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

Utilizing 13C-Labeled internal standards to advance the analysis of heparan sulfate

Heparan sulfate (HS) is a highly sulfated and structurally heterogeneous polysaccharide that plays key roles in numerous biological processes. Due to its complex structure and variable sulfation patterns, accurately characterizing and quantifying HS in biological samples poses significant analytical challenges. This review presents an advanced high-performance liquid chromatography-tandem mass spectroscopy (LC-MS/MS) methodology that utilizes isotope-labeled internal standards for the precise quantification of HS disaccharides and rare 3-O-sulfated tetrasaccharides, alongside monitoring 6-O-endosulfatase enzyme activity and the metabolism of synthetic HS oligosaccharides in biological systems. The combination of isotope-labeled standards with LC-MS/MS technology provides a powerful and sensitive approach for comprehensive analysis of HS modifications, offering valuable insights into HS metabolism and its alterations across various biological contexts.

High-throughput glycosaminoglycan extraction and UHPLC-MS/MS quantification in human biofluids

Glycosaminoglycans (GAGs) are linear, unbranched heteropolysaccharides whose structural complexity determines their function. Accurate quantification of GAGs in biofluids at high throughput is relevant for numerous biomedical applications. However, because of the structural variability of GAGs in biofluids, existing protocols require complex pre-analytical procedures, have limited throughput and lack accuracy. Here, we describe the extraction and quantification of GAGs by using ultra-high-performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-MS/MS). Designed for 96-well plates, this method enables the processing of up to 82 study samples per plate, with the remaining 14 wells used for calibrators and controls. Key steps include the enzymatic depolymerization of GAGs, their derivatization with 2-aminoacridone and their quantification via UHPLC-MS/MS. Each plate can be analyzed in a single UHPLC-MS/MS run, offering the quantitative and scalable analysis of 17 disaccharides from chondroitin sulfate, heparan sulfate and hyaluronic acid, with a level of precision and reproducibility sufficient for their use as biomarkers. The procedure from sample thawing to initiating the UHPLC-MS/MS run can be completed in ~1.5 d plus 15 min of MS runtime per sample, and it is structured to fit within ordinary working shifts, thus making it a valuable tool for clinical laboratories seeking high-throughput analysis of GAGs. The protocol requires expertise in UHPLC-MS/MS.

Heparan sulfate regulates the fate decisions of human pluripotent stem cells

Heparan sulfate (HS) is an anionic polysaccharide generated by all animal cells, but our understanding of its roles in human pluripotent stem cell (hPSC) self-renewal and differentiation is limited. We derived HS-deficient hPSCs by disrupting the EXT1 glycosyltransferase. These EXT1-/- hPSCs maintain self-renewal and pluripotency under standard culture conditions that contain high levels of basic fibroblast growth factor(bFGF), a requirement for sufficient bFGF signaling in the engineered cells. Intriguingly, Activin/Nodal signaling is also compromised in EXT1-/- hPSCs, highlighting HS's previously unexplored involvement in this pathway. As a result, EXT1-/- hPSCs fail to differentiate into mesoderm or endoderm lineages. Unexpectedly, HS is dispensable for early ectodermal differentiation of hPSCs but still critical in generating motor neurons. Those derived from HS-deficient hPSCs lack proper neuronal projections and show alterations in axonogenesis gene expression. Thus, our study uncovers expected and unexpected mechanistic roles of HS in hPSC fate decisions.

Separation and purification of bovine nasal cartilage-derived chondroitin sulfate and evaluation of its binding to bovine serum albumin

This study employs an optimized and environmentally friendly method to extract and purify chondroitin sulfate (CS) from bovine nasal cartilage using enzymatic hydrolysis, ethanol precipitation, and DEAE Sepharose Fast Flow column chromatography. The extracted CS, representing 44.67 % ± 0.0016 of the cartilage, has a molecular weight of 7.62 kDa. Characterization through UV, FT-IR, NMR spectroscopy, and 2-aminoacridone derivatization HPLC revealed a high content of sulfated disaccharides, particularly ΔDi4S (73.59 %) and ΔDi6S (20.61 %). Interaction studies with bovine serum albumin (BSA) using fluorescence spectroscopy and molecular docking confirmed a high-affinity, static quenching interaction with a single binding site, primarily mediated by van der Waals forces and hydrogen bonding. The interaction did not significantly alter the polarity or hydrophobicity of BSA aromatic amino acids. These findings provide a strong foundation for exploring the application of CS in tissue engineering and drug delivery systems, leveraging its unique interaction with BSA for targeted delivery and enhanced efficacy.

Urinary Free Glycosaminoglycans Identify Adults at High Risk of Developing Early-stage High-grade Bladder Cancer

Background and objective

Screening for bladder cancer (BCa) could reduce mortality via early detection of early-stage high-grade (Ta/T1 N0 M0 grade 2-3) disease. Noninvasive biomarkers could aid in screening, but current markers lack the specificity required. The urinary free glycosaminoglycan profile (GAGome) is a promising biomarker for early detection of BCa metabolism.

Methods

In a prospective case-control development study, we included patients with BCa or no evidence of disease (NED) and measured the urinary GAGome. We then developed a score to predict the probability of BCa using GAGome features that correlated with BCa versus NED according to Bayesian regression. Next, in a retrospective, population-based, case-control study, we included adults from the Lifelines Cohort Study who were presumed healthy at baseline. All cases with BCa confirmed in the cancer registry by the 2-yr or 6-yr study visit were matched to randomly selected control subjects. We developed a reference logistic regression model using age and sex to predict BCa at 7 yr after baseline. We then added the GAGome score to the model and assessed model improvement using the likelihood ratio test. We dichotomized outputs for the reference model and saturated model (reference + GAGome score) into high-risk versus low-risk categories using a 99% specificity cutoff and estimated the sensitivity for association with BCa at 7 yr.

Key findings and limitations

We prospectively included 51 individuals with BCa and 38 with NED and observed alterations in three GAGome features compatible with BCa. We developed a score that discriminated BCa with an area under the receiver operating characteristic curve of 0.77 (95% confidence interval [CI] 0.67-0.87). We retrospectively selected a cohort of 1088 presumed healthy adults (median age 48 yr, 56% females), of whom 48 had developed BCa by 7 yr after baseline (median time to diagnosis 1.4 yr). The GAGome score was an independent predictor of BCa at 7 yr when added to the reference model (p < 0.001). The sensitivity for BCa at 7 yr for high-risk subjects was 31% (95% CI 20-43%) using the saturated model and 17% (95% CI 4.7-29%) using the reference model at 99% specificity (95% CI 98-99%).

Conclusions and clinical implications

The urinary free GAGome is specifically altered in BCa and can be used for noninvasive identification of adults at high risk of developing BCa, independent of age and sex. This information could be useful for the design of risk-stratified targeted screening programs for BCa.

Patient summary

We tested whether measurement of a class of sugars called glycosaminoglycans (GAGs) in urine could be used for early detection of bladder cancer. Our results show that GAG levels in urine can distinguish people at high risk of developing bladder cancer within 7 years, even if they are healthy at the time of the urine sampling.

Discriminating Benign from Malignant Lung Diseases Using Plasma Glycosaminoglycans and Cell-Free DNA

We aimed to investigate the use of free glycosaminoglycan profiles (GAGomes) and cfDNA in plasma to differentiate between lung cancer and benign lung disease, in a cohort of 113 patients initially suspected of lung cancer. GAGomes were analyzed in all samples using the MIRAM® Free Glycosaminoglycan Kit with ultra-high-performance liquid chromatography and electrospray ionization triple quadrupole mass spectrometry. In a subset of samples, cfDNA concentration and NGS-data was available. We detected two GAGome features, 0S chondroitin sulfate (CS), and 4S CS, with cancer-specific changes. Based on the observed GAGome changes, we devised a model to predict lung cancer. The model, named the GAGome score, could detect lung cancer with 41.2% sensitivity (95% CI: 9.2-54.2%) at 96.4% specificity (95% CI: 95.2-100.0%, n = 113). When we combined the GAGome score with a cfDNA-based model, the sensitivity increased from 42.6% (95% CI: 31.7-60.6%, cfDNA alone) to 70.5% (95% CI: 57.4-81.5%) at 95% specificity (95% CI: 75.1-100%, n = 74). Notably, the combined GAGome and cfDNA testing improved the sensitivity, compared to cfDNA alone, especially in ASCL stage I (55.6% vs 11.1%). Our findings show that plasma GAGome profiles can enhance cfDNA testing performance, highlighting the applicability of a multiomics approach in lung cancer diagnostics.

Glycosaminoglycans: Participants in Microvascular Coagulation of Sepsis

Sepsis represents a syndromic response to infection and frequently acts as a common pathway leading to fatality in the context of various infectious diseases globally. The pathology of severe sepsis is marked by an excess of inflammation and activated coagulation. A substantial contributor to mortality in sepsis patients is widespread microvascular thrombosis-induced organ dysfunction. Multiple lines of evidence support the notion that sepsis induces endothelial damage, leading to the release of glycosaminoglycans, potentially causing microvascular dysfunction. This review aims to initially elucidate the relationship among endothelial damage, excessive inflammation, and thrombosis in sepsis. Following this, we present a summary of the involvement of glycosaminoglycans in coagulation, elucidating interactions among glycosaminoglycans, platelets, and inflammatory cells. In this section, we also introduce a reasoned generalization of potential signal pathways wherein glycosaminoglycans play a role in clotting. Finally, we discuss current methods for detecting microvascular conditions in sepsis patients from the perspective of glycosaminoglycans. In conclusion, it is imperative to pay closer attention to the role of glycosaminoglycans in the mechanism of microvascular thrombosis in sepsis. Dynamically assessing glycosaminoglycan levels in patients may aid in predicting microvascular conditions, enabling the monitoring of disease progression, adjustment of clinical treatment schemes, and mitigation of both acute and long-term adverse outcomes associated with sepsis.

Inhibition of catechol-O-methyltransferase (COMT) by heparin oligosaccharides with specific structures

COMT inhibitors are commonly used to improve the effectiveness of levodopa in treating Parkinson's disease by inhibiting its conversion to 3-O-methyldopa. Because of the serious side effect of nitrocatechol COMT inhibitors, it is necessary to develop non-nitrocatechol COMT inhibitors with a higher safety profile. Heparin has been observed to bind to COMT. However, the exact functional significance of this interaction is not fully understood. In this study, the contribution of different substitution of heparin to its binding with COMT was investigated. In vitro and in vivo, heparin oligosaccharides can bind to COMT and inhibit its activity. Furthermore, we enriched the functional heparin oligosaccharides that bind to COMT and identified the sequence UA2S-GlcN(S/Ac)6(S/H)-UA2S-GlcNS6(S/H)-UA2(S/H)-GlcNS6S as the characteristic structural domain of these functional oligosaccharides. This study has elucidated the relationship between the structure of heparin oligosaccharides and their activity against COMT, providing valuable insights for the development of non-nitrocatechol COMT inhibitors with improved safety and efficacy.

Distinct mechanisms underlying the therapeutic effects of low-molecular-weight heparin and chondroitin sulfate on Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder influenced by various factors, including age, genetics, and the environment. Current treatments provide symptomatic relief without impeding disease progression. Previous studies have demonstrated the therapeutic potential of exogenous heparin and chondroitin sulfate in PD. However, their therapeutic mechanisms and structure-activity relationships remain poorly understood. In this study, low-molecular-weight heparin (L-HP) and chondroitin sulfate (L-CS) exhibited favorable therapeutic effects in a mouse model of PD. Proteomics revealed that L-HP attenuated mitochondrial dysfunction through its antioxidant properties, whereas L-CS suppressed neuroinflammation by inhibiting platelet activation. Two glycosaminoglycan (GAG)-binding proteins, manganese superoxide dismutase (MnSOD2) and fibrinogen beta chain (FGB), were identified as potential targets of L-HP and L-CS, and we investigated their structure-activity relationships. The IdoA2S-GlcNS6S/GlcNAc6S unit in HP bound to SOD2, whereas the GlcA-GalNAc4S and GlcA-GalNAc4S6S units in CS preferred FGB. Furthermore, N-S and 2-O-S in L-HP, and 4-O-S, 6-O-S, and -COOH in L-CS contributed significantly to the binding process. These findings provide new insights and evidence for the development and use of glycosaminoglycan-based therapeutics for PD.

Discrimination of Disaccharide Isomers of Different Glycosidic Linkages Using a Modified MspA Nanopore

Disaccharides are composed of two monosaccharide subunits joined by a glycosidic linkage in an α or β configuration. Different combinations of isomeric monosaccharide subunits and different glycosidic linkages result in different isomeric disaccharide products. Thus, direct discrimination of these disaccharide isomers from a mixture is extremely difficult. In this paper, a hetero-octameric Mycobacterium smegmatis porin A (MspA) nanopore conjugated with a phenylboronic acid (PBA) adapter was applied for disaccharide sensing, with which three most widely known disaccharides in nature, including sucrose, lactose and maltose, were clearly discriminated. Besides, all six isomeric α-D-glucopyranosyl-D-fructoses, differing only in their glycosidic linkages, were also well resolved. Assisted by a custom machine learning algorithm, a 0.99 discrimination accuracy is achieved. Nanopore discrimination of disaccharide isomers with different glycosidic linkages, which has never been previously demonstrated, is inspiring for nanopore saccharide sequencing. This sensing capacity was also applied in direct identification of isomaltulose additives in a commercial sucrose-free yogurt, from which isomaltulose, lactose and L-lactic acid were simultaneously detected.

Disaccharide compositional analysis of chondroitin sulphate using WAX HILIC-MS with pre-column procainamide labelling; application to the placenta in pre-eclampsia

Chondroitin sulphate (CS) and dermatan sulphate are negatively charged linear heteropolysaccharides. These glycosaminoglycans (GAG) are involved in cellular signalling via binding to growth factors. CS is expressed in a range of tissue and biological fluids and is highly expressed in the placenta. There is evidence that decorin; a CS proteoglycan is significantly decreased in pre-eclampsia and fetal growth restriction. It is considered that GAG chain composition may influence cellular processes that are altered in pre-eclampsia. The goal of the present study was to develop an LC-MS method with precolumn procainamide labelling for the disaccharide compositional analysis of CS. The method was used to investigate whether the disaccharide composition of placenta-extracted CS is altered in pre-eclampsia. The study revealed differential disaccharide compositions of placental chondroitin sulphate between pre-eclampsia and other pregnancy conditions. This suggests that the method may have diagnostic potential for pregnancy disorders. Furthermore, the findings suggest that CS sulphation might play a significant role in maternal labour.

Regional and disease-specific glycosaminoglycan composition and function in decellularized human lung extracellular matrix

Decellularized lung scaffolds and hydrogels are increasingly being utilized in ex vivo lung bioengineering. However, the lung is a regionally heterogenous organ with proximal and distal airway and vascular compartments of different structures and functions that may be altered as part of disease pathogenesis. We previously described decellularized normal whole human lung extracellular matrix (ECM) glycosaminoglycan (GAG) composition and functional ability to bind matrix-associated growth factors. We now determine differential GAG composition and function in airway, vascular, and alveolar-enriched regions of decellularized lungs obtained from normal, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF) patients. Significant differences were observed in heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA) content and CS/HS compositions between both different lung regions and between normal and diseased lungs. Surface plasmon resonance demonstrated that HS and CS from decellularized normal and COPD lungs similarly bound fibroblast growth factor 2, but that binding was decreased in decellularized IPF lungs. Binding of transforming growth factor β to CS was similar in all three groups but binding to HS was decreased in IPF compared to normal and COPD lungs. In addition, cytokines dissociate faster from the IPF GAGs than their counterparts. The differences in cytokine binding features of IPF GAGs may result from different disaccharide compositions. The purified HS from IPF lung is less sulfated than that from other lungs, and the CS from IPF contains more 6-O-sulfated disaccharide. These observations provide further information for understanding functional roles of ECM GAGs in lung function and disease. STATEMENT OF SIGNIFICANCE: Lung transplantation remains limited due to donor organ availability and need for life-long immunosuppressive medication. One solution, the ex vivo bioengineering of lungs via de- and recellularization has not yet led to a fully functional organ. Notably, the role of glycosaminoglycans (GAGs) remaining in decellularized lung scaffolds is poorly understood despite their important effects on cell behaviors. We have previously investigated residual GAG content of native and decellularized lungs and their respective functionality, and role during scaffold recellularization. We now present a detailed characterization of GAG and GAG chain content and function in different anatomical regions of normal diseased human lungs. These are novel and important observations that further expand knowledge about functional GAG roles in lung biology and disease.

Enzymatic preparation of chondroitin sulfate oligosaccharides and its alleviating effect on ovariectomy-induced osteoporosis in rats

Postmenopausal osteoporosis is the most common type of osteoporosis. Chondroitin sulfate (CS) has been successfully employed as food supplement against osteoarthritis, while the therapeutic potential on postmenopausal osteoporosis is little explored. In this study, CS oligosaccharides (CSOs) were enzymatically prepared through the lysis of CS by a chondroitinase from Microbacterium sp. Strain. The alleviating effects of CS, CSOs and Caltrate D (a clinically used supplement) on ovariectomy (OVX) - induced rat's osteoporosis were comparatively investigated. Our data showed that the prepared CSOs was basically unsaturated CS disaccharide mixture of ∆Di4S (53.1%), ∆Di6S (27.7%) and ∆Di0S (17.7%). 12 weeks' intragastric administration of Caltrate D (250 mg/kg/d), CS or CSOs (500 mg/kg/d, 250 mg/kg/d, 125 mg/kg/d) could obviously regulate the disorder of serum indices, recover the mechanical strength and mineral content of bone, improve the cortical bones' density and the number and length of trabecular bones in OVX rats. Both CS and CSOs in 500 mg/kg/d and 250 mg/kg/d could restore more efficiently the serum indices, bone fracture deflection and femur Ca than Caltrate D. As compared with CS at the same dosage, CSOs exhibited a more significant alleviating effect. These findings suggested that there was great potential of CSOs as daily interventions for delaying the progression of postmenopausal osteoporosis.

Microheterogeneity and Individual Differences of Human Urinary N-Glycome under Normal Physiological Conditions

Urine is considered an outstanding biological fluid for biomarker discovery, reflecting both systemic and urogenital physiology. However, analyzing the N-glycome in urine in detail has been challenging due to the low abundance of glycans attached to glycoproteins compared to free oligosaccharides. Therefore, this study aims to thoroughly analyze urinary N-glycome using LC-MS/MS. The N-glycans were released using hydrazine and labeled with 2-aminopyridine (PA), followed by anion-exchange fractionation before LC-MS/MS analysis. A total of 109 N-glycans were identified and quantified, of which 58 were identified and quantified repeatedly in at least 80% of samples and accounted for approximately 85% of the total urinary glycome signal. Interestingly, a comparison between urine and serum N-glycome revealed that approximately 50% of the urinary glycome could originate from the kidney and urinary tract, where they were exclusively identified in urine, while the remaining 50% were common in both. Additionally, a correlation was found between age/sex and the relative abundances of urinary N-glycome, with more age-related changes observed in women than men. The results of this study provide a reference for human urine N-glycome profiling and structural annotations.

Dynamic Changes in Heparan Sulfate Nanostructure in Human Pluripotent Stem Cell Differentiation

Heparan sulfate (HS) is a heterogeneous, cell-surface polysaccharide critical for transducing signals essential for mammalian development. Imaging of signaling proteins has revealed how their localization influences their information transfer. In contrast, the contribution of the spatial distribution and nanostructure of information-rich, signaling polysaccharides like HS is not known. Using expansion microscopy (ExM), we found striking changes in HS nanostructure occur as human pluripotent stem (hPS) cells differentiate, and these changes correlate with growth factor signaling. Our imaging studies show that undifferentiated hPS cells are densely coated with HS displayed as hair-like protrusions. This ultrastructure can recruit fibroblast growth factor for signaling. When the hPS cells differentiate into the ectoderm lineage, HS is localized into dispersed puncta. This striking change in HS distribution coincides with a decrease in fibroblast growth factor binding to neural cells. While developmental variations in HS sequence were thought to be the primary driver of alterations in HS-mediated growth factor signaling, our high-resolution images indicate a role for the HS nanostructure. Our study highlights the utility of high-resolution glycan imaging using ExM. In the case of HS, we found that changes in how the polysaccharide is displayed link to profound differences in growth factor binding.

Urinary Glycosaminoglycans Are Associated with Recurrent UTI and Urobiome Ecology in Postmenopausal Women

Glycosaminoglycans (GAGs) are linear, negatively charged polysaccharides composed of repeating disaccharide units of uronic acid and amino sugars. The luminal surface of the bladder epithelium is coated with a GAG layer. These urothelial GAGs are thought to provide a protective barrier and serve as a potential interaction site with the urinary microbiome (urobiome). Previous studies have profiled urinary GAG composition in mixed cohorts, but the urinary GAG composition in postmenopausal women remains undefined. To investigate the relationship between GAGs and recurrent urinary tract infection (rUTI), we profiled urinary GAGs in a controlled cohort of postmenopausal women. We found that chondroitin sulfate (CS) is the major urinary GAG in postmenopausal women and that urinary CS was elevated in women with active rUTI. We also associated urinary GAGs with urobiome composition and identified bacterial species that significantly associated with urinary GAG concentration. Corynebacterium amycolatum, Porphyromonas somerae, and Staphylococcus pasteuri were positively associated with heparin sulfate or hyaluronic acid, and bacterial species associated with vaginal dysbiosis were negatively correlated with urinary CS. Altogether, this work defines changes in urinary GAG composition associated with rUTI and identifies new associations between urinary GAGs and the urobiome that may play a role in rUTI pathobiology.

High sensitivity (zeptomole) detection of BODIPY-labelled heparan sulfate (HS) disaccharides by ion-paired RP-HPLC and LIF detection enables analysis of HS from mosquito midguts

The fine structure of heparan sulfate (HS), the glycosaminoglycan polysaccharide component of cell surface and extracellular matrix HS proteoglycans, coordinates the complex cell signalling processes that control homeostasis and drive development in multicellular animals. In addition, HS is involved in the infection of mammals by viruses, bacteria and parasites. The current detection limit for fluorescently labelled HS disaccharides (low femtomole; 10^-15 mol), has effectively hampered investigations of HS composition in small, functionally-relevant populations of cells and tissues that may illuminate the structural requirements for infection and other biochemical processes. Here, an ultra-high sensitivity method is described that utilises a combination of reverse-phase HPLC, with tetraoctylammonium bromide (TOAB) as the ion-pairing reagent and laser-induced fluorescence detection of BODIPY-FL-labelled disaccharides. The method provides an unparalleled increase in the sensitivity of detection by ∼six orders of magnitude, enabling detection in the zeptomolar range (∼10^-21 moles; <1000 labelled molecules). This facilitates determination of HS disaccharide compositional analysis from minute samples of selected tissues, as demonstrated by analysis of HS isolated from the midguts of Anopheles gambiae mosquitoes that was achieved without approaching the limit of detection.

Mucopolysaccharidoses Differential Diagnosis by Mass Spectrometry-Based Analysis of Urine Free Glycosaminoglycans—A Diagnostic Prediction Model

Impaired glycosaminoglycans (GAGs) catabolism may lead to a cluster of rare metabolic and genetic disorders called mucopolysaccharidoses (MPSs). Each subtype is caused by the deficiency of one of the lysosomal hydrolases normally degrading GAGs. Affected tissues accumulate undegraded GAGs in cell lysosomes and in the extracellular matrix, thus leading to the MPS complex clinical phenotype. Although each MPS may present with recognizable signs and symptoms, these may often overlap between subtypes, rendering the diagnosis difficult and delayed. Here, we performed an exploratory analysis to develop a model that predicts MPS subtypes based on UHPLC-MS/MS measurement of a urine free GAG profile (or GAGome). We analyzed the GAGome of 78 subjects (38 MPS, 37 healthy and 3 with other MPS symptom-overlapping disorders) using a standardized kit in a central-blinded laboratory. We observed several MPS subtype-specific GAGome changes. We developed a multivariable penalized Lasso logistic regression model that attained 91.2% balanced accuracy to distinguish MPS type II vs. III vs. any other subtype vs. not MPS, with sensitivity and specificity ranging from 73.3% to 91.7% and from 98.4% to 100%, depending on the predicted subtype. In conclusion, the urine GAGome was revealed to be useful in accurately discriminating the different MPS subtypes with a single UHPLC-MS/MS run and could serve as a reliable diagnostic test for a more rapid MPS biochemical diagnosis.

Brain inflammation induces alterations in glycosaminoglycan metabolism and subsequent changes in CS-4S and hyaluronic acid

It remains uncertain how brain glycosaminoglycans (GAGs) contribute to the progression of inflammatory disorders like multiple sclerosis (MS). We investigated here neuroinflammation-mediated changes in GAG composition and metabolism using the mouse model of experimental autoimmune encephalomyelitis (EAE) and sham-immunized mice as controls. Cerebellum, mid- and forebrain at different EAE phases were investigated using gene expression analysis (microarray and RT-qPCR) as well as HPLC quantification of CS and hyaluronic acid (HA). The cerebellum was the most affected brain region showing a downregulation of Bcan, Cspg5, and an upregulation of Dse, Gusb, Hexb, Dcn and Has2 at peak EAE. Upregulation of genes involved in GAG degradation as well as synthesis of HA and decorin persisted from onset to peak, and diminished at remission, suggesting a severity-related decrease in CS and increments in HA. Relative disaccharide quantification confirmed a 3.6 % reduction of CS-4S at peak and a normalization during remission, while HA increased in both phases by 26.1 % and 17.6 %, respectively. Early inflammatory processes led to altered GAG metabolism in early EAE stages and subsequent partially reversible changes in CS-4S and in HA. Targeting early modifications in CS could potentially mitigate progression of EAE/MS.

Identification of global inhibitors of cellular glycosylation

Small molecule inhibitors of glycosylation enzymes are valuable tools for dissecting glycan functions and potential drug candidates. Screening for inhibitors of glycosyltransferases are mainly performed by in vitro enzyme assays with difficulties moving candidates to cells and animals. Here, we circumvent this by employing a cell-based screening assay using glycoengineered cells expressing tailored reporter glycoproteins. We focused on GalNAc-type O-glycosylation and selected the GalNAc-T11 isoenzyme that selectively glycosylates endocytic low-density lipoprotein receptor (LDLR)-related proteins as targets. Our screen of a limited small molecule compound library did not identify selective inhibitors of GalNAc-T11, however, we identify two compounds that broadly inhibited Golgi-localized glycosylation processes. These compounds mediate the reversible fragmentation of the Golgi system without affecting secretion. We demonstrate how these inhibitors can be used to manipulate glycosylation in cells to induce expression of truncated O-glycans and augment binding of cancer-specific Tn-glycoprotein antibodies and to inhibit expression of heparan sulfate and binding and infection of SARS-CoV-2.

Urinary Glycosaminoglycans are Associated with Recurrent UTI and Urobiome Ecology in Postmenopausal Women

Glycosaminoglycans (GAGs) are linear, negatively charged polysaccharides composed of repeating disaccharide units of uronic acid and amino sugars. The luminal surface of the bladder epithelium is coated with a GAG layer. These urothelial GAGs are thought to provide a protective barrier and serve as a potential interaction site with the urinary microbiome (urobiome). Previous studies have profiled urinary GAG composition in mixed cohorts, but the urinary GAG composition in postmenopausal women remains undefined. To investigate the relationship between GAGs and recurrent UTI (rUTI), we profiled urinary GAGs in a controlled cohort of postmenopausal women. We found that chondroitin sulfate (CS) is the major urinary GAG in postmenopausal women and that urinary CS was elevated in women with active rUTI. We also associated urinary GAGs with urobiome composition and identified bacterial species that significantly associated with urinary GAG concentration. Corynebacterium amycolatum, Porphyromonas somerae , and Staphylococcus pasteuri were positively associated with heparin sulfate or hyaluronic acid and bacterial species associated with vaginal dysbiosis were negatively correlated to urinary CS. Altogether, this work defines changes in urinary GAG composition associated with rUTI and identifies new associations between urinary GAGs and the urobiome that may play a role in rUTI pathobiology.

State-of-the-art glycosaminoglycan characterization

Glycosaminoglycans (GAGs) are heterogeneous acidic polysaccharides involved in a range of biological functions. They have a significant influence on the regulation of cellular processes and the development of various diseases and infections. To fully understand the functional roles that GAGs play in mammalian systems, including disease processes, it is essential to understand their structural features. Despite having a linear structure and a repetitive disaccharide backbone, their structural analysis is challenging and requires elaborate preparative and analytical techniques. In particular, the extent to which GAGs are sulfated, as well as variation in sulfate position across the entire oligosaccharide or on individual monosaccharides, represents a major obstacle. Here, we summarize the current state-of-the-art methodologies used for GAG sample preparation and analysis, discussing in detail liquid chromatograpy and mass spectrometry-based approaches, including advanced ion activation methods, ion mobility separations and infrared action spectroscopy of mass-selected species.

GAAGs, COMP, and YKL-40 as Potential Markers of Cartilage Turnover in Blood of Children with Juvenile Idiopathic Arthritis Treated with Etanercept—Relationship with ADAMTS4, ADAMTS5, and PDGF-BB

We quantified galactosaminoglycans (GAAGs), oligomeric cartilage matrix protein (COMP), and human cartilage glycoprotein 39 (YKL-40) in blood obtained from juvenile idiopathic arthritis (JIA) before and during 2-year treatment with etanercept (ETA), as potential biomarkers of cartilage extracellular matrix (ECM) dysfunction and indicators of efficacy of biologic therapy. We also evaluated the relationship of the mentioned markers with the factors that regulate their metabolism, disintegrin and thrombospondin motif metalloproteinases 4 (ADAMTS4), ADAMTS5, and platelet-derived growth factor BB (PDGF-BB). Methods: We studied 38 children diagnosed with JIA and 45 healthy children. We quantified GAAGs by assessing the concentration of unsaturated disaccharide units formed by digestion of isolated glycosaminoglycans with chondroitinase ABC, while COMP, YKL-40, and PDGF-BB were quantified using immunoenzymatic methods. Results: Compared to the control group, GAAGs and COMP levels were significantly lower, while YKL-40 levels were higher in the blood of patients with aggressive JIA, qualified for ETA treatment. ETA therapy leading to clinical improvement simultaneously promoted normalization of COMP and YKL-40 levels, but not GAAGs. After 24 months of taking ETA, glycan levels were still significantly lower, relative to controls. GAAGs, COMP, and YKL-40 levels were significantly influenced by ADAMTS4, ADAMTS5, and PDGF-BB levels both before and during ETA treatment. Conclusions: The dynamics of changes in marker concentrations during treatment seem to indicate that measurement of COMP and YKL-40 levels can be used to assess the chondroprotective biological efficacy of therapy. In contrast, changes in GAAGs concentrations reflect systemic extracellular matrix transformations in the course of JIA.

Plasma Glycosaminoglycans in Children with Juvenile Idiopathic Arthritis Being Treated with Etanercept as Potential Biomarkers of Joint Dysfunction

We assessed the effect of two-year etanercept (ETA) therapy on the metabolism of the cartilage extracellular matrix (ECM) in patients with juvenile idiopathic arthritis (JIA). Methods: We performed a quantitative evaluation of glycosaminoglycans (GAGs) (performed by the multistage extraction and purification method) in blood obtained from patients before and during 24 months of ETA treatment, as potential biomarker of joint dysfunction and indicators of biological effectiveness of therapy. Since the metabolism of GAGs is related to the activity of proteolytic enzymes and prooxidant–antioxidant factors, we decided to evaluate the relationship between GAGs and the levels of metalloproteinases (MMP), i.e., MMP-1 and MMP-3 (using immunoenzymatic methods), as well as the total antioxidative status (TAS) (using the colorimetric method) in blood of the JIA patients. Results: When compared to the controls, GAGs and TAS concentrations were significantly lower in patients with an aggressive course of JIA qualified for ETA treatment. MMP-1 and MMP-3 levels were significantly higher versus control values. An anti-cytokine therapy leading to clinical improvement does not lead to the normalization of any of the assessed parameters. GAGs concentration is significantly related to MMP-1, MMP-3, TAS, TOS, and CRP levels. Conclusion: The results of the present study indicate the necessity of constant monitoring of the dynamics of destructive processes of articular cartilage in children with JIA. We suggest that GAGs may be a useful biomarker to assess the clinical status of the extracellular matrix of joints.

Site-specific glycosylation of proteoglycans: a revisited frontier in proteoglycan research

Proteoglycans (PGs), a class of carbohydrate-modified proteins, are present in essentially all metazoan organisms investigated to date. PGs are composed of glycosaminoglycan (GAG) chains attached to various core proteins and are important for embryogenesis and normal homeostasis. PGs exert many of their functions via their GAG chains and understanding the details of GAG-ligand interactions has been an essential part of PG research. Although PGs are also involved in many diseases, the number of GAG-related drugs used in the clinic is yet very limited, indicating a lack of detailed structure-function understanding. Structural analysis of PGs has traditionally been obtained by first separating the GAG chains from the core proteins, after which the two components are analyzed separately. While this strategy greatly facilitates the analysis, it precludes site-specific information and introduces either a "GAG" or a "core protein" perspective on the data interpretation. Mass-spectrometric (MS) glycoproteomic approaches have recently been introduced, providing site-specific information on PGs. Such methods have revealed a previously unknown structural complexity of the GAG linkage regions and resulted in identification of several novel CSPGs and HSPGs in humans and in model organisms, thereby expanding our view on PG complexity. In light of these findings, we discuss here if the use of such MS-based techniques, in combination with various functional assays, can also be used to expand our functional understanding of PGs. We have also summarized the site-specific information of all human PGs known to date, providing a theoretical framework for future studies on site-specific functional analysis of PGs in human pathophysiology.

Visualization of Inflammation in Experimental Colitis by Magnetic Resonance Imaging Using Very Small Superparamagnetic Iron Oxide Particles

Inflammatory bowel diseases (IBD) comprise mainly ulcerative colitis (UC) and Crohn´s disease (CD). Both forms present with a chronic inflammation of the (gastro) intestinal tract, which induces excessive changes in the composition of the associated extracellular matrix (ECM). In UC, the inflammation is limited to the colon, whereas it can occur throughout the entire gastrointestinal tract in CD. Tools for early diagnosis of IBD are still very limited and highly invasive and measures for standardized evaluation of structural changes are scarce. To investigate an efficient non-invasive way of diagnosing intestinal inflammation and early changes of the ECM, very small superparamagnetic iron oxide nanoparticles (VSOPs) in magnetic resonance imaging (MRI) were applied in two mouse models of experimental colitis: the dextran sulfate sodium (DSS)-induced colitis and the transfer model of colitis. For further validation of ECM changes and inflammation, tissue sections were analyzed by immunohistochemistry. For in depth ex-vivo investigation of VSOPs localization within the tissue, Europium-doped VSOPs served to visualize the contrast agent by imaging mass cytometry (IMC). VSOPs accumulation in the inflamed colon wall of DSS-induced colitis mice was visualized in T₂* weighted MRI scans. Components of the ECM, especially the hyaluronic acid content, were found to influence VSOPs binding. Using IMC, co-localization of VSOPs with macrophages and endothelial cells in colon tissue was shown. In contrast to the DSS model, colonic inflammation could not be visualized with VSOP-enhanced MRI in transfer colitis. VSOPs present a potential contrast agent for contrast-enhanced MRI to detect intestinal inflammation in mice at an early stage and in a less invasive manner depending on hyaluronic acid content.

Glycosaminoglycan signatures in body fluids of mucopolysaccharidosis type II mouse model under long-term enzyme replacement therapy

Abstract

Mucopolysaccharidosis type II (MPS II) is a neurometabolic disorder, due to the deficit of the lysosomal hydrolase iduronate 2-sulfatase (IDS). This leads to a severe clinical condition caused by a multi-organ accumulation of the glycosaminoglycans (GAGs/GAG) heparan- and dermatan-sulfate, whose elevated levels can be detected in body fluids. Since 2006, enzyme replacement therapy (ERT) has been clinically applied, showing efficacy in some peripheral districts. In addition to clinical monitoring, GAG dosage has been commonly used to evaluate ERT efficacy. However, a strict long-term monitoring of GAG content and composition in body fluids has been rarely performed. Here, we report the characterization of plasma and urine GAGs in Ids knock-out (Ids-ko) compared to wild-type (WT) mice, and their changes along a 24-week follow-up, with and without ERT. The concentration of heparan-sulfate (HS), chondroitin-sulfate (CS), and dermatan-sulfate (DS), and of the non-sulfated hyaluronic acid (HA), together with their differentially sulfated species, was quantified by capillary electrophoresis with laser-induced fluorescence. In untreated Ids-ko mice, HS and CS + DS were noticeably increased at all time points, while during ERT follow-up, a substantial decrease was evidenced for HS and, to a minor extent, for CS + DS. Moreover, several structural parameters were altered in untreated ko mice and reduced after ERT, however without reaching physiological values. Among these, disaccharide B and HS 2s disaccharide showed to be the most interesting candidates as biomarkers for MPS II. GAG chemical signature here defined provides potential biomarkers useful for an early diagnosis of MPS II, a more accurate follow-up of ERT, and efficacy evaluations of newly proposed therapies.

Key messages

Plasmatic and urinary GAGs are useful markers for MPS II early diagnosis and prognosis.

CE-LIF allows GAG structural analysis and the quantification of 17 different disaccharides.

Most GAG species increase and many structural features are altered in MPS II mouse model.

GAG alterations tend to restore to wild-type levels following ERT administration.

CS+DS/HS ratio, % 2,4dis CS+DS, and % HS 2s are potential markers for MPS II pathology and ERT efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-022-02221-3.

Determining Methyl-Esterification Patterns in Plant-Derived Homogalacturonan Pectins

Homogalacturonan (HG)-type pectins are nutrient components in plants and are widely used in the food industry. The methyl-esterification pattern is a crucial structural parameter used to assess HG pectins in terms of their nutraceutical activity. To better understand the methyl-esterification pattern of natural HG pectins from different plants, we purified twenty HG pectin-rich fractions from twelve plants and classified them by their monosaccharide composition, Fourier transform-infrared spectroscopy (FT-IR) signatures, and NMR analysis. FT-IR shows that these HG pectins are all minimally esterified, with the degree of methyl-esterification (DM) being 5 to 40%. To examine their methyl-esterification pattern by enzymatic fingerprinting, we hydrolyzed the HG pectins using endo-polygalacturonase. Hydrolyzed oligomers were derivatized with 2-aminobenzamide and subjected to liquid chromatography-fluorescence-tandem mass spectrometry (HILIC-FLR-MSn). Twenty-one types of mono-/oligo-galacturonides having DP values of 1–10 were found to contain nonesterified monomers, dimers, and trimers, as well as oligomers with 1 to 6 methyl-ester groups. In these oligo-galacturonides, MSn analysis demonstrated that the number of methyl-ester groups in the continuous sequence was 2 to 5. Mono- and di-esterified oligomers had higher percentages in total methyl-esterified groups, suggesting that these are a random methyl-esterification pattern in these HG pectins. Our study analyzes the characteristics of the methyl-esterification pattern in naturally occurring plant-derived HG pectins and findings that will be useful for further studying HG structure-function relationships.

In situ microenvironment remodeling using a dual-responsive system: photodegradable hydrogels and gene activation by visible light

A 3D microenvironment with dynamic cell-biomaterial interactions was developed using a dual-responsive system for in situ microenvironment remodeling and control of cellular function. A visible-light-responsive polymer was utilized to prepare a hydrogel with photodegradation properties, enabling in situ microenvironment remodeling. Additionally, a vascular endothelial growth factor (VEGF) gene activation unit that was responsive to the same wavelength of light was incorporated to support the potential application of the system in regenerative medicine. Following light exposure, the mechanical properties of the photodegradable hydrogel gradually deteriorated, and product analysis confirmed the degradation of the hydrogel, and thereby, 3D microenvironment remodeling. In situ microenvironment remodeling influenced stem cell proliferation and enlargement within the hydrogel. Furthermore, stem cells engineered to express light-activated VEGF and incorporated into the dual-responsive system were applied to wound healing and an ischemic hindlimb model, proving their potential application in regenerative medicine.

Straightforward Analysis of Sulfated Glycosaminoglycans by MALDI-TOF Mass Spectrometry from Biological Samples

Glycosaminoglycans (GAGs) are considered to be the most difficult type of glycoconjugates to analyze as they are constituted of linear long polysaccharidic chains having molecular weights reaching up to several million daltons. Bottom-up analysis of glycosaminoglycans from biological samples is a long and work-extensive procedure due to the many preparation steps involved. In addition, so far, only few research articles have been dedicated to the analysis of GAGs by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) because their intact ionization can be problematic due to the presence of labile sulfate groups. In this work, we had the aim of exploring the sulfation pattern of monosulfated chondroitin/dermatan sulfate (CS/DS) disaccharides in human tissue samples because they represent the most abundant form of sulfation in disaccharides. We present here an optimized strategy to analyze on-target derivatized CS/DS disaccharides via MALDI-TOF-MS using a fast workflow that does not require any purification after enzymatic cleavage. For the first time, we show that MALDI-TOF/TOF experiments allow for discrimination between monosulfated CS disaccharide isomers via specific fragments corresponding to glycosidic linkages and to cross-ring cleavages. This proof of concept is illustrated via the analysis of CS/DS disaccharides of atherosclerotic lesions of different histological origins, in which we were able to identify their monosulfation patterns.

Analysis of Normal Levels of Free Glycosaminoglycans in Urine and Plasma in Adults

Plasma and urine glycosaminoglycans (GAGs) are long, linear sulfated polysaccharides that have been proposed as potential noninvasive biomarkers for several diseases. However, owing to the analytical complexity associated with the measurement of GAG concentration and disaccharide composition (the so-called GAGome), a reference study of the normal healthy GAGome is currently missing. Here, we prospectively enrolled 308 healthy adults and analyzed their free GAGomes in urine and plasma using a standardized ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry method together with comprehensive demographic and blood chemistry biomarker data. Of 25 blood chemistry biomarkers, we mainly observed weak correlations between the free GAGome and creatinine in urine and hemoglobin or erythrocyte counts in plasma. We found a higher free GAGome concentration – but not a more diverse composition - in males. Partitioned by gender, we also established reference intervals for all detectable free GAGome features in urine and plasma. Finally, we carried out a transference analysis in healthy individuals from two distinct geographical sites, including data from the Lifelines Cohort Study, which validated the reference intervals in urine. Our study is the first large-scale determination of normal free GAGomes reference intervals in plasma and urine and represents a critical resource for future physiology and biomarker research.

Discrimination of sulfated isomers of chondroitin sulfate disaccharides by HILIC-MS

Chondroitin sulfate (CS) glycosaminoglycans are biologically active sulfated polysaccharides that pose an analytical challenge for their structural analysis and functional evaluation. In this study, we developed a hydrophilic interaction liquid chromatography separation method and its on-line coupling to mass spectrometry (MS) allowing efficient differentiation and sensitive detection of mono-, di-, and trisulfated CS disaccharides and their positional isomers, without requiring prior derivatization. The composition of the mobile phase in terms of pH and concentration showed great influence on the chromatographic separation and was varied to allow the distinction of each CS without signal overlap for a total analysis time of 25 min. This methodology was applied to determine the disaccharide composition of biological reaction media resulting from various enzymatic transformations of CS, such as enzymatic desulfation of CS disaccharides by a CS 4-O-endosulfatase, and depolymerization of the CS endocan by chondroitinase lyase ABC.

Decoding the consecutive lysosomal degradation of 3-O-sulfate containing heparan sulfate by Arylsulfatase G (ARSG)

The lysosomal degradation of heparan sulfate is mediated by the concerted action of nine different enzymes. Within this degradation pathway, Arylsulfatase G (ARSG) is critical for removing 3-O-sulfate from glucosamine, and mutations in ARSG are causative for Usher syndrome type IV. We developed a specific ARSG enzyme assay using sulfated monosaccharide substrates, which reflect derivatives of its natural substrates. These sulfated compounds were incubated with ARSG, and resulting products were analyzed by reversed-phase HPLC after chemical addition of the fluorescent dyes 2-aminoacridone or 2-aminobenzoic acid, respectively. We applied the assay to further characterize ARSG regarding its hydrolytic specificity against 3-O-sulfated monosaccharides containing additional sulfate-groups and N-acetylation. The application of recombinant ARSG and cells overexpressing ARSG as well as isolated lysosomes from wild-type and Arsg knockout mice validated the utility of our assay. We further exploited the assay to determine the sequential action of the different sulfatases involved in the lysosomal catabolism of 3-O-sulfated glucosamine residues of heparan sulfate. Our results confirm and extend the characterization of the substrate specificity of ARSG and help to determine the sequential order of the lysosomal catabolic breakdown of (3-O-)sulfated heparan sulfate.

Improving the Sensitivity for Quantifying Heparan Sulfate from Biological Samples

Heparan sulfates (HSs) are widely expressed glycans in the animal kingdom. HS plays a role in regulating cell differentiation/proliferation, embryonic development, blood coagulation, inflammatory response, and viral infection. The amount of HS and its structural information are critically important for investigating the functions of HS in vivo. A sensitive and reliable quantitative technique for the analysis of HS from biological samples is under development. Here, we report a new labeling reagent for HS disaccharides analysis, 6-amino-N-(2-diethylamino)ethyl quinoline-2-carboamide (AMQC). The AMQC-conjugated disaccharides are analyzed by LC-MS/MS in positive mode, significantly improving the sensitivity. The use of AMQC coupled with authentic ¹³C-labeled HS disaccharide internal standards empowered us to determine the amount and the disaccharide composition of the HS on a single histological slide. We used this method to profile the levels of HS in the plasma/serum and tissues/organs to assist the disease prognosis in two animal models, including the acetaminophen (APAP)-induced acute liver injury mouse model and the burn injury mouse model. The method may uncover the roles of HS contributing to the diseases as well as provide a potential new set of biomarkers for disease diagnosis and prognosis.

Fluorometric coupled enzyme assay for N-sulfotransferase activity of N-deacetylase/N-sulfotransferase (NDST)

N-Deacetylase/N-sulfotransferases (NDST) are critical enzymes in heparan sulfate (HS) biosynthesis. Radioactive labeling assays are the preferred methods to determine the N-sulfotransferase activity of NDST. In this study, we developed a fluorometric coupled enzyme assay that is suitable for the study of enzyme kinetics and inhibitory properties of drug candidates derived from a large-scale in silico screening targeting the sulfotransferase moiety of NDST1. The assay measures recombinant mouse NDST1 (mNDST1) sulfotransferase activity by employing its natural substrate adenosine 3'-phophoadenosine-5'-phosphosulfate (PAPS), a bacterial analog of desulphated human HS, Escherichia coli K5 capsular polysaccharide (K5), the fluorogenic substrate 4-methylumbelliferylsulfate, and a double mutant of rat phenol sulfotransferase SULT1A1 K56ER68G. Enzyme kinetic analysis of mNDST1 performed with the coupled assay under steady state conditions at pH 6.8 and 37 °C revealed Km (K5) 34.8 μM, Km (PAPS) 10.7 μM, Vmax (K5) 0.53 ± 0.13 nmol/min/μg enzyme, Vmax (PAPS) 0.69 ± 0.05 nmol/min/μg enzyme, and the specific enzyme activity of 394 pmol/min/μg enzyme. The pH optimum of mNDST1 is pH 8.2. Our data indicate that mNDST1 is specific for K5 substrate. Finally, we showed that the mNDST1 coupled assay can be utilized to assess potential enzyme inhibitors for drug development.

Analytical performance of a standardized kit for mass spectrometry-based measurements of human glycosaminoglycans

Glycosaminoglycans (GAGs) are long linear sulfated polysaccharides implicated in processes linked to disease development such as mucopolysaccharidosis, respiratory failure, cancer, and viral infections, thereby serving as potential biomarkers. A successful clinical translation of GAGs as biomarkers depends on the availability of standardized GAG measurements. However, owing to the analytical complexity associated with the quantification of GAG concentration and structural composition, a standardized method to simultaneously measure multiple GAGs is missing. In this study, we sought to characterize the analytical performance of a ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-MS/MS)-based kit for the quantification of 17 free GAG disaccharides. The kit showed acceptable linearity, selectivity and specificity, accuracy and precision, and analyte stability in the absolute quantification of 15 disaccharides. In native human samples, here using urine as a reference matrix, the analytical performance of the kit was acceptable for the quantification of CS disaccharides. Intra- and inter-laboratory tests performed in an external laboratory demonstrated robust reproducibility of GAG measurements showing that the kit was acceptably standardized. In conclusion, these results indicated that the UHPLC-MS/MS kit was standardized for the simultaneous measurement of free GAG disaccharides allowing for comparability of measurements and enabling translational research.

Domain Mapping of Chondroitin/Dermatan Sulfate Glycosaminoglycans Enables Structural Characterization of Proteoglycans

Of all posttranslational modifications known, glycosaminoglycans (GAGs) remain one of the most challenging to study, and despite the recent years of advancement in MS technologies and bioinformatics, detailed knowledge about the complete structures of GAGs as part of proteoglycans (PGs) is limited. To address this issue, we have developed a protocol to study PG-derived GAGs. Chondroitin/dermatan sulfate conjugates from the rat insulinoma cell line, INS-1832/13, known to produce primarily the PG chromogranin-A, were enriched by anion-exchange chromatography after pronase digestion. Following benzonase and hyaluronidase digestions, included in the sample preparation due to the apparent interference from oligonucleotides and hyaluronic acid in the analysis, the GAGs were orthogonally depolymerized and analyzed using nano-flow reversed-phase LC-MS/MS in negative mode. To facilitate the data interpretation, we applied an automated LC-MS peak detection and intensity measurement via the Proteome Discoverer software. This approach effectively provided a detailed structural description of the nonreducing end, internal, and linkage region domains of the CS/DS of chromogranin-A. The copolymeric CS/DS GAGs constituted primarily consecutive glucuronic-acid-containing disaccharide units, or CS motifs, of which the N-acetylgalactosamine residues were 4-O-sulfated, interspersed by single iduronic-acid-containing disaccharide units. Our data suggest a certain heterogeneity of the GAGs due to the identification of not only CS/DS GAGs but also of GAGs entirely of CS character. The presented protocol allows for the detailed characterization of PG-derived GAGs, which may greatly increase the knowledge about GAG structures in general and eventually lead to better understanding of how GAG structures are related to biological functions.

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Protocol developed to structurally characterize glycosaminoglycans of proteoglycans.

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Comprehensive characterization of cellular glycosaminoglycan structures.

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Relative quantification of nonreducing end, internal, and linkage region domains.

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Overall chondroitin/dermatan sulfate glycosaminoglycan structures of chromogranin-A.

Investigation of the biological functions of heparan sulfate using a chemoenzymatic synthetic approach

Heparan sulfate (HS) is a highly sulfated polysaccharide playing essential physiological and pathophysiological roles in the animal kingdom. Heparin, a highly sulfated form of HS, is a widely used anticoagulant drug. Isolated from biological sources, both heparin and HS are polysaccharide mixtures with different sugar chain lengths and sulfation patterns. Structural heterogeneity of HS complicates the investigation of HS-related biological activities. The availability of structurally defined HS oligosaccharides is critical in understanding the contribution of saccharide structures to the functions. The chemoenzymatic synthetic approach is emerging as a cost-effective method to synthesize HS oligosaccharides. Structurally defined oligosaccharides are now widely available for biologists. This review summarizes our efforts in using this new synthetic method to develop new anticoagulant therapeutics and discover the role of HS to protect liver damage under pathological conditions. The synthetic method also allows us to prepare reference saccharide standards to improve structural analysis of HS.

Developments in Mass Spectrometry for Glycosaminoglycan Analysis: A Review

This review covers recent developments in glycosaminoglycan (GAG) analysis via mass spectrometry (MS). GAGs participate in a variety of biological functions, including cellular communication, wound healing, and anticoagulation, and are important targets for structural characterization. GAGs exhibit a diverse range of structural features due to the variety of O- and N-sulfation modifications and uronic acid C-5 epimerization that can occur, making their analysis a challenging target. Mass spectrometry approaches to the structure assignment of GAGs have been widely investigated, and new methodologies remain the subject of development. Advances in sample preparation, tandem MS techniques (MS/MS), online separations, and automated analysis software have advanced the field of GAG analysis. These recent developments have led to remarkable improvements in the precision and time efficiency for the structural characterization of GAGs.

Beware, commercial chondroitinases vary in activity and substrate specificity

Chondroitin sulfate (CS)and dermatan sulfate (DS) are negatively charged polysaccharides found abundantly in animal tissue and have been extensively described to play key roles in health and disease. The most common method to analyze their structure is by digestion into disaccharides with bacterial chondroitinases, followed by chromatography and/or mass spectrometry. While studying the structure of oncofetal CS, we noted a large variation in the activity and specificity of commercially available chondroitinases. Here studied the kinetics of the enzymes and used high-performance liquid chromatography-mass spectrometry to determine the di- and oligosaccharide products resulting from the digestion of commercially available bovine CS A, shark CS C and porcine DS, focusing on chondroitinases ABC, AC and B from different vendors. Application of a standardized assay setup demonstrated large variations in the enzyme-specific activity compared to the values provided by vendors, large variation in enzyme specific activity of similar enzymes from different vendors and differences in the extent of cleavage of the substrates and the generated products. The high variability of different chondroitinases highlights the importance of testing enzyme activity and monitoring product formation in assessing the content and composition of chondroitin and DSs in cells and tissues.

Emerging Approaches for Fluorescence-Based Newborn Screening of Mucopolysaccharidoses

Interest in newborn screening for mucopolysaccharidoses (MPS) is growing, due in part to ongoing efforts to develop new therapies for these disorders and new screening assays to identify increased risk for the individual MPSs on the basis of deficiency in the cognate enzyme. Existing tests for MPSs utilize either fluorescence or mass spectrometry detection methods to measure biomarkers of disease (e.g., enzyme function or glycosaminoglycans) using either urine or dried blood spot (DBS) samples. There are currently two approaches to fluorescence-based enzyme function assays from DBS: (1) manual reaction mixing, incubation, and termination followed by detection on a microtiter plate reader; and (2) miniaturized automation of these same assay steps using digital microfluidics technology. This article describes the origins of laboratory assays for enzyme activity measurement, the maturation and clinical application of fluorescent enzyme assays for MPS newborn screening, and considerations for future expansion of the technology.

Glycosaminoglycan Domain Mapping of Cellular Chondroitin/Dermatan Sulfates

Glycosaminoglycans (GAGs) are polysaccharides produced by most mammalian cells and involved in a variety of biological processes. However, due to the size and complexity of GAGs, detailed knowledge about the structure and expression of GAGs by cells, the glycosaminoglycome, is lacking. Here we report a straightforward and versatile approach for structural domain mapping of complex mixtures of GAGs, GAGDoMa. The approach is based on orthogonal enzymatic depolymerization of the GAGs to generate internal, terminating, and initiating domains, and nanoflow reversed-phase ion-pairing chromatography with negative mode higher-energy collision dissociation (HCD) tandem mass spectrometry (MS/MS) for structural characterization of the individual domains. GAGDoMa provides a detailed structural insight into the glycosaminoglycome, and offers an important tool for deciphering the complexity of GAGs in cellular physiology and pathology.

Pingyangmycin inhibits glycosaminoglycan sulphation in both cancer cells and tumour tissues

Pingyangmycin is a clinically used anticancer drug and induces lung fibrosis in certain cancer patients. We previously reported that the negatively charged cell surface glycosaminoglycans are involved in the cellular uptake of the positively charged pingyangmycin. However, it is unknown if pingyangmycin affects glycosaminoglycan structures. Seven cell lines and a Lewis lung carcinoma‐injected C57BL/6 mouse model were used to understand the cytotoxicity of pingyangmycin and its effect on glycosaminoglycan biosynthesis. Stable isotope labelling coupled with LC/MS method was used to quantify glycosaminoglycan disaccharide compositions from pingyangmycin‐treated and untreated cell and tumour samples. Pingyangmycin reduced both chondroitin sulphate and heparan sulphate sulphation in cancer cells and in tumours. The effect was persistent at different pingyangmycin concentrations and at different exposure times. Moreover, the cytotoxicity of pingyangmycin was decreased in the presence of soluble glycosaminoglycans, in the glycosaminoglycan‐deficient cell line CHO745, and in the presence of chlorate. A flow cytometry‐based cell surface FGF/FGFR/glycosaminoglycan binding assay also showed that pingyangmycin changed cell surface glycosaminoglycan structures. Changes in the structures of glycosaminoglycans may be related to fibrosis induced by pingyangmycin in certain cancer patients.

Functional role of glycosaminoglycans in decellularized lung extracellular matrix

Despite progress in use of decellularized lung scaffolds in ex vivo lung bioengineering schemes, including use of gels and other materials derived from the scaffolds, the detailed composition and functional role of extracellular matrix (ECM) proteoglycans (PGs) and their glycosaminoglycan (GAG) chains remaining in decellularized lungs, is poorly understood. Using a commonly utilized detergent-based decellularization approach in human autopsy lungs resulted in disproportionate losses of GAGs with depletion of chondroitin sulfate/dermatan sulfate (CS/DS) > heparan sulfate (HS) > hyaluronic acid (HA). Specific changes in disaccharide composition of remaining GAGs were observed with disproportionate loss of NS and NS2S for HS groups and of 4S for CS/DS groups. No significant influence of smoking history, sex, time to autopsy, or age was observed in native vs. decellularized lungs. Notably, surface plasmon resonance demonstrated that GAGs remaining in decellularized lungs were unable to bind key matrix-associated growth factors FGF2, HGF, and TGFβ1. Growth of lung epithelial, pulmonary vascular, and stromal cells cultured on the surface of or embedded within gels derived from decellularized human lungs was differentially and combinatorially enhanced by replenishing specific GAGs and FGF2, HGF, and TGFβ1. In summary, lung decellularization results in loss and/or dysfunction of specific GAGs or side chains significantly affecting matrix-associated growth factor binding and lung cell metabolism. GAG and matrix-associated growth factor replenishment thus needs to be incorporated into schemes for investigations utilizing gels and other materials produced from decellularized human lungs. STATEMENT OF SIGNIFICANCE: Despite progress in use of decellularized lung scaffolds in ex vivo lung bioengineering schemes, including use of gels and other materials derived from the scaffolds, the detailed composition and functional role of extracellular matrix (ECM) proteoglycans (PGs) and their glycosaminoglycan (GAG) chains remaining in decellularized lungs, is poorly understood. In the current studies, we demonstrate that glycosaminoglycans (GAGs) are significantly depleted during decellularization and those that remain are dysfunctional and unable to bind matrix-associated growth factors critical for cell growth and differentiation. Systematically repleting GAGs and matrix-associated growth factors to gels derived from decellularized human lung significantly and differentially affects cell growth. These studies highlight the importance of considering GAGs in decellularized lungs and their derivatives.

Structural analysis of glycosaminoglycans from Colla corii asini by liquid chromatography-electrospray ion trap mass spectrometry

Colla corii asini (CCA) made from donkey-hide has been widely used as a traditional animal-based Chinese medicine. Chondroitin sulfate (CS), dermatan sulfate (DS) and hyaluronic acid (HA) are structurally complex classes of glycosaminoglycans (GAGs) that have been implicated in a wide range of biological activities. However, their possible structural characteristics in CCA are not clear. In this study, GAG fractions containing CS/DS and HA were isolated from CCA and their disaccharide compositions were analyzed by high sensitivity liquid chromatography-ion trap/time-of-flight mass spectrometry (LC-MS-ITTOF). The result showed that CS/DS/HA disaccharides were detected in the three lower salt fractions from anion-exchange chromatography. The sulfation patterns and densities of CS/DS chains in these fractions differed greatly, while HA chains varied in their chain lengths. The quantitative analysis first revealed that the amount of GAGs in CCA varied significantly in total and in each fraction. This novel structural information could help clarify the possible involvement of these polysaccharides in the biological activities of CCA.

Proteoglycan serglycin promotes non-small cell lung cancer cell migration through the interaction of its glycosaminoglycans with CD44

Background

Serglycin (SRGN), previously recognized as an intracellular proteoglycan involved in the storage processes of secretory granules, has recently been shown to be upregulated in several solid tumors. We have previously shown that SRGN in non-small cell lung cancer (NSCLC) promotes malignant phenotypes in a CD44-dependent manner and increased expression of SRGN predicts poor prognosis of primary lung adenocarcinomas. However, the underlying mechanism remains to be defined.

Methods

Overexpression, knockdown and knockout approaches were performed to assess the role of SRGN in cell motility using wound healing and Boyden chamber migration assays. SRGN devoid of glycosaminoglycan (GAG) modification was produced by site-directed mutagenesis or chondroitinase treatment. Liquid chromatography/tandem mass spectrometry was applied for quantitative analysis of the disaccharide compositions and sulfation extent of SRGN GAGs. Western blot and co-immunoprecipitation analyses were performed to determine the expression and interaction of proteins of interest. Actin cytoskeleton organization was monitored by immunofluorescence staining.

Results

SRGN expressed by NSCLC cells is readily secreted to the extracellular matrix in a heavily glycosylated form attached with mainly chondroitin sulfate (CS)-GAG chains, and to a lesser extent with heparin sulfate (HS). The CS-GAG moiety serves as the structural motif for SRGN binding to tumor cell surface CD44 and promotes cell migration. SRGN devoid of CS-GAG modification fails to interact with CD44 and has lost the ability to promote cell migration. SRGN/CD44 interaction promotes focal adhesion turnover via Src-mediated paxillin phosphorylation and disassembly of paxillin/FAK adhesion complex, facilitating cell migration. In support, depletion of Src activity or removal of CS-GAGs efficiently blocks SRGN-mediated Src activation and cell migration. SRGN also promotes cell migration via inducing cytoskeleton reorganization mediated through RAC1 and CDC42 activation accompanied with increased lamellipodia and filopodia formation.

Conclusions

Proteoglycan SRGN promotes NSCLC cell migration via the binding of its GAG motif to CD44. SRGN/CD44 interaction induces Rho-family GTPase-mediated cytoskeleton reorganization and facilitates Src-mediated focal adhesion turnover, leading to increased cell migration. These findings suggest that targeting specific glycans in tumor microenvironment that serve as ligands for oncogenic pathways may be a potential strategy for cancer therapy.