NMR characterization of uniformly 13C- and/or 15N-labeled, unsulfated chondroitins with high molecular weights

Solution nuclear magnetic resonance (NMR) analysis of polysaccharides can provide valuable information not only on their primary structures but also on their conformation, dynamics, and interactions under physiological conditions. One of the main problems is that non-anomeric 1H signals typically overlap, and this often hinders detailed NMR analysis. Isotope enrichment, such as with 13C and 15N, will add a new dimension to the NMR spectra of polysaccharides, and spectral analysis can be performed with enhanced sensitivity using isolated peaks. For this purpose, here we have prepared uniformly 13C- and/or 15N-labeled chondroitin polysaccharides -4)-β-D-glucuronopyranosyl-(1-3)-2-acetamido-2-deoxy-β-D-galactopyranosyl-(1- with molecular weights in the range from 310 to 460 k by bacterial fermentation. The enrichment ratios for 13C and 15N were 98.9 and 99.8%, respectively, based on the mass spectrometric analysis of the constituent chondroitin disaccharides. 1H and 13C NMR signals were assigned mainly based on HSQC and 13C-detection experiments including INADEQUATE, HETCOR, and HETCOR-TOCSY. The carbonyl carbon signal of the N-acetyl-β-D-galactosamine residue was unambiguously distinguished from the C6 carbon of the β-D-glucuronic acid residue by the observation of 13C peak splitting due to 1JCN coupling in 13C- and 15N-labeled chondroitin. The T2* and T1 were measured and indicate that both rigid and mobile sites are present in the long sequence of chondroitin. The conformation, dynamics, and interactions of chondroitin and its derivatives will be further analyzed based on the results obtained in this study.

Reprogramming Metabolic Flux in Escherichia Coli to Enhance Chondroitin Production

Reprogramming metabolic flux is a promising approach for constructing efficient microbial cell factories (MCFs) to produce chemicals. However, how to boost the transmission efficiency of metabolic flux is still challenging in complex metabolic pathways. In this study, metabolic flux is systematically reprogrammed by regulating flux size, flux direction, and flux rate to build an efficient MCF for chondroitin production. The ammoniation pool for UDP-GalNAc synthesis and the carbonization pool for UDP-GlcA synthesis are first enlarged to increase flux size for providing enough precursors for chondroitin biosynthesis. Then, the ammoniation pool and the carbonization pool are rematched using molecular valves to shift flux direction from cell growth to chondroitin biosynthesis. Next, the adaptability of polymerization pool with the ammoniation and carbonization pools is fine-tuned by dynamic and static valve-based adapters to accelerate flux rate for polymerizing UDP-GalNAc and UDP-GlcA to produce chondroitin. Finally, the engineered strain E. coli F51 is able to produce 9.2 g L-1 chondroitin in a 5-L bioreactor. This strategy shown here provides a systematical approach for regulating metabolic flux in complex metabolic pathways for efficient biosynthesis of chemicals.

Production and purification of higher molecular weight chondroitin by metabolically engineered Escherichia coli K4 strains

The capsular polysaccharide obtained from Escherichia coli K4 is a glycosaminoglycan-like molecule, similar to chondroitin sulphate, that has established applications in the biomedical field. Recent efforts focused on the development of strategies to increase K4 polysaccharide fermentation titers up to technologically attractive levels, but an aspect that has not been investigated so far, is how changes in the molecular machinery that produces this biopolymer affect its molecular weight. In this work, we took advantage of recombinant E. coli K4 strains that overproduce capsular polysaccharide, to study whether the inferred pathway modifications also influenced the size of the produced polymer. Fed-batch fermentations were performed up to the 22 L scale, in potentially industrially applicable conditions, and a purification protocol that allows in particular the recovery of high molecular weight unsulphated chondroitin, was developed next. This approach allowed to determine the molecular weight of the purified polysaccharide, demonstrating that kfoF overexpression increased polymer size up to 133 kDa. Higher polysaccharide titers and size were also correlated to increased concentrations of UDP-GlcA and decreased concentrations of UDP-GalNAc during growth. These results are interesting also in view of novel potential applications of higher molecular weight chondroitin and chondroitin sulphate in the biomedical field.

Efficient Construction of Atomic-Resolution Models of Non-Sulfated Chondroitin Glycosaminoglycan Using Molecular Dynamics Data

Glycosaminoglycans (GAGs) are linear, structurally diverse, conformationally complex carbohydrate polymers that may contain up to 200 monosaccharides. These characteristics present a challenge for studying GAG conformational thermodynamics at atomic resolution using existing experimental methods. Molecular dynamics (MD) simulations can overcome this challenge but are only feasible for short GAG polymers. To address this problem, we developed an algorithm that applies all conformational parameters contributing to GAG backbone flexibility (i.e., bond lengths, bond angles, and dihedral angles) from unbiased all-atom explicit-solvent MD simulations of short GAG polymers to rapidly construct models of GAGs of arbitrary length. The algorithm was used to generate non-sulfated chondroitin 10- and 20-mer ensembles which were compared to MD-generated ensembles for internal validation. End-to-end distance distributions in constructed and MD-generated ensembles have minimal differences, suggesting that our algorithm produces conformational ensembles that mimic the backbone flexibility seen in simulation. Non-sulfated chondroitin 100- and 200-mer ensembles were constructed within a day, demonstrating the efficiency of the algorithm and reduction in time and computational cost compared to simulation.

Insights on the reactivity of chondroitin and hyaluronan toward 1,4-butanediol diglycidyl ether

Hyaluronic acid (HA) cross-linked with 1,4-butanediol diglycidyl ether (BDDE) are hydrogels with many biomedical applications. Degree of substitution, cross-linking and substitution position of the cross-linker might influence the properties of the hydrogels. We showed earlier that the most common substitution position of the cross-linker on the hyaluronan chain was the 4-hydroxyl of N-acetylglucosamine. This result has led us to investigate unsulfated chondroitin (CN) which only differ from HA in the primary structure by the configuration at C4 of the aminoglycan. In the present study, we have investigated (i) the substitution positions of the cross-linker in CN using NMR and LC-MS and compared the results to the data obtained for HA (ii) the effect of alkali on the ¹³C and ¹H chemical shifts in CN and HA (iii) the temperature coefficients and chemical shifts of hydroxyl protons in CN and HA. In CN, the 2-hydroxyl of glucuronic acid and 6-hydroxyl of N-acetylgalactosamine were found to be the major sites of substitution by BDDE. Moreover, while chondroitinase was not able to cleave HA tetrasaccharide substituted at the 4-hydroxyl GlcNAc reducing end by BDDE, it is able to degrade CN-BDDE down to disaccharide units.

Cloning and Expression of Recombinant Chondroitinase ACII and Its Comparison to the Arthrobacter aurescens Enzyme

Chondroitin sulfates are the glycosaminoglycan chains of proteoglycans critical in the normal development and pathophysiology of all animals. Chondroitinase ACII, a polysaccharide lyase originally isolated from Arthrobacter aurescens IAM 110 65, which is widely used in the analysis and study of chondroitin structure, is no longer commercially available. The aim of the current study is to prepare recombinant versions of this critical enzyme for the glycobiology research community. Two versions of recombinant chondroitinase ACII are prepared in Escherichia coli, and their activity, stability, specificity, and action pattern are examined, along with a non-recombinant version secreted by an Arthrobacter strain. The recombinant enzymes are similar to the enzyme obtained from Arthrobacter for all examined properties, except for some subtle specificity differences toward uncommon chondroitin sulfate substrates. These differences are believed to be due to either post-translational modification of the Arthrobacter-secreted enzyme or other subtle structural differences between the recombinant and natural enzymes. The secreted chondroitinase can serve as a suitable replacement for the original enzyme that is currently unavailable, while the recombinant ones can be applied generally in the structural determination of most standard chondroitin sulfates.

Decoration of Chondroitin Polysaccharide with Threonine: Synthesis, Conformational Study, and Ice-Recrystallization Inhibition Activity

Several threonine (Thr)- and alanine (Ala)-rich antifreeze glycoproteins (AFGPs) and polysaccharides act in nature as ice recrystallization inhibitors. Among them, the Thr-decorated capsular polysaccharide (CPS) from the cold-adapted Colwellia psychrerythraea 34H bacterium was recently investigated for its cryoprotectant activity. A semisynthetic mimic thereof was here prepared from microbial sourced chondroitin through a four-step strategy, involving a partial protection of the chondroitin polysaccharide as a key step for gaining an unprecedented quantitative amidation of its glucuronic acid units. In-depth NMR and computational analysis suggested a fairly linear conformation for the semisynthetic polysaccharide, for which the antifreeze activity by a quantitative ice recrystallization inhibition assay was measured. We compared the structure-activity relationships for the Thr-derivatized chondroitin and the natural Thr-decorated CPS from C. psychrerythraea.

Chondroitin fragments are odorants that trigger fear behavior in fish

The ability to detect and avoid predators is essential to survival. Various animals, from sea urchins to damselfly larvae, use injury of conspecifics to infer the presence of predators. In many fish, skin damage causes the release of chemicals that elicit escape and fear in members of the shoal. The chemical nature of the alarm substance ("Schreckstoff" in German), the neural circuits mediating the complex response, and the evolutionary origins of a signal with little obvious benefit to the sender, are unresolved. To address these questions, we use biochemical fractionation to molecularly characterize Schreckstoff. Although hypoxanthine-3 N-oxide has been proposed to be the alarm substance, it has not been reliably detected in the skin and there may be other active components. We show that the alarm substance is a mixture that includes the glycosaminoglycan (GAG) chondroitin. Purified chondroitins trigger fear responses. Like skin extract, chondroitins activate the mediodorsal posterior olfactory bulb, a region innervated by crypt neurons that has a unique projection to the habenula. These findings establish GAGs as a new class of odorants in fish, which trigger alarm behavior possibly via a specialized circuit.

Brain chondroitin/dermatan sulfate, from cerebral tissue to fine structure: extraction, preparation, and fully automated chip-electrospray mass spectrometric analysis

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans (GAGs) are covalently linked to proteins, building up a wide range of proteoglycans, with a prevalent expression in the extracellular matrix (ECM). In mammalian tissues, these GAG species are often found as hybrid CS/DS chains. Their structural diversity during chain elongation is produced by variability of sulfation in the repeating disaccharide units. In central nervous system, a large proportion of the ECM is composed of proteoglycans; therefore, CS/DS play a significant role in the functional diversity of neurons, brain development, and some brain diseases. A requirement for collecting consistent data on brain proteoglycan glycosylation is the development of adequate protocols for CS/DS extraction and detailed compositional and structure analysis. This chapter will present a strategy, which combines biochemical tools for brain CS/DS extraction, purification, and fractionation, with a modern analytical platform based on chip-nanoelectrospray multistage mass spectrometry (MS) able to provide information on the essential structural elements such as epimerization, chain length, sulfate content, and sulfation sites.

Mutually reinforced multicomponent polysaccharide networks

Networks made from chitosan and alginate have been utilized as prospective tissue engineering scaffolds due to material biocompatibility and degradability. Calcium (Ca(2+) ) is often added to these networks as a modifier for mechanical strength enhancement. In this work, we examined changes in the bulk material properties of different concentrations of chitosan/alginate mixtures (2, 3, or 5% w/w) upon adding another modifier, chondroitin. We further examined how material properties depend on the order the modifiers, Ca(2+) and chondroitin, were added. It was found that the addition of chondroitin significantly increased the mechanical strength of chitosan/alginate networks. Highest elastic moduli were obtained from samples made with mass fractions of 5% chitosan and alginate, modified by chondroitin first and then Ca(2+) . The elastic moduli in dry and hydrated states were (4.41 ± 0.52) MPa and (0.11 ± 0.01) MPa, respectively. Network porosity and density were slightly dependent on total polysaccharide concentration. Average pore size was slightly larger in samples modified by Ca(2+) first and then chondroitin and in samples made with 3% starting mass fractions. Here, small-angle neutron scattering (SANS) was utilized to examine mesh size of the fibrous networks, mass-fractal parameters and average dimensions of the fiber cross-sections prior to freeze-drying. These studies revealed that addition of Ca(2+) and chondroitin modifiers increased fiber compactness and thickness, respectively. Together these findings are consistent with improved network mechanical properties of the freeze-dried materials.

Design and synthesis of unnatural heparosan and chondroitin building blocks

Triazole linked heparosan and chondroitin disaccharide and tetrasaccharide building blocks were synthesized in a stereoselective manner by applying a very efficient copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction of appropriately substituted azido-glucuronic acid and propargyluted N-acetyl glucosamine and N-acetyl galactosamine derivative, respectively. The resulting suitably substituted tetrasaccharide analogues can be easily converted into azide and alkyne unit for further synthesis of higher oligosaccharide analogues.

Extraction of chondroitin/dermatan sulfate glycosaminoglycans from connective tissue for mass spectrometric analysis

Chondroitin/dermatan sulfate (CS/DS) glycosaminoglycans (GAGs) are present in high levels in connective tissue where they play roles as structural molecules and in protein-binding interactions. Recent developments in the techniques for analysis of CS/DS using capillary electrophoresis (CE) have enabled progress in the understanding of changes in CS/DS structure that accompany connective tissue diseases including osteoarthritis. Key to these developments is the ability to extract CS/DS GAGs from small quantities of connective tissue. This chapter describes a method for connective tissue GAG extraction, derivatization, and workup for subsequent capillary electrophoretic and/or mass spectrometric analysis.

Mass spectrometry for the characterization of unsulfated chondroitin oligosaccharides from 2-mers to 16-mers. Comparison with hyaluronic acid oligomers

This study reports for the first time the complete liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses performed in negative ion mode of saturated unsulfated chondroitin oligosaccharides up to 16-mers and comparison with hyaluronic acid (HA) oligomers differing only in the nature of the hexosamine residue. MS/MS of the chondroitin disaccharide on the singly charged precursor at m/z 396.1 afforded a glycosidic cleavage C1 product ion at m/z 192.9. In the tetrasaccharide, C2 (m/z 396.0) and C3 (m/z 572.0) product anions were generated by glycosidic cleavage. A C5 [M-2H]2- product ion at m/z 475.1 was generated by the glycosidic cleavage of the hexasaccharide, and a C7 ion (m/z 664.6, charge state of -2) was produced from the octasaccharide. The same fragmentation pattern of deprotonated oligomers was observed for the largest oligosaccharides, from 10- to 16-mers. There has been no previous report of MS/MS spectra for unsulfated chondroitin oligomers of these sizes. Unsulfated saturated chondroitin oligosaccharides with x-mer units and larger than a tetrasaccharide dissociate to almost exclusively form CX-1-type ions. Saturated HA oligomers also afforded the same fragmentation pattern as deprotonated oligomers by ESI-MS and MS/MS analyses. Thus, under the experimental conditions used in the current study, we were unable to distinguish between unsulfated chondroitin and HA.

Cartilage regeneration using a novel gelatin–chondroitin–hyaluronan hybrid scaffold containing bFGF-impregnated microspheres

Cartilage engineered from chondrocytes requires a scaffold to keep the cells in the cartilage defect and to act as a support for inducing hyaline cartilage formation on occasion. In this study, we developed a novel three-dimensional special scaffold in combination with a controlled release of bFGF, which provided structural support and stimulated repair. Gelatin microspheres loaded with bFGF (GM-bFGF) showed a fast release at the initial phase (28.23%) and the ultimate accumulated release was 92.9% by day 14. Three-dimensional gelatin-chondroitin-hyaluronan hybrid scaffolds seeded with cultured autologous chondrocytes were transplanted into the defects in rabbit knees and analyzed histologically at 12 and 24 weeks after the operation. Our findings showed that the defects were filled with smooth, shiny white cartilaginous tissue macroscopically and hyaline-like cartilage histologically 24 weeks postoperatively. The present study implied the great potential of the novel scaffold with GM-bFGF as a new way to promote the retention of chondrocytes and it might serve as a desirable cartilaginous tissue scaffolds to enhance the chondrogenesis.

The biological role of chondroitin sulfate in cancer and chondroitin-based anticancer agents

Chondroitin sulfate proteoglycans (CSPGs) such as versican accumulate in tumor stroma and play a key role in tumor growth and invasion. The high expression of CSPGs in fast growing tissues and cells is correlated with chondroitin sulfate (CS) chains and the sulfation pattern. The negatively charged CS chains interact with a large number of ligands and receptors and activate signalling pathways which stimulate tumor growth. However, the role of chondroitin sulfate in cancer promotion seems to be controversial, as recent studies support the use of modified CS as a potent anticancer agent. In this review, the biological roles of CSPGs in cancer and the anticancer effects of modified CS are presented and discussed.

Evaluation of self-dissolving needles containing low molecular weight heparin (LMWH) in rats

Feasibility study of self-dissolving needles containing polysaccharide was performed. Low molecular weight heparin (LMWH) was used as a representative polysaccharide. Using chondroitin, dextran and dextrin as the base, self-dissolving needles (SDN) were prepared. The obtained SDNs were evaluated in rat absorption experiment, where pharmacological availability (PA) was calculated by comparing the plasma anti-Xa activity vs. time curves between SDNs and i.v. solution. After the insertion of SDNs to rats skin where the doses of LMWH were 25, 50 and 100 IU/kg, plasma samples were collected for 6h and anti-Xa activity was measured as the pharmacological index of LMWH. The anti-Xa level was maintained above 0.2 IU/ml, the therapeutic level, for about 2h at a dose of 100 IU/kg. Almost the same PAs of LMWH were obtained with dextran and dextrin SDNs, 97.7% and 102.3%, though lower PA was obtained with chondroitin SDN, 81.5%. In vitro dissolution experiment showed that LMWH was released from dextran, dextrin and chondroitin SDNs within 10 min. The T(50%)s were 0.84+/-0.06 min for dextran SDN, 1.07+/-0.12 min for chondroitin SDN and 2.11+/-0.31 min for dextrin SDN, respectively. Plasma anti-Xa activity vs. time profiles showed good dose-dependency in the 25-100 IU/kg range and high PAs were obtained, 90.0% for 25 IU/kg, 95.4% for 50 IU/kg and 97.7% for 100 IU/kg from dextran SDNs. Stability experiment was performed with dextran SDNs for 3 months. Above 97% of LMWH were remained in SDNs under three different conditions, -80, 4 and 40 degrees C. These results suggest the usefulness of SDN to polysaccharide drug.

Potential role for heparan sulfate proteoglycans in regulation of transforming growth factor-beta (TGF-beta) by modulating assembly of latent TGF-beta-binding protein-1

Latent transforming growth factor-beta-binding proteins (LTBPs) are extracellular matrix (ECM) glycoproteins that play a major role in storage of latent TGF-beta in the ECM and regulate its availability. We have previously identified fibronectin as a key molecule for incorporation of LTBP1 and TGF-beta into the ECM of osteoblasts and fibroblasts. Here we provide evidence that heparan sulfate proteoglycans may mediate binding between LTBP1 and fibronectin. We have localized critical domains in the N terminus of LTBP1 that are required for co-localization with fibronectin in osteoblast cultures and have identified heparin binding sites in the N terminus of LTBP1 between residues 345 and 487. Solid-phase binding assays suggest that LTBP1 does not bind directly to fibronectin but that the binding is indirect. Heparin coupled to bovine serum albumin (heparin-BSA) was able to mediate binding between fibronectin and LTBP1. Treatment of primary osteoblast cultures with heparin or heparin-BSA but not with chondroitin sulfate impaired LTBP1 deposition onto fibronectin without inhibiting expression of LTBP1. Inhibition of LTBP1 incorporation was accompanied by reduced incorporation of latent TGF-beta into the ECM, with increased amounts of soluble latent TGF-beta. Inhibition of attachment of glycosaminoglycans to the core proteins of proteoglycans by beta-d-xylosides also reduced incorporation of LTBP1 into the ECM. These studies suggest that heparan sulfate proteoglycans may play a critical role in regulating TGF-beta availability by controlling the deposition of LTBP1 into the ECM in association with fibronectin.

Glycosaminoglycans in Hydra magnipapillata (Hydrozoa, Cnidaria): demonstration of chondroitin in the developing nematocyst, the sting organelle, and structural characterization of glycosaminoglycans

The hydrozoan is the simplest organism whose movements are governed by the neuromuscular system, and its de novo morphogenesis can be easily induced by the removal of body parts. These features make the hydrozoan an excellent model for studying the regeneration of tissues in vivo, especially in the nervous system. Although glycosaminoglycans (GAGs) and proteoglycans (PGs) have been implicated in the signaling functions of various growth factors and play critical roles in the development of the central nervous system, the isolation and characterization of GAGs from hydrozoans have never been reported. Here, we characterized GAGs of Hydra magnipapillata. Immunostaining using anti-GAG antibodies showed chondroitin or chondroitin sulfate (CS) in the developing nematocyst, which is a sting organelle specific to cnidarians. The CS-PGs might furnish an environment for assembling nematocyst components, and might themselves be components of nematocysts. Therefore, GAGs were isolated from Hydra and their structural features were examined. A considerable amount of CS, three orders of magnitude less heparan sulfate (HS), but no hyaluronan were found, as in Caenorhabditis elegans. Analysis of the disaccharide composition of HS revealed glucosamine 2-N-sulfation, glucosamine 6-O-sulfation, and uronate 2-O-sulfation. CS contains not only nonsulfated and 4-O-sulfated N-acetylgalactosamine (GalNAc) but also 6-O-sulfated GalNAc. The average molecular size of CS and HS was 110 and 10 kDa, respectively. It has also been established here that CS chains are synthesized on the core protein through the ubiquitous linkage region tetrasaccharide, suggesting that indispensable functions of the linkage region in the synthesis of GAGs have been conserved during evolution.

Enzymatic Copolymerization to Hybrid Glycosaminoglycans: A Novel Strategy for Intramolecular Hybridization of Polysaccharides

Hybrid glycosaminoglycans (GAGs) having an intramolecularly hybridized structure of hyaluronan-chondroitin (3a) and hyaluronan-chondroitin 4-sulfate (3b) have been synthesized via enzymatic copolymerization catalyzed by hyaluronidase (HAase). N-Acetylhyalobiuronate (GlcAbeta(1-->3)GlcNAc)-derived oxazoline (1) was copolymerized with N-acetylchondrosine (GlcAbeta(1-->3)GalNAc)-derived oxazoline (2a) by HAase catalysis at pH 7.5 and 30 degrees C, giving rise to copolymer 3a with Mn 7.4 x 103 in a 50% yield. Also, HAase-catalyzed copolymerization of monomer 1 with N-acetylchondrosine oxazoline having a sulfate group at C4 on GalNAc (2b) was carried out to produce copolymer 3b with Mn 1.4 x 104 in a 60% yield. The copolymer compositions were controllable by varying the comonomer feed ratio. These hybrid GAGs were successfully digested by the catalysis of hyaluronan lyase, clearly exhibiting that the products are not a blend of different homopolymers but an intramolecularly hybridized GAG.

Conjugation of oligosaccharides by reductive amination to amine modified chondroitin oligomer and γ-cyclodextrin

Carbohydrates present on cell surfaces participate in numerous biological recognition phenomena including cell-cell interactions, cancer metastasis and pathogen invasion. Therefore, synthetic carbohydrates have a potential to act as pharmaceutical substances for treatment of various pathological phenomena by inhibiting specifically the interaction between cell surface carbohydrates and their protein receptors (lectins). However, the inherently low affinity of carbohydrate-protein interactions has often been an obstacle for successful generation of carbohydrate based pharmaceuticals. Multivalent glycoconjugates, i.e. structures carrying several copies of the active carbohydrate sequence in a carrier molecule, have been constructed to overcome this problem. Here we present two novel types of multivalent carbohydrate conjugates based on chondroitin oligomer and cyclodextrin carriers. These carriers were modified to express primary amino groups, and oligosaccharides were then bound to carrier molecules by reductive amination. Multivalent conjugates were produced using the human milk type oligosaccharides LNDFH I (Lewis-b hexasaccharide), LNnT, and GlcNAcbeta1-3Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc.

Cartilage regeneration using mesenchymal stem cells and a PLGA-gelatin/chondroitin/hyaluronate hybrid scaffold

The study was to produce a novel hybrid poly-(lactic-co-glycolic acid) (PLGA)-gelatin/chondroitin/hyaluronate (PLGA-GCH) scaffold and evaluate its potentials in cartilage repair. The porous PLGA-GCH scaffold was developed to mimic the natural extra cellular matrix of cartilage. The differentiated mesenchymal stem cells (MSCs) seeded on PLGA-GCH or PLGA scaffold were incubated in vitro and showed that, compared to PLGA scaffold, the PLGA-GCH scaffold significantly augmented the proliferation of MSCs and GAG synthesis. Then autologous differentiated MSCs/PLGA-GCH was implanted to repair full-thickness cartilage defect in rabbit, while MSCs/PLGA for the contra lateral cartilage defect (n=30). Fifteen additional rabbits without treatment for defects were used as control. Histology observation showed the MSCs/PLGA-GCH repair group had better chondrocyte morphology, integration, continuous subchondral bone, and much thicker newly formed cartilage compared with MSCs/PLGA repair group 12 and 24 weeks postoperatively. There was a significant difference in histological grading score between these two groups, which both showed much better repair than control. The present study implied that the hybrid PLGA-GCH scaffold might serve as a new way to keep the differentiation of MSCs for enhancing cartilage repair.

Retention and removal of a new viscous dispersive ophthalmic viscosurgical device during cataract surgery in animal eyes

AIMS

To assess the retention and removal properties of a new viscous dispersive ophthalmic viscosurgical device (OVD), DisCoVisc, in comparison with those of cohesive (Provisc), dispersive (Viscoat), and viscoadaptive (Healon5) OVDs.

METHODS

In 20 porcine eyes, cataract surgery was simulated using one of the four OVDs which were stained with fluorescein for better visualisation. Three parameters were measured. Firstly, the presence/absence of OVDs in the chamber at the completion of phacoemulsification was recorded. Secondly, the time until the OVDs were completely removed from the anterior chamber using the phaco needle was measured. Thirdly, after intraocular lens (IOL) implantation, the time needed to completely remove the OVDs from the chamber with irrigation/aspiration tip was recorded.

RESULTS

At the completion of phacoemulsification, the OVDs retained in 0% (0/5) for Provisc, 80% (4/5) for Healon5, 100% (5/5) for DisCoVisc, and 100% (5/5) for Viscoat. The retention of OVDs during phacoemulsification was greatest with Viscoat followed by, in descending order, DisCoVisc, Healon5, and Provisc. The removal of OVDs after IOL implantation took longest with Viscoat followed by Healon5, DisCoVisc, and Provisc.

CONCLUSION

The viscous dispersive DisCoVisc showed excellent retention during phacoemulsification, while its removal after IOL implantation was very easy. When compared with the viscoadaptive Healon5, DisCoVisc was retained better in the chamber and was easier to remove. These features of DisCoVisc should be highly advantageous when considering covering the entire cataract surgery procedure with a single OVD.

Regulation of the chondroitin/dermatan fine structure by transforming growth factor-beta1 through effects on polymer-modifying enzymes

The chondroitin/dermatan sulfate proteoglycans (CS/DSPGs), biglycan, decorin, and versican play several important roles in extracellular matrix influencing matrix organization, cell proliferation, and recruitment. Moreover, they bind and regulate growth factors in the extracellular matrix. We have previously shown that cultured human lung fibroblasts treated with transforming growth factor-beta (TGF-beta) alone or in combination with epidermal growth factor and platelet-derived growth factor, increase the production of these PGs. In this report, we describe that the structure of their galactosaminoglycan side chains is altered, albeit there is no alteration of polysaccharide length. The findings showed that iduronic acid content is reduced by 50% in decorin and biglycan, whereas 4-O-sulfation is increased 2-fold in versican. To unravel the mechanism behind these changes, the activities of chondroitin C-5 epimerase and of O-sulfotransferases in cellular fractions prepared from fibroblasts were quantitated, and transcript levels of the relevant sulfotransferases were measured by real time polymerase chain reaction (RT-PCR). The C-5 epimerase activity was reduced by 25% in TGF-beta1 treated cells and 50% in fibroblasts treated with the growth factor combination. No change in activity in dermatan 4-O sulfotransferase was observed, and only a minor decrease in dermatan 4-O-sulfotransferase-1 (D4ST-1) mRNA was observed. On the other hand, chondroitin 4-O sulfotransferase activity increased 2-fold upon TGF-beta1 treatment and 3-fold upon treatment with the growth factor combination. This is in agreement with a 2-fold up-regulation of chondroitin-4-O-sulfotransferase 1 (C4ST-1) mRNA, and no changes in chondroitin-4-O-sulfotransferase 2 (C4ST-2) mRNA. Thus, cellular activity and transcript level correlated well with the changes in the structure of the dermatan/chondroitin sulfate chains.

A coarse-grained molecular model for glycosaminoglycans: application to chondroitin, chondroitin sulfate, and hyaluronic acid

A coarse-grained molecular model is presented for the study of the equilibrium conformation and titration behavior of chondroitin (CH), chondroitin sulfate (CS), and hyaluronic acid (HA)-glycosaminoglycans (GAGs) that play a central role in determining the structure and biomechanical properties of the extracellular matrix of articular cartilage. Systematic coarse-graining from an all-atom description of the disaccharide building blocks retains the polyelectrolytes' specific chemical properties while enabling the simulation of high molecular weight chains that are inaccessible to all-atom representations. Results are presented for the characteristic ratio, the ionic strength-dependent persistence length, the pH-dependent expansion factor for the end-to-end distance, and the titration behavior of the GAGs. Although 4-sulfation of the N-acetyl-D-galactosamine residue is found to increase significantly the intrinsic stiffness of CH with respect to 6-sulfation, only small differences in the titration behavior of the two sulfated forms of CH are found. Persistence length expressions are presented for each type of GAG using a macroscopic (wormlike chain-based) and a microscopic (bond vector correlation-based) definition. Model predictions agree quantitatively with experimental conformation and titration measurements, which support use of the model in the investigation of equilibrium solution properties of GAGs.

Glycosylation-related Gene Expression in Prion Diseases

Several lines of evidence indicate that some glycoconjugates are efficient effectors of the cellular prion protein (PrP(C)) conversion into its pathogenic (PrP(Sc)) isoform. To assess how glycoconjugate glycan moieties participate in the biogenesis of PrP(Sc), an exhaustive comparative analysis of the expression of about 200 glycosylation-related genes was performed on prion-infected or not, hypothalamus-derived GT1 cells by hybridization of DNA microarrays, semiquantitative RT-PCR, and biochemical assays. A significant up- (30-fold) and down- (17-fold) regulation of the expression of the ChGn1 and Chst8 genes, respectively, was observed in prion-infected cells. ChGn1 and Chst8 are involved in the initiation of the synthesis of chondroitin sulfate and in the 4-O-sulfation of non-reducing N-acetylgalactosamine residues, respectively. A possible role for a hyposulfated chondroitin in PrP(Sc) accumulation was evidenced at the protein level and by determination of chondroitin and heparan sulfate amounts. Treatment of Sc-GT1 cells with a heparan mimetic (HM2602) induced an important reduction of the amount of PrP(Sc), associated with a total reversion of the transcription pattern of the N-acetylgalactosamine-4-O-sulfotransferase 8. It suggests a link between the genetic control of 4-O-sulfation and PrP(Sc) accumulation.

Nematode Chondroitin Polymerizing Factor Showing Cell-/Organ-specific Expression Is Indispensable for Chondroitin Synthesis and Embryonic Cell Division

Chondroitin polymerization was first demonstrated in vitro when human chondroitin synthase (ChSy) was coexpressed with human chondroitin polymerizing factor (ChPF), which is homologous to ChSy but has little glycosyltransferase activity. To analyze the biological function of chondroitin, the Caenorhabditis elegans ortholog of human ChSy (sqv-5) was recently cloned, and the expression of its product was depleted by RNA-mediated interference (RNAi) and deletion mutagenesis. Blocking of chondroitin synthesis resulted in defects of cytokinesis in early embryogenesis, and eventually, cell division stopped. Here, we cloned the ortholog of human ChPF in C. elegans, PAR2.4. Despite little glycosyltransferase activity of the gene product, chondroitin polymerization was demonstrated as in the case of mammals when PAR2.4 was coexpressed with cChSy in vitro. The worm phenotypes including the reversion of cytokinesis, observed after the depletion of PAR2.4 by RNAi, were very similar to the cChSy (sqv-5)-RNAi phenotypes. Thus, PAR2.4 in addition to cChSy is indispensable for the biosynthesis of chondroitin in C. elegans, and the two cooperate to synthesize chondroitin in vivo. The expression of the PAR2.4 protein was observed in seam cells, which can act as neural stem cells in early embryonic lineages. The expression was also detected in vulva and distal tip cells of the growing gonad arms from L3 through to the young adult stage. These findings are consistent with the notion that chondroitin is involved in the organogenesis of the vulva and maturation of the gonad and also indicative of an involvement in distal tip cell migration and neural development.

Silicone oil content in ophthalmic viscosurgical devices

PURPOSE

To examine the silicone oil content in 5 brands of ophthalmic viscoelastic devices (OVDs).

SETTING

Department of Ophthalmology, Central Hospital of Vasteras, Vasteras, Sweden.

METHODS

Phacoemulsification with intraocular lens (IOL) implantation was performed in 250 patients. Five brands of OVD were used, each one in 50 procedures. From each brand, 5 separate batches, each consisting of 10 syringes, were used. The 250 samples from identical batches were sent for spectrophotometric analysis, and 250 samples were used during surgery.

RESULTS

The silicone oil content varied significantly between the OVD brands.

CONCLUSIONS

Silicone oil is a common contaminant in many OVDs. Ophthalmic viscosurgical devices with relatively low silicone oil content are available.

Separation of capsular polysaccharide K4 and defructosylated K4 by high-performance capillary electrophoresis

A rapid, highly sensitive and reproducible high-performance capillary electrophoresis (HPCE) method (electrokinetic chromatography with sodium dodecyl sulfate) is described for the determination of the polysaccharide from the uropathogenic Escherichia coli K4 bacteria (05:K4:H4) and its defructosylated product. The two polyanions, K4 and defructosylated K4, are separated and readily determined within 30 min on an uncoated fused-silica capillary using normal polarity at 20 kV and detection at 200 nm. A linear relationship was found for the two polysaccharides over a wide range of concentrations, from approximately 30 ng (0.5 microg/microL) to 210 ng (3.5 microg/microL). The described method was used to evaluate the defructosylation process of K4 under drastic acid conditions.

The synthesis of a novel thio-linked disaccharide of chondroitin as a potential inhibitor of polysaccharide lyases

A thio-linked disaccharide based on the structure of the glycosaminoglycan chondroitin was synthesized as a potential inhibitor of chondroitin AC lyase from Flavobacterium heparinum for structural analysis of the active site. Instead it was found to be a slow substrate, thereby demonstrating that lyases, in contrast to glycosidases, can cleave thioglycoside links between sugars.

Structures of Streptococcus pneumoniae Hyaluronate Lyase in Complex with Chondroitin and Chondroitin Sulfate Disaccharides

Streptococcus pneumoniae hyaluronate lyase is a surface enzyme of this Gram-positive bacterium. The enzyme degrades hyaluronan and chondroitin/chondroitin sulfates by cleaving the beta1,4-glycosidic linkage between the glycan units of these polymeric substrates. This degradation helps spreading of this bacterial organism throughout the host tissues and facilitates the disease process caused by pneumococci. The mechanism of this degradative process is based on beta-elimination, is termed proton acceptance and donation, and involves selected residues of a well defined catalytic site of the enzyme. The degradation of hyaluronan alone is thought to proceed through a processive mode of action. The structures of complexes between the enzyme and chondroitin as well as chondroitin sulfate disaccharides allowed for the first detailed insights into these interactions and the mechanism of action on chondroitins. This degradation of chondroitin/chondroitin sulfates is nonprocessive and is selective for the chondroitin sulfates only with certain sulfation patterns. Chondroitin sulfation at the 4-position on the nonreducing site of the linkage to be cleaved or 2-sulfation prevent degradation due to steric clashes with the enzyme. Evolutionary studies suggest that hyaluronate lyases evolved from chondroitin lyases and still retained chondroitin/chondroitin sulfate degradation abilities while being specialized in the degradation of hyaluronan. The more efficient processive degradation mechanism has come to be preferred for the unsulfated substrate hyaluronan.

Tandem mass spectrometric strategies for determination of sulfation positions and uronic acid epimerization in chondroitin sulfate oligosaccharides

Chondroitin sulfate (CS) is a glycosaminoglycan consisting of repeating (HexA-GalNAc sulfate) disaccharides, the functions of which depend on patterns of sulfation and uronic acid epimerization. The correlation of biological activities with structure requires a strategy to determine the sequences of CS oligosaccharides without the need for total isolation. Tandem mass spectrometry has enabled the development of proteomics, based on CID fragmentation of ions produced from complex mixtures of proteolytic peptides, and has the potential for rapid sequencing of CS and other glycosaminoglycan classes. The most challenging aspects of CS sequencing are to distinguish GalNAc residues sulfated at the 4- versus the 6-position and uronic acid epimers. This work describes the utility of (1) reducing terminal derivatives and (2) control of precursor ion charge state for tandem mass spectrometric strategies for determining GalNAc sulfation positional isomers of CS. The capability of tandem MS to differentiate uronic acid epimers is also shown, providing evidence that complete or nearly complete information on CS covalent structure may be obtained using tandem MS.

Milligram-scale preparation and purification of oligosaccharides of defined length possessing the structure of chondroitin from defructosylated capsular polysaccharide K4

Escherichia coli K4 bacterium synthesizes a nonsulfated capsule polysaccharide (K4) composed of a repeating disaccharide subunit of D-glucuronic acid (beta1-->3) and N-acetyl-D-galactosamine (beta1-->4) to which beta-fructofuranose units are linked to C-3 of D-glucuronic acid residues. The K4 polyanion is easily defructosylated under acid conditions with no fragmentation of the polymer to produce a polysaccharide having a repeated disaccharide unit of chondroitin consisting of D-glucuronic acid (beta1-->3) and N-acetyl-D-galactosamine (beta1-->4) (K4d). K4 and K4d were depolymerized by partial digestion with testicular hyaluronidase and separated into uniform-size oligosaccharides from 4-mers to 16-mers by preparative anion-exchange chromatography after removal of the hyaluronidase. The purity and size of each oligosaccharide was confirmed by using anion-exchange HPLC, HPSEC analysis, and FACE. Mg-scale K4d oligosaccharides were obtained from 50 mg K4d starting material. Under the conditions used to degrade the K4 polysaccharide by testicular hyaluronidase, fructose is slowly liberated forming the defructosylated K4. As a consequence, a mixture of uniform- size K4 and K4d oligosaccharide species, from approximately 4- to 20-mers, are generated and size-separated by anion-exchange chromatography. These pure, uniform-size, and large ranges of K4d oligosaccharides having the structure of a chondroitin, -->4)-GlcUA-beta(1-->3)GalNAc-beta(1-->, will be available for investigating important biological functions of this polymer.

Chondroitin sulfate synthase-2. Molecular cloning and characterization of a novel human glycosyltransferase homologous to chondroitin sulfate glucuronyltransferase, which has dual enzymatic activities

Chondroitin sulfate is found in a variety of tissues as proteoglycans and consists of repeating disaccharide units of N-acetylgalactosamine and glucuronic acid residues with sulfate residues at various places. We found a novel human gene (GenBank accession number AB086063) that possesses a sequence homologous with the human chondroitin sulfate glucuronyltransferase gene which we recently cloned and characterized. The full-length open reading frame encodes a typical type II membrane protein comprising 775 amino acids. The protein had a domain containing beta 3-glycosyltransferase motif but lacked a typical beta 4-glycosyltransferase motif, which is the same as chondroitin sulfate glucuronyltransferase, whereas chondroitin synthase had both domains. The putative catalytic domain was expressed in COS-7 cells as a soluble enzyme. Surprisingly, both glucuronyltransferase and N-acetylgalactosaminyltransferase activities were observed when chondroitin, chondroitin sulfate, and their oligosaccharides were used as the acceptor substrates. The reaction products were identified to have the linkage of GlcUA beta 1-3GalNAc and GalNAc beta 1-4GlcUA at the non-reducing terminus of chondroitin for glucuronyltransferase activity and N-acetylgalactosaminyltransferase activity, respectively. Quantitative real time PCR analysis revealed that the transcripts were ubiquitously expressed in various human tissues but highly expressed in the pancreas, ovary, placenta, small intestine, and stomach. These results indicate that this enzyme could synthesize chondroitin sulfate chains as a chondroitin sulfate synthase that has both glucuronyltransferase and N-acetylgalactosaminyltransferase activities. Sequence analysis based on three-dimensional structure revealed the presence of not typical but significant beta 4-glycosyltransferase architecture.

Initiation of the decorin glycosaminoglycan chain in the endoplasmic reticulum-Golgi intermediate compartment

We have transiently expressed decorin with a C-terminal KDEL endoplasmic reticulum retention signal peptide in COS-7 cells to study initiation of galactosaminoglycan synthesis in the endoplasmic reticulum-Golgi intermediate compartment. All decorin-KDEL molecules were substituted with N-linked oligosaccharides sensitive to endoglycosidase H, indicating that the core protein was located proximal to the medial-Golgi. O-Linked glycosylation was only initiated in a minor fraction of the molecules. The O-linked saccharides were characterized by gel filtration after stepwise degradations using chondroitin ABC/AC-I lyases, beta1-3-glycuronidase, beta-galactosidase, and alkaline phosphatase. The major O-linked saccharide was the linkage region pentasaccharide GalNAcbeta1-4GlcUAbeta1-3Galbeta1-3Galbeta1-4Xyl-2-phosphate, demonstrating initiation of chondroitin synthesis in the endoplasmic reticulum-Golgi intermediate compartment. In the presence of brefeldin A, partial elongation of a chondroitin chain took place, indicating retrieval of polymerases but not of sulfotransferases.

Conformational behavior of chondroitin and chondroitin sulfate in relation to their physical properties as inferred by molecular modeling

Chondroitin and chondroitin sulfates belong to the family of glycosaminoglycans. They are most widely distributed in animal tissues, where they are involved in structural functions and in cell-cell communication. Their basic structures consist of a disaccharidic repeating unit of beta-D-glucuronic acid (GlcA) and 2-acetamido-2-deoxy-beta-D-galactose (GalNAc), this latter being sulfated at different positions. Molecular mechanics has been applied to calculate the adiabatic energy maps for each of the constituting disaccharides of chondroitin, chondroitin 4-sulfate, and chondroitin 6-sulfate using the MM3 force field. Based on these maps, higher levels of structural organization have been simulated. On one hand, the disordered state is studied through a Metropolis-based algorithm; the resulting chains present a behavior of semirigid polymers, with an order of stiffness: chondroitin 4-sulfate > chondroitin > chondroitin 6-sulfate. On the other hand, the exploration of the stable ordered forms leads to numerous helical conformations of comparable energies. Several of these conformations correspond to the experimentally observed ones. The ability of coordination with cations has also been explored, resulting in a preferential stereospecificity for calcium ions when compared to sodium ions.

Reconstruction of glycosaminoglycan chains in decorin

The glycosaminoglycan chain of decorin from human spinal ligaments was digested using the hydrolysis of bovine testicular hyaluronidase. As a result, decorin with hexasaccharide, octasaccharide, and decasaccharide including the linkage region, GlcA-Gal-Gal-Xyl, was obtained. The obtained decorin as an acceptor and hyaluronic acid as a donor were incubated with bovine testicular hyaluronidase under the condition of transglycosylation reaction. The transglycosylation reaction product had hexasaccharide to triacontasaccharide. Judging from the analysis of glycosaminoglycan chain in the transglycosylation reaction product, it was confirmed that hyaluronic acid chain as a donor was transferred to the retained glycosaminoglycan chain of decorin as an acceptor. Similarly, it was possible to reconstruct the glycosaminoglycan chain in decorin to chondroitin, chondroitin 4-sulfate or chondroitin 6-sulfate. Therefore, we succeeded in synthesizing an artificial family of decorins.

Identification of the capsular polysaccharides of Type D and F Pasteurella multocida as unmodified heparin and chondroitin, respectively

Pasteurella multocida is a pathogenic Gram-negative bacterial species that infects a wide variety of animals and humans. A notable morphological feature of many isolates is the extracellular capsule. The ability to remove the capsule by treatment with certain glycosidases has been utilized to discern various capsular types called A, D and F. Based on this preliminary evidence, these microbes have capsules made of glycosaminoglycans, linear polysaccharides composed of repeating disaccharide units containing an amino sugar. Glycosaminoglycans are also abundant components of the vertebrate extracellular matrix. It has been shown previously that the major Type A capsular material was hyaluronan (hyaluronic acid). We report that the Type D polymer is an unmodified heparin (N-acetylheparosan) with a -->4)-beta-D-Glcp-UA-(1-->4)-alpha-D-Glcp-NAc-(1--> repeating unit and the Type F polymer is an unmodified chondroitin with a -->4)-beta-D-Glcp-UA-(1-->3)-beta-D-Galp-NAc-(1--> repeating unit. The monosaccharide compositions, disaccharide profiles, and 1H NMR analyses are consistent with these identifications. The molecular size of the Pasteurella polymers is approximately 100-300 kDa as determined by gel electrophoresis and multi-angle laser light scattering; this size is much greater than the 10-30 kDa size of the analogous polymers isolated from animal tissues. The glycosaminoglycan capsular polymers are relatively non-immunogenic virulence factors that enhance microbial pathogenicity.

Molecular cloning and characterization of chondroitin polymerase from Escherichia coli strain K4

Escherichia coli strain K4 produces the K4 antigen, a capsule polysaccharide consisting of a chondroitin backbone (GlcUA beta(1-3)-GalNAc beta(1-4))(n) to which beta-fructose is linked at position C-3 of the GlcUA residue. We molecularly cloned region 2 of the K4 capsular gene cluster essential for biosynthesis of the polysaccharide, and we further identified a gene encoding a bifunctional glycosyltransferase that polymerizes the chondroitin backbone. The enzyme, containing two conserved glycosyltransferase sites, showed 59 and 61% identity at the amino acid level to class 2 hyaluronan synthase and chondroitin synthase from Pasteurella multocida, respectively. The soluble enzyme expressed in a bacterial expression system transferred GalNAc and GlcUA residues alternately, and polymerized the chondroitin chain up to a molecular mass of 20 kDa when chondroitin sulfate hexasaccharide was used as an acceptor. The enzyme exhibited apparent K(m) values for UDP-GlcUA and UDP-GalNAc of 3.44 and 31.6 microm, respectively, and absolutely required acceptors of chondroitin sulfate polymers and oligosaccharides at least longer than a tetrasaccharide. In addition, chondroitin polymers and oligosaccharides and hyaluronan polymers and oligosaccharides served as acceptors for chondroitin polymerization, but dermatan sulfate and heparin did not. These results may lead to elucidation of the mechanism for chondroitin chain synthesis in both microorganisms and mammals.

Structural characterization of chondroitin/dermatan sulfate oligosaccharides from bovine aorta by capillary electrophoresis and electrospray ionization quadrupole time-of-flight tandem mass spectrometry

An analytical approach based on high-performance capillary electrophoresis (CE) in conjunction with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) has been developed for providing the basis to obtain new insights into the domain structure of the glycosaminoglycan (GAG) moiety of proteoglycans. The feasibility and performance of the off-line CE/ESI-QTOF-MS approach in GAG oligosaccharide analysis were assessed by screening a chondroitin/dermatan sulfate (DS) oligosaccharide mixture obtained from bovine aorta by enzymatic depolymerization by chondroitin B lyase. The CS/DS mixture was analyzed by CE using 50 mM ammonium acetate, pH 12.0, dissolved in aqueous methanol (2:3; v/v), as a CE carrier. Structural identification of the GAG components was achieved using off-line CE/nanoESI-QTOF-MS and-MS/MS experiments. ESI-QTOF instrumental parameters were found to play an important role in the MS screening of the CE-separated GAG species. By optimizing the ESI conditions, oligosaccharides differing in chain length and degree of sulfation could be detected. The building block composition, the size of the carbohydrate chain, as well as structural features of the repeating HexA-GalNAc, HexA-GalNAc(S) units, have been determined using MS/MS by applying collision-induced dissociation at low energies. Cleavage of GAG chains by chondroitin B lyase occurs with formation of structural markers useful for identification of IdoA-containing domains.

The nematode Caenorhabditis elegans synthesizes unusual O-linked glycans: identification of glucose-substituted mucin-type O-glycans and short chondroitin-like oligosaccharides

The free-living nematode Caenorhabditis elegans is a relevant model for studies on the role of glycoconjugates during development of multicellular organisms. Several genes coding for glycosyltransferases involved in the synthesis of N- and O-linked glycans have already been isolated, but, apart from repetitive dimers of glycosaminoglycans, no detailed structure of either type of component has been published so far. This study aimed to establish the structures of the major O-glycans synthesized by C. elegans to give an insight into the endogenous glycosyltransferase activities expressed in this organism. By the use of NMR and MS, we have resolved the sequence of seven of these components that present very unusual features. Most of them were characterized by the type-1 core substituted on Gal and/or GalNAc by (beta1-4)Glc and (beta1-6)Glc residues. Another compound exhibited the GalNAc(beta1-4)N-acetylglucosaminitol sequence in the terminal position, to which was attached a tetramer of beta-Gal substituted by both Fuc and 2-O-methyl-fucose residues. Our experimental procedure led also to the isolation of glycosaminoglycan-like components and oligomannosyl-type N-glycans. In particular, the data confirmed that C. elegans synthesizes the ubiquitous linker sequence GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl.

Synthesis of linear-type chondroitin clusters having a C8 spacer between disaccharide moieties and enzymatic transfer of D-glucuronic acid to the artificial glycans

Newly designed linear-type glycoclusters were synthesized which involve a chondroitin repeating disaccharide ligand and a hydrophobic octyl ether spacer. The spacer mimics the corresponding disaccharide unit. Repeating elongation of the pseudo-tetrasaccharide that was derived from the common cluster unit [-->8)-octyl-(1-->3)-beta-D-Gal-NAc-(1-->4)-beta-D-GlcA-(1-->] allowed the syntheses of up to the pseudo-decasaccharide analog of chondroitin. An enzymatic D-GlcA transfer at the non-reducing end of the synthesized artificial glycans by GlcATase II was observed.

Determination and structural characterisation of dermatan sulfate in the presence of other galactosaminoglycans

Chondroitin sulfate and dermatan sulfate are galactosaminoglycans that have similar size and charge density thus making difficult their separation and accurate determination from tissue preparations. A procedure was developed, which was based on the specific action of chondroitinase B, that allowed the determination of dermatan sulfate content in a mixture of chondroitin sulfate/dermatan sulfate, its molecular mass (Mr), and iduronic acid content and distribution throughout the chain. According to this procedure, the galactosaminoglycan sample was treated with chondroitinase B and its profile, upon gel chromatography on Sepharose CL-6B, was compared to that of the initial sample. The differences in uronic acid content of the fractions of the gel chromatographies were plotted and a secondary profile was constructed, which corresponded to the elution profile of intact dermatan sulfate in the sample. From this profile, the size distribution of dermatan sulfate was obtained and its Mr was calculated. In addition, the accurate content of dermatan sulfate in the sample was determined. The digest contained oligosaccharides of variable size that were separated on BioGel P-10. From the separated oligosaccharides the distribution of iduronic acid throughout the dermatan sulfate chains was determined. The procedure was applied to the determination and partial characterisation of dermatan sulfate from sheep nasal cartilage, in which it is reported for the first time that it contains a significant proportion of dermatan sulfate chains of low iduronic acid content.

Dermatan is a better substrate for 4-O-sulfation than chondroitin: implications in the generation of 4-O-sulfated, L-iduronate-rich galactosaminoglycans

The biosynthesis of dermatan sulfate is a complex process that involves, inter alia, formation of L-iduronic acid residues by C5-epimerization of D-glucuronic acid residues already incorporated into the growing polymer. It has been shown previously that this reaction is promoted by the presence of the sulfate donor 3'-phosphoadenosine-5'-phosphosulfate. In the present investigation, the role of sulfation in the biosynthesis of L-iduronic acid-rich galactosaminoglycans was examined more closely by a study of the substrate specificities and kinetic properties of the sulfotransferases involved in dermatan sulfate biosynthesis. Comparison of the acceptor reactivities of oligosaccharides from chondroitin and dermatan, in an in vitro system containing microsomes from cultured human skin fibroblasts and 3'-phosphoadenosine-5'-phosphosulfate, showed that Km values for the dermatan fragments were substantially lower than those for their chondroitin counterparts. Calculation of Vmax values likewise showed that dermatan was the better substrate. Whereas dermatan incorporated [35S]sulfate exclusively at the C4 position of N-acetylgalactosamine residues, approximately equal amounts of radioactivity were found at the C4 and C6 positions in the labelled chondroitin. Under standard assay conditions, the 4-O-sulfation of dermatan proceeded about six times faster than the 4-O-sulfation of chondroitin. On the basis of these results, we propose that L-iduronic acids, formed in the course of the biosynthesis of dermatan sulfates, enhance sulfation of their adjacent N-acetylgalactosamine residues, and will thereby be locked in the L-ido configuration.

Glycosaminoglycan conformation: do aqueous molecular dynamics simulations agree with x-ray fiber diffraction?

Glycosaminoglycan-protein interactions are biologically important and require an appreciation of glycan molecular shape in solution, which is presently unavailable. In previous studies we found strong similarity between aqueous molecular dynamics (MD) simulations and published x-ray diffraction refinements of hyaluronan. We have applied a similar approach here to chondroitin and dermatan, attempting to clarify some of the issues raised by the x-ray diffraction literature relating to chondroitin and dermatan sulfate. We predict that chondroitin has the same beta(1-->4) linkage conformation as hyaluronan, and that their average beta(1-->3) conformations differ. This is explained by changes in hydrogen-bonding across this linkage, resulting from its axial hydroxyl, causing a different sampling of left-handed helices in chondroitin (2.5- to 3.5-fold) as compared with hyaluronan (3.0- to 4.0-fold). Few right-handed helices, which lack intramolecular hydrogen-bonds, were sampled during our MD simulations. Thus, we propose that the 8-fold helix observed in chondroitin-6-sulfate, represented in the literature as an 8(3) helix (right-handed), though it has never been refined, is more likely to be 8(5) (left-handed) helix. Molecular dynamics simulations implied that (4)C(1) and (2)S(O), but not (1)C(4), forms of iduronate could be used in refinements of dermatan x-ray fiber diffraction patterns. Current models of 8-fold dermatan sulfate chains containing (4)C(1) iduronate refine to right-handed helices, which possess no intramolecular hydrogen-bonds. However, MD simulations predict that models containing (2)S(O) iduronate could provide better (8(5) helix) starting structures for refinement. Thus, the 8-fold dermatan sulfate refinement (8(3) helix) could be in error.

Comparison of the effects of viscoelastic agents on clinical properties of the Unfolder lens injection system

PURPOSE

To evaluate the effect of 7 viscoelastic materials on the physical properties of the Unfolder lens injection system.

SETTING

John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA.

METHODS

New sterile SI-40NB intraocular lenses (IOLs) were loaded into the Unfolder (AMO PhacoFlex II SofTip insertion system (Allergan) using 7 viscoelastic materials: sodium hyaluronate 1.0% (Healon, Provisc), sodium hyaluronate 1.4% (Healon GV), sodium hyaluronate 1.6% (Amvisc Plus), hydroxypropyl methylcellulose 2.0% (Occucoat), sodium chondroitin 4.0%--sodium hyaluronate 3.0% (Viscoat), and hyaluronate 3.0% (Vitrax). The IOLs were then injected after 10 or 120 seconds in the chamber (chamber dwell time) and 10, 60, or 180 seconds in the barrel of the Unfolder cartridge (barrel dwell time). Torque values (g/cm) required to extrude the lenses were measured with a torque gauge, and the cartridges and IOLs were inspected for damage.

RESULTS

Longer chamber dwell times resulted in lower torque values to extrude the IOLs (P < .001). Conversely, longer barrel dwell times resulted in higher torque requirements for IOL extrusion (P < .001). Furthermore, rates of adverse events, such as nondelivery, IOL damage, or Unfolder cartridge damage, were higher with shorter chamber dwell times and longer barrel dwell times (P < .001). However, IOL damage was avoided when the manufacturer's recommended chamber and barrel times were used.

CONCLUSION

Increasing chamber dwell time and decreasing barrel dwell time resulted in lower torque values to extrude IOLs from the Unfolder and increased successful use. Moreover, dispersive viscoelastic agents tended to be more forgiving of changing dwell times and therefore had lower torque values and adverse event rates overall.

Dispersive-cohesive viscoelastic soft shell technique

Based on their physical properties, ophthalmic viscoelastic agents can be divided into 2 groups: higher-viscosity cohesive and lower-viscosity dispersive. Higher-viscosity cohesive agents are best at creating and preserving space, while lower-viscosity dispersive agents are retained better in the anterior chamber and are capable of partitioning spaces. The viscoelastic soft shell technique maximizes the advantages and minimizes the disadvantages of both groups by using dispersive and cohesive agents together in sequence based on the desired surgical goal.