Analytical method for the determination of disaccharides derived from keratan, heparan, and dermatan sulfates in human serum and plasma by high-performance liquid chromatography/turbo ionspray ionization tandem mass spectrometry

A novel LC-MS/MS assay for heparan sulfate screening in the cerebrospinal fluid of mucopolysaccharidosis IIIA patients

AIMS

Heparan sulfate (HS) accumulates in the central nervous system in mucopolysaccharidosis III type A (MPS IIIA). A validated LC-MS/MS assay was developed to measure HS in human cerebrospinal fluid (CSF).

METHODS & RESULTS

HS was extracted and digested and the resultant disaccharides were derivatized with a novel label, 4-butylaniline, enabling isoform separation and isotope-tagged analog introduction as an internal standard for LC-MS/MS. The assay has a LLOQ for disaccharides of 0.1 μM, ±20% accuracy and ≤20% precision. CSF samples from patients with MPS IIIA showed elevated HS levels (mean 4.9 μM) compared with negative controls (0.37 μM).

CONCLUSION

This assay detected elevated HS levels in the CSF of patients with MPS IIIA and provides a method to assess experimental therapies.

Development of a rapid method for simultaneous separation of hyaluronic acid, chondroitin sulfate, dermatan sulfate and heparin by capillary electrophoresis

This study reports the use of diethylenetriamine as background electrolyte for the simultaneous separation of hyaluronan acid, chondroitin sulfate, dermatan sulfate and heparin. The analytes were baseline separated by using an uncoated fused silica capillary at 37°C with a run time of 23min. The migration order, with hyaluronan acid at first and heparin at last, was related to the sulfation degree. The effect of salt concentration on resolution and migration order was also investigated. The developed method was applied to the simultaneous determination of hyaluronan acid and chondroitin sulfate in mouse plasma. Interferences in plasma were removed by protein precipitation and glycosaminoglycans were further purified by ethanol precipitation. The method was validated over the concentration range from 50 to 600μg/mL for hyaluronan acid and 500 to 6000μg/mL for chondroitin sulfate in mouse plasma. Results from assay validations showed that the method was selective and robust.

A Multiplex Assay for the Diagnosis of Mucopolysaccharidoses and Mucolipidoses

Introduction

Diagnosis of the mucopolysaccharidoses (MPSs) generally relies on an initial analysis of total glycosaminoglycan (GAG) excretion in urine. Often the dimethylmethylene blue dye-binding (DMB) assay is used, although false-negative results have been reported. We report a multiplexed diagnostic test with a high sensitivity for all MPSs and with the potential to identify patients with I-cell disease (ML II) and mucolipidosis III (ML III).

Methods

Urine samples of 100 treatment naive MPS patients were collected and analyzed by the conventional DMB assay and a multiplex assay based on enzymatic digestion of heparan sulfate (HS), dermatan sulfate (DS) and keratan sulfate (KS) followed by quantification by LC-MS/MS. Specificity was calculated by analyzing urine samples from a cohort of 39 patients suspected for an inborn error of metabolism, including MPSs.

Results

The MPS cohort consisted of 18 MPS I, 16 MPS II, 34 MPS III, 10 MPS IVA, 3 MPS IVB, 17 MPS VI and 2 MPS VII patients. All 100 patients were identified by the LC-MS/MS assay with typical patterns of elevation of HS, DS and KS, respectively (sensitivity 100%). DMB analysis of the urine was found to be in the normal range in 10 of the 100 patients (sensitivity 90%). Three out of the 39 patients were identified as false-positive, resulting in a specificity of the LS-MS/MS assay of 92%. For the DMB this was 97%. All three patients with MLII/MLIII had elevated GAGs in the LC-MS/MS assay while the DMB test was normal in 2 of them.

Conclusion

The multiplex LC-MS/MS assay provides a robust and very sensitive assay for the diagnosis of the complete spectrum of MPSs and has the potential to identify MPS related disorders such as MLII/MLIII. Its performance is superior to that of the conventional DMB assay.

Positive Mode LC-MS/MS Analysis of Chondroitin Sulfate Modified Glycopeptides Derived from Light and Heavy Chains of The Human Inter-α-Trypsin Inhibitor Complex

The inter-α-trypsin inhibitor complex is a macromolecular arrangement of structurally related heavy chain proteins covalently cross-linked to the chondroitin sulfate (CS) chain of the proteoglycan bikunin. The inter-α-trypsin inhibitor complex is abundant in plasma and associated with inflammation, kidney diseases, cancer and diabetes. Bikunin is modified at Ser-10 by a single low-sulfated CS chain of 23-55 monosaccharides with 4-9 sulfate groups. The innermost four monosaccharides (GlcAβ3Galβ3Galβ4Xylβ-O-) compose the linkage region, believed to be uniform with a 4-O-sulfation to the outer Gal. The cross-linkage region of the bikunin CS chain is located in the nonsulfated nonreducing end, (GalNAcβ4GlcAβ3)(n), to which heavy chains (H1-H3) may be bound in GalNAc to Asp ester linkages. In this study we employed a glycoproteomics protocol to enrich and analyze light and heavy chain linkage and cross-linkage region CS glycopeptides derived from the IαI complex of human plasma, urine and cerebrospinal fluid samples. The samples were trypsinized, enriched by strong anion exchange chromatography, partially depolymerized with chondroitinase ABC and analyzed by LC-MS/MS using higher-energy collisional dissociation. The analyses demonstrated that the CS linkage region of bikunin is highly heterogeneous. In addition to sulfation of the Gal residue, Xyl phosphorylation was observed although exclusively in urinary samples. We also identified novel Neu5Ac and Fuc modifications of the linkage region as well as the presence of mono- and disialylated core 1 O-linked glycans on Thr-17. Heavy chains H1 and H2 were identified cross-linked to GalNAc residues one or two GlcA residues apart and H1 was found linked to either the terminal or subterminal GalNAc residues. The fragmentation behavior of CS glycopeptides under variable higher-energy collisional dissociation conditions displays an energy dependence that may be used to obtain complementary structural details. Finally, we show that the analysis of sodium adducts provides confirmatory information about the positions of glycan substituents.

Sanfilippo syndrome: Overall review

Mucopolysaccharidosis type III (MPS III, Sanfilippo syndrome) is a lysosomal storage disorder, caused by a deficiency in one of the four enzymes involved in the catabolism of glycosaminoglycan heparan sulfate. It is characterized by progressive cognitive decline and severe hyperactivity, with relatively mild somatic features. This review focuses on clinical features, diagnosis, treatment, and follow-up of MPS III, and provides information about supplementary tests and differential diagnosis. Given that few reviews of MPS III have been published, several studies were compiled to establish diagnostic recommendations. Quantitative urinary glycosaminoglycan analysis is strongly recommended, and measurement of disaccharides, heparin cofactor II-thrombin complex and gangliosides is also used. Enzyme activity of the different enzymes in blood serum, leukocytes or fibroblasts, and mutational analysis for SGSH, NAGLU, HGSNAT or GNS genes are required to confirm diagnosis and differentiate four subtypes of MPS III. Although there is no global consensus for treatment, enzyme replacement therapy and gene therapy can provide appropriate results. In this regard, recent publications on treatment and follow-up are discussed.

Glycosaminoglycanomics of cultured cells using a rapid and sensitive LC-MS/MS approach

Glycosaminoglycans (GAGs), a family of polysaccharides widely distributed in eukaryotic cells, are responsible for a wide array of biological functions. Quantitative disaccharide compositional analysis is one of the primary ways to characterize the GAG structure. This structural analysis is typically time-consuming (1-2 weeks) and labor intensive, requiring GAG recovery and multistep purification, prior to the enzymatic/chemical digestion of GAGs, and finally their analysis. Moreover, 10(5)-10(7) cells are usually required for compositional analysis. We report a sensitive, rapid, and quantitative analysis of GAGs present in a small number of cells. Commonly studied cell lines were selected based on phenotypic properties related to the biological functions of GAGs. These cells were lysed using a commercial surfactant reagent, sonicated, and digested with polysaccharide lyases. The resulting disaccharides were recovered by centrifugal filtration, labeled with 2-aminoacridone, and analyzed by liquid chromatography (LC)-mass spectrometry (MS). Using a highly sensitive MS method, multiple reaction monitoring (MRM), the limit of detection for each disaccharide was reduced to 0.5-1.0 pg, as compared with 1.0-5.0 ng obtained using standard LC-MS analysis. Sample preparation time was reduced to 1-2 days, and the cell number required was reduced to 5000 cells for complete GAG characterization to as few as 500 cells for the characterization of the major GAG disaccharide components. Our survey of the glycosaminoglycanomes of the 20 selected cell lines reveals major differences in their GAG amounts and compositions. Structure-function relationships are explored using these data, suggesting the utility of this method in cellular glycobiology.

Molecular Genetics and Metabolism Report Long-term follow-up of post hematopoietic stem cell transplantation for Hurler syndrome: clinical, biochemical, and pathological improvements

Mucopolysaccharidosis type I (MPS I; Hurler Syndrome) is a lysosomal storage disease caused by a deficiency of the enzyme α-L-iduronidase which affects multiple organs such as central nervous system (CNS), skeletal system, and physical appearance. Hematopoietic stem cell transplantation (HSCT) is recommended as a primary therapeutic option at an early stage of MPS I with a severe form to ameliorate CNS involvement; however, no description of pathological improvement in skeletal dysplasia has been investigated to date. We here report a 15-year-old male case with MPS I post-HSCT. This patient received successful HSCT at the age of 2 years and 1 month, followed for over 10 years. His activity of daily living including cognitive performance has been kept normal and the present height and weight are 162 cm and 55 kg. Bone deformity has been still developed, resulting in hemiepiphysiodesis of bilateral medial proximal tibia at 12 years of age and successive arthrodesis of thoraco-lumbar spine at 13 years of age; however, skeletal histopathology from surgical remnants showed substantial improvement in bone lesion with markedly reduced occurrence and cell size of vacuolated cells. After a series of surgical procedures, he became ambulant and independent in daily activity. The levels of GAGs in blood were substantially reduced. In conclusion, this long-term post-HSCT observation should shed light on a new aspect of therapeutic effect associated with skeletal pathology and GAG levels as a biomarker, indicating that HSCT is a primary choice at an early stage for not only CNS but skeletal system in combination of appropriate surgical procedures.

Di-sulfated Keratan Sulfate as a Novel Biomarker for Mucopolysaccharidosis II, IVA, and IVB

Keratan sulfate (KS) is a storage material in mucopolysaccharidosis IV (MPS IV). However, no detailed analysis has been reported on subclasses of KS: mono-sulfated KS and di-sulfated KS. We established a novel method to distinguish and quantify mono- and di-sulfated KS using liquid chromatography-tandem mass spectrometry and measured both KS levels in various specimens.Di-sulfated KS was dominant in shark cartilage and rat serum, while mono-sulfated KS was dominant in bovine cornea and human serum. Levels of both mono- and di-sulfated KS varied with age in the blood and urine from control subjects and patients with MPS II and IVA. The mean levels of both forms of KS in the plasma/serum from patients with MPS II, IVA, and IVB were elevated compared with that in age-matched controls. Di-sulfated KS provided more significant difference between MPS IVA and the age-matched controls than mono-sulfated KS. The ratio of di-sulfated KS to total KS in plasma/serum increased with age in control subjects and patients with MPS II but was age independent in MPS IVA patients. Consequently, this ratio can discriminate younger MPS IVA patients from controls. Levels of mono- and di-sulfated KS in urine of MPS IVA and IVB patients were all higher than age-matched controls for all ages studied.In conclusion, the level of di-sulfated KS and its ratio to total KS can distinguish control subjects from patients with MPS II, IVA, and IVB, indicating that di-sulfated KS may be a novel biomarker for these disorders.

Biomarker responses correlate with antibody status in mucopolysaccharidosis type I patients on long-term enzyme replacement therapy

BACKGROUND

Antibody formation can interfere with effects of enzyme replacement therapy (ERT) in lysosomal storage diseases. Biomarkers are used as surrogate marker for disease burden in MPS I, but large systematic studies evaluating the response of biomarkers to ERT are lacking. We, for the first time, investigated the response of a large panel of biomarkers to long term ERT in MPS I patients and correlate these responses with antibody formation and antibody mediated cellular uptake inhibition.

METHODS

A total of 428 blood and urine samples were collected during long-term ERT in 24 MPS I patients and an extensive set of biomarkers was analyzed, including heparan sulfate (HS) and dermatan sulfate (DS) derived disaccharides; total urinary GAGs (DMBu); urinary DS:CS ratio and serum heparin co-factor II thrombin levels (HCII-T). IgG antibody titers and the effect of antibodies on cellular uptake of the enzyme were determined for 23 patients.

RESULTS

Median follow-up was 2.3 years. In blood, HS reached normal levels more frequently than DS (50% vs 12.5%, p=0.001), though normalization could take several years. DMBu normalized more rapidly than disaccharide levels in urine (p=0.02). Nineteen patients (83%) developed high antibody titers. Significant antibody-mediated inhibition of enzyme uptake was observed in 8 patients (35%), and this correlated strongly with a poorer biomarker response for HS and DS in blood and urine as well as for DMBu, DS:CS-ratio and HCII-T (all p<0.006).

CONCLUSIONS

This study shows that, despite a response of all studied biomarkers to initiation of ERT, some biomarkers were less responsive than others, suggesting residual disease activity. In addition, the correlation of cellular uptake inhibitory antibodies with a decreased biomarker response demonstrates a functional role of these antibodies which may have important clinical consequences.

A straightforward, quantitative ultra-performance liquid chromatography-tandem mass spectrometric method for heparan sulfate, dermatan sulfate and chondroitin sulfate in urine: an improved clinical screening test for the mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are complex storage disorders that result in the accumulation of glycosaminoglycans (GAGs) in urine, blood, brain and other tissues. Symptomatic patients are typically screened for MPS by analysis of GAG in urine. Current screening methods used in clinical laboratories are based on colorimetric assays that lack the sensitivity and specificity to reliably detect mild GAG elevations that occur in some patients with MPS. We have developed a straightforward, reliable method to quantify chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) in urine by stable isotope dilution tandem mass spectrometry. The GAGs were methanolyzed to uronic acid-N-acetylhexosamine or iduronic acid-N-glucosamine dimers and mixed with stable isotope labeled internal standards derived from deuteriomethanolysis of GAG standards. Specific dimers derived from HS, DS and CS were separated by ultra-performance liquid chromatography and analyzed by electrospray ionization tandem mass spectrometry using selected reaction monitoring for each targeted GAG product and its corresponding internal standard. The method was robust with a mean inaccuracy from 1 to 15%, imprecision below 11%, and a lower limit of quantification of 0.4mg/L for CS, DS and HS. We demonstrate that the method has the required sensitivity and specificity to discriminate patients with MPS III, MPS IVA and MPS VI from those with MPS I or MPS II and can detect mildly elevated GAG species relative to age-specific reference intervals. This assay may also be used for the monitoring of patients following therapeutic intervention. Patients with MPS IVB are, however, not detectable by this method.

Distribution of Heparan Sulfate Oligosaccharides in Murine Mucopolysaccharidosis Type IIIA

Heparan sulfate (HS) catabolism begins with endo-degradation of the polysaccharide to smaller HS oligosaccharides, followed by the sequential action of exo-enzymes to reduce these oligosaccharides to monosaccharides and inorganic sulfate. In mucopolysaccharidosis type IIIA (MPS IIIA) the exo-enzyme, N-sulfoglucosamine sulfohydrolase, is deficient resulting in an inability to hydrolyze non-reducing end glucosamine N-sulfate esters. Consequently, partially degraded HS oligosaccharides with non-reducing end glucosamine sulfate esters accumulate. We investigated the distribution of these HS oligosaccharides in tissues of a mouse model of MPS IIIA using high performance liquid chromatography electrospray ionization-tandem mass spectrometry. Oligosaccharide levels were compared to total uronic acid (UA), which was used as a measure of total glycosaminoglycan. Ten oligosaccharides, ranging in size from di- to hexasaccharides, were present in all the tissues examined including brain, spleen, lung, heart, liver, kidney and urine. However, the relative levels varied up to 10-fold, suggesting different levels of HS turnover and storage. The relationship between the di- and tetrasaccharides and total UA was tissue specific with spleen and kidney showing a different disaccharide:total UA ratio than the other tissues. The hexasaccharides showed a stronger correlation with total UA in all tissue types suggesting that hexasaccharides may more accurately reflect the storage burden in these tissues.

Clinical Glycomics Employing Graphitized Carbon Liquid Chromatography-Mass Spectrometry

Glycoconjugates and free glycan are involved in a variety of biological processes such as cell-cell interaction and cell trafficking. Alterations in the complex glycosylation machinery have been correlated with various pathological processes including cancer progression and metastasis. Mass Spectrometry (MS) has evolved as one of the most powerful tools in glycomics and glycoproteomics and in combination with porous graphitized carbon-liquid chromatography (PGC-LC) it is a versatile and sensitive technique for the analysis of glycans and to some extent also glycopeptides. PGC-LC-ESI-MS analysis is characterized by a high isomer separation power enabling a specific glycan compound analysis on the level of individual structures. This allows the investigation of the biological relevance of particular glycan structures and glycan features. Consequently, this strategy is a very powerful technique suitable for clinical research, such as cancer biomarker discovery, as well as in-depth analysis of recombinant glycoproteins. In this review, we will focus on how PGC in conjunction with MS detection can deliver specific structural information for clinical research on protein-bound N-glycans and mucin-type O-glycans. In addition, we will briefly review PGC analysis approaches for glycopeptides, glycosaminoglycans (GAGs) and human milk oligosaccharides (HMOs). The presented applications cover systems that vary vastly with regard to complexity such as purified glycoproteins, cells, tissue or body fluids revealing specific glycosylation changes associated with various biological processes including cancer and inflammation.

Quantitative analysis of glycosaminoglycans, chondroitin/dermatan sulfate, hyaluronic acid, heparan sulfate, and keratan sulfate by liquid chromatography-electrospray ionization-tandem mass spectrometry

We developed a method using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) with a selected reaction monitoring (SRM) mode for simultaneous quantitative analysis of glycosaminoglycans (GAGs). Using one-shot analysis with our MS/MS method, we demonstrated the simultaneous quantification of a total of 23 variously sulfated disaccharides of four GAG classes (8 chondroitin/dermatan sulfates, 1 hyaluronic acid, 12 heparan sulfates, and 2 keratan sulfates) with a sensitivity of less than 0.5 pmol within 20 min. We showed the differences in the composition of GAG classes and the sulfation patterns between porcine articular cartilage and yellow ligament. In addition to the internal disaccharides described above, some saccharides derived from the nonreducing terminal were detected simultaneously. The simultaneous quantification of both internal and nonreducing terminal saccharides could be useful to estimate the chain length of GAGs. This method would help to establish comprehensive "GAGomic" analysis of biological tissues.

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.

Establishment of glycosaminoglycan assays for mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by deficiency of the lysosomal enzymes essential for catabolism of glycosaminoglycans (GAGs). Accumulation of undegraded GAGs results in dysfunction of multiple organs, resulting in distinct clinical manifestations. A range of methods have been developed to measure specific GAGs in various human samples to investigate diagnosis, prognosis, pathogenesis, GAG interaction with other molecules, and monitoring therapeutic efficacy. We established ELISA, liquid chromatography tandem mass spectrometry (LC-MS/MS), and an automated high-throughput mass spectrometry (HT-MS/MS) system (RapidFire) to identify epitopes (ELISA) or disaccharides (MS/MS) derived from different GAGs (dermatan sulfate, heparan sulfate, keratan sulfate, and/or chondroitin sulfate). These methods have a high sensitivity and specificity in GAG analysis, applicable to the analysis of blood, urine, tissues, and cells. ELISA is feasible, sensitive, and reproducible with the standard equipment. HT-MS/MS yields higher throughput than conventional LC-MS/MS-based methods while the HT-MS/MS system does not have a chromatographic step and cannot distinguish GAGs with identical molecular weights, leading to a limitation of measurements for some specific GAGs. Here we review the advantages and disadvantages of these methods for measuring GAG levels in biological specimens. We also describe an unexpected secondary elevation of keratan sulfate in patients with MPS that is an indirect consequence of disruption of catabolism of other GAGs.

Lysosomal diseases: diagnostic update

Technological developments in newborn and population screening, biomarker discovery for monitoring treatment and rapid high throughput DNA sequencing are having a great impact on the diagnostic procedure for symptomatic patients with lysosomal storage diseases. The use of dried blood spots, initially for newborn screening, has stimulated the introduction of automated, rapid and more sensitive methods for the assay of lysosomal enzymes, including the synthesis of novel substrates. Storage products and secondary metabolites in urine and cells can be identified and measured very accurately and sensitively by high performance liquid chromatography and tandem mass spectrometry. This has enhanced the preliminary metabolite screen for LSDs and facilitated the diagnosis of transport defects. Fast, reliable and affordable high throughput DNA sequencing, such as whole or selected exome sequencing, is helping to make diagnoses in difficult cases, to reveal novel gene defects, to widen the clinical spectrum of diseases and possibly to identify modifying genetic factors. Bioinformatics will be necessary to handle the data generated by these new technologies. Notwithstanding, these technical innovations, accurate and reliable diagnosis will still depend on the knowledge and experience of skilled laboratory staff.

FACE analysis as a fast and reliable methodology to monitor the sulfation and total amount of chondroitin sulfate in biological samples of clinical importance

Glycosaminoglycans (GAGs) due to their hydrophilic character and high anionic charge densities play important roles in various (patho)physiological processes. The identification and quantification of GAGs in biological samples and tissues could be useful prognostic and diagnostic tools in pathological conditions. Despite the noteworthy progress in the development of sensitive and accurate methodologies for the determination of GAGs, there is a significant lack in methodologies regarding sample preparation and reliable fast analysis methods enabling the simultaneous analysis of several biological samples. In this report, developed protocols for the isolation of GAGs in biological samples were applied to analyze various sulfated chondroitin sulfate- and hyaluronan-derived disaccharides using fluorophore-assisted carbohydrate electrophoresis (FACE). Applications to biologic samples of clinical importance include blood serum, lens capsule tissue and urine. The sample preparation protocol followed by FACE analysis allows quantification with an optimal linearity over the concentration range 1.0–220.0 µg/mL, affording a limit of quantitation of 50 ng of disaccharides. Validation of FACE results was performed by capillary electrophoresis and high performance liquid chromatography techniques.

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.

Capillary electrophoresis for total glycosaminoglycan analysis

A capillary zone electrophoresis-laser-induced fluorescence detection (CZE-LIF) method was developed for the simultaneous analysis of disaccharides derived from heparan sulfate, chondroitin sulfate/dermatan sulfate, hyaluronan, and keratan sulfate. Glycosaminoglycans (GAGs) were first depolymerized with the mixture of GAG lyases (heparinase I, II, III and chondroitinase ABC and chondroitinase AC II) and GAG endohydrolase (keratinase II) and the resulting disaccharides were derivatized by reductive amination with 2-aminoacridone. Nineteen fluorescently labeled disaccharides were separated using 50 mM phosphate buffer (pH 3.3) under reversed polarity at 25 kV. Using these conditions, all the disaccharides examined were baseline separated in less then 25 min. This CZE-LIF method gave good reproducibility for both migration time (≤1.03% for intraday and ≤4.4% for interday) and the peak area values (≤5.6% for intra- and ≤8.69% for interday). This CZE-LIF method was used for profiling and quantification of GAG derivative disaccharides in bovine cornea. The results show that the current CZE-LIF method offers fast, simple, sensitive, reproducible determination of disaccharides derived from total GAGs in a single run.

Glycan-based biomarkers for mucopolysaccharidoses

The mucopolysaccharidoses (MPS) result from attenuation or loss of enzyme activities required for lysosomal degradation of the glycosaminoglycans, hyaluronan, heparan sulfate, chondroitin/dermatan sulfate, and keratan sulfate. This review provides a summary of glycan biomarkers that have been used to characterize animal models of MPS, for diagnosis of patients, and for monitoring therapy based on hematopoietic stem cell transplantation and enzyme replacement therapy. Recent advances have focused on the non-reducing terminus of the glycosaminoglycans that accumulate as biomarkers, using a combination of enzymatic digestion with bacterial enzymes followed by quantitative liquid chromatography/mass spectrometry. These new methods provide a simple, rapid diagnostic strategy that can be applied to samples of urine, blood, cerebrospinal fluid, cultured cells and dried blood spots from newborn infants. Analysis of the non-reducing end glycans provides a method for monitoring enzyme replacement and substrate reduction therapies and serves as a discovery tool for uncovering novel biomarkers and new forms of mucopolysaccharidoses.

Assay for Glycosaminoglycans by Tandem Mass Spectrometry and its Applications

Glycosaminoglycans (GAGs) are distributed in the whole body and play a variety of important physiological roles associated with inflammation, growth, coagulation, fibrinolysis, lipolysis, and cell-matrix biology. Accumulation of undegraded GAGs in lysosomes gives rise to a distinct clinical syndrome, mucopolysaccharidoses. Measurement of each specific GAG in a variety of specimens is urgently required to understand GAG interaction with other molecules, physiological status of patients, and prognosis and pathogenesis of the disease. We established a highly sensitive and accurate tandem mass spectrometry (LC-MS/MS) method for measurements of disaccharides derived from four specific GAGs [dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and chondroitin sulfate (CS)]. Disaccharides were produced by specific enzyme digestion of each GAG, and quantified by negative ion mode of multiple reaction monitoring. Subclasses of HS and GAGs with identical molecular weights can be separated using a Hypercarbcolumn (2.0 mm×50 mm, 5 μm) with an aectonitrile gradient in ammonium acetate (pH 11.0). We also developed a GAG assay by RapidFire with tandem mass spectrometry (RF-MS/MS). The RF system consists of an integrated solid phase extraction robot that binds and de-salts samples from assay plates and directly injects them into a MS/MS detector, reducing sample processing time to ten seconds. RF-MS/MS consequently yields much faster throughput than conventional LC-MS/MS-based methods. However, the RF system does not have a chromatographic step, and therefore, cannot distinguish GAGs that have identical molecular weights. Both methods can be applied to analysis of dried blood spots, blood, and urine specimens. In this article, we compare the assay methods for GAGs and describe their potential applications.

Circulating glycosaminoglycan species in septic shock

BACKGROUND

Glycosaminoglycans (GAGs) are negatively charged polysaccharides present, e.g., on the luminal face of the blood vessels as heparan sulphate (HS) and hyaluronic acid (HA), in the interstitium as HA, and in neutrofils and plasma as chondroitin sulphate (CS) and HA. Total plasma levels of GAG are increased in human septic shock, but the origin and pathophysiological implications are unclear. In order to determine the source of circulating GAG in sepsis, we compared plasma levels of HS, HA, CS and keratan sulphate (KS) in patients with septic shock and controls.

METHODS

HS and KS were measured with enzyme-linked immunosorbent assay, and HA and CS disaccharides with liquid chromatography tandem mass spectrometry in plasma obtained from patients admitted to intensive care fulfilling criteria for septic shock as well as from matched control patients scheduled for neurosurgery.

RESULTS

Median levels of HS and HA were fourfold increased in septic shock and were higher in patients that did not survive 90 days (threefold and fivefold for HS and HA, respectively). Median CS levels were unaltered, while KS levels were slightly decreased in sepsis patients. HS and HA levels correlated with levels of interleukin-6 and interleukin-10. Except for HA, GAG levels did not correlate to liver or kidney sequential organ function score.

CONCLUSION

Median plasma level of HS and HA is increased in septic shock patients, are higher in patients that do not survive, and correlates with inflammatory activation and failing circulation. The increased levels could be due to vascular damage.

Newborn screening and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are caused by deficiency of lysosomal enzyme activities needed to degrade glycosaminoglycans (GAGs), which are long unbranched polysaccharides consisting of repeating disaccharides. GAGs include: chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and hyaluronan. Their catabolism may be blocked singly or in combination depending on the specific enzyme deficiency. There are 11 known enzyme deficiencies, resulting in seven distinct forms of MPS with a collective incidence of higher than 1 in 25,000 live births. Accumulation of undegraded metabolites in lysosomes gives rise to distinct clinical syndromes. Generally, the clinical conditions progress if untreated, leading to developmental delay, systemic skeletal deformities, and early death. MPS disorders are potentially treatable with enzyme replacement therapy or hematopoietic stem cell transplantation. For maximum benefit of available therapies, early detection and intervention are critical. We recently developed a novel high-throughput multiplex method to assay DS, HS, and KS simultaneously in blood samples by using high performance liquid chromatography/tandem mass spectrometry for MPS. The overall performance metrics of HS and DS values on MPS I, II, and VII patients vs. healthy controls at newborns were as follows using a given set of cut-off values: sensitivity, 100%; specificity, 98.5-99.4%; positive predictive value, 54.5-75%; false positive rate, 0.62-1.54%; and false negative rate, 0%. These findings show that the combined measurements of these three GAGs are sensitive and specific for detecting all types of MPS with acceptable false negative/positive rates. In addition, this method will also be used for monitoring therapeutic efficacy. We review the history of GAG assay and application to diagnosis for MPS.

Review of clinical presentation and diagnosis of mucopolysaccharidosis IVA

Mucopolysaccharidosis type IVA (MPS IVA) was described in 1929 by Luis Morquio from Uruguay and James Brailsford from England, and was later found as an autosomal recessive lysosomal storage disease. MPS IVA is caused by mutations in the gene encoding the enzyme, N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Reduced GALNS activity results in impaired catabolism of two glycosaminoglycans (GAGs), chondroitin-6-sulfate (C6S) and keratan sulfate (KS). Clinical presentations of MPS IVA reflect a spectrum of progression from a severe "classical" phenotype to a mild "attenuated" phenotype. More than 180 different mutations have been identified in the GALNS gene, which likely explains the phenotypic heterogeneity of the disorder. Accumulation of C6S and KS manifests predominantly as short stature and skeletal dysplasia (dysostosis multiplex), including atlantoaxial instability and cervical cord compression. However, abnormalities in the visual, auditory, cardiovascular, and respiratory systems can also affect individuals with MPS IVA. Diagnosis is typically based on clinical examination, skeletal radiographs, urinary GAG, and enzymatic activity of GALNS in blood cells or fibroblasts. Deficiency of GALNS activity is a common assessment for the laboratory diagnosis of MPS IVA; however, with recently increased availability, gene sequencing for MPS IVA is often used to confirm enzyme results. As multiple clinical presentations are observed, diagnosis of MPS IVA may require multi-system considerations. This review provides a history of defining MPS IVA and how the understanding of the disease manifestations has changed over time. A summary of the accumulated knowledge is presented, including information from the International Morquio Registry. The classical phenotype is contrasted with attenuated cases, which are now being recognized and diagnosed more frequently. Laboratory based diagnoses of MPS IVA are also discussed.

The Morquio A Clinical Assessment Program: baseline results illustrating progressive, multisystemic clinical impairments in Morquio A subjects

OBJECTIVES

The objectives of this study are to quantify endurance and respiratory function and better characterize spectrum of symptoms and biochemical abnormalities in mucopolysaccharidosis IVA subjects.

METHODS

MorCAP was a multicenter, multinational, cross sectional study amended to be longitudinal in 2011. Each study visit required collection of medical history, clinical assessments, and keratan sulfate (KS) levels.

RESULTS

Data from the first visit of 325 subjects (53% female) were available. Mean age was 14.5 years. Mean ± SD height z-scores were -5.6 ± 3.1 as determined by the CDC growth charts. Mean ± SD from the 6-minute-walk-test was 212.6 ± 152.2m, revealing limitations in functional endurance testing, and 30.0 ± 24.0 stairs/min for the 3-minute-stair-climb test. Respiratory function showed limitations comparable to MPS VI patients; mean ± SD was 1.2 ± 0.9l based on forced vital capacity and 34.8 ± 25.5l/min based on maximum voluntary ventilation. Mean urinary keratan sulfate (uKS) was elevated for all ages, and negatively correlated with age. Higher uKS correlated with greater clinical impairment based on height z-scores, endurance and respiratory function tests. The MPS Health Assessment Questionnaire reveals impairments in mobility and activities of daily living in comparison to an age-matched control population.

CONCLUSIONS

MPS IVA is a multisystem disorder with a continuum of clinical presentation. All affected individuals experience significant functional limitations and reduced quality of life. Older patients have more severe exercise and respiratory capacity limitations, and more frequent cardiac pathology illustrating the progressive nature of disease.

Diagnosing mucopolysaccharidosis IVA

Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is an autosomal recessive lysosomal storage disorder resulting from a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) activity. Diagnosis can be challenging and requires agreement of clinical, radiographic, and laboratory findings. A group of biochemical genetics laboratory directors and clinicians involved in the diagnosis of MPS IVA, convened by BioMarin Pharmaceutical Inc., met to develop recommendations for diagnosis. The following conclusions were reached. Due to the wide variation and subtleties of radiographic findings, imaging of multiple body regions is recommended. Urinary glycosaminoglycan analysis is particularly problematic for MPS IVA and it is strongly recommended to proceed to enzyme activity testing even if urine appears normal when there is clinical suspicion of MPS IVA. Enzyme activity testing of GALNS is essential in diagnosing MPS IVA. Additional analyses to confirm sample integrity and rule out MPS IVB, multiple sulfatase deficiency, and mucolipidoses types II/III are critical as part of enzyme activity testing. Leukocytes or cultured dermal fibroblasts are strongly recommended for enzyme activity testing to confirm screening results. Molecular testing may also be used to confirm the diagnosis in many patients. However, two known or probable causative mutations may not be identified in all cases of MPS IVA. A diagnostic testing algorithm is presented which attempts to streamline this complex testing process.

Plasma and urinary levels of dermatan sulfate and heparan sulfate derived disaccharides after long-term enzyme replacement therapy (ERT) in MPS I: correlation with the timing of ERT and with total urinary excretion of glycosaminoglycans

INTRODUCTION

Mucopolysaccharidosis type I (MPS I) results in a defective breakdown of the glycosaminoglycans (GAGs) heparan sulfate and dermatan sulfate, which leads to a progressive disease. Enzyme replacement therapy (ERT) results in clearance of these GAGs from a range of tissues and can significantly ameliorate several symptoms. The biochemical efficacy of ERT is generally assessed by the determination of the total urinary excretion of GAGs. However, this has limitations. We studied the concentrations of heparan sulfate and dermatan sulfate derived disaccharides (HS and DS, respectively) in the plasma and urine of seven patients and compared these levels with total urinary GAGs (uGAGs) levels.

METHODS

Plasma and urine samples were collected at different time points relative to the weekly ERT for three non-consecutive weeks in seven MPS I patients who had been treated with ERT for at least 2.5 years. Heparan and dermatan sulfate in plasma and urine were enzymatically digested into disaccharides, and HS and DS levels were determined by HPLC-MS/MS analysis. uGAGs were measured by the DMB test.

RESULTS

The levels of HS and DS were markedly decreased compared with the levels before the initiation of ERT. However, the concentrations of DS in plasma and of both HS and DS in urine remained significantly elevated in all studied patients, while in six patients the level of total uGAGs had normalized. The concentrations of plasma and urinary HS during the weekly ERT followed a U-shaped curve. However, the effect size is small. The concentrations of plasma and urinary DS and uGAGs appeared to be in a steady state.

CONCLUSIONS

HS and DS are sensitive biomarkers for monitoring the biochemical treatment efficacy of ERT and remain elevated despite long-term treatment. This finding may be related to the labeled dose or antibody status of the patient. The timing of the sample collection is not relevant, at least at the current dose of 100 IU/kg/weekly.

Disaccharide analysis of glycosaminoglycans using hydrophilic interaction chromatography and mass spectrometry

Heparan sulfate (HS) and chondroitin sulfate/dermatan sulfate (CS/DS) glycosaminoglycans (GAGs) participate in many important biological processes. Quantitative disaccharide analysis of HS and CS/DS is essential for the characterization of GAGs and enables modeling of the GAG domain structure. Methods involving enzymatic digestion and chemical depolymerization have been developed to determine the type and location of sulfation/acetylation modifications as well as uronic acid epimerization. Enzymatic digestion generates disaccharides with Δ-4,5-unsaturation at the nonreducing end. Chemical depolymerization with nitrous acid retains the uronic acid epimerization. This work shows the use of hydrophilic interaction liquid chromatography mass spectrometry (HILIC-MS) for quantification of both enzyme-derived and nitrous acid depolymerization products for structural analysis of HS and CS/DS. This method enables biomedical researchers to determine complete disaccharide profiles on GAG samples using a single LC-MS platform.

Heparan sulfate and dermatan sulfate derived disaccharides are sensitive markers for newborn screening for mucopolysaccharidoses types I, II and III

INTRODUCTION

Mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders (LSDs) caused by a defect in the degradation of glycosaminoglycans (GAGs). The accumulation of GAGs in MPS patients results in extensive, severe and progressive disease. Disease modifying therapy is available for three of the MPSs and is being developed for the other types. Early initiation of treatment, before the onset of irreversible tissue damage, clearly provides a favorable disease outcome. However, early diagnosis is difficult due to the rarity of these disorders in combination with the wide variety of clinical symptoms. Newborn screening (NBS) is probably the optimal approach, and several screening techniques for different MPSs have been studied. Here we describe a relatively simple and sensitive method to measure levels of dermatan and heparan sulfate derived disaccharides in dried blood spots (DBS) with HPLC-MS/MS, and show that this reliably separates MPS I, II and MPS III newborns from controls and heterozygotes.

METHODS

Newborn DBS of 11 MPS I, 1 MPS II, and 6 MPS III patients, with phenotypes ranging from severe to relatively attenuated, were collected and levels of dermatan and heparan sulfate derived disaccharides in these DBS were compared with levels in DBS of newborn MPS I and MPS III heterozygotes and controls.

RESULTS

The levels of dermatan and heparan sulfate derived disaccharides were clearly elevated in all newborn DBS of MPS I, II and III patients when compared to controls. In contrast, DBS of MPS I and III heterozygotes showed similar disaccharide levels when compared to control DBS.

CONCLUSIONS

Our study demonstrates that measurement of heparan and dermatan sulfate derived disaccharides in DBS may be suitable for NBS for MPS I, II and MPS III. We hypothesize that this same approach will also detect MPS VI, and VII patients, as heparan sulfate and/or dermatan sulfate is also the primary storage products in these disorders.

Inhibition of hepatic sulfatase-2 in vivo: a novel strategy to correct diabetic dyslipidemia

Type 2 diabetes mellitus (T2DM) impairs hepatic clearance of atherogenic postprandial triglyceride-rich lipoproteins (TRLs). We recently reported that livers from T2DM db/db mice markedly overexpress the heparan sulfate glucosamine-6-O-endosulfatase-2 (SULF2), an enzyme that removes 6-O sulfate groups from heparan sulfate proteoglycans (HSPGs) and suppresses uptake of TRLs by cultured hepatocytes. In the present study, we evaluated whether Sulf2 inhibition in T2DM mice in vivo could correct their postprandial dyslipidemia. Selective second-generation antisense oligonucleotides (ASOs) targeting Sulf2 were identified. Db/db mice were treated for 5 weeks with Sulf2 ASO (20 or 50 mg/kg per week), nontarget (NT) ASO, or phosphate-buffered saline (PBS). Administration of Sulf2 ASO to db/db mice suppressed hepatic Sulf2 messenger RNA expression by 70%-80% (i.e., down to levels in nondiabetic db/m mice) and increased the ratio of tri- to disulfated disaccharides in hepatic HSPGs (P < 0.05). Hepatocytes isolated from db/db mice on NT ASO exhibited a significant impairment in very-low-density lipoprotein (VLDL) binding that was entirely corrected in db/db mice on Sulf2 ASO. Sulf2 ASO lowered the random, nonfasting plasma triglyceride (TG) levels by 50%, achieving nondiabetic values. Most important, Sulf2 ASO treatment flattened the plasma TG excursions in db/db mice after corn-oil gavage (iAUC, 1,500 ± 470 mg/dL·h for NT ASO versus 160 ± 40 mg/dL · h for Sulf2 ASO\P < 0.01).

CONCLUSIONS

Despite extensive metabolic derangements in T2DM mice, inhibition of a single dys-regulated molecule, SULF2, normalizes the VLDL-binding capacity of their hepatocytes and abolishes postprandial hypertriglyceridemia. These findings provide a key proof of concept in vivo to support Sulf2 inhibition as an attractive strategy to improve metabolic dyslipidemia.

Disease-specific non-reducing end carbohydrate biomarkers for mucopolysaccharidoses

A considerable need exists for improved biomarkers for differential diagnosis, prognosis and monitoring of therapeutic interventions for mucopolysaccharidoses (MPS), inherited metabolic disorders that involve lysosomal storage of glycosaminoglycans. Here we report a simple, reliable method based on the detection of abundant nonreducing ends of the glycosaminoglycans that accumulate in cells, blood and urine of individuals with MPS. In this method, glycosaminoglycans are enzymatically depolymerized, releasing unique mono-, di- or trisaccharides from the nonreducing ends of the chains. The composition of the released mono- and oligosaccharides depends on the nature of the lysosomal enzyme deficiency, and therefore they serve as diagnostic biomarkers. Analysis by LC/MS allowed qualitative and quantitative assessment of the biomarkers in biological samples. We provide a simple conceptual scheme for diagnosing MPS in uncharacterized samples and a method to monitor efficacy of enzyme replacement therapy or other forms of treatment.

Sulfate migration in oligosaccharides induced by negative ion mode ion trap collision-induced dissociation

Migration of sulfate groups between hydroxyl groups was identified after collision-induced dissociation (CID) of sulfated oligosaccharides in an ion trap mass spectrometer in negative ion mode. Analysis of various sulfated oligosaccharides showed that this was a common phenomenon and was particularly prominent in sulfated oligosaccharides also containing sialic acid. It was also shown that the level of migration was increased when the sulfate was positioned on the flexible areas of the oligosaccharides not involved in the pyranose ring, such as the extra-cyclic C-6 carbon of hexoses or N-acetylhexosamines, or on reduced oligosaccharide. This suggested that migration is dependent on the spatial availability of the sulfate in the ion trap during collision. It is proposed that the migration is initiated when the negatively charged -SO3 (-) residue attached to the oligosaccharide precursor becomes protonated by a CID-induced proton transfer. This is supported by the CID fragmentation of precursor ions depleted of acidic protons such as doubly charged [M - 2H](2-) ions or the sodiated [M + Na - 2H](-) ions of oligosaccharides containing one sulfate and one sialic acid in the same molecule. Compared to the CID fragmentation of their monocharged [M - H](-) ions, no migration was observed in CID of proton depleted precursors. Alternative fragmentation parameters to suppress migration of sulfated oligosaccharides also showed that it was not present when sulfated oligosaccharides were fragmented by HCD (High-Energy C-trap Dissociation) in an Orbitrap mass spectrometer.

Analysis of glycosaminoglycans in cerebrospinal fluid from patients with mucopolysaccharidoses by isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry

BACKGROUND

New therapies for the treatment of mucopolysaccharidoses that target the brain, including intrathecal enzyme replacement, are being explored. Quantitative analysis of the glycosaminoglycans (GAGs) that accumulate in these disorders is required to assess the disease burden and monitor the effect of therapy in affected patients. Because current methods lack the required limit of quantification and specificity to analyze GAGs in small volumes of cerebrospinal fluid (CSF), we developed a method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

METHODS

Samples of CSF (25 μL) were evaporated to dryness and subjected to methanolysis. The GAGs were degraded to uronic acid-N-acetylhexosamine dimers and mixed with internal standards derived from deuteriomethanolysis of GAG standards. Specific dimers derived from heparan, dermatan and chondroitin sulfates (HS, DS and CS) were separated by UPLC and analyzed by electrospray ionization MS/MS using selected reaction monitoring for each targeted GAG product and its corresponding internal standard.

RESULTS

CSF from control pediatric subjects (n = 22) contained <0.38 mg/L HS, 0.26 mg/L DS, and 2.8 mg/L CS, whereas CSF from patients with Hurler syndrome (n = 7) contained concentrations of DS and HS that were at least 6-fold greater than the upper control limits. These concentrations were reduced by 17.5% to 82.5% after allogeneic transplantation and treatment with intrathecal and intravenous enzyme replacement therapy.

CONCLUSIONS

The method described here has potential value in monitoring patients with mucopolysaccharidoses receiving treatment targeted to the brain.

A comprehensive compositional analysis of heparin/heparan sulfate-derived disaccharides from human serum

The analysis of heparan sulfate glycosaminoglycans (HSGAGs) variations in human serum at the disaccharide level has a great potential for disease diagnosis and prognosis. However, the lack of available analytical methodology for the compositional analysis of HSGAGs in human serum remains to be addressed to delineate the possible role of HSGAGs on the onset and/or progression of a disease. In this study, we have developed a method for the in-depth compositional analysis of the 12 heparin/HS-derived disaccharides from human serum using a combination of technologies--fractionation, exhaustive digestion, solid phase extraction, and LC-MS/MS. The method exhibits high recovery (72-110%) and good reproducibility (standard deviation of less than 5%) with a low limit of detection and quantification. Errors from the method validation were within 1.1%. Nondetectable non- or low-sulfated disaccharides in human serum were also detected using the optimized protocol. Further applying this method, the comprehensive analysis of HSGAGs compositions in human sera from female donors showed considerable variations in disaccharide patterns and compositions.

Efficient analysis of urinary glycosaminoglycans by LC-MS/MS in mucopolysaccharidoses type I, II and VI

Mucopolysaccharidoses (MPSs) are complex storage disorders caused by specific lysosomal enzyme deficiencies, resulting in the accumulation of glycosaminoglycans (GAGs) in urine, plasma, as well as in various tissues. We devised and validated a straightforward, but accurate and precise tandem mass spectrometry methodology coupled to high performance liquid chromatography (LC-MS/MS) for the quantification of GAGs in urine. The method is applicable to the investigation of patients with MPS I, II, and VI, by quantifying dermatan sulfate (DS) and heparan sulfate (HS) in urine. We analyzed urine samples from 28 MPS patients, aged 1 to 42 years, and 55 control subjects (41 days to 18 years old). Levels of DS and HS in urine from healthy controls of all ages were below the limit of quantification. The levels of DS and HS in urine from 6 treated patients with MPS I were lower than in 6 untreated patients in DS (0.7-45 vs 9.3-177 mg/mmol creat) and HS (0-123 mg/mmol creatinine vs 38-418 mg/mmol creatinine); similar results were obtained for 9 patients with MPS II and 7 patients with MPS VI. Analyses were performed on as little as 250 μL of urine. Methanolysis took 75 min per sample; the total analysis run time for each LC-MS/MS injection was 8 min. Results indicate that the method is applicable to a wide variety of situations in which high accuracy and precision are required, including the evaluation of the effectiveness of existing and emerging treatments.

High-throughput determination of urinary hexosamines for diagnosis of mucopolysaccharidoses by capillary electrophoresis and high-performance liquid chromatography

Mucopolysaccharidoses (MPS) diagnosis is often delayed and irreversible organ damage can occur, making possible therapies less effective. This highlights the importance of early and accurate diagnosis. A high-throughput procedure for the simultaneous determination of glucosamine and galactosamine produced from urinary galactosaminoglycans and glucosaminoglycans by capillary electrophoresis (CE) and HPLC has been performed and validated in subjects affected by various MPS including their mild and severe forms, Hurler and Hurler-Scheie, Hunter, Sanfilippo, Morquio, and Maroteaux-Lamy. Contrary to other analytical approaches, the present single analytical procedure, which is able to measure total abnormal amounts of urinary GAGs, high molecular mass, and related fragments, as well as specific hexosamines belonging to a group of GAGs, would be useful for possible application in their early diagnosis. After a rapid urine pretreatment, free hexosamines are generated by acidic hydrolysis, derivatized with 2-aminobenzoic acid and separated by CE/UV in ∼10min and reverse-phase (RP)-HPLC in fluorescence in ∼21min. The total content of hexosamines was found to be indicative of abnormal urinary excretion of GAGs in patients compared to the controls, and the galactosamine/glucosamine ratio was observed to be related to specific MPS syndromes in regard to both their mild and severe forms. As a consequence, important correlations between analytical response and clinical diagnosis and the severity of the disorders were observed. Furthermore, we can assume that the severity of the syndrome may be ascribed to the quantity of total GAGs, as high-molecular-mass polymers and fragments, accumulated in cells and directly excreted in the urine. Finally, due to the high-throughput nature of this approach and to the equipment commonly available in laboratories, this method is suitable for newborn screening in preventive public health programs for early detection of MPS disorders, diagnosis, and their treatment.

Modern developments in mass spectrometry of chondroitin and dermatan sulfate glycosaminoglycans

Chondroitin sulfate (CS) and dermatan sulfate (DS) are special types of glycosaminoglycan (GAG) oligosaccharides able to regulate vital biological functions that depend on precise motifs of their constituent hexose sequences and the extent and location of their sulfation. As a result, the need for better understanding of CS/DS biological role called for the elaboration and application of straightforward strategies for their composition and structure elucidation. Due to its high sensitivity, reproducibility, and the possibility to rapidly generate data on fine CS/DS structure determinants, mass spectrometry (MS) based on either electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI) brought a major progress in the field. Here, modern developments in MS of CS/DS GAGs are gathered in a critical review covering the past 5 years. The first section is dedicated to protocols for CS/DS extraction from parent proteoglycan, digestion, and purification that are among critical prerequisites of a successful MS experiment. The second part highlights several MALDI MS aspects, the requirements, and applications of this ionization method to CS/DS investigation. An ample chapter is devoted to ESI MS strategies, which employ either capillary- or advanced chip-based sample infusion in combination with multistage MS (MS(n)) using either collision-induced (CID) or electron detachment dissociation (EDD). At last, the potential of two versatile separation techniques, capillary electrophoresis (CE), and liquid chromatography (LC) in off- and/or on-line coupling with ESI MS and MS(n), is discussed, alongside an assessment of particular buffer/solvent conditions and instrumental parameters required for CS/DS mixture separation followed by on-line mass analysis of individual components.

Dermatan sulfate and heparan sulfate as a biomarker for mucopolysaccharidosis I

Mucopolysaccharidosis I (MPS I) is an autosomal recessive disorder caused by deficiency of alpha-L-iduronidase leading to accumulation of its catabolic substrates, dermatan sulfate (DS) and heparan sulfate (HS), in lysosomes. This results in progressive multiorgan dysfunction and death in early childhood. The recent success of enzyme replacement therapy (ERT) for MPS I highlights the need for biomarkers that reflect response to such therapy. To determine which biochemical markers are better, we determined serum and urine DS and HS levels by liquid chromatography tandem mass spectrometry in ERT-treated MPS I patients. The group included one Hurler, 11 Hurler/Scheie, and two Scheie patients. Seven patients were treated from week 1, whereas the other seven were treated from week 26. Serum and urine DS (DeltaDi-4S/6S) and HS (DeltaDiHS-0S, DeltaDiHS-NS) were measured at baseline, week 26, and week 72. Serum DeltaDi-4S/6S, DeltaDiHS-0S, and DeltaDiHS-NS levels decreased by 72%, 56%, and 56%, respectively, from baseline at week 72. Urinary glycosaminoglycan level decreased by 61.2%, whereas urine DeltaDi-4S/6S, DeltaDiHS-0S, and DeltaDiHS-NS decreased by 66.8%, 71.8%, and 71%, respectively. Regardless of age and clinical severity, all patients showed marked decrease of DS and HS in blood and urine samples. We also evaluated serum DS and HS from dried blood-spot samples of three MPS I newborn patients, showing marked elevation of DS and HS levels compared with those in control newborns. In conclusion, blood and urine levels of DS and HS provide an intrinsic monitoring and screening tool for MPS I patients.

Validation of disaccharide compositions derived from dermatan sulfate and heparan sulfate in mucopolysaccharidoses and mucolipidoses II and III by tandem mass spectrometry

Glycosaminoglycans (GAGs) are accumulated in various organs in both mucopolysaccharidoses (MPS) and mucolipidoses II and III (ML II and III). MPS and ML II and III patients can not properly degrade dermatan sulfate (DS) and/or heparan sulfate (HS). HS storage occurs in the brain leading to neurological signs while DS storage involves mainly visceral and skeletal manifestations. Excessive DS and HS released into circulation and thus blood levels of both are elevated, therefore, DS and HS in blood could be critical biomarkers for MPS and ML. Such measurement can provide a potential early screening, assessment of the clinical course and efficacy of therapies. We here assay DS and HS levels in MPS and ML patients using liquid chromatography tandem mass spectrometry (LC/MS/MS). Plasma samples were digested by heparitinase and chondroitinase B to obtain disaccharides of DS and HS, followed by LC/MS/MS analysis. One hundred-twenty samples from patients and 112 control samples were analyzed. We found that all MPS I, II, III and VI patients had a significant elevation of all DS+HS compositions analyzed in plasma, compared with the controls (P<0.0001). Specificity and sensitivity was 100% if the cut off value is 800 ng/ml between control and these types of MPS group. All MPS I, II and III patients also had a significant elevation of plasma HS, compared with the controls (P<0.0001). All MPS VI patients had a significant elevation of plasma DS, compared with the controls (P<0.0001). These findings suggest measurement of DS and/or HS levels by LC/MS/MS is applicable to the screening for MPS I, II, III and VI patients.

Mutations and polymorphisms in GUSB gene in mucopolysaccharidosis VII (Sly Syndrome)

Mucopolysaccharidosis VII (MPS VII; Sly syndrome) is an autosomal recessive disorder caused by a deficiency of beta-glucuronidase (GUS, EC 3.2.1.31; GUSB). GUS is required to degrade glycosaminoglycans (GAGs), including heparan sulfate (HS), dermatan sulfate (DS), and chondroitin-4,6-sulfate (CS). Accumulation of undegraded GAGs in lysosomes of affected tissues leads to mental retardation, short stature, hepatosplenomegaly, bone dysplasia, and hydrops fetalis. We summarize information on the 49 unique, disease-causing mutations determined so far in the GUS gene, including nine novel mutations (eight missense and one splice-site). This heterogeneity in GUS gene mutations contributes to the extensive clinical variability among patients with MPS VII. One pseudodeficiency allele, one polymorphism causing an amino acid change, and one silent variant in the coding region are also described. Among the 103 analyzed mutant alleles, missense mutations accounted for 78.6%; nonsense mutations, 12.6%; deletions, 5.8%; and splice-site mutations, 2.9%. Transitional mutations at CpG dinucleotides made up 40.8% of all the described mutations. The five most frequent mutations (accounting for 44/103 alleles) were exonic point mutations, p.L176F, p.R357X, p.P408S, p.P415L, and p.A619 V. Genotype/phenotype correlation was attempted by correlating the effects of certain missense mutations or enzyme activity and stability within phenotypes. These were in turn correlated with the location of the mutation in the tertiary structure of GUS. A total of seven murine, one feline, and one canine model of MPS VII have been characterized for phenotype and genotype.

Retention studies of 2'-2'-difluorodeoxycytidine and 2'-2'-difluorodeoxyuridine nucleosides and nucleotides on porous graphitic carbon: development of a liquid chromatography-tandem mass spectrometry method

The development of a method for the separation of 2'-2'-difluorodeoxycytidine (gemcitabine, dFdC), 2'-2'-difluorodeoxyuridine (dFdU) and their mono-, di- and triphosphates using a porous graphitic carbon column (Hypercarb), without ion-pairing agent, is described. The retention of dFdC and dFdU could be controlled with an organic modifier (acetonitrile, CH(3)CN) and the retention of the anionic nucleotides with an eluting ion (bicarbonate). Separation of all analytes was achieved using a 0-25 mM ammonium bicarbonate gradient in CH(3)CN-H(2)O (15:85, v/v). Under these conditions, however, very long re-equilibration times were required. Injection of an acidic solution (100 microL 10% formic acid in H(2)O, v/v; 2.65 M) after running a gradient directly restored the separation capabilities of the column. Still, separation between the analytes slowly deteriorated over a period of months. These problems were solved by preconditioning the column with a pH buffered hydrogen peroxide (H(2)O(2)) solution (0.05% H(2)O(2) in CH(3)CN-H(2)O (15:85, v/v), pH 4) before starting an analytical run. The oxidation of the stationary phase with H(2)O(2) prevented its slow reduction, which most likely caused the decreasing retention times. The analytes were detected using tandem mass spectrometry.