Quantification of Glycosaminoglycans in Urine by Isotope‐Dilution Liquid Chromatography‐Electrospray Ionization Tandem Mass Spectrometry

Quantification of Glycosaminoglycans in Urine by Isotope-Dilution Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry

Mucopolysaccharidoses (MPSs) are complex lysosomal storage disorders that result in the accumulation of glycosaminoglycans (GAGs) in urine, blood, and tissues. Lysosomal enzymes responsible for GAG degradation are defective in MPSs. GAGs including chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), and keratan sulfate (KS) are disease-specific biomarkers for MPSs. This article describes a stable isotope dilution-tandem mass spectrometric method for quantifying CS, DS, and HS in urine samples. The GAGs are methanolyzed to uronic or iduronic acid-N-acetylhexosamine or iduronic acid-N-sulfo-glucosamine dimers and mixed with internal standards derived from deuteriomethanolysis of GAG standards. Specific dimers derived from HS, DS, and CS are separated by ultra-performance liquid chromatography (UPLC) and analyzed by electrospray ionization tandem mass spectrometry (MS/MS) using selected reaction monitoring for each targeted GAG product and its corresponding internal standard. This UPLC-MS/MS GAG assay is useful for identifying patients with MPS types I, II, III, VI, and VII. © 2023 Wiley Periodicals LLC. Basic Protocol: Urinary GAG analysis by ESI-MS/MS Support Protocol 1: Prepare calibration samples Support Protocol 2: Preparation of stable isotope-labeled internal standards Support Protocol 3: Preparation of quality controls for GAG analysis in urine Support Protocol 4: Optimization of the methanolysis time Support Protocol 5: Measurement of the concentration of methanolic HCl.

High-Throughput Glycomic Methods

Glycomics aims to identify the structure and function of the glycome, the complete set of oligosaccharides (glycans), produced in a given cell or organism, as well as to identify genes and other factors that govern glycosylation. This challenging endeavor requires highly robust, sensitive, and potentially automatable analytical technologies for the analysis of hundreds or thousands of glycomes in a timely manner (termed high-throughput glycomics). This review provides a historic overview as well as highlights recent developments and challenges of glycomic profiling by the most prominent high-throughput glycomic approaches, with N-glycosylation analysis as the focal point. It describes the current state-of-the-art regarding levels of characterization and most widely used technologies, selected applications of high-throughput glycomics in deciphering glycosylation process in healthy and disease states, as well as future perspectives.

Chemically modified recombinant human sulfamidase (SOBI003) in mucopolysaccharidosis IIIA patients: Results from an open, non-controlled, multicenter study

PURPOSE

Mucopolysaccharidosis IIIA (MPS IIIA) is an inherited lysosomal storage disorder caused by mutations in the N-sulfoglucosamine sulfohydrolase gene that result in deficient enzymatic degradation of heparan sulfate (HS), resulting in progressive neurodegeneration in early childhood and premature death. A chemically modified variant of recombinant human sulfamidase, SOBI003, has shown to cross the blood-brain barrier (BBB) in mice and achieve pharmacologically relevant levels in cerebrospinal fluid (CSF). We report on a phase 1/2, open-label, first-in-human (FIH) study (NCT03423186) and its extension study (NCT03811028) to evaluate the long-term safety, tolerability, pharmacokinetics/pharmacodynamics (PK/PD) and clinical efficacy of SOBI003 in patients with MPS IIIA for up to 104 weeks.

METHODS

Six patients aged 1-6 years with confirmed MPS IIIA with developmental age ≥ 12 months received weekly intravenous injections of SOBI003 at 3 mg/kg (Cohort 1, n = 3) or 10 mg/kg (Cohort 2, n = 3). During the extension study, the individual dose of SOBI003 could be adjusted up to 20 mg/kg at the discretion of the investigator.

RESULTS

SOBI003 was generally well tolerated. Serum concentrations of SOBI003 increased in proportion to dose, and presence in CSF confirmed that SOBI003 crosses the BBB. Anti-drug antibodies (ADA) were detected in serum and CSF in all patients, with subsequent reductions in serum SOBI003 exposure at high ADA titers. SOBI003 exerted a clear PD effect: a mean reduction in HS levels in CSF of 79% was recorded at the last assessment, together with reductions in HS levels in serum and urine. Neurocognitive development age-equivalent scores showed a stabilization of cognition for all patients, whereas no clear overall clinical effect was observed on adaptive behavior, sleep pattern or quality of life.

CONCLUSION

SOBI003 was well tolerated when administered as weekly intravenous infusions at doses of up to 20 mg/kg for up to 104 weeks. ADA development was common and likely affected both PK and PD parameters. SOBI003 crossed the BBB and showed pharmacological activity on HS in CSF.

Diagnosis of Mucopolysaccharidoses and Mucolipidosis by Assaying Multiplex Enzymes and Glycosaminoglycans

Mucopolysaccharidoses (MPS) and mucolipidosis (ML II/III) are a group of lysosomal storage disorders (LSDs) that occur due to a dysfunction of the lysosomal hydrolases responsible for the catabolism of glycosaminoglycans (GAGs). However, ML is caused by a deficiency of the enzyme uridine-diphosphate N-acetylglucosamine:lysosomal-enzyme-N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase, EC2.7.8.17), which tags lysosomal enzymes with a mannose 6-phosphate (M6P) marker for transport to the lysosome. A timely diagnosis of MPS and ML can lead to appropriate therapeutic options for patients. To improve the accuracy of diagnosis for MPS and ML in a high-risk population, we propose a combination method based on known biomarkers, enzyme activities, and specific GAGs. We measured five lysosomal enzymes (α-L-iduronidase (MPS I), iduronate-2-sulfatase (MPS II), α-N-acetylglucosaminidase (MPS IIIB), N-acetylglucosamine-6-sulfatase (MPS IVA), and N-acetylglucosamine-4-sulfatase (MPS VI)) and five GAGs (two kinds of heparan sulfate (HS), dermatan sulfate (DS), and two kinds of keratan sulfate (KS)) in dried blood samples (DBS) to diagnose suspected MPS patients by five-plex enzyme and simultaneous five GAGs assays. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) for both assays. These combined assays were tested for 43 patients with suspected MPS and 103 normal control subjects. We diagnosed two MPS I, thirteen MPS II, one MPS IIIB, three MPS IVA, two MPS VI, and six ML patients with this combined method, where enzymes, GAGs, and clinical manifestations were compatible. The remaining 16 patients were not diagnosed with MPS or ML. The five-plex enzyme assay successfully identified MPS patients from controls. Patients with MPS I, MPS II, and MPS IIIB had significantly elevated HS and DS levels in DBS. Compared to age-matched controls, patients with ML and MPS had significantly elevated mono-sulfated KS and di-sulfated KS levels. The results indicated that the combination method could distinguish these affected patients with MPS or ML from healthy controls. Overall, this study has shown that this combined method is effective and can be implemented in larger populations, including newborn screening.

The combined use of enzyme activity and metabolite assays as a strategy for newborn screening of mucopolysaccharidosis type I

Objectives Mucopolysaccharidosis type I (MPS I) was added to our expanded screening panel in 2015. Since then, 127,869 newborns were screened by measuring α-L-iduronidase (IDUA) enzyme activity with liquid chromatography tandem mass spectrometry (LC-MS/MS). High false positives due to frequent pseudodeficiency alleles prompted us to develop a second-tier test to quantify glycosaminoglycan (GAG) levels in dried blood spot (DBS). Methods Heparan-sulfate (HS) and dermatan-sulfate (DS) were measured with LC-MS/MS after methanolysis. DBSs were incubated with methanolic-HCl 3 N at 65 °C for 45 min. Chromatographic separation used an amide column with a gradient of acetonitrile and water with 10 mM ammonium acetate in a 9-min run. The method was validated for specificity, linearity, lower limit of quantification (LOQ), accuracy and precision. Results Intra- and inter-day coefficients of variation were <15% for both metabolites. Reference values in 40 healthy newborns were: HS mean 1.0 mg/L, 0-3.2; DS mean 1.5 mg/L, 0.5-2.7). The two confirmed newborn MPS I patients had elevated HS (4.9-10.4 mg/L, n.v. <3.2) and DS (7.4-8.8 mg/L, n.v. <2.7). Since its introduction in February 2019, the second-tier test reduced the recall rate from 0.046% to 0.006%. Among 127,869 specimens screened, the incidence was 1:63,935 live births. Both patients started enzyme replacement therapy (ERT) within 15 days of birth and one of them received allogenic hematopoietic stem cell transplantation (HSCT) at ht age of 6 months. Conclusions GAGs in DBS increased the specificity of newborn screening for MPS I by reducing false-positives due to heterozygosity or pseudodeficiency. Early diagnosis and therapeutical approach has improved the outcome of our patients with MPS I.

Placental pathology in an unsuspected case of mucolipidosis type II with secondary hyperparathyroidism in a premature infant

Mucolipidosis type II (MLII, MIM 252500) is a lysosomal storage disorders caused by defects in GNPTAB gene which encodes alpha and beta subunits of N-acetylglucosamine (GlcNAc)-1-phosphotransferase. Neonatal presentation includes coarse facial features, restricted postnatal growth, generalized hypotonia, gingival hypertrophy and multiple skeletal anomalies. Here we present a case of a 26-week gestational age preterm infant with MLII who did not exhibit the typical facial features at birth; however, the diagnosis was suggested from abnormal placental pathology showing trophoblastic lipidosis and initial skeletal abnormalities from chest radiograph revealing generalized diffuse severe bone demineralizing disease and multiple fractures. Biochemical testing revealed elevation of plasma lysosomal enzymes. Homozygous pathogenic variant, designated c.3505_3504del, was discovered from GNPTAB sequencing. Her course was complicated by respiratory distress, secondary hyperparathyroidism, abdominal distention and feeding difficulties. Urine mucopolysaccharides analysis revealed mild elevation of total and individual glycosaminoglycan species in a non-specific pattern. To our knowledge, our case is the most premature example of mucolipidosis type II that has ever been reported to date. This report highlights the importance of placental pathological studies in the diagnosis of lysosomal storage disorders.

Advances in glycosaminoglycan detection

BACKGROUND

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

SCOPE OF REVIEW

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

GENERAL SIGNIFICANCE

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

Neonatal Mass Urine Screening Approach for Early Detection of Mucopolysaccharidoses by UPLC-MS/MS

Mucopolysaccharidoses (MPSs) are lysosomal storage disorders caused by deficiencies of enzymes involved in the catabolism of glycosaminoglycans (GAGs). Various treatments such as enzyme replacement therapy and/or hematopoietic stem cell transplant are available for MPSs. Early initiation of treatment improves the outcome and delays the onset of symptoms, highlighting the need for newborn screening for MPSs. The main objective of this project was to devise and validate a multiplex urine filter paper method for GAG analysis using a tandem mass spectrometry (MS/MS) approach to screen newborns for MPSs. Eluted urine samples from 21-day-old newborns were evaporated and a methanolysis reaction was performed. Samples were resuspended and analyzed using a UPLC-MS/MS system. A one-minute chromatographic method allowed the absolute quantification of heparan sulfate (HS), dermatan sulfate (DS), and creatinine. Method validation revealed high precision (< 9% relative standard deviation) and accuracy (< 7% bias) for all analytes. The reference values normalized to creatinine obtained by the analysis of five hundred 21-day-old newborn urine samples were 34.6 +/-6.2 mg/mmol of creatinine and 17.3 +/-3.9 mg/mmol of creatinine for HS and DS, respectively. We present a rapid and efficient method for populational newborn urine screening using MS/MS, which could also be applied to high-risk screening.

Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance

Introduction

Mucopolysaccharidosis (MPS) VI or Maroteaux-Lamy syndrome (253200) is an autosomal recessive lysosomal storage disorder caused by deficiency in N-acetylgalactosamine-4-sulfatase (arylsulfatase B). The heterogeneity and progressive nature of MPS VI necessitates a multidisciplinary team approach and there is a need for robust guidance to achieve optimal management. This programme was convened to develop evidence-based, expert-agreed recommendations for the general principles of management, routine monitoring requirements and the use of medical and surgical interventions in patients with MPS VI.

Methods

26 international healthcare professionals from various disciplines, all with expertise in managing MPS VI, and three patient advocates formed the Steering Committee group (SC) and contributed to the development of this guidance. Members from six Patient Advocacy Groups (PAGs) acted as advisors and attended interviews to ensure representation of the patient perspective. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with expertise and experience managing patients with MPS VI and the manuscript has been evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers.

Results

A total of 93 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions. Consensus was reached on all statements after two rounds of voting. The greatest challenges faced by patients as relayed by consultation with PAGs were deficits in endurance, dexterity, hearing, vision and respiratory function. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance).

Conclusion

This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS VI and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1080-y) contains supplementary material, which is available to authorized users.

Evaluation of cerebrospinal fluid heparan sulfate as a biomarker of neuropathology in a murine model of mucopolysaccharidosis type II using high-sensitivity LC/MS/MS

Mucopolysaccharidosis type II (MPS II or Hunter syndrome) is a lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS), an enzyme that catabolizes glycosaminoglycans (GAGs) including heparan sulfate (HS) and dermatan sulfate (DS). GAG accumulation leads to severe neurological and somatic impairments. At present, the most common treatment for MPS II is intravenous enzyme replacement therapy; however, the inability of recombinant IDS to cross the blood-brain barrier (BBB) restricts therapeutic efficacy for neurological manifestations. We recently developed a BBB-penetrating IDS fusion protein, JR-141, and demonstrated its ability to reduce GAG accumulation in the brain of human transferrin receptor knock-in and Ids knock-out mice (TFRC-KI/Ids-KO), an animal model of MPS II, following intravenous administration. Given the impossibility of measuring GAG accumulation in the brains of human patients with MPS II, we hypothesized that GAG content in the cerebrospinal fluid (CSF) might serve as an indicator of brain GAG burden. To test this hypothesis, we optimized a high-sensitivity method for quantifying HS and DS in low-volume samples by combining acidic methanolysis and liquid chromatography-tandem mass spectrometry (LC/MS/MS). We employed this method to quantify HS and DS in samples from TFRC-KI/Ids-KO mice and revealed that HS but not DS accumulated in the central nerve system (CNS). Moreover, concentrations of HS in CSF correlated with those in brain. Finally, intravenous treatment with JR-141 reduced levels of HS in the CSF and brain in TFRC-KI/Ids-KO mice. These results suggest that CSF HS content may be a useful biomarker for evaluating the brain GAG accumulation and the therapeutic efficacy of drugs in patients with MPS II.

Urinary proteomics and metabolomics in the diagnosis of pediatric disorders

Proteomics is the study of structures and functions of proteins, while metabolomics is the study of small-molecule metabolites in the cells, tissues, and organs of the organism. Proteomic technologies have wide applications in medical field. The current revolution in proteomics has led to the discovery of several new protein markers for various disorders. Urinary proteomics and metabolomics have also evolved in the recent years, for the diagnosis of both renal and nonrenal disorders. The urinary proteome varies in normal and abnormal conditions. Different techniques are employed for the analysis of pediatric urinary proteome, the commonest being MS. Before introduction into clinical use, there is the need for careful standardization. Available data suggest that there are differences in urinary proteome between adult and pediatric populations. It is noted that infant urine contains proteins involved in translation and transcription, cellular growth, and metabolic processes, which are not predominant in adult urine. Available data on urinary proteomic and metabolomic profile in common pediatric disorders are also reviewed here.

Development of a fluorometric microtiter plate based enzyme assay for MPS IVA (Morquio type A) using dried blood spots

Mucopolysaccharidosis type IVA or Morquio type-A disease is a hereditary lysosomal storage disorder caused by deficient activity of the lysosomal enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS). The disease is caused by lysosomal accumulation of unprocessed glycosaminoglycans (GAGs) that manifests with severe to mild skeletal and cardiopulmonary abnormalities. We have developed a modified microtiter plate-based enzyme activity assay using dried blood spots and a fluorescent substrate for measuring specific GALNS activity to identify patients with MPS IVA.

The laboratory diagnosis of mucopolysaccharidosis III (Sanfilippo syndrome): A changing landscape

Mucopolysaccharidosis type III (MPS III) is characterized by progressive neurological deterioration, behavioral abnormalities, a relatively mild somatic phenotype, and early mortality. Because of the paucity of somatic manifestations and the rarity of the disease, early diagnosis is often difficult. Therapy targeting the underlying disease pathophysiology may offer the greatest clinical benefit when started prior to the onset of significant neurologic sequelae. Here we review current practices in the laboratory diagnosis of MPS III in order to facilitate earlier patient identification and diagnosis. When clinical suspicion of MPS III arises, the first step is to order a quantitative assay that screens urine for the presence of glycosaminoglycan biomarkers using a spectrophotometric compound (e.g., dimethylmethylene blue). We recommend testing all patients with developmental delay and/or behavioral abnormalities as part of the diagnostic work-up because quantitative urine screening is inexpensive and non-invasive. Semi-quantitative urine screening assays using cationic dyes on filter paper (e.g., spot tests) have relatively high rates of false-positives and false-negatives and are obsolete. Of note, a negative urinary glycosaminoglycan assay does not necessarily rule out MPS because, in some patients, an overlap in excretion levels with healthy controls may occur. All urine samples that test positive for glycosaminoglycans with a quantitative assay should be confirmed by electrophoresis, thin layer chromatography, or tandem mass spectrometry, which further improves the sensitivity and specificity. The gold standard for diagnosis remains the enzyme activity assay in cultured skin fibroblasts, leukocytes, plasma, or serum, which can be used as a first-line diagnostic test in some regions. Molecular genetic analysis should be offered to all families of patients to allow genetic counseling for informed family planning. For a small number of variants, genotype-phenotype correlations are available and can offer prognostic value. Prenatal testing via enzyme activity assay in chorionic villi or amniotic fluid cells is available at a limited number of centers worldwide, but whenever possible, a molecular genetic analysis is preferred for prenatal diagnosis. To conclude, we discuss the development of newborn screening assays in dried blood spots and high-throughput methods for sequencing the protein-coding regions of the genome (whole exome sequencing) and their relevance to future changes in the MPS III diagnostic landscape.

Mucopolysaccharidoses and other lysosomal storage diseases

Mucopolysaccharidosis and other lysosomal storage diseases are rare, chronic, and progressive inherited diseases caused by a deficit of lysosomal enzymes. Patients are affected by a wide variety of symptoms. For some lysosomal storage diseases, effective treatments to arrest disease progression, or slow the pathologic process, and increase patient life expectancy are available or being developed. Timely diagnosis is crucial. Rheumatologists, orthopedics, and neurologists are commonly consulted due to unspecific musculoskeletal signs and symptoms. Pain, stiffness, contractures of joints in absence of clinical signs of inflammation, bone pain or abnormalities, osteopenia, osteonecrosis, secondary osteoarthritis or hip dysplasia are the alerting symptoms that should induce suspicion of a lysosomal storage disease.