Validation of Liquid Chromatography-Tandem Mass Spectrometry-Based 5-Plex Assay for Mucopolysaccharidoses.

Mucopolysaccharidoses (MPSs) are rare lysosomal storage diseases caused by the accumulation of undegraded glycosaminoglycans in cells and tissues. The effectiveness of early intervention for MPS has been reported. Multiple-assay formats using tandem mass spectrometry have been developed. Here, we developed a method for simultaneous preparation and better measurement of the activities of five enzymes involved in MPSs, i.e., MPS I, MPS II, MPS IIIB, MPS IVA, and MPS VI, which were validated using 672 dried blood spot samples obtained from healthy newborns and 23 patients with MPS. The mean values of the enzyme activities and standard deviations in controls were as follows: α-iduronidase (IDUA), 4.19 ± 1.53 µM/h; iduronate-2-sulfatase (I2S), 8.39 ± 2.82 µM/h; N-acetyl-α-glucosaminidase (NAGLU), 1.96 ± 0.57 µM/h; N-acetylgalactosamine-6-sulfatase (GALNS), 0.50 ± 0.20 µM/h; and N-acetylgalactosamine-4-sulfatase (ARSB), 2.64 ± 1.01 µM/h. All patients displayed absent or low enzyme activity. In MPS I, IIIB, and VI, each patient group was clearly separated from controls, whereas there was some overlap between the control and patient groups in MPS II and IVA, suggesting the occurrence of pseudo-deficiencies. Thus, we established a multiplex assay for newborn screening using liquid chromatography tandem mass spectrometry, allowing simultaneous pretreatment and measurement of five enzymes relevant to MPSs.

Estimated birth prevalence of mucopolysaccharidoses in Brazil.

Several studies have been published on the frequency of the mucopolysaccharidoses (MPS) in different countries. The objective of the present study was to estimate the birth prevalence (BP) of MPS in Brazil. MPS diagnosis registered at MPS-Brazil Network and in Instituto Vidas Raras were reviewed. BP was estimated by (a) the number of registered patients born between 1994 and 2015 was divided by the number of live births (LBs), and (b) a sample of 1,000 healthy individuals was tested for the most frequent variant in IDUA gene in MPS I (p.Trp402Ter) to estimate the frequency of heterozygosity and homozygosity. (a) The BP based on total number of LBs was (cases per 100,000 LBs): MPS overall: 1.25; MPS I: 0.24; MPS II: 0.37; MPS III: 0.21; MPS IV: 0.14; MPS VI: 0.28; MPS VII: 0.02. (b) The overall frequency of p.Trp402Ter was 0.002. Considering the frequency of heterozygotes for the p.Trp402Ter IDUA variant in the RS state, the frequency of this variant among MPS I patients and the relative frequency of the different MPSs, we estimated the birth prevalence of MPS in total and of each MPS type, as follows: MPS overall: 4.62; MPS I: 0.95; MPS II: 1.32; MPS III: 0.56; MPS IV: 0.57; MPS VI: 1.02; MPS VII: 0.05. This study provided original data about BP and relative frequency of the MPS types, in Brazil, based on the frequency of the commonest IDUA pathogenic variant and in the records of two large patient databases.

Evaluation of biomarkers for Sanfilippo syndrome.

Sanfilippo syndrome or mucopolysaccharidosis type III (MPS III) is a childhood metabolic disorder marked by neuropathology arising due to impaired heparan sulphate (HS) catabolism. Consequently, partially degraded HS accumulates in the lysosomes of affected cells and is excreted in the urine. The measurement of HS in urine has long been considered a biomarker of Sanfilippo syndrome although it is largely non-specific. Using blood, urine and CSF collected from a cohort of Sanfilippo patients we investigated the utility of primary and secondary biomarkers to inform on disease activity. These included enzyme activity, specific oligosaccharides with non-reducing end residues reflective of the enzyme deficiency, and gangliosides. The diagnostic oligosaccharides - a HS disaccharide and tetrasaccharide - were elevated in the urine, plasma and CSF of all MPS IIIA and IIIB patients, respectively. There was no correlation between the concentrations in any of the matrices suggesting they reflect specific tissues and not overall disease burden. Enzyme activity did not inform on disease severity, with no measurable activity in CSF and activity approaching normal in MPS IIIA plasma. The concentration of gangliosides, GM2 and GM3, were significantly higher in the CSF of all MPS III subjects when compared to controls and correlated with the age of onset of first symptoms. Given that these gangliosides reflect delayed brain development they may be useful measures of disease burden, within the limitations of the clinical surrogates. Observation of these biochemical measurements in MPS III patients enrolled in clinical trials may determine whether they represent true pharmacodynamics biomarkers.

Detection of mucopolysaccharidosis III-A (Sanfilippo Syndrome-A) in dried blood spots (DBS) by tandem mass spectrometry.

BACKGROUND: With ongoing efforts to develop improved treatments for Sanfilippo Syndrome Type A (MPS-IIIA), a disease caused by the inability to degrade heparan sulfate in lysosomes, we sought to develop an enzymatic activity assay for the relevant enzyme, sulfamidase, that uses dried blood spots (DBS). METHODS: We designed and synthesized a new sulfamidase substrate that can be used to measure sulfamidase activity in DBS using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Sulfamidase activity was readily detected in DBS using the new substrate and LC-MS/MS. Sulfamidase activity showed acceptable linearity proportional to the amount of enzyme and reaction time. Sulfamidase activity in 238 random newborns was well elevated compared to the range of activities measured in DBS from 8 patients previously confirmed to have MPS-IIIA. CONCLUSIONS: This is the first report of an assay capable of detecting sulfamidase in DBS. The new assay could be useful in diagnosis and potentially for newborn screening of MPS-IIIA.

Glycosaminoglycans analysis in blood and urine of patients with mucopolysaccharidosis.

To explore the correlation between glycosaminoglycan (GAG) levels and mucopolysaccharidosis (MPS) type, we have evaluated the GAG levels in blood of MPS II, III, IVA, and IVB and urine of MPS IVA, IVB, and VI by tandem mass spectrometry. Dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS; mono-sulfated KS, di-sulfated KS), and the ratio of di-sulfated KS in total KS were measured. Patients with untreated MPS II had higher levels of DS and HS in blood while untreated MPS III had higher levels of HS in blood than age-matched controls. Untreated MPS IVA had higher levels of KS in blood and urine than age-matched controls. The ratio of blood di-sulfated KS/total KS in untreated MPS IVA was constant and higher than that in controls for children up to 10 years of age. The ratio of urine di-sulfated KS/total KS in untreated MPS IVA was also higher than that in age-matched controls, but the ratio in untreated MPS IVB was lower than controls. ERT reduced blood DS and HS in MPS II, and urine KS in MPS IVA patients, although GAGs levels remained higher than the observed in age-matched controls. ERT did not change blood KS levels in MPS IVA. MPS VI under ERT still had an elevation of urine DS level compared to age-matched controls. There was a positive correlation between blood and urine KS in untreated MPS IVA patients but not in MPS IVA patients treated with ERT. Blood and urine KS levels were secondarily elevated in MPS II and VI, respectively. Overall, measurement of GAG levels in blood and urine is useful for diagnosis of MPS, while urine KS is not a useful biomarker for monitoring therapeutic efficacy in MPS IVA.

Glycosaminoglycan levels and structure in a mucopolysaccharidosis IIIA mice and the effect of a highly secreted sulfamidase engineered to cross the blood-brain barrier.

Mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo A) is a neurodegenerative lysosomal storage disorder caused by the deficiency of sulphamidase enzyme (SGSH) leading to accumulation of heparan sulfate (HS). We quantitatively and structurally characterize primary stored HS and other glycosaminoglycans (GAGs) possibly accumulated through a secondary storage in brain, liver, kidney and lung of MPS IIIA mouse model. This analysis was also performed in MPS IIIA mice upon the intravenous treatment with an engineered human sulphamidase (chimeric hSGSH) capable to increase its secretion from the liver and to cross the blood-brain barrier. MPS IIIA animals showed a huge accumulation of HS, from ~15 up to ~24-times higher than wild type and also of hyaluronic acid (HA) (from 2.5 up to ~5.0-times more) and chondroitin sulfate (CS)/dermatan sulfate (DS) (from ~2 up to ~5-times more) in all studied organs. We also observed a significant increase in the overall HS charge density and in particular of 2-O-sulfation in MPS IIIA mice organs. 8 months after a systemic treatment with an engineered SGSH, the enzyme was highly efficient in the reduction of all accumulated GAGs in liver, brain and lung up to values of wild type mice. On the contrary, even if reduced, GAGs levels still remained significantly elevated in kidney. Overall data obtained by this detailed analysis of GAGs in the different organs of affected and treated animals with chimeric hSGSH may have implications for the evaluation of an effective therapeutic option of MPS IIIA and for the reduction of related neuropathology.

Heparan sulfate derived disaccharides in plasma and total urinary excretion of glycosaminoglycans correlate with disease severity in Sanfilippo disease.

BACKGROUND: Sanfilippo disease (Mucopolysaccharidosis III) is a neurodegenerative lysosomal disorder characterized by accumulation of the glycosaminoglycan heparan sulfate (HS). MPS III has a large phenotypic variability and early assessment of disease severity is difficult. We investigated the correlation between disease severity and the plasma concentration of HS (pHS, defined by the sum of the heparan sulfate derived disaccharides obtained after enzymatic digestion) and urinary total GAGs level (uGAGs, measured by the dimethylene blue test) in a cross-sectional cohort of 44 MPS III patients. METHODS: Disease severity was established on the basis of the age of complete loss of independent walking and of full loss of speech in all patients. Hazard ratios (HR) were obtained with cox-regression analysis. In order to allow prediction of a severe phenotype based on a cut-off value for pHS, patients were divided in two groups (severely affected and less severely affected) based on predictive mutations or on the age of full loss of speech. Receiver operator characteristics (ROC) were obtained for pHS. RESULTS: pHS and uGAGs were independently and linearly associated with an increased risk of speech loss with a HR of 1.8 (95 % CI 1.3-2.7) per 500 ng/ml increase of HS in plasma (p = 0.002), and a HR of 2.7 (95 % CI 1.6-4.4) per 10 mg/mmol creatinine increase of uGAGs (p < 0.001). pHS and uGAGS were less strongly associated with loss of walking. The area under the ROC curve for pHS was 0.85, indicating good discrimination. CONCLUSION: pHS and uGAGs may be useful biomarkers for prediction of severity in MPS III.

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

INTRODUCTION: Mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders (LSDs) caused by a defect in the degradation of glycosaminoglycans (GAGs). The accumulation of GAGs in MPS patients results in extensive, severe and progressive disease. Disease modifying therapy is available for three of the MPSs and is being developed for the other types. Early initiation of treatment, before the onset of irreversible tissue damage, clearly provides a favorable disease outcome. However, early diagnosis is difficult due to the rarity of these disorders in combination with the wide variety of clinical symptoms. Newborn screening (NBS) is probably the optimal approach, and several screening techniques for different MPSs have been studied. Here we describe a relatively simple and sensitive method to measure levels of dermatan and heparan sulfate derived disaccharides in dried blood spots (DBS) with HPLC-MS/MS, and show that this reliably separates MPS I, II and MPS III newborns from controls and heterozygotes. METHODS: Newborn DBS of 11 MPS I, 1 MPS II, and 6 MPS III patients, with phenotypes ranging from severe to relatively attenuated, were collected and levels of dermatan and heparan sulfate derived disaccharides in these DBS were compared with levels in DBS of newborn MPS I and MPS III heterozygotes and controls. RESULTS: The levels of dermatan and heparan sulfate derived disaccharides were clearly elevated in all newborn DBS of MPS I, II and III patients when compared to controls. In contrast, DBS of MPS I and III heterozygotes showed similar disaccharide levels when compared to control DBS. CONCLUSIONS: Our study demonstrates that measurement of heparan and dermatan sulfate derived disaccharides in DBS may be suitable for NBS for MPS I, II and MPS III. We hypothesize that this same approach will also detect MPS VI, and VII patients, as heparan sulfate and/or dermatan sulfate is also the primary storage products in these disorders.

Impact of high-dose, chemically modified sulfamidase on pathology in a murine model of MPS IIIA.

Mucopolysaccharidosis type IIIA (MPS IIIA) is a neurodegenerative lysosomal storage disorder that results from a deficiency of sulfamidase (N-sulfoglucosamine sulfohydrolase), with consequential accumulation of its substrate, partially degraded heparan sulfate. Conventional doses (e.g. 1mg/kg) of intravenously delivered recombinant human sulfamidase (rhSGSH) do not improve neuropathology in MPS IIIA mice due to an inability to traverse the blood-brain barrier; however high-dose treatment or administration of enzyme that has been chemically modified to remove mannose-6-phosphate glycans has been shown to reduce neuropathology in related animal models. We have combined these approaches to evaluate the ability of 1, 5, 10 or 20mg/kg of similarly chemically modified or unmodified rhSGSH to reduce neuropathology following repeated intravenous delivery to adult MPS IIIA mice. rhSGSH was detected in brain homogenates from mice treated with all doses of modified rhSGSH and those receiving the two higher doses of unmodified rhSGSH, albeit at significantly lower levels. Immunohistochemically, rhSGSH visualized in the brain was localized to the endothelium, meninges and choroid plexus, with no convincing punctate intra-neuronal staining seen. This presumably underlies the failure of the treatment to reduce the relative level of a heparan sulfate-derived oligosaccharide (GlcNS-UA), or secondarily stored substrates that accumulate in MPS IIIA brain cells. However, modification of rhSGSH significantly increased its effectiveness in degrading GlcNS-UA in non-CNS tissues, potentially as a result of its reduced plasma clearance. If this observation is generally applicable, chemical modification may permit the use of significantly lower doses of lysosomal enzymes in patients currently receiving intravenous enzyme replacement therapy.

Serum MIP-1 alpha level: a biomarker for the follow-up of lentiviral therapy in mucopolysaccharidosis IIIB mice.

Mucopolysaccharidosis (MPS) IIIB is an inherited lysosomal storage disorder caused by deficiency of alpha-N-acetylglucosaminidase (NAGLU). The disease is characterized by mild somatic features and severe neurological involvement, with high mortality rates. Although some therapeutic approaches have been applied to the murine model of the disease, no effective therapy is available. Moreover, assessing therapeutic efficacy is challenged by the lack of markers to for progression and severity. In this study, we examined the effect of brain-directed lentiviral (LV) gene therapy on serum levels of macrophage inflammatory protein 1 alpha (MIP-1alpha) and brain-derived neurotrophic factor (BDNF) proteins in the murine model of MPS IIIB to identify novel serum biomarkers. The cytokine MIP-1alpha was elevated in MPS IIIB mouse serum, and following gene therapy, it was reduced to normal levels. For neurotrophin BDNF, the difference in serum levels between MPS IIIB and normal mice was not statistically significant; after LV gene therapy, an increase in protein was found in treated mice, although the values were not statistically significant. Our studies suggest MIP-1alpha as the first serum biomarker that could be used to monitor disease progression and treatment for MPS IIIB disease.

Storage correction in cells of patients suffering from mucopolysaccharidoses types IIIA and VII after treatment with genistein and other isoflavones.

Mucopolysaccharidoses are autosomal and recessive lysosomal storage disorders caused by the deficiency of a lysosomal enzyme involved in glycosaminoglycan catabolism. The Sanfilippo type A disease (MPS III A) results from sulfamidase deficiency, which leads to accumulation of heparan sulfate, whereas Sly disease (MPS VII) results from beta-glucuronidase deficiency, leading to accumulation of heparan, dermatan, and chondroitin sulfates. These syndromes are characterized by severe central nervous system degeneration, resulting in progressive mental retardation, and fatality occurs in severely affected children. To date, no effective treatment is available except for bone marrow transplantation in specific cases. Recently, the use of genistein, an isoflavone that inhibits glycosaminoglycans synthesis, has been tested as substrate reduction therapy for neuronopathic forms of these diseases.We tested five natural analogs to genistein in human fibroblasts from both Sanfilippo A and Sly patients. Four molecules were as efficient as genistein in decreasing glycosaminoglycan accumulation. Moreover, a combination of several isoflavones was more efficient than one single isoflavone, suggesting a synergistic effect. These preliminary data may offer new perspectives for treating Sly and Sanfilippo A diseases and could be relevant to other neurological forms of mucopolysaccharidoses.

Evaluation of heparin cofactor II-thrombin complex as a biomarker on blood spots from mucopolysaccharidosis I, IIIA and IIIB mice.

Mucopolysaccharide (MPS) diseases are lysosomal storage disorders caused by deficiencies of enzymes catabolising glycosaminoglycans (GAGs). Abnormal GAG accumulation leads to symptoms including severe progressive neurological decline, skeletal deformities, organomegally, respiratory compromise and premature death. Treatment is available for some MPS diseases; enzyme replacement therapy for MPS I, II and VI, and haematopoietic stem cell transplantation for MPS I, VI and VII. These treatments are reliant on early diagnosis of the disease and accurate monitoring of treatment outcomes. Blood enzyme levels and total urinary GAGs are commonly used biomarkers in diagnosis of MPS but are not good measures of treatment outcome. Serum heparin cofactor II-thrombin complex (HCII-T), which is a GAG regulated serpin-protease complex, has recently been identified as a promising biomarker for MPS diseases. Here we present an assessment of the HCII-T biomarker in mouse models of MPS I, IIIA and IIIB, which suggests that HCII-T is a reliable marker for MPS I when measured in serum or dried blood spots stored for over a year at 4 degrees C, but that murine MPS IIIA and IIIB cannot be reliably detected using this biomarker. We also show that HCII-T formation in vivo is dependent on the presence of excess intravenous dermatan sulphate (DS), whilst intravenous heparan sulphate (HS), does not promote complex formation effectively. This suggests that HCII-T will prove effective as a biomarker for MPS I, II, VI and VII diseases, storing dermatan sulphate but may not be as appropriate for MPS III, storing heparan sulphate. With careful sample preparation, HCII-T ELISA could prove to be a useful biomarker for both newborn screening and measurement of treatment outcomes in selected MPS diseases.

Molecular analysis of the alpha-N-acetylglucosaminidase gene in seven Japanese patients from six unrelated families with mucopolysaccharidosis IIIB (Sanfilippo type B), including two novel mutations.

Molecular analysis of the alpha-N-acetylglucosaminidase gene in seven Japanese patients with Sanfilippo syndrome type B from six unrelated families was carried out, and six disease-causing mutations were found. The parents of Patient 2 had a consanguinous marriage, but other families did not have any record of consanguinity. Two families were from Okinawa Island, where more patients with Sanfilippo syndrome were found than in other areas in Japan. Patients 1 and 6 showed the most severe phenotype with rapid progression. Patients 2, 5, and 7 were moderate. Patients 3 and 4 (sib cases) showed an attenuated form compared with other patients. Patients 1, 2, and 6 were homozygous for R482W, R565W, and R565P, respectively. Patients 3 and 4 were compound heterozygous for F314L and R565P. Patient 5 had delTG2171-2172 in exon 6 in one allele, and the other allele was unknown. Patient 7 was compound heterozygous for V241M and R482W. The family of Patients 3 and 4 and that of Patient 6 are unrelated, although both families are from Okinawa Island, and the patients have the same mutation, R565P; thus, R565P might be a common mutation in the Okinawa district. F314L and V241M are novel mutations.

Mucopolysaccharidosis type IIIB (Sanfilippo B): identification of 18 novel alpha-N-acetylglucosaminidase gene mutations.

Mucopolysaccharidosis type IIIB (MPS IIIB or Sanfilippo B disease) is an autosomal recessive storage disorder caused by deficiency of the lysosomal enzyme a-N-acetylglucosaminidase. Mutation screening was performed on a group of 22 patients using a combination of SSCP/heteroduplex analysis of amplified genomic fragments and direct sequencing of cDNA fragments. Twenty-one different mutations were identified, 18 of them novel. Together they account for 82% of the disease alleles. The mutation spectrum consists of two small insertions, two small deletions, three nonsense mutations, and 14 different missense mutations, one of them (M1L) affecting the initiation codon. The vast genetic heterogeneity seen in this disorder is reflected by the fact that only three of the mutations were identified in more than one patient.

Human mucopolysaccharidosis IIID: clinical, biochemical, morphological and immunohistochemical characteristics.

Mucopolysaccharidosis IIID (MPS IIID) is one of the rarest of the MPS-III syndromes. To date, the clinical manifestations of 10 patients have been reported, the deficient N-acetylglucosamine 6-sulfatase (G6S) enzyme has been purified, and the G6S gene has been cloned, sequenced and localized. However, morphological manifestations of this condition have not been reported and the pathogenesis of the severe neurological deficits remains an enigma. In this paper we describe and correlate the clinical, biochemical and pathological observations for 2 cases of MPS IIID. We used monoclonal antibodies against heparan sulfate (HS) and GM2-ganglioside, thin layer chromatography, mass spectrometry, and morphological techniques to demonstrate the nature and the distribution of the uncatabolized substrates. The majority of the cells in various tissues showed morphological changes expected with lysosomal storage of HS. The central nervous system (CNS) was most severely affected because of the secondary storage of GM2 and GM3 gangliosides in addition to the primary accumulation of HS. The extent as well as the distribution of the diverse storage materials varied within and among different neurons as observed in MPS-III A, B, and C syndromes. This study supports the hypothesis that the neurological dysfunction and neurodegeneration common to the Sanfilippo syndromes is, in part, due to the secondary metabolic perturbations induced by HS accumulation.

Carrier detection in Sanfilippo A syndrome.

Leucocytes or fibroblasts from 10 obligate heterozygotes for Sanfilippo A syndrome gave decreased heparan N-sulphatase levels, using a modification of the method of Hall et al. (1978), which did not overlap normal control values. Five family members gave decreased values and are presumed heterozygotes.

A semi-quantitative micromethod for the determination of free glycosaminoglycans in serum. Results from studies on serum of healthy children of various age and patients affected by mucopolysaccharidosis.

A method is presented for the determination of free glycosaminoglycan (GAG) concentration in as little as 30 microliter serum. By filtration of the serum through DEAE-cellulose paper, the free GAG fraction is selectively adsorbed and concentrated on a circular area of 15.9 mm2; these GAG spots are stained with Alcian Blue. The relationship between the amounts of adsorbed GAG and the optical density of the Alcian Blue spots is linear with a certain range; e.g. for chondroitin sulfate (mixed isomers), from 0.25 to 1.00 micrograms. With this method--which we will refer to as the "DEAE Alcian Blue" method--we estimated the free GAG concentration in sera of individuals of various ages including newborns.