes

One of the barriers to understanding structure-property relations for glycosaminoglycans has been the lack of constructive interplay between the principles and methodologies of the life sciences (molecular biology, biochemistry and cell biology) and the physical sciences, particularly in the field of polyelectrolytes. To address this, we first review the similarities and differences between the physicochemical properties of GAGs and other statistical chain polyelectrolytes of both natural and abioitic origin. Since the biofunctionality and regulation of the structures of GAGs is intimately connected with interactions with their cognate proteins, we particularly compare and contrast aspects of protein binding, i.e. effects of both GAGs and other polyelectrolytes on protein stability, protein aggregation and phase behavior. The protein binding affinities and their dependences on pH and ionic strength for the two groups are discussed not only in terms of observable differences, but also with regard to contrasting descriptions of the bound state and the role of electrostatics. We conclude that early studies of the heparin-Antithromin system, proceeding to a large extent through the methods and models of protein chemistry and drug discovery, established not only many enabling precedents but also constraining paradigms. Current studies on heparan sulfate and chondroitin sulfate seem to reflect a more ecumenical view likely to be more compatible with concepts from physical and polymer chemistry.

The NC2 domain of collagen IX provides chain selection and heterotrimerization

The mechanism of chain selection and trimerization of fibril-associated collagens with interrupted triple helices (FACITs) differs from that of fibrillar collagens that have special C-propeptides. We recently showed that the second carboxyl-terminal non-collagenous domain (NC2) of homotrimeric collagen XIX forms a stable trimer and substantially stabilizes a collagen triple helix attached to either end. We then hypothesized a general trimerizing role for the NC2 domain in other FACITs. Here we analyzed the NC2 domain of human heterotrimeric collagen IX, the only member of FACITs with all three chains encoded by distinct genes. Upon oxidative folding of equimolar amounts of the alpha1, alpha2, and alpha3 chains of NC2, a stable heterotrimer with a disulfide bridge between alpha1 and alpha3 chains is formed. Our experiments show that this heterotrimerization domain can stabilize a short triple helix attached at the carboxyl-terminal end and allows for the proper oxidation of the cystine knot of type III collagen after the short triple helix.

Chondrogenic differentiation on perlecan domain I, collagen II, and bone morphogenetic protein-2-based matrices

Extracellular matrix (ECM) molecules in cartilage cooperate with growth factors to regulate chondrogenic differentiation and cartilage development. Domain I of perlecan (Pln) bears heparan sulfate chains that bind and release heparin binding growth factors (HBGFs). We hypothesized that Pln domain I (PlnDI) might be complexed with collagen II (P-C) fibrils to improve binding of bone morphogenetic protein-2 (BMP-2) and better support chondrogenesis and cartilage-like tissue formation in vitro. Our results showed that P-C fibrils bound more BMP-2 than collagen II fibrils alone, and better sustained BMP-2 release. Polylactic acid (PLA)-based scaffolds coated with P-C fibrils immobilized more BMP-2 than either PLA scaffolds or PLA scaffolds coated with collagen II fibrils alone. Multipotential mouse embryonic mesenchymal cells, C3H10T1/2, were cultured on 2-dimensional P-C fibrils or 3-dimensional P-C/BMP-2-coated (P-C-B) PLA scaffolds. Chondrogenic differentiation was indexed by glycosaminoglycan (GAG) production, and expression of the pro-chondrogenic transcription factor, Sox9, as well as cartilaginous ECM proteins, collagen II, and aggrecan. Immunostaining for aggrecan, perlecan, tenascin, and collagen X revealed that both C3H10T1/2 cells and primary mouse embryonic fibroblasts cultured on P-C-B fibrils showed the highest expression of chondrogenic markers among all treatment groups. Safranin O-Fast Green staining indicated that cartilage-like tissue was formed in the P-C-B scaffolds, while no obvious cartilage-like tissue formed in other scaffolds. We conclude that P-C fibrils provide an improved biomimetic material for the binding and retention of BMP-2 and support chondrogenic differentiation.

Structural Requirements for Heparin/Heparan Sulfate Binding to Type V Collagen

Collagen-proteoglycan interactions participate in the regulation of matrix assembly and in cell-matrix interactions. We reported previously that a fragment (Ile824-Pro950) of the collagen alpha1(V) chain, HepV, binds to heparin via a cluster of three major basic residues, Arg912, Arg918, and Arg921, and two additional residues, Lys905 and Arg909 (Delacoux, F., Fichard, A., Cogne, S., Garrone, R., and Ruggiero, F. (2000) J. Biol. Chem. 275, 29377-29382). Here, we further characterized the binding of HepV and collagen V to heparin and heparan sulfate by surface plasmon resonance assays. HepV bound to heparin and heparan sulfate with a similar affinity (KD approximately 18 and 36 nM, respectively) in a cation-dependent manner, and 2-O-sulfation of heparin was shown to be crucial for the binding. An octasaccharide of heparin and a decasaccharide of heparan sulfate were required for HepV binding. Studies with HepV mutants showed that the same basic residues were involved in the binding to heparin, to heparan sulfate, and to the cell surface. The contribution of Lys905 and Arg909 was found to be significant. The triple-helical peptide GPC(GPP)5G904-R918(GPP)5GPC-NH2 and native collagen V molecules formed much more stable complexes with heparin than HepV, and collagen V bound to heparin/heparan sulfate with a higher affinity (in the nanomolar range) than HepV. Heat and chemical denaturation strongly decreased the binding, indicating that the triple helix plays a major role in stabilizing the interaction with heparin. Collagen V and HepV may play different roles in cell-matrix interactions and in matrix assembly or remodeling mediated by their specific interactions with heparan sulfate.

Evaluation of the effect of collagen network degradation on the frictional characteristics of articular cartilage using a simultaneous analysis of the contact condition

BACKGROUND

Superficial conditions and integrity of collagen network play an important role on the lubrication performance of articular cartilage. In this work, a technique based on the evanescent waves is used for the evaluation of contact condition during friction tests.

METHODS

The frictional and superficial characteristics of the normal and degraded articular cartilages with high and low concentration of collagenase were evaluated. The optical apparatus was set in order to decrease the intensity of a light reflected at the interface between a prism and specimens when collagen fibers are found near the interface.

FINDINGS

For all conditions, an increase in the attenuation of reflectance as the friction coefficient increases was observed with reasonable correlation. For the specimens degraded with collagenase, low friction and reduced attenuation of reflectance were observed at the beginning of sliding followed by a gradual increase in both friction and attenuation of reflectance. In comparison to the degraded specimens, normal specimens presented high friction at beginning and low friction at the end of test.

INTERPRETATION

The superficial conditions and the presence of water at the articular surface play an important role in the lubrication of synovial joints. The ability to retain water for degraded specimens is impaired due to the loss of proteoglycan observed in the histological sections and hence, their low friction observed at the beginning of the test is not sustained for a long time. The use of evanescent waves demonstrated to be very useful in the analysis of the contact condition of articular cartilage.

Interaction between proteoglycans and alpha-elastin in construction of extracellular matrix of human yellow ligament

One type of large proteoglycan and three types of small proteoglycans (decorin, decorin-subtype, and biglycan) were purified by chromatography, and alpha-elastin was isolated by alkali treatment from human yellow ligaments taken at the time of operation. The interaction of the proteoglycans with immobilized alpha-elastin on a sensor was analyzed by surface plasmon resonance, and we confirmed that each of the small proteoglycans exhibited a specific binding to alpha-elastin. The binding sites of small proteoglycans were contained in the protein cores. In addition, the differences in the interaction of the small proteoglycans with alpha-elastin of normal and ossified ligaments were compared. The interactions of the small proteoglycans with alpha-elastin of the ossified ligaments were lower than those with alpha-elastin of the normal ligaments. In the ossified ligaments, neodesmosine, one of the cross-linking amino acids, was significantly less than in the normal ligaments (p < .05).

Differential interactions of decorin and decorin mutants with type I and type VI collagens

The small leucine-rich proteoglycan decorin can bind via its core protein to different types of collagens such as type I and type VI. To test whether decorin can act as a bridging molecule between these collagens, the binding properties of wild-type decorin, two full-length decorin species with single amino acid substitutions (DCN E180K, DCN E180Q), which previously showed reduced binding to collagen type I fibrils, and a truncated form of decorin (DCN Q153) to the these collagens were investigated. In a solid phase assay dissociation constants for wild-type decorin bound to methylated, therefore monomeric, triple helical type I collagen were in the order of 10(-10) m, while dissociation constants for fibrillar type I collagen were approximately 10(-9) m. The dissociation constant for type VI was approximately 10(-7) m. Using real-time analysis for a more detailed investigation DCN E180Q and DCN E180K exhibited lower association and higher dissociation constants to type I collagen, compared to wild-type decorin, deviating by at least one order of magnitude. In contrast, the affinities of these mutants to type VI collagen were 10 times higher than the affinity of wild-type decorin (K(D) approximately 10(-8) m). Further investigations verified that complexes of type VI collagen and decorin bound type I collagen and that the affinity of collagen type VI to type I was increased by the presence of decorin. These data show that decorin not only can regulate collagen fibril formation but that it also can act as an intermediary between type I and type VI collagen and that these two types of collagen interact via different binding sites.

Characterization of recombinant amino-terminal NC4 domain of human collagen IX: interaction with glycosaminoglycans and cartilage oligomeric matrix protein

The N-terminal NC4 domain of collagen IX is a globular structure projecting away from the surface of the cartilage collagen fibril. Several interactions have been suggested for this domain, reflecting its location and its characteristic high isoelectric point. In an attempt to characterize the NC4 domain in more detail, we set up a prokaryotic expression system to produce the domain. The purified 27.5-kDa product was analyzed for its glycosaminoglycan-binding potential by surface plasmon resonance and solid-state assays. The results show that the NC4 domain of collagen IX specifically binds heparin with a K(d) of 0.6 microm, and the full-length recombinant collagen IX has an even stronger interaction with heparin, with an apparent K(d) of 3.6 nm. The heparin-binding site of the NC4 domain was located in the extreme N terminus, containing a heparin-binding consensus sequence, whereas electron microscopy suggested the presence of at least three additional heparin-binding sites on full-length collagen IX. The NC4 domain was also shown to bind cartilage oligomeric matrix protein. This interaction and the association of cartilage oligomeric matrix protein with other regions of collagen IX were found to be heparin-competitive. Circular dichroism analyses of the NC4 domain indicated the presence of stabilizing disulfide bonds and a thermal denaturation point of about 80 degrees C. The pattern of disulfide bond formation within the NC4 domain was identified by tryptic peptide mass mapping of the NC4 in native and reduced states. A similar pattern was demonstrated for the NC4 domain of full-length recombinant collagen IX.

Domain structure of chondroitin sulfate E octasaccharides binding to type V collagen

We demonstrated previously that chondroitin sulfate E (ChS-E) binds to type V collagen (Munakata, H., Takagaki, K., Majima, M., and Endo, M. (1999) Glycobiology 9, 1023--1027). In this study, we investigated the structure and binding of ChS-E oligosaccharides. Eleven oligosaccharides were isolated from ChS-E by gel filtration chromatography and anion-exchange high performance liquid chromatography after hydrolysis with testicular hyaluronidase. Separately, seven oligosaccharides were custom synthesized using the transglycosylation reaction of testicular hyaluronidase. Structural analysis was performed by enzymatic digestions in conjunction with high performance liquid chromatography and mass spectrometry. This library of 18 oligosaccharides was used as a source of model molecules to clarify the structural requirements for binding to type V collagen. Binding was analyzed by a biosensor based on surface plasmon resonance. The results indicated that to bind to type V collagen the oligosaccharides must have the following carbohydrate structures: 1) octasaccharide or larger in size; 2) a continuous sequence of three GlcAbeta1--3GalNAc(4S,6S) units; 3) a GlcAbeta1--3GalNAc(4S,6S) unit, GlcAbeta1--3GalNAc(4S) unit or GlcAbeta1--3GalNAc(6S) unit at the reducing terminal; 4) a GlcAbeta1--3GalNAc(4S,6S) unit at the nonreducing terminal. It is likely that these characteristic oligosaccharide sequences play key roles in cell adhesion and extracellular matrix assembly.

Structural characterization of heparan sulfate and chondroitin sulfate of syndecan-1 purified from normal murine mammary gland epithelial cells. Common phosphorylation of xylose and differential sulfation of galactose in the protein linkage region tetrasaccharide sequence

Syndecan-1, present on the surfaces of normal murine mammary gland epithelial cells, is a transmembrane hybrid proteoglycan, which bears glycosaminoglycan (GAG) side chains of heparan sulfate (HS) and chondroitin sulfate (CS). Purified syndecan-1 ectodomains were analyzed for disaccharide composition and the GAG-protein linkage region after digestion with bacterial lyases. The HS chains contained predominantly a nonsulfated unit with smaller proportions of two monosulfated, two disulfated, and a trisulfated unit, whereas CS chains were demonstrated for the first time to bear GlcUA-GalNAc(4-O-sulfate) as a major component as well as GlcUA-GalNAc, GlcUA-GalNAc(6-O-sulfate), and an E disaccharide unit GlcUA-GalNAc(4,6-O-disulfate) as minor yet appreciable components. Two kinds of linkage region tetrasaccharides, GlcUA-Gal-Gal-Xyl and GlcUA-Gal-Gal-Xyl(2-O-phosphate), were found for the HS chains in a molar ratio of 55:45. In marked contrast, an additional sulfated tetrasaccharide, GlcUA-Gal(4-O-sulfate)-Gal-Xyl, was demonstrated only for the CS chains, and the unmodified phosphorylated and sulfated components were present at a molar ratio of 55:26:19. The present study thus provided conclusive evidence for the hypothesis that 4-O-sulfation of Gal is peculiar to CS chains in contrast to the phosphorylation of Xyl, which is common to both HS and CS chains. These modifications may be required for biosynthetic maturation of the linkage region tetrasaccharide sequence, which is a prerequisite for creating the repeating disaccharide region of GAG chains and/or biosynthetic selective chain assembly of CS and HS chains.

Neuronal cell adhesion, mediated by the heparin-binding neuroregulatory factor midkine, is specifically inhibited by chondroitin sulfate E. Structural ans functional implications of the over-sulfated chondroitin sulfate

The heparin-binding neurotrophic factor midkine (MK) has been proposed to mediate neuronal cell adhesion and neurite outgrowth promotion by interacting with cell-surface heparan sulfate. We have observed that over-sulfated chondroitin sulfate (CS) D and CS-E show neurite outgrowth-promoting activity in embryonic day (E) 18 rat hippocampal neurons (Nadanaka, S., Clement, A., Masayama, K., Faissner, A., and Sugahara, K. (1998) J. Biol. Chem. 273, 3296-3307). In the present study, various CS isoforms were examined for their ability to inhibit the MK-mediated cell adhesion of cortical neuronal cells in comparison with heparin from porcine intestine and heparan sulfate from bovine kidney. E17-18 rat cortical neuronal cells were cultured on plates coated with recombinant MK in a grid pattern. The cells attached to and extended their neurites along the MK substratum. Cell adhesion was inhibited by squid cartilage over-sulfated CS-E as well as by heparin, but not by heparan sulfate or other CS isoforms. Direct interactions of MK with various glycosaminoglycans were then evaluated using surface plasmon resonance, showing that CS-E bound MK as strongly as heparin, followed by other over-sulfated CS isoforms, CS-H and CS-K. Furthermore, E18 rat brain extracts showed an E disaccharide unit, GlcUAbeta1-3GalNAc(4,6-O-disulfate). These findings indicate that CS chains containing the E unit as well as heparin-like glycosaminoglycans may be involved in the expression and/or modulation of the multiple neuroregulatory functions of MK such as neuronal adhesion and migration and promotion of neurite outgrowth.

Survey of the 1999 surface plasmon resonance biosensor literature

The application of surface plasmon resonance biosensors in life sciences and pharmaceutical research continues to increase. This review provides a comprehensive list of the commercial 1999 SPR biosensor literature and highlights emerging applications that are of general interest to users of the technology. Given the variability in the quality of published biosensor data, we present some general guidelines to help increase confidence in the results reported from biosensor analyses.

Structural requirements of heparan sulfate for the binding to the tumor-derived adhesion factor/angiomodulin that induces cord-like structures to ECV-304 human carcinoma cells

Tumor-derived adhesion factor/angiomodulin (AGM) is accumulated in tumor blood vessels and on the endothelial cell surface (Akaogi, K., Okabe, Y., Sato, J., Nagashima, Y., Yasumitsu, H., Sugahara, K., and Miyazaki, K. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 8384-8389). In cell culture, it promotes cell adhesion and morphological changes to form cord-like structures of the human bladder carcinoma cell line ECV-304. The cord formation is prevented by heparin, which inhibits the binding of AGM to ECV-304 cells. This observation suggests that AGM interacts with cell surface heparan sulfate (HS) proteoglycans. In this study, HS glycosaminoglycans and core proteins of integral transmembrane proteoglycans, syndecan-1 and -4, were identified by immunocytochemistry on ECV-304 cells, and the structural requirements for the interaction of HS with AGM were characterized. Inhibition experiments with sulfated polysaccharides and chemically modified heparin derivatives indicated that sulfate groups were essential for both AGM-HS binding and cord-like structure formation and that the rank order of the different sulfate groups in terms of their contribution was N-sulfate > 6-O-sulfate > 2-O-sulfate. The minimum size of heparin, a chemical analog of HS, required for the binding to AGM was a dodecasaccharide as determined by competition experiments using size-defined heparin oligosaccharides. Thus, a specific sulfation pattern in the HS of cell surface syndecans of ECV-304 cells is required for AGM binding and the morphological changes.