Nicola Volpi

Role, Metabolism, Chemical Modifications and Applications of Hyaluronan

Hyaluronan (hyaluronic acid, HA) is a linear naturally occurring polysaccharide formed from repeating disaccharide units of N-acetyl-D-glucosamine and D-glucuronate. Despite its relatively simple structure, HA is an extraordinarily versatile glycosaminoglycan currently receiving attention across a wide front of research areas. It has a very high molar mass, usually in the order of millions of Daltons, and possesses interesting visco-elastic properties based on its polymeric and polyelectrolyte characteristics. HA is omnipresent in the human body and in other vertebrates, occurring in almost all biological fluids and tissues, although the highest amounts of HA are found in the extracellular matrix of soft connective tissues. HA is involved in several key processes, including cell signaling, wound repair and regeneration, morphogenesis, matrix organization and pathobiology. Clinically, it is used as a diagnostic marker for many disease states including cancer, rheumatoid arthritis, liver pathologies, and as an early marker for impending rejection following organ transplantation. It is also used for supplementation of impaired synovial fluid in arthritic patients, following cataract surgery, as a filler in cosmetic and soft tissue surgery, as a device in several surgical procedures, particularly as an anti-adhesive following abdominal procedures, and also in tissue engineering. This review will provide an overview of the structure and physiological role of HA, as well as of its biomedical and industrial applications. Recent advances in biotechnological approaches for the preparation of HA-based materials, and as a component of tissue scaffolding for artificial organs will also be presented.

A 96-well assay for uronic acid carbazole reaction

Abstract A sensitive and reproducible 96-well assay of uronic acid permitting a rapid processing of a number of samples with a very low consumption of reagents is described for the determination of complex uronic acid-bearing polyanions such as hyaluronic acid, chondroitin sulfate, dermatan sulfate and heparin. The sensitivity of the reaction was approx. 1 μg for glucuronic acid and 2 μg for complex polysaccharides, with a linear function of glucuronic acid concentration between 1 and 100 μg. The relative coefficient of variations ranged from 1.5 to 8.7% for the assay performed in the 96-well plate. These values were found to be lower than those obtained by the conventional procedure.

Therapeutic applications of glycosaminoglycans

Complex polysaccharides, hyaluronic acid or hyaluronan (HA), keratan sulfate (KS), chondroitin sulfates (CSs) and heparin (Hep)/heparan sulfate (HS), are a class of ubiquitous molecules exhibiting a wide range of biological functions. They are widely distributed as glycosaminoglycans (GAGs) sidechains of proteoglycans (PGs) in the extracellular matrix and at cellular level. The recent emergence of improved enzymatic and analytical tools for the study of these complex sugars has produced a virtual explosion in the field of glycomics. In particular, the study of the GAG family of polysaccharides has shed considerable light on the way in which specific carbohydrate structures modulate cellular phenotypes. In addition to the well-known therapeutic applications of some of these macromolecules, such as HA and derivatives as structure modifying molecules and possessing gel-like properties able to provide functional support for tissues, Hep as an anticoagulant and antithrombotic drug and CS in the treatment of osteoarthritis (OA), this increased understanding of GAG structure-function relationship has led to the discovery of novel pharmaceuticals for the possible treatment of serious diseases, such as cancer. In this paper, the structure and the therapeutic applications of several complex natural polysaccharides, including HA, CS/DS, Hep and their derivatives, are presented and discussed also in the light of the many questions still left unanswered, such as improved preparation and GAG-based drugs with improved properties and new possible therapeutic applications.

Quality of different chondroitin sulfate preparations in relation to their therapeutic activity

Objectives Chondroitin sulfate is currently recommended by the European League Against Rheumatism (EULAR) as a SYSADOA (symptomatic slow acting drug for osteoarthritis) in Europe in the treatment of knee and hand osteoarthritis based on research evidence and meta‐analysis of numerous clinical studies. Furthermore, recent clinical trials demonstrated its possible structure‐modifying effects. Chondroitin sulfate, alone or in combination with glucosamine or other ingredients, is also utilized as a nutraceutical in dietary supplements in Europe and the USA. However, it 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. We aim to review the quality control of chondroitin sulfate in pharmaceutical‐grade preparations and nutraceuticals.

1H and 13C nuclear magnetic resonance identification and characterization of components of chondroitin sulfates of various origin

Abstract Three natural chondroitin sulfates (CSs), from porcine and bovine trachea, and from shark cartilage, were studied using a variety of NMR techniques (DQS, TOCSY, NOESY, HMQC). A good 1H and 13C characterization of the major components, chondroitin 4-sulfate (CS4) and chondroitin 6-sulfate (CS6), was obtained and a number of signals coming from chondroitin 2,6-disulfate (CS2,6) (present only in shark CS) was identified. The study of a chemically desulfated CS was necessary in order to understand the difficulties encountered in detecting signals from the chondroitin non-sulfate (CS0) component of porcine and bovine CSs. The singular pattern of UC-4 and NC-1 signals was recognized and explained in terms of a diad model. The “excess of multiplicity” affecting mainly these two signals was attributed to the differences in the conformation of the N 1:4 U glycosidic bond. Further support to this hypothesis comes from the comparison of the NOESY spectra of the three CSs.

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.

Oral absorption and bioavailability of ichthyic origin chondroitin sulfate in healthy male volunteers

OBJECTIVE Chondroitin sulfate (CS) has proven to be a valuable therapeutic tool as a symptomatic slow-acting drug for the treatment of osteoarthritis after oral administration. The aim of this study was to assess the absorption of CS of ichthyic origin after oral administration to 20 healthy male volunteers. DESIGN Ichthyic origin CS (from shark cartilage, 4 g) was orally administered to 20 healthy human volunteers, and then extracted and purified from plasma over a 48 h period. The polysaccharide absorbed by oral route was characterized and quantified by agarose-gel electrophoretic technique, and densitometric scanning. In addition, the percentage of constituent disaccharides and charge density were measured. RESULTS After oral administration, ichthyic CS plasma levels increased (more than 120%) with a peak concentration at 8.7h, with the increase reaching significance from 4 to 16 h. A significant decrease in the relative amount of non-sulfated disaccharide was measured (reaching the minimum relative percentage of 30.86+/-20.79% at 8h). At the same time, 4-sulfated disaccharide increased to a maximum of 51.91+/-25.91% at 6h, and 6-sulfated and disulfated disaccharides appeared in blood, reaching maximum concentrations of 15.24+/-16.60% at 8h and 2.93+/-4.82% at 12h, respectively. Concomitantly, the mean charge density rose from 0.40+/-0.14 at predose to a maximum of 0.72+/-0.22 and 0.72+/-0.21 measured 8 and 12h after ichthyic CS administration. CONCLUSIONS Ichthyic CS is absorbed slowly, with a t(max)=8.7+/-4.5h and the C(max)averaged 4.87+/-2.05 microg/ml. The differences in the absorption and bioavailability of the various CS formulations is strongly influenced by the structure and characteristics, such as molecular mass, charge density, and cluster of disulfated disaccharides, of the parental molecules.

Quantitative capillary electrophoresis determination of oversulfated chondroitin sulfate as a contaminant in heparin preparations.

A simple, accurate, and robust quantitative capillary electrophoresis (CE) method for the determination of oversulfated chondroitin sulfate (OSCS) as a contaminant in heparin (Hep) preparations is described. After degradation of the polysaccharides by acidic hydrolysis, the hexosamines produced (i.e., GlcN from Hep and GalN from OSCS) were derivatized with anthranilic acid (AA) and separated by means of CE in approximately 10 min with high sensitivity detection at 214 nm (limit of detection [LOD] of approximately 200 pg). Furthermore, AA-derivatized GlcN and GalN showed quite similar molar absorptivity, allowing direct and simple quantification of OSCS in Hep samples. Moreover, a preliminary step of specific enzymatic treatment by using chondroitin ABC lyase may be applied for the specific elimination of interference in the analysis due to the possible presence in Hep samples of natural chondroitin sulfate and dermatan sulfate impurities, making this analytical approach highly specific for OSCS contamination given that chondroitin ABC lyase is unable to act on this semisynthetic polymer. The CE method was validated for specificity, linearity, accuracy, precision, LOD, and limit of quantification (LOQ). Due to the very high sensitivity of CE, as little as 1% OSCS contaminant in Hep sample could be detected and quantified. Finally, a contaminated raw Hep sample was found to contain 38.9% OSCS, whereas a formulated contaminated Hep was calculated to have 39.7% OSCS.

Analysis of glycosaminoglycan-derived, precolumn, 2-aminoacridone–labeled disaccharides with LC-fluorescence and LC-MS detection

Glycosaminoglycans (GAGs) possess considerable heterogeneity in average molecular mass, molecular mass range, disaccharide composition and content and position of sulfo groups. Despite recent technological advances in the analysis of GAGs, the determination of GAG disaccharide composition still remains challenging and provides key information required for understanding GAG function. Analysis of GAG-derived disaccharides relies on enzymatic treatment, providing one of the most practical and quantitative approaches for compositional mapping. Tagging the reducing end of disaccharides with an aromatic fluorescent label affords stable derivatives with properties that enable improved detection and resolution. HPLC with on-line electrospray ionization mass spectrometry (ESI-MS) offers a relatively soft ionization method for detection and characterization of sulfated oligosaccharides. GAGs obtained from tissues, biological fluids or cells are treated with various enzymes to obtain disaccharides that are fluorescently labeled with 2-aminoacridone (AMAC) and resolved by different LC systems for high-sensitivity detection by fluorescence, and then they are unambiguously characterized by MS. The preparation and labeling of GAG-derived disaccharides can be performed in ∼1–2 d, and subsequent HPLC separation and on-line fluorescence detection and ESI-MS analysis takes another 1–2 h.

Anomalous Structure of Urinary Glycosaminoglycans in Patients with Pseudoxanthoma Elasticum

BACKGROUND Pseudoxanthoma elasticum (PXE) is a hereditary connective tissue disease in which proteoglycans have altered properties. We investigated whether altered proteoglycan metabolism occurs in vivo and may be reflected in the urine of PXE individuals by analyzing the excreted polysaccharides. METHODS We measured sulfated glycosaminoglycans in the urine of 10 PXE-affected patients, 12 healthy carriers, and 20 healthy controls by agarose gel electrophoresis. Chondroitin sulfate and heparan sulfate disaccharides were also quantified by treatment with specific lyases and separation of products by chromatography. RESULTS Total polysaccharides were 34% lower in the urine of PXE-affected patients and 17% lower in healthy carriers than in the control group. Chondroitin sulfate was significantly (P <0.01) decreased, and heparan sulfate was significantly increased. The ratio of chondroitin sulfate to heparan sulfate was 2.7 for PXE-affected patients, 2.3 for healthy carriers, and 10.7 for controls. In PXE-affected individuals and carriers, chondroitin sulfate contained more 4-sulfated disaccharide, less 6-sulfated disaccharide, and decreased nonsulfated disaccharide. Heparan sulfate from PXE-affected individuals and healthy carriers produced significantly less N-sulfated disaccharide and more disaccharide sulfated at the C-6 position with no significant abnormality of the nonsulfated disaccharide percentage and sulfates:disaccharide ratio. CONCLUSIONS The urinary data support the concept that the inherited defect of the ABCC6/MRP6 transporter in PXE alters metabolism of key polysaccharides. Structural analysis of urinary sulfated polyanions may be useful in the diagnosis of PXE.