High-performance liquid chromatographic analysis of glycosaminoglycan-derived oligosaccharides

A seminal perspective on the role of chondroitin sulfate in biomineralization

Chondroitin sulfate (CS) is an important extracellular matrix component of mineralized tissues. It participates in biomineralization, osteoblast differentiation and promotes bone tissue repair in vitro. However, the mechanism in which CS functions is unclear. Accordingly, an in-depth investigation of how CS participates in mineralization was conducted in the present study. Chondroitin sulfate was found to directly induce intrafibrillar mineralization of the collagen matrix. The mineralization outcome was dependent on whether CS remained free in the extracellular matrix or bound to core proteins; mineralization only occurred when CS existed in a free state. The efficacy of mineralization appeared to increase with ascending CS concentration. This discovery spurred the authors to identify the cause of heterotopic ossification in the Achilles tendon. Chondroitin sulfate appeared to be a therapeutic target for the management of diseases associated with heterotopic calcification. A broader perspective was presented on the applications of CS in tissue engineering.

Development of effective heparin extraction method from pig by-products and analysis of their bioavailability

This study was conducted to develop an effective heparin extraction method by using low-cost and highly effective enzymes from six pig by-products (liver, lung, heart, stomach, small intestine, and large intestine), and analyze their bioavailability. Low-cost and highly effective enzymes (alkaline-AK and papain) and a common enzyme (trypsin) were used for the heparin extraction. The angiotensin I - converting enzyme (ACE) inhibitory activity and the antimicrobial activity of extracted heparin were analyzed to verify their bioavailability. The average amount of heparin extracted per kilogram of pig by-products was 439 mg from the liver, 127 mg from the lung, 398 mg from the heart, 261 mg from the stomach, 197 mg from the small intestine, and 239 mg from the large intestine. Various enzymes were used to extract heparin, and the amount of extracted heparin was similar. Based on 1 g of pig by-product, the enzymes trypsin, papain, and alkaline-AK could extract 1,718 mg, 1,697 mg, and 1,905 mg of heparin, respectively. Heparin extracted from pig by-products showed antihypertensive activity and antimicrobial activity against Staphylococcus aureus at low populations. These results indicated that heparin can be obtained from pig by-products at a low cost.

Determination of glycosaminoglycans in biological matrices using a simple and sensitive reversed-phase HPLC method with fluorescent detection

This paper suggests a sensitive reversed-phase gradient HPLC method combined with fluorescence detection that has been developed, optimized and tested via the quantitative analysis of authentic biological material in an effort to determine and subsequently compare the total content of glycosaminoglycans (GAGs) in various collagen-based biomaterials intended for medical application. The proposed analytical method enabled the identification and separation of the GAGs present from the other components in the samples using commonly-available laboratory equipment; moreover, the very low detection limit of the method permits the determination of GAGs even for very small samples. This study describes the development of the method, including the isolation and processing of the collagen samples prior to HPLC analysis and the optimal parameters applied during the chromatographic analysis. The application of the method in laboratory practice is documented by means of several examples of the determination of GAGs employing both commercial standards and real collagen samples isolated from various animal tissues.

Podocalyxin as a major pluripotent marker and novel keratan sulfate proteoglycan in human embryonic and induced pluripotent stem cells

Podocalyxin (PC) was first identified as a heavily sialylated transmembrane protein of glomerular podocytes. Recent studies suggest that PC is a remarkable glycoconjugate that acts as a universal glyco-carrier. The glycoforms of PC are responsible for multiple functions in normal tissue, human cancer cells, human embryonic stem cells (hESCs), and human induced pluripotent stem cells (hiPSCs). PC is employed as a major pluripotent marker of hESCs and hiPSCs. Among the general antibodies for human PC, TRA-1-60 and TRA-1-81 recognize the keratan sulfate (KS)-related structures. Therefore, It is worthwhile to summarize the outstanding chemical characteristic of PC, including the KS-related structures. Here, we review the glycoforms of PC and discuss the potential of PC as a novel KS proteoglycan in undifferentiated hESCs and hiPSCs.

Podocalyxin as a major pluripotent marker and novel keratan sulfate proteoglycan in human embryonic and induced pluripotent stem cells

Podocalyxin (PC) was first identified as a heavily sialylated transmembrane protein of glomerular podocytes. Recent studies suggest that PC is a remarkable glycoconjugate that acts as a universal glyco-carrier. The glycoforms of PC are responsible for multiple functions in normal tissue, human cancer cells, human embryonic stem cells (hESCs), and human induced pluripotent stem cells (hiPSCs). PC is employed as a major pluripotent marker of hESCs and hiPSCs. Among the general antibodies for human PC, TRA-1-60 and TRA-1-81 recognize the keratan sulfate (KS)-related structures. Therefore, It is worthwhile to summarize the outstanding chemical characteristic of PC, including the KS-related structures. Here, we review the glycoforms of PC and discuss the potential of PC as a novel KS proteoglycan in undifferentiated hESCs and hiPSCs.

Validated capillary electrophoretic assays for disaccharide composition analysis of galactosaminoglycans in biologic samples and drugs/nutraceuticals

Capillary electrophoresis is a separation technique with high resolving power and sensitivity with applications in glycosaminoglycan analysis. In this chapter, we present validated protocols for determining the variously sulfated chondroitin or dermatan sulfate-derived disaccharides. These approaches involve degradation of the polysaccharides with specific chondro/dermato-lyases and electrophoretic analysis with capillary zone electrophoresis in a low pH operating buffer and reversed polarity. This methodology has been applied to drug/nutraceutical formulations or to biologic samples (blood serum, lens capsule) and has been validated. Analysis of biologic tissue samples is often more demanding in terms of detection sensitivity, and thus concentration pretreatment steps and/or a derivatization step with 2-aminoacridone are often advisable.

Chondroitin 6-Sulfate as a Novel Biomarker for Mucopolysaccharidosis IVA and VII

Chondroitin 6-sulfate (C6S), a glycosaminoglycan (GAG), is distributed mainly in the growth plates, aorta, and cornea; however, the physiological function of C6S is not fully understood. One of the limitations is that no rapid, accurate quantitative method to measure C6S has been established. Mucopolysaccharidosis IVA and VII (MPS IVA and VII) are caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase and β-D-glucuronidase, respectively, resulting in accumulation of C6S and other GAG(s). While levels of keratan sulfate (KS), heparan sulfate, and dermatan sulfate in samples from MPS patients are well described, this is the first report of quantitative analysis of C6S levels in samples from MPS IVA and VII patients.We developed a method to digest polymeric C6S and measure resultant disaccharides using liquid chromatography-tandem mass spectrometry (LC-MS/MS). C6S levels were measured in the blood from control subjects and patients with MPS IVA and VII aged from 0 to 58 years of age. We also assayed KS levels in the same samples for comparison with C6S.Levels of C6S in the blood decreased with age and were significantly elevated in patients with MPS IVA and VII, compared with age-matched controls. Levels of KS in patients with MPS IVA were also higher than those in age-matched controls, although differences were less pronounced than with C6S. Combining KS and C6S data, discriminated patients with MPS IVA from age-matched control subjects were better than either C6S or KS levels alone.In conclusion, this first report showing that blood levels of C6S are quantitatively evaluated in patients with MPS IVA and VII indicates that C6S could be a useful biomarker for these metabolic disorders.

Plasmatic kinetics of dermatan sulfate during enzyme replacement therapy with iduronate-2-sulfatase in a mucopolysaccharidosis II patient

Enzyme replacement therapy (ERT) is the worldwide standard of care for a number of mucopolysaccharidosis (MPS) diseases. We report a kinetic study of plasmatic dermatan sulfate (DS) in a 3-year-old subject affected by a severe form of MPS II during the first 10 months of ERT with Idursulfase. A strong increase in the DS plasmatic concentration was measured immediately after the first enzyme infusion, with a maximum after 3 h, followed by a continuous decrease in the 8-15 days following the beginning of treatment. After this, a constant plasmatic content of DS concentration was observed. Overall, during the 10-month treatment period, ERT reduced the plasmatic concentration of DS up to ~80-85 %, but it was unable to totally remove it from the blood. We can suppose that immediately after the first enzyme administrations, a large amount of abnormal DS is removed from tissues reaching the blood compartment and eliminated via the urine, and thereafter only minimal changes are observed. The persistency of the residual amounts of DS with the actually recommended dosage in our Patient may suggest the opportunity to promote further studies with increased enzyme dosages to completely remove the accumulation of lysosomal DS.

Recent advances in cellular glycomic analyses

A large variety of glycans is intricately located on the cell surface, and the overall profile (the glycome, given the entire repertoire of glycoconjugate-associated sugars in cells and tissues) is believed to be crucial for the diverse roles of glycans, which are mediated by specific interactions that control cell-cell adhesion, immune response, microbial pathogenesis and other cellular events. The glycomic profile also reflects cellular alterations, such as development, differentiation and cancerous change. A glycoconjugate-based approach would therefore be expected to streamline discovery of novel cellular biomarkers. Development of such an approach has proven challenging, due to the technical difficulties associated with the analysis of various types of cellular glycomes; however, recent progress in the development of analytical methodologies and strategies has begun to clarify the cellular glycomics of various classes of glycoconjugates. This review focuses on recent advances in the technical aspects of cellular glycomic analyses of major classes of glycoconjugates, including N- and O-linked glycans, derived from glycoproteins, proteoglycans and glycosphingolipids. Articles that unveil the glycomics of various biologically important cells, including embryonic and somatic stem cells, induced pluripotent stem (iPS) cells and cancer cells, are discussed.

Glycosaminoglycans: oligosaccharide analysis by liquid chromatography, capillary electrophoresis, and specific labeling

Glycosaminoglycans (GAGs) are a class of biopolymers that include chondrotin sulfate, dermatan sulfate, keratan sulfate, hyaluronic acid, heparin, and heparan sulfate. The GAGs are linear polysaccharides that are microheterogeneous in composition and polydisperse in size. Because they have the most complex structures, this article is aimed at describing a step-by-step procedure for processing and analyzing heparin and heparan sulfate-derived oligosaccharides, although the basic protocols and procedures apply equally well to other members of the GAG family. The methods described in this manuscript include the preparation of oligosaccharides through enzymatic depolymerization, size fractionation by preparative scale size-exclusion chromatography (SEC), and disaccharide isomer analysis by reverse-phase ion-pair high-performance liquid chromatography (RPIP-HPLC) and capillary electrophoresis (CE).

Understanding the effect of the counterion on the reverse-phase ion-pair high-performance liquid chromatography (RPIP-HPLC) resolution of heparin-related saccharide anomers

Reverse-phase ion-pair high-performance liquid chromatography (RPIP-HPLC) is an increasingly popular chromatographic technique for the separation of charged compounds, including oligosaccharides derived from the glycosaminoglycans (GAGs) heparin and heparan sulfate (HS). This family of heparin disaccharides has been shown to be useful compounds to probe the details of the RPIP-HPLC separation mechanism, the aspects of which are still being debated. In this manuscript, the effects of ion-pairing reagent (IPR) concentration, counterion, and mobile phase pH on the quality of the RPIP-UPLC separation were examined with particular emphasis on how these factors impact the separation of the disaccharide anomers. These results highlight the role of the IPR counterion and demonstrate that the resolution of the disaccharide anomers can be minimized by conducting the separation at low pH, simplifying chromatographic analysis and improving resolution. The results presented herein can also provide insights into strategies for developing more sensitive and efficient reverse-phase separations for other charged analytes including larger GAG oligosaccharides.

Heparin characterization: challenges and solutions

Although heparin is an important and widely prescribed pharmaceutical anticoagulant, its high degree of sequence microheterogeneity and size polydispersity make molecular-level characterization challenging. Unlike nucleic acids and proteins that are biosynthesized through template-driven assembly processes, heparin and the related glycosaminoglycan heparan sulfate are actively remodeled during biosynthesis through a series of enzymatic reactions that lead to variable levels of O- and N-sulfonation and uronic acid epimers. As summarized in this review, heparin sequence information is determined through a bottom-up approach that relies on depolymerization reactions, size- and charge-based separations, and sensitive mass spectrometric and nuclear magnetic resonance experiments to determine the structural identity of component oligosaccharides. The structure-elucidation process, along with its challenges and opportunities for future analytical improvements, is reviewed and illustrated for a heparin-derived hexasaccharide.

High-performance liquid chromatography-mass spectrometry for mapping and sequencing glycosaminoglycan-derived oligosaccharides

Glycosaminoglycans (GAGs) have proven to be very difficult to analyze and characterize because of their high negative charge density, polydispersity and sequence heterogeneity. As the specificity of the interactions between GAGs and proteins results from the structure of these polysaccharides, an understanding of GAG structure is essential for developing a structure-activity relationship. Electrospray ionization (ESI) mass spectrometry (MS) is particularly promising for the analysis of oligosaccharides chemically or enzymatically generated by GAGs because of its relatively soft ionization capacity. Furthermore, on-line high-performance liquid chromatography (HPLC)-MS greatly enhances the characterization of complex mixtures of GAG-derived oligosaccharides, providing important structural information and affording their disaccharide composition. A detailed protocol for producing oligosaccharides from various GAGs, using controlled, specific enzymatic or chemical depolymerization, is presented, together with their HPLC separation, using volatile reversed-phase ion-pairing reagents and on-line ESI-MS structural identification. This analysis provides an oligosaccharide map together with sequence information from a reading frame beginning at the nonreducing end of the GAG chains. The preparation of oligosaccharides can be carried out in 10 h, with subsequent HPLC analysis in 1-2 h and HPLC-MS analysis taking another 2 h.

NMR methods to monitor the enzymatic depolymerization of heparin

Heparin and the related glycosaminoglycan, heparan sulfate, are polydisperse linear polysaccharides that mediate numerous biological processes due to their interaction with proteins. Because of the structural complexity and heterogeneity of heparin and heparan sulfate, digestion to produce smaller oligosaccharides is commonly performed prior to separation and analysis. Current techniques used to monitor the extent of heparin depolymerization include UV absorption to follow product formation and size exclusion or strong anion exchange chromatography to monitor the size distribution of the components in the digest solution. In this study, we used ¹H nuclear magnetic resonance (NMR) survey spectra and NMR diffusion experiments in conjunction with UV absorption measurements to monitor heparin depolymerization using the enzyme heparinase I. Diffusion NMR does not require the physical separation of the components in the reaction mixture and instead can be used to monitor the reaction solution directly in the NMR tube. Using diffusion NMR, the enzymatic reaction can be stopped at the desired time point, maximizing the abundance of larger oligosaccharides for protein-binding studies or completion of the reaction if the goal of the study is exhaustive digestion for characterization of the disaccharide composition. In this study, porcine intestinal mucosa heparin was depolymerized using the enzyme heparinase I. The unsaturated bond formed by enzymatic cleavage serves as a UV chromophore that can be used to monitor the progress of the depolymerization and for the detection and quantification of oligosaccharides in subsequent separations. The double bond also introduces a unique multiplet with peaks at 5.973, 5.981, 5.990, and 5.998 ppm in the ¹H-NMR spectrum downfield of the anomeric region. This multiplet is produced by the proton of the C-4 double bond of the non-reducing end uronic acid at the cleavage site. Changes in this resonance were used to monitor the progression of the enzymatic digestion and compared to the profile obtained from UV absorbance measurements. In addition, in situ NMR diffusion measurements were explored for their ability to profile the different-sized components generated over the course of the digestion.

Figure

Analysis of oligosaccharides derived from heparin by ion-pair reversed-phase chromatography/mass spectrometry

Current chromatographic and mass spectrometric techniques have limitations for analyzing heparin and heparin oligomers due to their high polarity, structural diversity, and sulfate lability. A rapid method for the analysis of heparin oligosaccharides was developed using ion-pair reversed-phase ultraperformance liquid chromatography coupled with electrospray quadruple time-of-flight mass spectrometry (IPRP-UPLC ESI Q-TOF MS). The method utilizes an optimized buffer system containing a linear pentylamine and a unique additive, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), to achieve highly efficient separation together with enhanced mass response of heparin oligosaccharides. Analyses of a heparin oligosaccharide test mixture, dp6 through dp22, reveal that the chromatographic conditions enable baseline resolution of isomeric heparin oligosaccharides (dp6) and produce intact molecular ions with no sulfate losses during mass spectrometric analysis. In addition, the described conditions are amenable to the detection of heparin oligosaccharides in positive ion mode, yield stronger positive ion signals for corresponding oligosaccharides compared to the negative ion mode, and allow identification of structural isomers by an MS/MS approach. Because sensitive detection of oligosaccharides is also achieved with ultraviolet (UV) detection, the method utilizes a dual detection scheme (UV and MS in series) along with IPRP UPLC to simultaneously obtain quantification (UV) and characterization (MS) data for heparin oligosaccharides. The broad potential of this new method is further demonstrated for the analysis of a low-molecular-weight heparin (LMWH) preparation from porcine heparin. This approach will be of particular utility for profiling the molecular entities of heparin materials, as well as for structural variability comparison for samples from various sources.

Improved workup for glycosaminoglycan disaccharide analysis using CE with LIF detection

This work describes improved workup and instrumental conditions to enable robust, sensitive glycosaminoglycan (GAG) disaccharide analysis from complex biological samples. In the process of applying CE with LIF to GAG disaccharide analysis in biological samples, we have made improvements to existing methods. These include (i) optimization of reductive amination conditions, (ii) improvement in sensitivity through the use of a cellulose cleanup procedure for the derivatization, and (iii) optimization of separation conditions for robustness and reproducibility. The improved method enables analysis of disaccharide quantities as low as 1 pmol prior to derivatization. Biological GAG samples were exhaustively digested using lyase enzymes, the disaccharide products and standards were derivatized with the fluorophore 2-aminoacridone and subjected to reversed polarity CE-LIF detection. These conditions resolved all known chondroitin sulfate (CS) disaccharides or 11 of 12 standard heparin/heparan sulfate disaccharides, using 50 mM phosphate buffer, pH 3.5, and reversed polarity at 30 kV with 0.3 psi pressure. Relative standard deviation in migration times of CS ranged from 0.1 to 2.0% over 60 days, and the relative standard deviations of peak areas were less than 3.2%, suggesting that the method is reproducible and precise. The CS disaccharide compositions are similar to those obtained by our group using tandem MS. The reversed polarity CE-LIF disaccharide analysis protocol yields baseline resolution and quantification of heparin/heparan sulfate and CS/dermatan sulfate disaccharides from both standard preparations and biologically relevant proteoglycan samples. The improved CE-LIF method enables disaccharide quantification of biologically relevant proteoglycans from small samples of intact tissue.

Capillary electrophoresis of complex natural polysaccharides

Complex natural polysaccharides, glycosaminoglycans (GAGs), are a class of ubiquitous macromolecules that exhibit a wide range of biological functions and participate and regulate multiple cellular events and (patho)physiological processes. They are generally present either as free chains (hyaluronic acid and bacterial acidic polysaccharides) or as side chains of proteoglycans (PGs; chondroitin/dermatan sulfate, heparin/heparan sulfate, and keratan sulfate) and are most often found in cell membranes and in the extracellular matrix. The recent emergence of modern analytical tools for their study has produced a virtual explosion in the field of glycomics. CE, due to its high resolving power and sensitivity, has been useful in the analysis of intact GAGs and GAG-derived oligosaccharides and disaccharides affording concentration and structural characterization data essential for understanding the biological functions of GAGs. In this review, novel off-line and on-line CE-MS and MS/MS methods for screening of GAG-derived oligosaccharides and disaccharides will be discussed.

Ultraperformance ion-pair liquid chromatography coupled to electrospray time-of-flight mass spectrometry for compositional profiling and quantification of heparin and heparan sulfate

Heparin and heparan sulfate (HS) are important pharmaceutical targets because they bind a large number of proteins, including growth factors and cytokines, mediating many biological processes. Because of their biological significance and complexity, there is a need for development of rapid and sensitive analytical techniques for the characterization and compositional analysis of heparin and HS at the disaccharide level, as well as for the structure elucidation of larger glycosaminoglycan (GAG) sequences important for protein binding. In this work, we present a rapid method for analysis of disaccharide composition using reversed-phase ion-pairing ultraperformance liquid chromatography coupled with electrospray time-of-flight mass spectrometry ((RPIP)-UPLC-MS). Heparin disaccharide standards were eluted in less than 5 min. The method was used to determine the constituents of GAGs from unfractionated heparin/HS from various bovine and porcine tissues, and the results were compared with literature values.

Analytical aspects of pharmaceutical grade chondroitin sulfates

Chondroitin sulfate is a very heterogeneous polysaccharide in terms of relative molecular mass, charge density, chemical properties, biological and pharmacological activities. It is actually recommended by EULAR as a symptomatic slow acting drug (SYSADOA) in Europe in the treatment of knee osteoarthritis based on meta-analysis of numerous clinical studies. Chondroitin sulfate is also utilized as a nutraceutical in dietary supplements mainly in the United States. On the other hand, chondroitin sulfate is derived from animal sources by extraction and purification processes. As a consequence, source material, manufacturing processes, the presence of contaminants, and many other factors contribute to the overall biological and pharmacological actions of these agents. The aim of this review is to evaluate new possible more specific analytical approaches to the determination of the origin and purity of chondroitin sulfate preparations for pharmaceutical application and in nutraceuticals, such as the evaluation of the molecular mass values, the constituent disaccharides, and the specific and sensitive agarose-gel electrophoresis technique. Furthermore, a critical evaluation is presented, together with a discussion of the limits of these analytical approaches. Finally, the necessity for reference standards having high specificity, purity and well-known physico-chemical properties useful for accurate and reproducible quantitative analyses will be discussed.

Chondroitin C lyase [4.2.2.] is unable to cleave fructosylated sequences inside the partially fructosylated Escherichia coli K4 polymer

Chondroitin C lyase was demonstrated to be unable to act on fructosylated sequences inside a partially fructosylated polysaccharide having the chondroitin backbone structure, the Escherichia coli K4 polymer, using different analytical approaches. Chondroitin C lyase produced various unsaturated oligosaccharides by acting on an approximately 27%-fructosylated K4 polymer. The online HPLC-ESI-MS approach showed the disaccharide nature of the main species produced by chondroitinase C as DeltaHexA-GalNAc. Furthermore, the non-digested sequences inside the K4 polymer were demonstrated to be oligosaccharides bearing a fructose for each glucuronic acid unit. In fact, unsaturated fully fructosylated oligomers, from tetrasaccharide to decasaccharide (DeltaHexA(Fru)-GalNAc-[GlcA(Fru)-GalNAc](n) with n between 1 and 4), at decreasing percentages, were produced by the enzyme. These results clearly indicate that chondroitinase C cleaved the innermost glucuronic acid-N-acetylgalactosamine linkage without affecting the 1,4 glycosidic linkage between fructosylated glucuronic acid and N-acetylgalactosamine residues, confirming that the 3-O-fructosylation of the GlcA residue renders the polysaccharide resistant to the enzyme action. This novel specific activity of chondroitinase C was also useful for the production of discrete microgram amounts of fully fructosylated oligomers, from 4- to 10-mers, from E. coli K4 for possible further studies and applications.

On-line HPLC/ESI-MS separation and characterization of hyaluronan oligosaccharides from 2-mers to 40-mers

A new method for the separation and identification of oligosaccharides obtained by enzymatic digestion of hyaluronic acid (HA) with hyaluronidase (EC 3.2.1.35) using on-line high-performance liquid chromatography/electrospray mass spectrometry (HPLC/ESI-MS) is presented. Reversed-phase ion pairing-HPLC, based on tributylamine salts and a volatile mobile phase, provided excellent chromatographic resolution and separation was achieved for HA oligosaccharides containing 2-40 monomers (from 2- to 40-mers). Using the on-line ion trap mass analyzer, complete identification and structural information for each HA oligomer species was obtained. In particular, a series of negatively charged species of different m/z ratios are seen for each oligosaccharide. Smaller HA species, from 2- to 4-mers, exhibit mainly [M-H](-1) anions, whereas the 6-10-mers exist predominantly as the charge state of -2. The HA oligomers from 12- to 18-mers are mainly represented by [M-3H](-3) anions while species from 20- to 28/30-mers are characterized by a charge state of -4. HA oligosaccharides from 32- to 40-mers exist as [M-5H](-5) anions. Furthermore, for smaller HA species, from 4/6- to 18/20-mers, ESI-MS revealed, generally in low relative abundance, anions related to the loss of one/two monosaccharide unit(s) from the oligomers, and no odd-numbered anions were produced for HA species greater than 20-mers.

A novel LIF-CE method for the separation of hyaluronan- and chondroitin sulfate-derived disaccharides: Application to structural and quantitative analyses of human plasma low- and high-charged chondroitin sulfate isomers

The report describes a rapid and simple CE method using LIF detection for the analysis of unsaturated disaccharides obtained from enzymatic depolymerization of plasma chondroitin sulfate (CS) isomers. The disaccharide reducing groups were labeled with 2-aminoacridone (AMAC). The fluorotagged products can be separated by reversed-polarity CE using a sodium acetate buffer, pH 3.8, in the presence of 0.05% methylcellulose. The choice of the appropriate electrophoretic conditions was performed after a deep analysis of the most important parameters affecting analyte separation. In particular, the effect of both run buffer concentration and pH on resolution, efficiency, migration times, and peak area was evaluated. The selected electrophoretic conditions allowed us to separate the CS isomers-derived Delta-disaccharides in less than 12 min, also resolving the nonsulfated disaccharides released from CS isomers from those released from hyaluronan (HA). Moreover, these conditions gave a good reproducibility of both the migration times (CV%, 0.25) and the peak areas (CV%, 1.4). Intra- and interassay CV were 5.37 and 7.23%, respectively, and analytical recovery was about 86%. The applicability of the above method to the quantitative and structural disaccharide analyses of plasma CS isomers was investigated. Data obtained from 44 healthy human subjects were compared with those obtained by a fluorophore-assisted carbohydrate electrophoresis (FACE) reference assay, by using the Passing and Bablok regression and Bland-Altman tests. The developed method could represent a good tool for an ultrasensitive analysis of CS isomers in biological samples from different sources, particularly when samples are available in very low amounts.

Enhanced electrophoretic resolution of monosulfate glycosaminoglycan disaccharide isomers on poly(methyl methacrylate) chips

To improve the separation of monosulfate glycosaminoglycan disaccharide isomers by microchip electrophoresis, we found that addition of 1,4-dioxane (DO) dramatically improved analyte resolution, probably due to solvation effects. Methylcellulose (MC) was tested for the ability to suppress EOF and analyte adsorption to the chip. To improve analyte resolution, buffer pH, beta-CD, and DO were systematically investigated. Fast separation was achieved by increasing the electric field strength, and field-amplified sample stacking occurred with increasing buffer concentrations. Therefore, based on our findings, we describe an efficient method for the separation of monosulfate and trisulfate unsaturated disaccharides (DeltaDi-UA2S, DeltaDi-4S, DeltaDi-6S, and DeltaDi-triS) derivatized with 2-aminoacridone hydrochloride. A mixture of monosulfate disaccharide isomers (DeltaDi-UA2S, DeltaDi-4S, and DeltaDi-6S) was baseline-separated within 75 s on a poly(methyl methacrylate) chip using a mixed buffer (DO/running buffer 57:43 v:v), 0.5% MC, pH 6.81, with an E(sep) of 558 V/cm. The theoretical plate was in the range of 5 x 10(5) to 1 x 10(6) m-1.

Improved matrix-assisted laser desorption/ionization mass spectrometric detection of glycosaminoglycan disaccharides as cesium salts

Ultraviolet matrix-assisted laser desorption/ionization mass spectrometric (UV-MALDI-MS) analysis of highly acidic, thermally labile species such as glycosaminoglycan-derived oligosaccharides is complicated by their poor ionization efficiency and tendency to fragment through the loss of sulfo groups. We have utilized a systematic approach to evaluate the effect of alkali metal counterions on the degree of fragmentation through SO3 loss from a highly sulfated model compound, sucrose octasulfate (SOS). The lithium, sodium, potassium, rubidium, and cesium salts of SOS were analyzed by UV-MALDI-time-of-flight (TOF)MS using an ionic liquid matrix, bis-1,1,3,3-tetramethylguanidinium alpha-cyano-4-hydroxycinnamate. The positive-ion and negative-ion MALDI mass spectra of five alkali metal salts of SOS were compared in terms of the degree of analyte fragmentation through the SO3 loss and the absolute intensity of a molecular ion signal. Experimental results demonstrate that the lithium, sodium, and potassium salts of SOS undergo some degree of fragmentation through the loss of SO3, whereas the fragmentation through the loss of SO3 in the rubidium and cesium salts of SOS is suppressed. A high detection sensitivity associated with the stability of sulfate half-esters was achieved for the cesium salt of SOS using positive-ion detection. Finally, the cesium salt of chondroitin sulfate A disaccharide was successfully analyzed using UV-MALDI-TOFMS.

Isolation and characterization of heparan sulfate from various murine tissues

Heparan sulfate (HS), is a proteoglycan (PG) found both in the extracellular matrix and on cell surface. It may represent one of the most biologically important glycoconjugates, playing an essential role in a variety of different events at molecular level. The publication of the mouse genome, and the intensive investigations aimed at understanding the proteome it encodes, has motivated us to initiate studies in mouse glycomics focused on HS. The current study is aimed at determining the quantitative and qualitative organ distribution of HS in mice. HS from brain, eyes, heart, lung, liver, kidney, spleen, intestine and skin was purified from 6-8 week old male and female mice. The recovered yield of HS from these organs is compared with the recovered whole body yield of HS. Structural characterization of the resulting HS relied on disaccharide analysis and (1)H-NMR spectroscopy. Different organs revealed a characteristic HS structure. These data begin to provide a structural understanding of the role of HS in cell-cell interactions, cell signaling and sub-cellular protein trafficking as well as a fundamental understanding of certain aspects of protein-carbohydrate interactions.

GLYCOMICS APPROACH TO STRUCTURE-FUNCTION RELATIONSHIPS OF GLYCOSAMINOGLYCANS

Extracellular modulation of phenotype is an emerging paradigm in this current postgenomics age of molecular and cell biology. Glycosaminoglycans (GAGs) are primary components of the cell surface and the cell-extracellular matrix (ECM) interface. Advances in the technology to analyze GAGs and in whole-organism genetics have led to a dramatic increase in the known important biological role of these complex polysaccharides. Owing to their ubiquitous distribution at the cell-ECM interface, GAGs interact with numerous proteins and modulate their activity, thus impinging on fundamental biological processes such as cell growth and development. Many recent reviews have captured important aspects of GAG structure and biosynthesis, GAG-protein interactions, and GAG biology. GAG research is currently at a stage where there is a need for an integrated systems or glycomics approach, which involves an integration of all of the above concepts to define their structure-function relationships. Focusing on heparin/heparan (HSGAGs) and chondroitin/dermatan sulfate (CSGAGs), this review highlights the important aspects of GAGs and summarizes these aspects in the context of taking a glycomics approach that integrates the different technologies to define structure-function relationships of GAGs.

Less Use of NSAIDs in Long-Term than in Recent Chondroitin Sulphate Users in Osteoarthritis: a Pharmacy-based Observational Study in France

In clinical trials, long-term use of a specific chondroitin sulphate, Chondrosult 400 (CS400) has demonstrated symptomatic efficacy in osteoarthritis comparable to that of nonsteroidal anti-inflammatory drugs (NSAIDs) with significantly fewer side-effects. CS400 could therefore reduce the use of and risks associated with NSAIDs. A cross-sectional observational study was therefore devised in 199 randomly selected pharmacies in France to verify the concomitant use of analgesic and NSAIDs medication in patients prescribed CS400. Consecutive patients filling a prescription for CS400 were prospectively recruited and classified into recent users (3 months or less of continuous use) and long-term users (more than 3 months of continuous use) of CS400. The main outcome measure was current and long-term use of analgesics and NSAIDs. The 844 participating patients included 623 (73.8%) women and 221 (26.2%) men. Mean age was 65.9 years. Ninety eight (11.6%) patients did not use any analgesic or NSAIDs for osteoarthritis: 746 (88.4%) reported the use of at least one of these drugs. Compared to recent users, long-term users of CS400 had a significantly lower current (44.4 versus 52.5%, p < 0.05) and long-term use of NSAIDs (11.8% versus 18.5%, p < 0.05), and of analgesics (70.3 versus 79.3%, p < 0.01).

Mutational and functional analyses of xylosyltransferases and their implication in osteoarthritis

OBJECTIVE

The hallmark in osteoarthritis (OA) is the loss of proteoglycans (PGs) in articular cartilage (AC). Xylosyltransferase I (XT-I) catalyzes the transfer of xylose to serine residues in the core protein and initiates the biosynthesis of PGs in AC. The XYLT-II gene encodes a highly homologous protein but its biological function is not yet known. Here we investigate for the first time genetic variations in the XYLT-genes and serum XT-I activities and their implication in OA.

METHODS

Denaturing high-performance liquid chromatography (DHPLC) was used for the screening of the XYLT-genes in 49 OA patients. For a detailed characterization of XT-I amino acid exchanges we performed recombinant expression of XT-I mutants in insect cells. Furthermore, the XT activity was measured in the patients' serum.

RESULTS

The variation c.1569C>T (XYLT-II) occurs with a significantly higher frequency in younger OA patients in comparison with the older ones (P<0.001) and the controls (P<0.02). Furthermore, significantly higher serum XT activities were found in patients with a long disease duration of OA (P<0.04). The recombinant XT-I mutants p.P385L and p.I552S had reduced enzymatic activity (85% and 74%) compared with the wildtype (wt).

CONCLUSIONS

Our findings indicate a correlation of the c.1569 T-allele in XYLT-II with an earlier manifestation of OA and that the serum XT activity is a potential biochemical marker for staging and monitoring the progression of AC damage in OA. Comparison of XT-I activity in mutant enzymes in vivo and in vitro revealed that heterozygous mutations are not involved in OA.

Electrophoretic approaches to the analysis of complex polysaccharides

Complex polysaccharides, glycosaminoglycans (GAGs), are a class of ubiquitous macromolecules exhibiting a wide range of biological functions. They are widely distributed as sidechains of proteoglycans (PGs) in the extracellular matrix and at cellular level. The recent emergence of enhanced analytical tools for their study has triggered a virtual explosion in the field of glycomics. Analytical electrophoretic separation techniques, including agarose-gel, capillary electrophoresis (HPCE) and fluorophore-assisted carbohydrate electrophoresis (FACE), of GAGs and GAG-derived oligosaccharides have been employed for the structural analysis and quantification of hyaluronic acid (HA), chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS), heparan sulfate (HS), heparin (Hep) and acidic bacterial polysaccharides. Furthermore, recent developments in the electrophoretic separation and detection of unsaturated disaccharides and oligosaccharides derived from GAGs by enzymatic or chemical degradation have made it possible to examine alterations of GAGs with respect to their amounts and fine structural features in various pathological conditions, thus becoming applicable for diagnosis. In this paper, the electromigration procedures developed to analyze and characterize complex polysaccharides are reviewed. Moreover, a critical evaluation of the biological relevance of the results obtained by these electrophoresis approaches is presented.