Neuropathology in mouse models of mucopolysaccharidosis type I, IIIA and IIIB

Mucopolysaccharide diseases (MPS) are caused by deficiency of glycosaminoglycan (GAG) degrading enzymes, leading to GAG accumulation. Neurodegenerative MPS diseases exhibit cognitive decline, behavioural problems and shortened lifespan. We have characterised neuropathological changes in mouse models of MPSI, IIIA and IIIB to provide a better understanding of these events.Wild-type (WT), MPSI, IIIA and IIIB mouse brains were analysed at 4 and 9 months of age. Quantitative immunohistochemistry showed significantly increased lysosomal compartment, GM2 ganglioside storage, neuroinflammation, decreased and mislocalised synaptic vesicle associated membrane protein, (VAMP2), and decreased post-synaptic protein, Homer-1, in layers II/III-VI of the primary motor, somatosensory and parietal cortex. Total heparan sulphate (HS), was significantly elevated, and abnormally N-, 6-O and 2-O sulphated compared to WT, potentially altering HS-dependent cellular functions. Neuroinflammation was confirmed by significantly increased MCP-1, MIP-1α, IL-1α, using cytometric bead arrays. An overall genotype effect was seen in all parameters tested except for synaptophysin staining, neuronal cell number and cortical thickness which were not significantly different from WT. MPSIIIA and IIIB showed significantly more pronounced pathology than MPSI in lysosomal storage, astrocytosis, microgliosis and the percentage of 2-O sulphation of HS. We also observed significant time progression of all genotypes from 4-9 months in lysosomal storage, astrocytosis, microgliosis and synaptic disorganisation but not GM2 gangliosidosis. Individual genotype*time differences were disparate, with significant progression from 4 to 9 months only seen for MPSIIIB with lysosomal storage, MPSI with astrocytocis and MPSIIIA with microgliosis as well as neuronal loss. Transmission electron microscopy of MPS brains revealed dystrophic axons, axonal storage, and extensive lipid and lysosomal storage. These data lend novel insight to MPS neuropathology, suggesting that MPSIIIA and IIIB have more pronounced neuropathology than MPSI, yet all are still progressive, at least in some aspects of neuropathology, from 4-9 months.     

Identification of a mutation causing mucopolysaccharidosis type IIIA in New Zealand Huntaway dogs

Mucopolysaccharidosis type IIIA (MPS IIIA) is an autosomal recessive disease that occurs due to a deficiency of heparan sulfate sulfamidase (SGSH). The deficiency of SGSH results in the lysosomal accumulation and urinary excretion of the glycosaminoglycan heparan sulfate. The clinical severity of MPS IIIA is predominantly characterized by severe central nervous system degeneration. Naturally occurring MPS IIIA has recently been described in New Zealand Huntaway dogs, with similar disease progression and biochemical characteristics observed in severely affected MPS IIIA patients. Here, we identify the disease-causing mutation in the MPS IIIA Huntaway dog as 708-709insC. The frequency of the 708-709insC mutation in a sample group of 203 New Zealand Huntaway dogs was determined to be 3.8%. The identification of the 708-709insC mutation will permit the identification of heterozygous carriers as an initial step toward establishing a breeding colony of MPS IIIA dogs for the study of various therapeutic strategies targeted to the central nervous system.     

Gastrointestinal pathology in a mouse model of mucopolysaccharidosis type IIIA

Mucopolysaccharidosis type IIIA (MPS IIIA) is a lysosomal storage disorder caused by a deficiency in sulphamidase (NS), a lysosomal enzyme required for the degradation of heparan sulphate glycosaminoglycans (gags). The MPS IIIA mouse is a naturally occurring model that accurately reflects the human pathology and disease course. It displays primarily central nervous system pathology accompanied by widespread accumulation of gag in somatic tissues. MPS IIIA mice exhibit greater bodyweight gain than normal littermates and attain a higher mature bodyweight. In this study, gastrointestinal morphology and function was characterised in the IIIA mouse. Stomach and duodenum weight increased in MPS IIIA mice and duodenum length also increased. An increased submucosal thickness was observed in MPS IIIA intestine compared to normal mice and lysosomal storage of gag was observed in this region. Storage was also observed in the lamina propria of the villus tip. All other morphometric measurements including villus height and crypt depth fell within the normal range. The gastric emptying half‐life of solid and liquid meals decreased with age in normal mice whereas the T_½ of solid meals did not alter with age in MPS IIA mice such that they were elevated above normal by 38 weeks of age. Sucrase activity was higher than normal in MPS IIIA at all ages tested. These abnormalities in GI structure and function observed in MPS IIIA may contribute to weight gain in this disorder. J. Cell. Physiol. 219: 259–264, 2009. © 2009 Wiley‐Liss, Inc.     

Sulphamidase

Sulphamidase is one of four lysosomal proteins whose deficiency clinically manifests as Sanfilippo syndrome. Deficiency of sulphamidase results in the lysosomal storage of the glycosaminoglycan (GAG) heparan sulphate (HS) and is termed mucopolysaccharidosis type IIIA (MPS IIIA). Sulphamidase catalyses the hydrolysis of an N-linked sulphate from the nonreducing terminal glucosaminide residue of HS (Fig. 1). It is unique among the known lysosomal sulphatases involved in GAG degradation in that it is an N-sulphatase, all the others being O-sulphatases. Purification of sulphamidase from human liver has facilitated the amino-terminal sequencing of the protein and hence the isolation of cDNA and genomic clones for sulphamidase. This has in turn made possible a range of further studies aimed at better diagnosis, treatment and understanding of MPS IIIA.     

Helper-dependent canine adenovirus vector-mediated transgene expression in a neurodegenerative lysosomal storage disorder

Mucopolysaccharidosis type IIIA (MPS-IIIA) is a severe neurodegenerative lysosomal storage disorder caused by a deficiency of N-sulfoglucosamine sulfohydrolase (SGSH) activity with subsequent accumulation of partially-degraded heparan sulfate and other glycolipids. In this study, we have evaluated a gene therapy approach using a helper-dependent canine adenovirus vector that expresses human SGSH as a means of delivering sustained transgene expression to the brain. Initial testing in a mixed neural cell culture model demonstrated that the vector could significantly increase SGSH activity in transduced cells, resulting in near-normalization of heparan sulfate-derived fragments. While administration of vector by direct injection into the brain of adult MPS-IIIA mice enabled transgene expression for at least 8.5 months post-treatment, it was only in discrete areas of brain. Heparan sulfate storage was reduced in some regions following treatment, however there was no improvement in secondary neuropathological changes. These data demonstrate that helper-dependent canine adenovirus vectors are capable of neural transduction and mediate long-term transgene expression, but increased SGSH expression throughout the brain is likely to be required in order to effectively treat all aspects of the MPS-IIIA phenotype.     

Female mucopolysaccharidosis IIIA mice exhibit hyperactivity and a reduced sense of danger in the open field test

Reliable behavioural tests in animal models of neurodegenerative diseases allow us to study the natural history of disease and evaluate the efficacy of novel therapies. Mucopolysaccharidosis IIIA (MPS IIIA or Sanfilippo A), is a severe, neurodegenerative lysosomal storage disorder caused by a deficiency in the heparan sulphate catabolising enzyme, sulfamidase. Undegraded heparan sulphate accumulates, resulting in lysosomal enlargement and cellular dysfunction. Patients suffer a progressive loss of motor and cognitive function with severe behavioural manifestations and premature death. There is currently no treatment. A spontaneously occurring mouse model of the disease has been described, that has approximately 3% of normal enzyme activity levels. Behavioural phenotyping of the MPS IIIA mouse has been previously reported, but the results are conflicting and variable, even after full backcrossing to the C57BL/6 background. Therefore we have independently backcrossed the MPS IIIA model onto the C57BL/6J background and evaluated the behaviour of male and female MPS IIIA mice at 4, 6 and 8 months of age using the open field test, elevated plus maze, inverted screen and horizontal bar crossing at the same circadian time point. Using a 60 minute open field, we have demonstrated that female MPS IIIA mice are hyperactive, have a longer path length, display rapid exploratory behaviour and spend less time immobile than WT mice. Female MPS IIIA mice also display a reduced sense of danger and spend more time in the centre of the open field. There were no significant differences found between male WT and MPS IIIA mice and no differences in neuromuscular strength were seen with either sex. The altered natural history of behaviour that we observe in the MPS IIIA mouse will allow more accurate evaluation of novel therapeutics for MPS IIIA and potentially other neurodegenerative disorders.     

Tissue distribution of DNA-Hsp65/TDM-loaded PLGA microspheres and uptake by phagocytic cells

Background

Mucopolysaccharidosis type IIIA (MPS IIIA) is the most common of the mucopolysaccharidoses. The disease is caused by a deficiency of the lysosomal enzyme sulphamidase and results in the storage of the glycosaminoglycan (GAG), heparan sulphate. MPS IIIA is characterised by widespread storage and urinary excretion of heparan sulphate, and a progressive and eventually profound neurological course. Gene therapy is one of the few avenues of treatment that hold promise of a sustainable treatment for this disorder.

Methods

The murine sulphamidase gene cDNA was cloned into a lentiviral vector and high-titre virus produced. Human MPS IIIA fibroblast cultures were transduced with the sulphamidase vector and analysed using molecular, enzymatic and metabolic assays. High-titre virus was intravenously injected into six 5-week old MPS IIIA mice. Three of these mice were pre-treated with hyperosmotic mannitol. The weight of animals was monitored and GAG content in urine samples was analysed by polyacrylamide gel electrophoresis.

Results

Transduction of cultured MPS IIIA fibroblasts with the sulphamidase gene corrected both the enzymatic and metabolic defects. Sulphamidase secreted by gene-corrected cells was able to cross correct untransduced MPS IIIA cells. Urinary GAG was found to be greatly reduced in samples from mice receiving the vector compared to untreated MPS IIIA controls. In addition, the weight of treated mice became progressively normalised over the 6-months post-treatment.

Conclusion

Lentiviral vectors appear promising vehicles for the development of gene therapy for MPS IIIA.     

Peripheral Nervous System Neuropathology and Progressive Sensory Impairments in a Mouse Model of Mucopolysaccharidosis IIIB

The lysosomal storage pathology in Mucopolysaccharidosis (MPS) IIIB manifests in cells of virtually all organs. However, it is the profound role of the neurological pathology that leads to morbidity and mortality in this disease, and has been the major challenge to developing therapies. To date, MPS IIIB neuropathologic and therapeutic studies have focused predominantly on changes in the central nervous system (CNS), especially in the brain, and little is known about the disease pathology in the peripheral nervous system (PNS). This study demonstrates characteristic lysosomal storage pathology in dorsal root ganglia affecting neurons, satellite cells (glia) and Schwann cells. Lysosomal storage lesions were also observed in the myoenteric plexus and submucosal plexus, involving enteric neurons with enteric glial activation. Further, MPS IIIB mice developed progressive impairments in sensory functions, with significantly reduced response to pain stimulation that became detectable at 4–5 months of age as the disease progressed. These data demonstrate that MPS IIIB neuropathology manifests not only in the entire CNS but also the PNS, likely affecting both afferent and efferent neural signal transduction. This study also suggests that therapeutic development for MPS IIIB may benefit from targeting the entire nervous system.     

Defects in the medial entorhinal cortex and dentate gyrus in the mouse model of Sanfilippo syndrome type B

Sanfilippo syndrome type B (MPS IIIB) is characterized by profound mental retardation in childhood, dementia and death in late adolescence; it is caused by deficiency of α-N-acetylglucosaminidase and resulting lysosomal storage of heparan sulfate. A mouse model, generated by homologous recombination of the Naglu gene, was used to study pathological changes in the brain. We found earlier that neurons in the medial entorhinal cortex (MEC) and the dentate gyrus showed a number of secondary defects, including the presence of hyperphosphorylated tau (Ptau) detected with antibodies raised against Ptau in Alzheimer disease brain. By further use of immunohistochemistry, we now show staining in neurons of the same area for beta amyloid, extending the resemblance to Alzheimer disease. Ptau inclusions in the dentate gyrus of MPS IIIB mice were reduced in number when the mice were administered LiCl, a specific inhibitor of Gsk3β. Additional proteins found elevated in MEC include proteins involved in autophagy and the heparan sulfate proteoglycans, glypicans 1 and 5, the latter closely related to the primary defect. The level of secondary accumulations was associated with elevation of glypican, as seen by comparing brains of mice at different ages or with different mucopolysaccharide storage diseases. The MEC of an MPS IIIA mouse had the same intense immunostaining for glypican 1 and other markers as MPS IIIB, while MEC of MPS I and MPS II mice had weak staining, and MEC of an MPS VI mouse had no staining at all for the same proteins. A considerable amount of glypican was found in MEC of MPS IIIB mice outside of lysosomes. We propose that it is the extralysosomal glypican that would be harmful to neurons, because its heparan sulfate branches could potentiate the formation of Ptau and beta amyloid aggregates, which would be toxic as well as difficult to degrade.     

Phenotypic rescue after adeno-associated virus-mediated delivery of 4-sulfatase to the retinal pigment epithelium of feline mucopolysaccharidosis VI

Background

Mucopolysaccharidosis VI (MPS VI), due to recessively inherited 4‐sulfatase (4S) deficiency, results in lysosomal storage of dermatan sulfate in numerous tissues. Retinal involvement is limited to the retinal pigment epithelium (RPE). This study aimed to determine whether recombinant adeno‐associated virus (AAV)‐mediated delivery of 4S would reverse the RPE pathology seen in MPS VI cats.

Methods

AAV.f4S, containing the feline 4S cDNA, was delivered unilaterally to eyes of affected cats by subretinal or intravitreal injection. Contralateral eyes received AAV with the green fluorescent protein (GFP) reporter gene as control. At 2–11 months post‐injection, the cats were sacrificed and the treatment effects were evaluated histologically.

Results

By ophthalmoscopy and histological analyses, GFP was evident as early as 4 weeks and persisted through the latest time point (11 months). Untreated and AAV.GFP‐treated diseased retinas contained massively hypertrophied RPE cells secondary to accumulation of dilated lysosomal inclusions containing dermatan sulfate. MPS VI eyes treated subretinally with AAV.f4S had minimal RPE cell inclusions and, consequently, were not hypertrophied.

Conclusions

AAV‐mediated subretinal delivery of f4S provided correction of the disease phenotype in RPE cells of feline MPS VI, supporting the utility of AAV as a vector for the treatment of RPE‐specific as well as lysosomal storage diseases. Copyright © 2002 John Wiley & Sons, Ltd.

     

NEUROCHEMISTRY OF THE MUCOPOLYSACCHARIDOSES: BRAIN LIPIDS AND LYSOSOMAL ENZYMES IN PATIENTS WITH FOUR TYPES OF MUCOPOLYSACCHARIDOSIS AND IN NORMAL CONTROLS

Abstract— Lipids and certain lysosomal enzymes were measured in the cerebral gray and white matter and in the liver of unaffected controls and six patients with mucopolysaccharidosis (MPS). Three of the patients had MPS Type I (Hurler), one Type II (Hunter), one Type IIIA (Sanfilippo A) and one Type V (Scheie). The glycosaminoglycans (GAG) of those tissues have been fully characterized previously (C onstantopoulos et al. , 1976).
Results of the present study: the normally minor brain monosialogangliosides G_M2 and G_M3 were markedly increased in the gray and to a lesser extent in the white matter of all the patients, except the patient with MPS Type V. On an average G_M2 comprised 8.2 and 6.3, and G_M3 11.8 and 6.0% of the total ganglioside neuraminic acid of the gray and white matter respectively in all patients with MPS I, II, and IIIA (normal subjects had less than 1).
Ceramide dihexoside was also increased in the gray matter of the patients with MPS I, MPS II and MPS IIIA.
The sphingolipid abnormalities were found only in tissues containing excessive amounts of partially degraded dermatan and heparan sulfates or heparan sulfate alone.
Of the six acid hydrolases assayed, the activity of /f-glucosaminidase was increased in both brain and liver, while that of α-galactosidase and β-galactosidase was diminished, particularly in the liver.
These results suggest that the partially degraded heparan sulfate (and perhaps the dermatan sulfate) which accumulate in the tissues of the patients with MPS may inhibit catabolic enzymes of various sphingolipids. In turn, accumulation of sphingolipids could be responsible at least for some of the brain damage and the mental retardation in MPS I, II and IIIA.     

A defect in exodegradative pathways provides insight into endodegradation of heparan and dermatan sulfates

Within cells, dermatan sulfate (DS) and heparan sulfate (HS) are degraded in two steps. The initial endohydrolysis of these polysaccharides is followed by the sequential action of lysosomal exoenzymes to reduce the resulting oligosaccharides to monosaccharides and inorganic sulfate. Mucopolysaccharidosis (MPS) type II is a lysosomal storage disorder caused by a deficiency of the exoenzyme iduronate-2-sulfatase (I2S). Consequently, partially degraded fragments of DS and HS have been shown to accumulate in the lysosomes of affected cells and are excreted in the urine. Di- to hexadecasaccharides, isolated from the urine of a MPS II patient using anion exchange and gel filtration chromatography, were identified using electrospray ionization-tandem mass spectrometry (ESI-MS/MS). These oligosaccharides were shown to have non-reducing terminal iduronate-2-sulfate residues by digestion with recombinant I2S. A pattern of growing oligosaccharide chains composed of alternating uronic acid and N-acetylhexosamine residues was identified and suggested to originate from DS. A series of oligosaccharides consisting of hexosamine/N-acetylhexosamine alternating with uronic acid residues was also identified and on the basis of the presence of unacetylated hexosamine; these oligosaccharides are proposed to derive from HS. The presence of both odd and even-length oligosaccharides suggests both endo-beta-glucuronidase and endo-N-acetylhexosaminidase activities toward both glycosaminoglycans. Furthermore, the putative HS oligosaccharide structures identified indicate that heparanase activities are directed toward regions of both low and high sulfation, while the N-acetylhexosaminidase activity acted only in regions of low sulfation in this polysaccharide.     

The Structure of Human GALNS Reveals the Molecular Basis for Mucopolysaccharidosis IV A

Lysosomal enzymes catalyze the breakdown of macromolecules in the cell. In humans, loss of activity of a lysosomal enzyme leads to an inherited metabolic defect known as a lysosomal storage disorder. The human lysosomal enzyme galactosamine-6-sulfatase (GALNS, also known as N-acetylgalactosamine-6-sulfatase and GalN6S; E.C. 3.1.6.4) is deficient in patients with the lysosomal storage disease mucopolysaccharidosis IV A (also known as MPS IV A and Morquio A). Here, we report the three-dimensional structure of human GALNS, determined by X-ray crystallography at 2.2 Å resolution. The structure reveals a catalytic gem diol nucleophile derived from modification of a cysteine side chain. The active site of GALNS is a large, positively charged trench suitable for binding polyanionic substrates such as keratan sulfate and chondroitin-6-sulfate. Enzymatic assays on the insect‐cell-expressed human GALNS indicate activity against synthetic substrates and inhibition by both substrate and product. Mapping 120 MPS IV A missense mutations onto the structure reveals that a majority of mutations affect the hydrophobic core of the structure, indicating that most MPS IV A cases result from misfolding of GALNS. Comparison of the structure of GALNS to paralogous sulfatases shows a wide variety of active‐site geometries in the family but strict conservation of the catalytic machinery. Overall, the structure and the known mutations establish the molecular basis for MPS IV A and for the larger MPS family of diseases.     

A Genetic Model of Substrate Reduction Therapy for Mucopolysaccharidosis

Inherited defects in the ability to catabolize glycosaminoglycans result in lysosomal storage disorders known as mucopolysaccharidoses (MPS), causing severe pathology, particularly in the brain. Enzyme replacement therapy has been used to treat mucopolysaccharidoses; however, neuropathology has remained refractory to this approach. To test directly whether substrate reduction might be feasible for treating MPS disease, we developed a genetic model for substrate reduction therapy by crossing MPS IIIa mice with animals partially deficient in heparan sulfate biosynthesis due to heterozygosity in Ext1 and Ext2, genes that encode the copolymerase required for heparan sulfate chain assembly. Reduction of heparan sulfate by 30–50% using this genetic strategy ameliorated the amount of disease-specific biomarker and pathology in multiple tissues, including the brain. In addition, we were able to demonstrate that substrate reduction therapy can improve the efficacy of enzyme replacement therapy in cell culture and in mice. These results provide proof of principle that targeted inhibition of heparan sulfate biosynthetic enzymes together with enzyme replacement might prove beneficial for treating mucopolysaccharidoses.     

Genetic manipulation of murine embryonic stem cells with enhanced green fluorescence protein and sulfatase-modifying factor I genes

Background aimsMucopolysaccharidosis type IIIA (MPS IIIA) is a lysosomal storage disorder (LSD) in which an absence of sulfamidase results in incomplete degradation and subsequent accumulation of its substrate, heparan sulfate. Most neurodegenerative LSD remain untreatable. However, therapy options, such as gene, enzyme end cell therapy, are under investigation. Previously, we have constructed an embryonic stem (ES) cell line (NS21) that over-expresses human sulphamidase as a potential treatment for murine MPS IIIA.MethodsIn the present study the sulfatase-modifying factor I (SUMF1) and enhanced green fluorescence protein (eGFP) genes were co-introduced under a cytomegalovirus (CMV) promoter into NS21 cells, to enhance further sulfamidase activity and provide a marker for in vivo cell tracking, respectively. eGFP was also introduced under the control of the human elongation factor-1α (hEF-1α) promoter to compare the stability of transgene expression.ResultsDuring differentiation of ES cells into glial precursors, SUMF1 was down-regulated and was hardly detectable by day 18 of differentiation. Likewise, eGFP expression was heterogeneous and highly unstable. Use of a human EF-1α promoter resulted in more homogeneous eGFP expression, with ～ 50% of cells eGFP positive following differentiation into glial precursors. Compared with NS21 cells, the outgrowth of eGFP-expressing cells was not as confluent when differentiated into glial precursors.ConclusionsOur data suggest that SUMF1 enhances sulfamidase activity in ES cells, hEF-1α is a stronger promoter than CMV for ES cells and over-expression of eGFP may affect cell growth and contribute to unstable gene expression.     

Glycosaminoglycan Storage in Cultured Neonatal Murine Mucopolysaccharidosis Type VII Neuroglial Cells and Correction by β-Glucuronidase Gene Transfer

Abstract: The inherited deficiency of β-glucuronidase activity causes the lysosomal storage disorder mucopolysaccharidosis (MPS) type VII (Sly disease). The sequential catabolism of glycosaminoglycans in lysosomes is blocked, and undegraded substrates accumulate in cells of many tissues, including neurons and glia in the brain. To evaluate the deficient metabolic pathway, primary cultures of mixed brain cells were established from newborn MPS VII mice. β-Glucuronidase levels and glycosaminoglycan accumulation were studied in normal, carrier, and MPS VII cells. Retroviral vector-mediated transfer of a normal β-glucuronidase cDNA corrected the enzymatic deficiency in MPS VII cells and restored glycosaminoglycan catabolism to normal. High levels of β-glucuronidase expression were sustained in vector-corrected nondividing glial cell cultures for >2 months. These studies provide an in vitro model for evaluating somatic gene transfer in neural cells affected in mucopolysaccharidoses.     

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome): a Y210C mutation causes either altered protein handling or altered protein function of N-acetylgalactosamine 4-sulfatase at multiple points in the vacuolar network

The lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (4-sulfatase) is required for the degradation of the glycosaminoglycan substrates dermatan and chondroitin sulfate. A 4-sulfatase deficiency results in the accumulation of undegraded substrate and causes the severe lysosomal storage disorder mucopolysaccharidosis type VI (MPS VI) or Maroteaux-Lamy syndrome. A wide variation in clinical severity is observed between MPS VI patients and reflects the number of different 4-sulfatase mutations that can cause the disorder. The most common 4-sulfatase mutation, Y210C, was detected in approximately 10% of MPS VI patients and has been associated with an attenuated clinical phenotype when compared to the archetypical form of MPS VI. To define the molecular defect caused by this mutation, Y210C 4-sulfatase was expressed in Chinese hamster ovary (CHO-K1) cells for protein and cell biological analysis. Biosynthetic studies revealed that Y210C 4-sulfatase was synthesized at a comparable molecular size and amount to wild-type 4-sulfatase, but there was evidence of delayed processing, traffic, and stability of the mutant protein. Thirty-three percent of the intracellular Y210C 4-sulfatase remained as a precursor form, for at least 8 h post labeling and was not processed to the mature lysosomal form. However, unlike other 4-sulfatase mutations causing MPS VI, a significant amount of Y210C 4-sulfatase escaped the endoplasmic reticulum and was either secreted from the expression cells or underwent delayed intracellular traffic. Sixty-seven percent of the intracellular Y210C 4-sulfatase was processed to the mature form (43, 8, and 7 kDa molecular mass forms) by a proteolytic processing step known to occur in endosomes-lysosomes. Treatment of Y210C CHO-K1 cells with the protein stabilizer glycerol resulted in increased amounts of Y210C 4-sulfatase in endosomes, which was eventually trafficked to the lysosome after a long, 24 h chase time. This demonstrated delayed traffic of Y210C 4-sulfatase to the lysosomal compartment. The endosomal Y210C 4-sulfatase had a low specific activity, suggesting that the mutant protein also had problems with stability. Treatment of Y210C CHO-K1 cells with the protease inhibitor ALLM resulted in an increased amount of mature Y210C 4-sulfatase localized in lysosomes, but this protein had a very low level of activity. This indicated that the mutant protein was being inactivated and degraded at an enhanced rate in the lysosomal compartment. Biochemical analysis of Y210C 4-sulfatase revealed a normal pH optimum for the mutant protein but demonstrated a reduced enzyme activity with time, also consistent with a protein stability problem. This study indicated that multiple subcellular and biochemical processes can contribute to the biogenesis of mutant protein and may in turn influence the clinical phenotype of a patient. In MPS VI patients with a Y210C allele, the composite effect of different stages of intracellular processing/handling and environment has been shown to cause a reduced level of Y210C 4-sulfatase protein and activity, resulting in an attenuated clinical phenotype.     

Pentosan Polysulfate: Oral Versus Subcutaneous Injection in Mucopolysaccharidosis Type I Dogs

BackgroundWe previously demonstrated the therapeutic benefits of pentosan polysulfate (PPS) in a rat model of mucopolysaccharidosis (MPS) type VI. Reduction of inflammation, reduction of glycosaminoglycan (GAG) storage, and improvement in the skeletal phenotype were shown. Herein, we evaluate the long-term safety and therapeutic effects of PPS in a large animal model of a different MPS type, MPS I dogs. We focused on the arterial phenotype since this is one of the most consistent and clinically significant features of the model.ConclusionsPPS treatment led to reductions of pro-inflammatory cytokines and GAG storage in urine and tissues of MPS I dogs, which were most evident after subQ administration. SubQ administration also led to significant cytokine reductions in the CSF. Both treatment groups exhibited markedly reduced carotid and aortic inflammation, increased vessel integrity, and improved histopathology. We conclude that PPS may be a safe and useful therapy for MPS I, either as an adjunct or as a stand-alone treatment that reduces inflammation and GAG storage.