A new electrophoretic method for the complete separation of all known animal glycosaminoglycans in a monodimensional run

Detection of Glycosaminoglycans in Biological Specimens

Proteoglycans (PGs) are macromolecules formed by a protein backbone to which one or more glycosaminoglycan (GAG) side chains are covalently attached. Most PGs are present in connective tissues, cell surfaces, and intracellular compartments. The major biological function of PGs derives from the GAG component of the molecule, which is involved in cell growth and proliferation, embryogenesis, maintenance of tissue hydration, and interactions of the cells via receptors. PGs are categorized into four groups based on their cellular and subcellular localization, including cell surfaces and extracellular, intracellular, and pericellular locations. GAGs are a crucial component of PGs involved in various physiological and pathological processes. GAGs also serve as biomarkers of metabolic diseases such as mucopolysaccharidoses and mucolipidoses. Detection of specific GAGs in various biological fluids helps manage various genetic metabolic disorders before it causes irreversible damage to the patient (Amendum et al., Diagnostics (Basel) 11(9):1563, 2021). There are several methods for detecting GAGs; this chapter focuses on measuring GAGs using enzyme-linked immunosorbent assay, liquid chromatographic tandem mass spectrometry, and automated high-throughput mass spectrometry.

Advances in glycosaminoglycan detection

BACKGROUND

Glycosaminoglycans (GAGs) are negatively charged long linear (highly sulfated) polysaccharides consisting of repeating disaccharide units that are expressed on the surfaces of all nucleated cells. The expression of GAGs is required for embryogenesis, regulation of cell growth and proliferation, maintenance of tissue hydration, and interactions of the cells via receptors. Mucopolysaccharidoses (MPS) are caused by deficiency of specific lysosomal enzymes that result in the accumulation of GAGs in multiple tissues leading to organ dysfunction. Therefore, GAGs are important biomarkers for MPS. Without any treatment, patients with severe forms of MPS die within the first two decades of life.

SCOPE OF REVIEW

Accurate measurement of GAGs is important to understand the diagnosis and pathogenesis of MPS and to monitor therapeutic efficacy before, during, and after treatment of the disease. This review covers various qualitative and quantitative methods for measurement of GAGs, including dye specific, thin layer chromatography (TLC), capillary electrophoresis, high-performance liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography, ELISA, and automated high-throughput mass spectrometry. Major conclusion: There are several methods for GAG detection however, specific GAG detection in the various biological systems requires rapid, sensitive, specific, and cost-effective methods such as LC-MS/MS.

GENERAL SIGNIFICANCE

This review will describe different methods for GAG detection and analysis, including their advantages and limitation.

Glycosaminoglycan functionalization of electrospun scaffolds enhances Schwann cell activity

Nerve fibers of the peripheral nervous system (PNS) have a remarkable ability to regenerate up to an almost complete recovery of normal function following a crush or a Sunderland Type II injury. This process is governed by glial cells, known as Schwann cells, through their unique capacity to dedifferentiate into cells that drive the healing process. Despite that many progresses have occurred in restorative medicine and microsurgery, the regenerative process after a severe lesion of a major nerve trunk (e.g., Sunderland Types III-V) is often incomplete and functional recovery is unsatisfactory. In this aspect, it is known that glycosaminoglycans (GAGs) of the extracellular matrix are involved in proliferation, synaptogenesis, neural plasticity, and regeneration of the PNS. Here, we developed poly(caprolactone) (PCL) fibrous scaffolds functionalized with GAGs, which allowed us to assess their influence on the adhesion, proliferation, and differentiation of Schwann cells. We found that both aligned and random fiber scaffolds functionalized with GAGs resulted in increased cell proliferation on day 1. In addition, aligned functionalized scaffolds also resulted in increased GAG presence on day 1, probably because of cell extracellular matrix (ECM) formation and an increased syndecan-4 expression on day 7. A different modification and activation of Schwann cells in the presence of GAG versus no-GAG scaffolds was underlined by proteomic comparative analysis, where a general downregulation of the expression of intracellular/structural and synthetic proteins was shown on day 7 for GAG-functionalized scaffolds with regard to the nonfunctionalized ones. In conclusion, we have shown that GAG-functionalized scaffolds are effective in modulating Schwann cell behavior in terms of adhesion, proliferation, and differentiation and should be considered in strategies to improve PNS repair. STATEMENT OF SIGNIFICANCE: Nerve fibers functional recovery following a severe trauma of the Peripheral Nervous System (PNS) still represents a huge challenge for neurosurgery nowadays. In this respect, tissue engineering is committed to develop new constructs able to guide Schwann cells by mimicking the natural extracellular matrix environment. To this purpose, we successfully fabricated polycaprolactone (PCL) scaffolds with two well-defined fiber deposition patterns, functionalized with glycosaminoglycans (GAGs) and assessed for their potential as support for Schwann cells adhesion, growth and differentiation, by both classical biochemistry and LC-MS-based proteomic profiling. By this way, we showed that PCL-GAGs scaffolds could represent a promising artificial substrate that closely mimics the recently established pattern of Schwann cells migration into the regenerating nerve and, therefore, it should be considered in strategies to improve PNS repair.

Multiple Sulfatase Deficiency: A Case Series With a Novel Mutation

Multiple sulfatase deficiency is an autosomal recessive lysosomal storage disorder due to a deficiency in formylglycine-generating enzyme, which is encoded by the Sulfatase Modifying Factor 1 ( SUMF1) gene. Clinically, the disorder is variable. The most common characteristics are developmental regression, intellectual disability, ichthyosis, and periventricular white matter disease. Herein, we report 6 Saudi patients with multiple sulfatase deficiency caused by a novel homozygous missense mutation in the SUMF1 gene (NM_182760.3; c.785A>G [p.Gln262Arg]). The patients are 2 females and 4 males between 5 and 13 years of age, with an age of onset of 1 to 3 years. All patients are consanguineous and suffer from developmental regression, intellectual disability, ichthyosis, and periventricular white matter disease. This cohort differs from previous cohorts because of the absence of organomegaly and skeletal abnormalities.

Intercellular Glycosaminoglycans in Human Cancer

Intercellular glycosaminoglycans (GAGs) from various tissues were analyzed by cellulose acetate electrophoresis and enzymatic treatment with specific mucopolysaccharidases. Each tissue exhibits a particular composition of sulfated and unsulfated molecular species. Invariably, malignant human neoplasias and their metastases show striking variations in the electrophoretic pattern typical of the corresponding normal tissue. An absolute or relative increase in surface ChS A/C and HA seems to be a consistent feature of neoplastic transformation. On the other hand, the GAGs composition of benign noninfiltrative tumors does not vary greatly with respect to the original normal tissue.

Levels of Urinary Trypsin Inhibitor and Structure of Its Chondroitin Sulphate Moiety in Type 1 and Type 2 Diabetes

BACKGROUND

Diabetes mellitus is a global health problem representing the fifth leading cause of mortality and a major risk factor for cardiovascular diseases. In the last years, we reported an association among urinary trypsin inhibitor (UTI), a small proteoglycan that plays pleiotropic roles in many inflammatory processes, and both type 1 and 2 diabetes and developed a method for its direct quantitation and structural characterization.

METHODS

Urine from 39 patients affected by type 1 diabetes, 32 patients with type 2 diabetes, and 52 controls were analysed. UTI was separated from the main glycosaminoglycans physiologically present in urine by anion exchange chromatography, treated for chondroitin sulphate (CS) chain complete depolymerisation, and analysed for both UTI content and CS structure. UTI identification was performed by nano-LC-MS/MS analysis.

RESULTS

We evidenced increased UTI levels, as well as reduced sulphation of its CS moiety in association with diabetes, regardless of both age and medium-term glycaemic control. Furthermore, no association between UTI and albumin excretion rate was found.

CONCLUSIONS

Evidences suggest that UTI levels are not directly correlated with renal function or, otherwise, that they may increase before the onset of renal impairment in diabetes, representing a potential marker for the underlying inflammatory condition.

Investigation of newborns with abnormal results in a newborn screening program for four lysosomal storage diseases in Brazil

Lysosomal storage diseases (LSDs) are genetic disorders, clinically heterogeneous, mainly caused by defects in genes encoding lysosomal enzymes that degrade macromolecules. Several LSDs already have specific therapies that may improve clinical outcomes, especially if introduced early in life. With this aim, screening methods have been established and newborn screening (NBS) for some LSDs has been developed. Such programs should include additional procedures for the confirmation (or not) of the cases that had an abnormal result in the initial screening. We present here the methods and results of the additional investigation performed in four babies with positive initial screening results in a program of NBS for LSDs performed by a private laboratory in over 10,000 newborns in Brazil. The suspicion in these cases was of Mucopolysaccharidosis I - MPS I (in two babies), Pompe disease and Gaucher disease (one baby each). One case of pseudodeficiency for MPS I, 1 carrier for MPS I, 1 case of pseudodeficiency for Pompe disease and 1 carrier for Gaucher disease were identified. This report illustrates the challenges that may be encountered by NBS programs for LSDs, and the need of a comprehensive protocol for the rapid and precise investigation of the babies who have an abnormal screening result.

A poly-L-lactic acid/ collagen/glycosaminoglycan matrix for tissue engineering applications

Adhesion of tissue cells to biomaterials is a prerequisite of paramount importance for the effectiveness of a tissue engineering construct (cell and scaffolds). Functionalization of polymeric scaffolds with organic polymers, such as collagen or proteoglycans, is a promising approach in order to improve the cytocompatibility. As a matter of fact, organic polymers, isolated directly from the extracellular matrix, contain a multitude of surface ligand (fibronectin, laminin, vitronectin) and arginine–glycine–aspartic acid-containing peptides that promote cell adhesion. In tissue engineering, the combination of organic and synthetic polymers gives rise to scaffolds characterized simultaneously by the mechanical strength of synthetic materials and the biocompatibility of natural materials. In this work, porous poly-L-lactide acid scaffolds were functionalized with a synthetic collagen–glycosaminoglycans matrix in order to improve cell adhesion. For this purpose, a protocol for collagen–glycosaminoglycans conjugation into the pores of the scaffolds was set up. Moreover, an innovative protocol for the quantification of the conjugated glycosaminoglycans inside the scaffolds was created and adopted. The results have confirmed the effectiveness of the developed protocol: a collagen–glycosaminoglycans conjugation, with an efficiency of about 21% was obtained inside the scaffold. Moreover, SEM analysis highlighted the presence of the homogeneous synthetic matrix into the bulk of porous scaffolds. Finally, cell culture assays carried out by utilizing mouse embryonic fibroblasts showed that cell proliferation on poly-L-lactide acid-collagen–glycosaminoglycans scaffold is higher than on poly-L-lactide acid collagen scaffold (utilized as control). Therefore, it can be stated that the presence of glycosaminoglycans not only increases the mechanical strength of the matrix, thanks to their cross-linking effect, but also it seems to lead to a more significant cell growth. Overall, it is reasonable to state that the concerned protocol may be proposed as a reliable route to increase the rate of proliferation and in some cases to stimulate the cell differentiation in tissue engineering devices.

Glycosaminoglycans detection methods: Applications of mass spectrometry

Glycosaminoglycans (GAGs) are long blocks of negatively charged polysaccharides. They are one of the major components of the extracellular matrix and play multiple roles in different tissues and organs. The accumulation of undegraded GAGs causes mucopolysaccharidoses (MPS). GAGs are associated with other pathological conditions such as osteoarthritis, inflammation, diabetes mellitus, spinal cord injury, and cancer. The need for further understanding of GAG functions and mechanisms of action boosted the development of qualitative and quantitative (alcian blue, toluidine blue, paper and thin layer chromatography, gas chromatography, high pressure liquid chromatography, capillary electrophoresis, 1,9-dimethylmethylene blue, enzyme linked-immunosorbent assay, mass spectrometry) techniques. The availability of quantitative techniques has facilitated translational research on GAGs into the medical field for: 1) diagnosis, monitoring, and screening for MPS; 2) analysis of GAG synthetic and degradation pathways; and 3) determination of physiological and pathological roles of GAGs. This review provides a history of development of GAG assays and insights about the use of tandem mass spectrometry and its applications for GAG analysis.

Importance of the combined urinary procedure for the diagnosis of Mucopolysaccharidoses

BACKGROUND

Mucopolysaccharidoses are characterized by the accumulation of undegraded glycosaminoglycans in lysosomes in multiple organs and by their excretion in high amounts in urine. The aim of this study is to determine if this simple, reliable and reproducible method is useful for the diagnosis of Mucopolysaccharidoses.

METHODS

The study included 2154 normal urine samples and 210 samples from 73 patients affected by different types of Mucopolysaccharidoses. The glycosaminoglycans were quantified by a dimethylmethylene blue method and size-fractionated by a modified one-dimensional electrophoresis method.

RESULTS

The combination of the two methods allowed to identify all the patients affected by the different types of Mucopolysaccharidosis with 100% sensitivity and specificity.

CONCLUSION

This combined approach gives fast diagnostic orientation about the different types of Mucopolysaccharidoses, offering an important tool for a better understanding of diagnosis and patient management.

Screening for Attenuated Forms of Mucopolysaccharidoses in Patients with Osteoarticular Problems of Unknown Etiology

INTRODUCTION

The mucopolysaccharidoses (MPS) are a group of 11 inborn errors of metabolism (IEM) which are part of the lysosomal storage diseases (LSDs). The MPS are multisystemic conditions that affect the entire body, with variations in the clinical presentation, having specific treatments available depending on the type of MPS. Nearly all MPS disorders compromise the osteoarticular system in different ways, and virtually all patients have abnormal urinary excretion of glycosaminoglycans (GAGs). MPS are rare diseases that are underdiagnosed due to health-care professionals' lack of awareness, to poor access to screening and diagnostic methods, and to their extensive clinical heterogeneity. Attenuated forms may occur, which can make diagnosis of MPS even more difficult.

METHODS

This study was conducted prospectively from March 2012 to January 2014 and included 55 patients at rheumatology and/or orthopedic services in Porto Alegre, Brazil. The screened patients presented with articular manifestations with no defined etiology. These patients were screened by quantitative and qualitative assessment of urinary GAGs.

RESULTS AND DISCUSSION

Among the 55 cases investigated, one 15-year-old patient exhibited increased urinary GAG excretion; this patient was subsequently diagnosed with an attenuated form of MPS II, which was previously undetected.

CONCLUSION

Although the proportion of patients with MPS identified in the study sample was small (1/55), this study shows that these diseases are underdiagnosed and that systematic screening can help identify patients who may benefit from specific treatments already available for several MPS types.

Glycosaminoglycan blotting and detection after electrophoresis separation

Separation of glycosaminoglycans (GAGs) by electrophoresis and their characterization to the microgram level are integral parts of biochemical research. Their blotting on membranes after electrophoresis offers the advantage to perform further analysis on single separated species such as identification with antibodies and/or recovery of single band. A method for the blotting and immobilizing of several nonsulfated and sulfated complex GAGs on membranes made hydrophilic and positively charged by cationic detergent after their separation by conventional agarose-gel electrophoresis is illustrated. This approach to the study of these complex macromolecules utilizes the capacity of agarose-gel electrophoresis to separate single species of polysaccharides from mixtures and the membrane technology for further preparative and analytical uses. Nitrocellulose membranes are derivatized with the cationic detergent cetylpyridinium chloride (CPC) and mixtures of GAGs are capillary blotted after their separation in agarose-gel electrophoresis. Single purified species of variously sulfated polysaccharides are transferred on derivatized membranes with an efficiency of 100 % and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining). This enables a lower amount limit of detection of 0.1 μg. Nonsulfated polyanions, for example hyaluronic acid (HA), may also be transferred to membranes with a limit of detection of approximately 0.1-0.5 μg after irreversible or reversible staining. The membranes may be stained with reversible staining and the same lanes used for immunological detection or other applications.

Novel heparan sulfate assay by using automated high-throughput mass spectrometry: Application to monitoring and screening for mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are caused by deficiency of one of a group of specific lysosomal enzymes, resulting in excessive accumulation of glycosaminoglycans (GAGs). We previously developed GAG assay methods using liquid chromatography tandem mass spectrometry (LC-MS/MS); however, it takes 4-5 min per sample for analysis. For the large numbers of samples in a screening program, a more rapid process is desirable. The automated high-throughput mass spectrometry (HT-MS/MS) system (RapidFire) integrates a solid phase extraction robot to concentrate and desalt samples prior to direction into the MS/MS without chromatographic separation; thereby allowing each sample to be processed within 10s (enabling screening of more than one million samples per year). The aim of this study was to develop a higher throughput system to assay heparan sulfate (HS) using HT-MS/MS, and to compare its reproducibility, sensitivity and specificity with conventional LC-MS/MS. HS levels were measured in the blood (plasma and serum) from control subjects and patients with MPS II, III, or IV and in dried blood spots (DBS) from newborn controls and patients with MPS I, II, or III. Results obtained from HT-MS/MS showed 1) that there was a strong correlation of levels of disaccharides derived from HS in the blood, between those calculated using conventional LC-MS/MS and HT-MS/MS, 2) that levels of HS in the blood were significantly elevated in patients with MPS II and III, but not in MPS IVA, 3) that the level of HS in patients with a severe form of MPS II was higher than that in an attenuated form, 4) that reduction of blood HS level was observed in MPS II patients treated with enzyme replacement therapy or hematopoietic stem cell transplantation, and 5) that levels of HS in newborn DBS were elevated in patients with MPS I, II or III, compared to those of control newborns. In conclusion, HT-MS/MS provides much higher throughput than LC-MS/MS-based methods with similar sensitivity and specificity in an HS assay, indicating that HT-MS/MS may be feasible for diagnosis, monitoring, and newborn screening of MPS.

Urine bikunin as a marker of renal impairment in Fabry's disease

Fabry's disease is a rare lysosomal storage disorder caused by the deficiency of α-galactosidase A that leads to the accumulation of neutral glycosphingolipids in many organs including kidney, heart, and brain. Since end-stage renal disease represents a major complication of this pathology, the aim of the present work was to evaluate if urinary proteoglycan/glycosaminoglycan excretion could represent a useful marker for monitoring kidney function in these patients at high risk. Quali-quantitative and structural analyses were conducted on plasma and urine from 24 Fabry's patients and 43 control subjects. Patients were sorted for presence and degree of renal impairment (proteinuria/renal damage). Results showed that levels of urine bikunin, also known as urinary trypsin inhibitor (UTI), are significantly higher in patients with renal impairment than in controls. In this respect, no differences were evidenced in plasma chondroitin sulfate isomers level/structure indicating a likely direct kidney involvement. Noteworthy, urine bikunin levels are higher in patients since early symptoms of renal impairment occur (proteinuria). Overall, our findings suggest that urine bikunin level, as well as proteinuria, could represent a useful parameter for monitoring renal function in those patients that do not present any symptoms of renal insufficiency.

Validation of an LC-MS/MS assay for detecting relevant disaccharides from keratan sulfate as a biomarker for Morquio A syndrome

BACKGROUND

Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is an inherited lysosomal storage disease caused by deficiency of N-acetylgalactosamine-6-sulfatase (GALNS), an enzyme required for stepwise degradation of keratan sulfate (KS). We have developed a selective, sensitive, accurate and precise LC-MS/MS assay for the KS-derived disaccharides Galβ1-4GlcNAc(6S) and Gal(6S)β1-4GlcNAc(6S) in human urine and plasma using keratanase II digestion.

RESULTS

Mean accuracy was 96-106% in urine and 97-108% in plasma. Precision was high, with relative standard deviations of 1-2% (intra-day) and 2-5% (inter-day) in urine and 1-2% (intra-day) and 4-7% (inter-day) in plasma. The lower limit of quantitation was 0.026 µg/ml (plasma) and 0.104 µg/ml (urine), with a quantitation range of 0.026-5 µg/ml (plasma) and 0.104-20 µg/ml (urine).

CONCLUSION

Clinical sample analysis in 168 MPS IVA patients and 225 healthy controls demonstrates the clinical utility of this method.

Capillary blotting of glycosaminoglycans on nitrocellulose membranes after agarose-gel electrophoresis separation

A method for the blotting and immobilizing of several nonsulfated and sulfated complex polysaccharides on membranes made hydrophilic and positively charged by cationic detergent after their separation by conventional agarose gel electrophoresis is illustrated. This new approach to the study of glycosaminoglycans (GAGs) utilizes the capacity of agarose gel electrophoresis to separate single species of polysaccharides from mixtures and the membrane technology for further preparative and analytical uses.Nitrocellulose membranes are derivatized with the cationic detergent cetylpyridinium chloride and mixtures of GAGs are capillary blotted after their separation in agarose gel electrophoresis. Single purified species of variously sulfated polysaccharides are transferred on derivatized membranes with an efficiency of 100% and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining). This enables a lower amount limit of detection of 0.1 microg. Nonsulfated polyanions, for example hyaluronic acid, may also be transferred to membranes with a limit of detection of approximately 0.1-0.5 microg after irreversible or reversible staining. The membranes may be stained with reversible staining and the same lanes are used for immunological detection or other applications.

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.

Improved method for analysis of glycosaminoglycans in glycosaminoglycan/protein mixtures: Application in Cohn–Oncley fractions of human plasma

BACKGROUND

Glycosaminoglycans are found in human tissues including plasma. They encompass chondroitin sulphates, heparan sulphate/heparin, hyaluronic acid, and keratan sulphate. Glycosaminoglycans, in particular heparan sulphate and heparin, are strongly associated with plasma proteins, so that their purification results quite difficult.

METHODS

In order to study the distribution of glycosaminoglycans in plasma subfractions, we developed a novel method that allows their identification even if they were still associated with proteins or peptides. Plasma was fractionated following the procedure of Cohn-Oncley, and each fraction was treated with proteases. After centrifugation, glycosaminoglycan/protein complexes in the supernatant were analysed using a modified cellulose acetate electrophoresis which allowed identification of glycosaminoglycans in mixtures of glycosaminoglycans/proteins.

RESULTS

Chondroitin sulphate was recovered in cryoprecipitate and in all Cohn-Oncley fractions. Glycosaminoglycans belonging to the class of heparan sulphate/heparin, however, were recovered in the cryoprecipitate and in fractions I and IV-1, and, in smaller amount, in fraction II+III.

CONCLUSIONS

Since the largest amount of plasma proteins is partitioned in Factions II+III and V, these results demonstrate that heparan sulphate/heparin are not randomly distributed in Cohn-Oncley fractions and are associated with certain plasma proteins. This association might play a role in the physiological function of heparan sulphate/heparin, regulating hemostasis and atherogenesis.

Effect of Cryopreservation Techniques on Aortic Valve Glycosaminoglycans

This study was designed to evaluate the effect of cryopreservation on the glycosaminoglycan (GAG) content of the aortic allografts. Twenty-one porcine aortic valves were obtained. Five aortic roots were immediately analyzed without cryopreservation, eight were cryopreserved in closed leaflet position, and eight in open leaflet position. The groups were compared in terms of GAG concentration and subclass proportion in three different zones including the aortic root wall, the commissures, and the leaflets. GAG content at the commissures was significantly lower in the closed leaflet group than in the other groups (P = 0.001). The electrophoretic analysis did not show any significant difference in the zonal distribution of GAG classes between groups. Quantitative analysis in various aortic valve zones suggests that cryopreservation can alter the GAG content. Cryopreservation of the aortic valve in an open leaflet position can preserve the matrix more efficiently and might prolong the durability of the aortic allograft.

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.

Low molecular weight hyaluronan from stretched lung enhances interleukin-8 expression

Mechanical ventilation has been shown to cause ventilator-induced lung injury (VILI), probably by overdistending or stretching the lung. Hyaluronan (HA), a component of the extracellular matrix, in low molecular weight (LMW) forms has been shown to induce cytokine production. LMW HA is produced by hyaluronan synthase 3 (HAS 3). We found that HAS 3 mRNA expression was upregulated and that LMW HA accumulated in an animal model of VILI. We hypothesized that stretch-induced LMW HA production that causes cytokine release in VILI was dependent on HAS 3 mRNA expression. We explored this hypothesis with in vitro lung cell stretch. Cell stretch induced HAS 3 mRNA expression and LMW HA in fibroblasts. Nonspecific inhibitors of HAS 3 (cyclohexamide and dexamethasone), a nonspecific inhibitor of protein tyrosine kinases (genistein), and a janus kinase 2 inhibitor (AG490) blocked stretch-induced HAS 3 expression and synthesis of LMW HA. Stretch-induced LMW HA from fibroblasts caused a significant dose-dependent increase in interleukin-8 production both in static and stretched epithelial cells. These results indicated that de novo synthesis of LMW HA was induced in lung fibroblasts by stretch via tyrosine kinase signaling pathways, and may play a role in augmenting induction of proinflammatory cytokines in VILI.

Effect of chondroitinase ABC on purulent sputum from cystic fibrosis and other patients

Cystic fibrosis (CF) patients develop chronic lung infections associated with airway obstruction by viscous and insoluble mucus secretions. Although mucus glycoproteins (mucins) are thought to be responsible for mucus plugs, other glycoconjugate components of airway secretions have not been systematically evaluated. The aim of the present study was to determine whether chondroitin sulfate proteoglycans (CSPG) contribute to the insolubility of CF sputum. Sputa obtained from 18 CF patients were incubated with chondroitinase ABC (ChABC) or buffer (control) for 18 h at 37 degrees C, and after centrifugation at 12,000 g, the volume of the insoluble pellet and turbidity of the supernatant were determined as measures of solubility. ChABC caused a 70-90% reduction in supernatant turbidity and a 60-70% decrease in pellet volume of the 13 purulent CF sputa, but had much less effect on the five nonpurulent CF sputa tested. Similar results were obtained with two non-CF purulent and two non-CF, nonpurulent sputa. Gel electrophoresis, Western blot, and slot blot immunoassays with antichondroitin sulfate and antimucin antibodies revealed that purulent sputa (CF and non-CF) contained more CSPG and less mucin than nonpurulent sputa. In vitro mixing experiments showed that mucin in nonpurulent sputa was reduced upon incubation with purulent sputa, presumably because of degradation or a loss of immunoreactive mucin epitopes from leukocyte and/or bacterial enzymes present in purulent sputa. Our results suggest that CSPG contribute more significantly than mucins to the insolubility of purulent tracheobronchial secretions from CF patients. Because purulent sputa from non-CF patients showed a similar pattern, our observations with CF sputa may have wider applicability.

Heparin oligosaccharide sequence and size essential for inhibition of pulmonary artery smooth muscle cell proliferation

Heparin has a wide range of important biological activities including inhibition of pulmonary artery smooth muscle cell proliferation. To determine the minimum size of the heparin glycosaminoglycan chain essential for antiproliferative activity, porcine intestinal mucosal heparin was partially depolymerized with heparinase and fractionated to give oligosaccharides of different sizes. The structure of these oligosaccharides was fully characterized by 1D and 2D 1H NMR spectroscopy. These oligosaccharides were assayed for antiproliferative effects on cultured bovine pulmonary artery smooth muscle cells (PASMCs). The tetrasaccharide (4-mer) exhibited no heparin-like activity. Decasaccharides (10-mers) and dodecasaccharides (12-mers) displayed a reduced level of activity when compared to full-length heparin. Little effect on activity was observed in deca- and dodecasaccharides with one less 2-O-sulfo group. The 14-, 16-, and 18-mers showed comparable growth-inhibition effects on PAMSC as porcine intestinal mucosal heparin. These data suggest that a 14-mer is the minimum size of oligosaccharide that is essential for full heparin-like antiproliferative activity. Since the 14- to 18-mers have no 3-O-sulfo groups in their glucosamine residues, their full activity confirms that these 3-O-sulfonated glucosamine residues, which are required for heparin's anticoagulant activity, are not an essential requirement for antiproliferative activity.

Additive effects of Simvastatin beyond its effects on LDL cholesterol in hypertensive type 2 diabetic patients

BACKGROUND

Experimental evidence indicates that statins might have direct vascular effects independently from low-density lipoprotein (LDL) cholesterol reduction and we reported that the reduction in urinary albumin excretion rate during Simvastatin treatment in type 2 diabetic patients was not correlated with LDL-cholesterol decrease. However in humans there are no data regarding possible additional effects of Simvastatin on blood pressure and urinary albumin excretion beyond its capacity to lower serum cholesterol.

PATIENTS AND METHODS

Twenty-six microalbuminuric hypertensive type 2 diabetic patients (diastolic blood pressure - after four months wash-out from the previous antihypertensive therapy - consistently > 90 and < 100 mmHg; plasma LDL-cholesterol > 3.9 and < 6.5 mmol L-1) were enrolled in the study. In random order, these patients received Simvastatin (20 mg day-1) or Cholestyramine (6 g three times a day) for a period of 10 months and after three months of wash-out (cross-over) the sequence was reversed for an additional 10 months. Blood pressure, lipid parameters, glycated haemoglobin and urinary albumin excretion were measured during the study. Additionally, in eight patients, urinary glycosaminoglycan excretion (GAG) was also measured during the study.

RESULTS

Simvastatin and Cholestyramine were equally effective in reducing total and LDL cholesterol. Only during Simvastatin treatment a significant reduction in diastolic blood pressure and both 24 h urinary albumin and GAG excretion rates were observed, while no significant changes were seen with Cholestyramine treatment.

CONCLUSIONS

Our results clearly show for the first time that the reduction of blood pressure, together with 24 h urinary albumin excretion rate - two established cardiovascular risk factors, obtained during Simvastatin therapy in hypertensive type 2 diabetic patients - is in large part independent from the reduction of LDL Cholesterol.

Urinary glycosaminoglycan excretion in healthy subjects and in patients with mucopolysaccharidoses

BACKGROUND

The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by deficiency of enzymes catalyzing the stepwise degradation of glycosaminoglycans (GAGs), and are transmitted in an autosomal recessive manner, except for Hunter syndrome.

METHODS

The levels of GAGs in 150 healthy subjects and 33 patients with MPS were determined, and results were expressed as milligrams of GAGs per grams of creatinine.

RESULTS

We found that this ratio decreased with age during the first 15 years of life, but had a constant low rate between the ages of 17-40 years in healthy individuals. A different tendency was present in patients with MPS, because levels of GAG excretion in this group were higher (by four standard deviations up) compared with healthy individuals. The electrophoretic patterns of urinary GAGs in healthy subjects showed that the higher levels detected in urine were chondroitin sulfate (4 and 6) and a smaller quantity of dermatan sulfate, but in each MPS type its characteristic pattern was identified.

CONCLUSIONS

This is a simple, reproducible method suitable for routine laboratory separation, identification, and quantity of urinary GAGs and for diagnosing MPS syndromes.

Effects of chondroitin sulfate and interleukin-1beta on human chondrocyte cultures exposed to pressurization: a biochemical and morphological study

Objective This study investigated the in vitro effects of chondroitin sulfate (CS) on human articular chondrocytes cultivated in the presence or in the absence of interleukin-1beta (IL-1beta) during 10 days of culture with and without pressurization cycles. Design The effects of CS (10 and 100 microg/ml) with and without IL-1beta were assessed in the culture medium of cells exposed to pressurization cycles in the form of synusoidal waves (minimum pressure 1 Mpa, maximum pressure 5 Mpa) and a frequency of 0.25 Hz for 3 h by immunoenzymatic method on microplates for the quantitative measurement of human proteoglycans (PG). On the 4th and 10th day of culture the cells were used for morphological analysis by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results The presence of IL-1beta determines a significant decrease in PG concentration measured in the culture medium. When the cells are cultured in the presence of IL-1beta and CS, a statistically significant restoration of PG levels is observed. Under pressurization conditions, we observed that PG concentration in the medium of cells presents a significant increase at baseline conditions, in the presence of IL-1beta+CS10 and IL-1beta+CS100, but not with IL-1beta alone. The results concerning metabolic evaluation are confirmed by the morphologic findings obtained by TEM and SEM. Conclusions These in vitro studies confirm the protective role of CS, which counteracts the IL-1beta induced effects and they confirm the importance of pressure on chondrocyte metabolism and morphology.

Developmental expression of dermatan sulfate proteoglycans in the elastic bovine nuchal ligament

The nuchal ligament of bovines is a useful system in which to study elastic fibre formation since it contains up to 83% elastin and undergoes a period of rapid elastinogenesis during the last trimester of fetal development and in the first four post-natal months. To identify proteoglycans (PGs) which may be involved in this process we initially investigated changes in the glycosaminoglycan (GAG) profiles during nuchal ligament development. In contrast to the collagenous Achilles tendon, nuchal ligament exhibited: (a) elevated hyaluronan (HA) levels in the peak period of elastin-associated microfibril (fibrillin) synthesis (130-200 days) which precedes elastinogenesis; and (b) markedly increased synthesis of a glucuronate-rich copolymeric form of dermatan sulfate (DS) in the period corresponding to elastin formation (200-270 days). Analysis of DSPGs isolated from 230-day nuchal ligament showed that this copolymer was predominantly associated with a glycoform of biglycan which was specifically elevated at this stage in development. This finding was consistent with Northern blot analysis which showed that steady-state biglycan mRNA levels increased significantly during the elastinogenic period. In contrast, the mRNA levels for decorin, the only other DSPG detected in this tissue, declined rapidly after 140 days of fetal development. In conclusion, the results suggest that HA may play a role in microfibril assembly and that a specific glycoform of biglycan may be associated with the elastinogenic phase of elastic fibre formation.

Mouse model of Sanfilippo syndrome type B produced by targeted disruption of the gene encoding alpha-N-acetylglucosaminidase

The Sanfilippo syndrome type B is an autosomal recessive disorder caused by mutation in the gene (NAGLU) encoding alpha-N-acetylglucosaminidase, a lysosomal enzyme required for the stepwise degradation of heparan sulfate. The most serious manifestations are profound mental retardation, intractable behavior problems, and death in the second decade. To generate a model for studies of pathophysiology and of potential therapy, we disrupted exon 6 of Naglu, the homologous mouse gene. Naglu-/- mice were healthy and fertile while young and could survive for 8-12 mo. They were totally deficient in alpha-N-acetylglucosaminidase and had massive accumulation of heparan sulfate in liver and kidney as well as secondary changes in activity of several other lysosomal enzymes in liver and brain and elevation of gangliosides G(M2) and G(M3) in brain. Vacuolation was seen in many cells, including macrophages, epithelial cells, and neurons, and became more prominent with age. Although most vacuoles contained finely granular material characteristic of glycosaminoglycan accumulation, large pleiomorphic inclusions were seen in some neurons and pericytes in the brain. Abnormal hypoactive behavior was manifested by 4.5-mo-old Naglu-/- mice in an open field test; the hyperactivity that is characteristic of affected children was not observed even in younger mice. In a Pavlovian fear conditioning test, the 4.5-mo-old mutant mice showed normal response to context, indicating intact hippocampal-dependent learning, but reduced response to a conditioning tone, perhaps attributable to hearing impairment. The phenotype of the alpha-N-acetylglucosaminidase-deficient mice is sufficiently similar to that of patients with the Sanfilippo syndrome type B to make these mice a good model for study of pathophysiology and for development of therapy.

Disaccharide analysis and molecular mass determination to microgram level of single sulfated glycosaminoglycan species in mixtures following agarose-gel electrophoresis

The separation of sulfated glycosaminoglycans in mixtures by agarose-gel electrophoresis and the recovery of single polysaccharide bands has been applied to the characterization of polysaccharides extracted from tissues without previous purification of single species. Sulfated glycosaminoglycans, heparin with its two components, slow-moving and fast-moving, heparan sulfate, dermatan sulfate, and chondroitin sulfate, were separated to microgram level by conventional agarose-gel electrophoresis. After their separation, they were fixed in the agarose-gel matrix by precipitation in a cetyltrimethylammonium bromide solution, making them visible on a dark background. After recovery of gel containing the fixed bands, high temperatures (90 degrees C for 15 min) were necessary to dissolve the gel matrix, and a solution of NaCl (3 M) was used to release sulfated polysaccharides from the complex with cetyltrimethylammonium. After precipitation of glycosaminoglycans in the presence of ethanol, the recovery of slow-moving heparin, fast-moving heparin, heparan sulfate, dermatan sulfate, and chondroitin sulfate was from 1 to 10 microg, with a percentage greater than 45% and a purity above 90%. Sulfated glycosaminoglycans in mixtures recovered from gel matrix as single species were evaluated for purity and characterized for unsaturated disaccharides after treatment with bacterial lyases (heparinases for heparin and heparan sulfate samples, and chondroitinases for dermatan sulfate and chondroitin sulfate) and molecular mass. Bovine lung and heart Glycosaminoglycans were extracted and separated into single species by agarose-gel electrophoresis and recovered from gel matrix after treatment in cetyltrimethylammonium solution. Unsaturated disaccharides pattern, the sulfate to carboxyl ratio, and the molecular mass of each single polysaccharide species were determined.

Discontinuous electrophoresis of glycosaminoglycans: a screening method for mucopolysaccharidoses

A modified discontinuous electrophoretic method for the separation of standard and urinary glycosaminoglycans has been reported. The merits of the method are the simple and easy to handle apparatus, non-requirement of elaborate cooling system, sensitivity and high reproducibility of the results and applicability of the method for the preliminary grouping of the MPS patients to reduce the number of enzyme assays to be done.

Influence of molecular weight, protein core and charge of native heparin fractions on pulmonary artery smooth muscle cell proliferation

Heparin macromolecules have been shown to inhibit cultured pulmonary artery smooth muscle cell proliferation in vitro and prevent hypoxic vascular remodeling in vivo. In an attempt to understand the structural determinants of heparin's antiproliferative properties, we have fractionated an antiproliferative preparation of commercial heparin into low and high molecular weight fractions. Then the high molecular weight heparin fraction was further fractionated on a DEAE-cellulose column by charge density eluting with 0 - 1 M NaCl linear gradient. The heparin protein peptides were both removed and isolated. These heparin fractions were assayed for antiproliferative effects on cultured bovine pulmonary artery smooth muscle cells. No appreciable differences were found among high and low molecular weight heparin fractions The core peptides showed no antiproliferative activity. However, higher charge density fraction was less antiproliferative.

Morphological and biochemical investigations of mitral valve endocardiosis in pigs

Pig endocardiosis is a pathological process affecting cardiac valves that is characterised by the accumulation of glycosaminoglycans (GAG) in the extracellular matrix. To investigate the involvement of GAG in the condition, the morphology of the mitral valves from 23 affected pigs and seven normal controls was studied and qualitative and quantitative biochemical analyses of GAG were made. Gross and histopathological lesions were characterised by valve enlargement, collagen disorganisation and myxoid degeneration. No differences between normal and diseased valves were detected by lectin histochemistry. Electron microscopy revealed myofibroblast differentiation of many fibroblasts. A statistically significant increase of total GAG and hyaluronan was detected in the mitral valves of the pigs with endocardiosis by spectrophotometric, electrophoretic and densitometric analysis of the extracted GAG. Although it is not known whether the change in hyaluronan is a primary event or a result of other changes in the extracellular matrix, its accumulation in association with myofibroblast differentiation suggests that it plays a pathogenetic role in pig endocardiosis.

Activity of chondroitin ABC lyase and hyaluronidase on free-radical degraded chondroitin sulfate

High molecular mass-chondroitin sulfate was characterized for M(r), charge density and constituent disaccharides. This glycosaminoglycan was depolymerized by a controlled free-radical process mediated by hydrogen peroxide in the absence or presence of cupric or ferrous ions. Hydrogen peroxide depolymerizes chondroitin sulfate, and the velocity of the reaction increases in the presence of cupric ions and, further, of ferrous ions. Different low molecular mass-chondroitin sulfate fractions were produced and analyzed by high-performance size-exclusion chromatography and polyacrylamide-gel electrophoresis. This last technique strongly supports the hypothesis that the free-radical process proceeds by the destruction of disaccharide units. The treatment of free-radical chondroitin sulfate samples with chondroitinase ABC and testicular hyaluronidase results in a lower capacity of these enzymes to degrade these glycosaminoglycan derivatives with respect to the natural sample. This was confirmed by polyacrylamide-gel electrophoresis and by the time-courses of enzymatic treatment evaluated by spectrophotometric technique (for treatment with chondroitin ABC lyase).

Structural heterogeneity of dermatan sulfate chains: correlation with heparin cofactor II activating properties

To obtain dermatan sulfate (DS) with different structural characteristics and biological properties we isolated three groups of chains from a bovine mucosal DS preparation, differently iduronated and sulfated. The selected DS chains were characterized by their total charge values, electrophoretic mobility, susceptibility to Chondroitinase AC II treatment and disaccharide composition of Chondroitinase ABC digests. Besides the major IdoUA-->GalNac-4-SO4 sequences, two DS fractions (s-DS 1.75 M and f-DS 1.75 M) contained more than 10% disulfated disaccharides sequences and the third DS fraction (s-DS 1.5 M) contained only 4% disulfated disaccharides. Chondroitinase AC II treatment indicated that both the electrophoretically retarded forms (s-DS) are iduronic acid rich, as they were only minimally degraded to disaccharides/oligosaccharides. The ability of DS crude preparation to activate the heparin cofactor II (HCII) mediated inhibition of thrombin depends on the relative amount of highly active DS chains; this activity is related to the overall charge of DS chains and particularly with the content of IdoUA-2-SO4-->GalNAc-4-SO4 and UA-->GalNAc-4,6-di-SO4 disaccharides.

The effects of KH 1060, a potent 20-epi analogue of the vitamin D3 hormone, on hairless mouse skin in vivo

Dermal effects of KH 1060, a novel, highly potent 20-epi analogue of 1 alpha,25-dihyroxyvitamin D3, were investigated in a hairless mouse model. During daily topical applications of a 0.4 microM solution of KH 1060 for 4 weeks, epidermal hyperplasia and an increase of dermal thickness and mass were observed. KH 1060 upregulated glycosaminoglycan and collagen synthesis in the skin, and increased glycosaminoglycan deposition in the subepidermal region. Reverse transcription-polymerase chain reaction amplification of the transforming growth factor (TGF) beta 1-specific mRNA revealed that KH 1060 stimulated expression of this growth factor in the epidermis, but not in the dermis. Changes observed after application of 1 alpha,25-dihydroxyvitamin D3 were much less pronounced but qualitatively similar to the effects of KH 1060, whereas structurally related but receptor inactive compounds, vitamin D3 and 1 beta,25-dihydroxyvitamin D3, did not produce any effects. Furthermore, we were unable to demonstrate the involvement of the non-genomic, receptor-independent vitamin D signalling in the skin, using a specific stimulator (Ro 24-2090) and a blocker (1 beta,25-dihydroxyvitamin D3) of this pathway. Our findings provide the first evidence that a strong vitamin D3 analogue triggers synthesis of skin connective tissue, possibly via vitamin D receptor activation and the paracrine action of epidermis-derived TGF-beta 1.

Glycosaminoglycan synthesis in the rat articular disk in response to mechanical stress

The mechanism by which compressive mechanical stress affects glycosaminoglycan synthesis in the articular disk was investigated with a modified organ culture technique. Forty-eight male Sprague-Dawley rats were divided into three experimental groups and one control group of 12 animals each, aged 7 and 9 weeks. The experimental groups followed different regimens of stress applied for 25%, 75%, or 100% of the time during the total test period of 24 hours. Articular disks were stressed with flexible bottomed dishes (Flex I dishes, Flexcell Corp., McKeesport, Pa.) using the Flexercell Strain Unit (Flexcell Corp., McKeesport, Pa.) and incubated with [3H]-glucosamine for 24 hours. Samples were then collected, digested with Pronase-E, and after precipitation with cetylpyridinium chloride (CPC) and ethanol, the different glycosaminoglycans (GAGs) were separated by using cellulose acetate electrophoresis. The significant GAG types with stress were chondroitin6sulfate (C6S), hyaluronic acid (HA), and dermatan sulfate (DS). There was no significant relationship in the experimental groups between age and regimen of stress applied in either age. Higher stress regimens showed significantly higher proportions of C6S when compared with the controls, whereas HA appeared to decrease slightly and DS was not affected. Since C6S is the major component of hyaline cartilage, the results of this study suggest that compressive forces in the articular disk may stimulate the development of more cartilagenous-like properties with respect to GAG content.

Iduronic acid-rich proteoglycans (PGIdoA) and human post-burn scar maturation: isolation and characterization

Proteoglycans (PGs) were extracted from human hypertrophic and normal scar tissues from two different stages of maturation after burn injury, under dissociative conditions (4 M guanidinium chloride containing proteinase inhibitors). The extracts were fractionated by ion-exchange chromatography, followed by ethanol precipitation, to give PG-containing iduronic acid (PGIdoA). The size of the PGIdoA decreased with the maturation of scars. Glycosaminoglycan (GAG) chains from PGIdoA were released by alkaline borohydride treatment, and their M(r) values were evaluated by polyacrylamide gel electrophoresis. The M(r) values for PGIdoA protein cores of the hypertrophic scars (5+ years and 2-5 years) and normal scar (5+ years and 2-5 years) were 22.6, 25, 19 and 21 kDa, respectively. The iduronic acid content of PGIdoA from both types of scar increased in their maturation phase. The M(r) values of PGIdoA decreased with maturation. PGIdoA carried the sulfate group mainly attached at C-4 of the 2-amino-2-deoxy-D-galactose residue. The NH2-terminal amino acid sequences of all the PGIdoA were similar to those of normal human skin or bone PG II (decorin) (i.e., Asp-Glu-Ala-B-Gly-Ile-Gly-Pro-Glu-Val-Pro-Asp-Asp-Arg).