Arylsulfatase B-deficient mucopolysaccharidosis in rats

Biomarkers of Glycosaminoglycans (GAG) accumulation in patients with mucopolysaccharidosis type VI-LeukoGAG, Corneal Opacification (COM) and Carotid Intima Media Thickening (CIMT)

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal storage disorder characterized by deficient activity of arylsulfatase B enzyme (ASB) resulting in cellular accumulation of dermatan sulfate (DS) and chondroitin sulfate (CS) that leads to cell injury. Urinary glycosaminoglycans (GAG) are often used as a biomarker in MPS diseases for diagnosis and to monitor treatment efficacy. This study evaluated leukocyte GAGs (leukoGAG) and skin GAGs as alternate biomarkers representing intracellular GAG changes in patients with MPS VI and treated with enzyme replacement therapy (ERT). In addition, we evaluated corneal opacification measurements (COM) and carotid intima media thickness (CIMT) as indicators of GAG accumulation and tissue injury. The study was performed in a serial two-step design in a single center. A quantitative method to measure leukoGAG levels in leukocytes was developed in Study 1 to compare the GAG levels between MPS VI patients and a control group and to assess correlations between leukoGAG and urineGAG. Study 2 validated the leukoGAG measurement, assessed the effect of ERT infusion on leukoGAG and ASB activity in leukocytes, identified correlations between leukoGAG and other biomarkers, and assessed differences in GAG accumulation between MPS VI patients and control subjects. In Study 1, leukoCS and leukoDS levels were significantly higher in the MPS VI group than the control group (leukoCS: 37.9 ± 10.2 and 2.9 ± 1.5 μg/μg protein, respectively, p = 0.005; leukoDS: 0.26 ± 0.2 and 0.0 ± 0.0 μg/μg protein, respectively, p = 0.028) with positive correlations between leukoCS and urine CS and leukoDS and urineDS. In Study 2, leukoCS (32.0 ± 11.8 vs 6.9 ± 3.1 μg/mg protein, p = 0.005) and leukoDS (0.4 ± 0.1 and 0.2 ± 0.1 μg/mg protein, p = 0.020) were significantly higher compared with control subjects. Thus, these results highlight the potential of leukoGAG as a new biomarker representing intracellular GAG accumulation in MPS VI patients and may be valuable for patient management.

MPSI Manifestations and Treatment Outcome: Skeletal Focus

Mucopolysaccharidosis type I (MPSI) (OMIM #252800) is an autosomal recessive disorder caused by pathogenic variants in the IDUA gene encoding for the lysosomal alpha-L-iduronidase enzyme. The deficiency of this enzyme causes systemic accumulation of glycosaminoglycans (GAGs). Although disease manifestations are typically not apparent at birth, they can present early in life, are progressive, and include a wide spectrum of phenotypic findings. Among these, the storage of GAGs within the lysosomes disrupts cell function and metabolism in the cartilage, thus impairing normal bone development and ossification. Skeletal manifestations of MPSI are often refractory to treatment and severely affect patients’ quality of life. This review discusses the pathological and molecular processes leading to impaired endochondral ossification in MPSI patients and the limitations of current therapeutic approaches. Understanding the underlying mechanisms responsible for the skeletal phenotype in MPSI patients is crucial, as it could lead to the development of new therapeutic strategies targeting the skeletal abnormalities of MPSI in the early stages of the disease.

Generation of a novel disease model mouse for mucopolysaccharidosis type VI via c. 252T>C human ARSB mutation knock-in

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal disorder caused by a mutation in the ARSB gene, which encodes arylsulfatase B (ARSB), and is characterized by glycosaminoglycan accumulation. Some pathogenic mutations have been identified in or near the substrate-binding pocket of ARSB, whereas many missense mutations present far from the substrate-binding pocket. Each MPS VI patient shows different severity of clinical symptoms. To understand the relationship between mutation patterns and the severity of MPS VI clinical symptoms, mutations located far from the substrate-binding pocket must be investigated using mutation knock-in mice. Here, I generated a knock-in mouse model of human ARSB Y85H mutation identified in Japanese MPS VI patients using a CRISPR-Cas9-mediated approach. The generated mouse model exhibited phenotypes similar to those of MPS VI patients, including facial features, mucopolysaccharide accumulation, and smaller body size, suggesting that this mouse will be a valuable model for understanding MPS VI pathology.

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We generated a mouse model of the Y85H ARSB mutation in humans using CRISPR-Cas9.

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The knock-in mice exhibited phenotypes similar to those of MPS VI patients.

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The mice showed facial features, mucopolysaccharide build-up, and smaller bodies.

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The model could successfully show the correlation between genotype and phenotype.

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These mice could serve as a useful model for novel therapeutic approaches.

Current treatment options and novel nanotechnology-driven enzyme replacement strategies for lysosomal storage disorders

Lysosomal storage disorders (LSDs) are a vast group of more than 50 clinically identified metabolic diseases. They are singly rare, but they affect collectively 1 on 5,000 live births. They result in most of the cases from an enzymatic defect within lysosomes, which causes the subsequent augmentation of unwanted substrates. This accumulation process leads to plenty of clinical signs, determined by the specific substrate and accumulation area. The majority of LSDs present a broad organ and tissue engagement. Brain, connective tissues, viscera and bones are usually afflicted. Among them, brain disease is markedly frequent (two-thirds of LSDs). The most clinically employed approach to treat LSDs is enzyme replacement therapy (ERT), which is practiced by administering systemically the missed or defective enzyme. It represents a healthful strategy for 11 LSDs at the moment, but it solves the pathology only in the case of Gaucher disease. This approach, in fact, is not efficacious in the case of LSDs that have an effect on the central nervous system (CNS) due to the existence of the blood-brain barrier (BBB). Additionally, ERT suffers from several other weak points, such as low penetration of the exogenously administered enzyme to poorly vascularized areas, the development of immunogenicity and infusion-associated reactions (IARs), and, last but not least, the very high cost and lifelong needed. To ameliorate these weaknesses lot of efforts have been recently spent around the development of innovative nanotechnology-driven ERT strategies. They may boost the power of ERT and minimize adverse reactions by loading enzymes into biodegradable nanomaterials. Enzyme encapsulation into biocompatible liposomes, micelles, and polymeric nanoparticles, for example, can protect enzymatic activity, eliminating immunologic reactions and premature enzyme degradation. It can also permit a controlled release of the payload, ameliorating pharmacokinetics and pharmacodynamics of the drug. Additionally, the potential to functionalize the surface of the nanocarrier with targeting agents (antibodies or peptides), could promote the passage through biological barriers. In this review we examined the clinically applied ERTs, highlighting limitations that do not allow to completely cure the specific LSD. Later, we critically consider the nanotechnology-based ERT strategies that have beenin-vitroand/orin-vivotested to improve ERT efficacy.

MPS VI associated ocular phenotypes in an MPS VI murine model and the therapeutic effects of odiparcil treatment

Maroteaux - Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a lysosomal storage disease resulting from insufficient enzymatic activity for degradation of the specific glycosaminoglycans (GAG) chondroitin sulphate (CS) and dermatan sulphate (DS). Among the most pronounced MPS VI clinical manifestations caused by cellular accumulation of excess CS and DS are eye disorders, in particular those that affect the cornea. Ocular manifestations are not treated by the current standard of care, enzyme replacement therapy (ERT), leaving patients with a significant unmet need. Using in vitro and in vivo models, we previously demonstrated the potential of the β-D-xyloside, odiparcil, as an oral GAG clearance therapy for MPS VI. Here, we characterized the eye phenotypes in MPS VI arylsulfatase B deficient mice (Arsb^-) and studied the effects of odiparcil treatment in early and established disease models. Severe levels of opacification and GAG accumulation were detected in the eyes of MPS VI Arsb^- mice. Histological examination of MPS VI Arsb^- eyes showed an aggregate of corneal phenotypes, including reduction in the corneal epithelium thickness and number of epithelial cell layers, and morphological malformations in the stroma. In addition, colloidal iron staining showed specifically GAG accumulation in the cornea. Orally administered odiparcil markedly reduced GAG accumulation in the eyes of MPS VI Arsb^- mice in both disease models and restored the corneal morphology (epithelial layers and stromal structure). In the early disease model of MPS VI, odiparcil partially reduced corneal opacity area, but did not affect opacity area in the established model. Analysis of GAG types accumulating in the MPS VI Arsb^- eyes demonstrated major contribution of DS and CS, with some increase in heparan sulphate (HS) as well and all were reduced with odiparcil treatment. Taken together, we further reveal the potential of odiparcil to be an effective therapy for eye phenotypes associated with MPS VI disease.

Delivering gene therapy for mucopolysaccharide diseases

Mucopolysaccharide diseases are a group of paediatric inherited lysosomal storage diseases that are caused by enzyme deficiencies, leading to a build-up of glycosaminoglycans (GAGs) throughout the body. Patients have severely shortened lifespans with a wide range of symptoms including inflammation, bone and joint, cardiac, respiratory and neurological disease. Current treatment approaches for MPS disorders revolve around two main strategies. Enzyme replacement therapy (ERT) is efficacious in treating somatic symptoms but its effect is limited for neurological functions. Haematopoietic stem cell transplant (HSCT) has the potential to cross the BBB through monocyte trafficking, however delivered enzyme doses limit its use almost exclusively to MPSI Hurler. Gene therapy is an emerging therapeutic strategy for the treatment of MPS disease. In this review, we will discuss the various vectors that are being utilised for gene therapy in MPS as well as some of the most recent gene-editing approaches undergoing pre-clinical and clinical development.

Mucopolysaccharidosis Type VI, an Updated Overview of the Disease

Mucopolysaccharidosis type VI, or Maroteaux-Lamy syndrome, is a rare, autosomal recessive genetic disease, mainly affecting the pediatric age group. The disease is due to pathogenic variants of the ARSB gene, coding for the lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). The enzyme deficit causes a pathological accumulation of the undegraded glycosaminoglycans dermatan-sulphate and chondroitin-sulphate, natural substrates of ASB activity. Intracellular and extracellular deposits progressively take to a pathological scenario, often severe, involving most organ-systems and generally starting from the osteoarticular apparatus. Neurocognitive and behavioral abilities, commonly described as maintained, have been actually investigated by few studies. The disease, first described in 1963, has a reported prevalence between 0.36 and 1.3 per 100,000 live births across the continents. With this paper, we wish to contribute an updated overview of the disease from the clinical, diagnostic, and therapeutic sides. The numerous in vitro and in vivo preclinical studies conducted in the last 10-15 years to dissect the disease pathogenesis, the efficacy of the available therapeutic treatment (enzyme replacement therapy), as well as new therapies under study are here described. This review also highlights the need to identify new disease biomarkers, potentially speeding up the diagnostic process and the monitoring of therapeutic efficacy.

Lysosomal sulfatases: a growing family

Sulfatases constitute a family of enzymes that specifically act in the hydrolytic degradation of sulfated metabolites by removing sulfate monoesters from various substrates, particularly glycolipids and glycosaminoglycans. A common essential feature of all known eukaryotic sulfatases is the posttranslational modification of a critical cysteine residue in their active site by oxidation to formylglycine (FGly), which is mediated by the FGly-generating enzyme in the endoplasmic reticulum and is indispensable for catalytic activity. The majority of the so far described sulfatases localize intracellularly to lysosomes, where they act in different catabolic pathways. Mutations in genes coding for lysosomal sulfatases lead to an accumulation of the sulfated substrates in lysosomes, resulting in impaired cellular function and multisystemic disorders presenting as lysosomal storage diseases, which also cover the mucopolysaccharidoses and metachromatic leukodystrophy. Bioinformatics analysis of the eukaryotic genomes revealed, besides the well described and long known disease-associated sulfatases, additional genes coding for putative enzymes with sulfatases activity, including arylsulfatase G as well as the arylsulfatases H, I, J and K, respectively. In this article, we review current knowledge about lysosomal sulfatases with a special focus on the just recently characterized family members arylsulfatase G and arylsulfatase K.

Growth Plate Pathology in the Mucopolysaccharidosis Type VI Rat Model-An Experimental and Computational Approach

BACKGROUND

Mucopolysaccharidoses (MPS) are a group of inherited metabolic diseases caused by impaired function or absence of lysosomal enzymes involved in degradation of glycosaminoglycans. Clinically, MPS are skeletal dysplasias, characterized by cartilage abnormalities and disturbances in the process of endochondral ossification. Histologic abnormalities of growth cartilage have been reported at advanced stages of the disease, but information regarding growth plate pathology progression either in humans or in animal models, as well as its pathophysiology, is limited.

METHODS

Histological analyses of distal femur growth plates of wild type (WT) and mucopolysaccharidosis type VI (MPS VI) rats at different stages of development were performed, including quantitative data. Experimental findings were then analyzed in a theoretical scenario.

RESULTS

Histological evaluation showed a progressive loss of histological architecture within the growth plate. Furthermore, in silico simulation suggest the abnormal cell distribution in the tissue may lead to alterations in biochemical gradients, which may be one of the factors contributing to the growth plate abnormalities observed, highlighting aspects that must be the focus of future experimental works.

CONCLUSION

The results presented shed some light on the progression of growth plate alterations observed in MPS VI and evidence the potentiality of combined theoretical and experimental approaches to better understand pathological scenarios, which is a necessary step to improve the search for novel therapeutic approaches.

Mucopolysaccharidosis Type VI in a Great Dane Caused by a Nonsense Mutation in the ARSB Gene

Mucopolysaccharidoses are inherited metabolic disorders that result from a deficiency of lysosomal enzymes required for the catabolism of glycosaminoglycans. Lysosomal glycosaminoglycan accumulation results in cell and organ dysfunction. This study characterized the phenotype and genotype of mucopolysaccharidosis VI in a Great Dane puppy with clinical signs of stunted growth, facial dysmorphia, skeletal deformities, corneal opacities, and increased respiratory sounds. Clinical and pathologic evaluations, urine glycosaminoglycan analyses, lysosomal enzyme assays, and ARSB sequencing were performed. The urine mucopolysaccharide spot test was strongly positive predominantly due to the accumulation of dermatan sulfate. Enzyme assays in leukocytes and tissues indicated a deficiency of arylsulfatase B (ARSB) activity. Histologic examination revealed cytoplasmic vacuoles in many tissues. Analysis of the exonic ARSB DNA sequences from the affected puppy compared to the published canine genome sequence revealed a homozygous nonsense mutation (c.295C>T) in exon 1, replacing glutamine with a premature stop codon (p.Gln99*), predicting no enzyme synthesis. A polymerase chain reaction-based restriction fragment length polymorphism test was established to assist with the clinical diagnosis and breeding of Great Danes. This genotyping test revealed that the clinically healthy parents and some other relatives of the puppy were heterozygous for the mutant allele, but all 200 clinically healthy dogs screened including 15 Great Danes were homozygous for the normal allele. This ARSB mutation is the fourth identified genetic variant causing canine mucopolysaccharidosis VI. Mucopolysaccharidosis VI is the first lysosomal storage disorder described in Great Danes but does not appear to be widespread in this breed.

Lysosomal enzyme replacement therapies: Historical development, clinical outcomes, and future perspectives

Lysosomes and lysosomal enzymes play a central role in numerous cellular processes, including cellular nutrition, recycling, signaling, defense, and cell death. Genetic deficiencies of lysosomal components, most commonly enzymes, are known as "lysosomal storage disorders" or "lysosomal diseases" (LDs) and lead to lysosomal dysfunction. LDs broadly affect peripheral organs and the central nervous system (CNS), debilitating patients and frequently causing fatality. Among other approaches, enzyme replacement therapy (ERT) has advanced to the clinic and represents a beneficial strategy for 8 out of the 50-60 known LDs. However, despite its value, current ERT suffers from several shortcomings, including various side effects, development of "resistance", and suboptimal delivery throughout the body, particularly to the CNS, lowering the therapeutic outcome and precluding the use of this strategy for a majority of LDs. This review offers an overview of the biomedical causes of LDs, their socio-medical relevance, treatment modalities and caveats, experimental alternatives, and future treatment perspectives.

Pathogenesis and treatment of spine disease in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.

Diagnostic and treatment strategies in mucopolysaccharidosis VI

Mucopolysaccharidosis VI (MPS VI) is a very rare autosomal recessive disorder caused by mutations in the ARSB gene, which lead to deficient activity of the lysosomal enzyme ASB. This enzyme is important for the breakdown of the glycosaminoglycans (GAGs) dermatan sulfate and chondroitin sulfate, which accumulate in body tissues and organs of MPS VI patients. The storage of GAGs (especially dermatan sulfate) causes bone dysplasia, joint restriction, organomegaly, heart disease, and corneal clouding, among several other problems, and reduced life span. Despite the fact that most cases are severe, there is a spectrum of severity and some cases are so attenuated that diagnosis is made late in life. Although the analysis of urinary GAGs and/or the measurement of enzyme activity in dried blood spots are useful screening methods, the diagnosis is based in the demonstration of the enzyme deficiency in leucocytes or fibroblasts, and/or in the identification of pathogenic mutations in the ARSB gene. Specific treatment with enzyme replacement has been available since 2005. It is safe and effective, bringing measurable benefits and increased survival to patients. As several evidences indicate that early initiation of therapy may lead to a better outcome, newborn screening is being considered for this condition, and it is already in place in selected areas where the incidence of MPS VI is increased. However, as enzyme replacement therapy is not curative, associated therapies should be considered, and research on innovative therapies continues. The management of affected patients by a multidisciplinary team with experience in MPS diseases is highly recommended.

Similar therapeutic efficacy between a single administration of gene therapy and multiple administrations of recombinant enzyme in a mouse model of lysosomal storage disease

Enzyme replacement therapy (ERT) has become the standard of care for several lysosomal storage disorders (LSDs). Despite ERT's undisputed efficacy, the requirement for multiple and costly administrations as well as ERT's limited improvement of some LSD manifestations prompts the search for better therapies. Using a mouse model of mucopolysaccharidosis VI, we compared the efficacy of a single intravascular administration of an adeno-associated viral vector targeting liver to weekly infusions of human recombinant enzyme at the same doses used in mucopolysaccharidosis VI patients. While gene therapy results in increased and stable levels of circulating enzyme up to 1 year after vector administration, ERT has typical peak-and-drop serum kinetics. Both therapies similarly reduced glycosaminoglycan levels in urine and tissues including heart valves and myocardium, with gene therapy improving skeletal skull abnormalities slightly better, although not significantly, than ERT. Both therapies seem to similarly improve animal motor performance, with gene therapy possibly associated with less animal distress. Thus, a single vector administration that converts liver into a factory organ for systemic secretion of therapeutic proteins is at least as effective as ERT in a mouse model of LSD, potentially eliminating problems with compliance and costs. Only testing in humans will prove whether this holds true in a clinical setting.

Sensory-motor behavioral characterization of an animal model of Maroteaux-Lamy syndrome (or Mucopolysaccharidosis VI)

Maroteaux-Lamy disease, also known as mucopolysaccharidosis (MPS) VI, is an MPS disorder caused by mutations in the ARSB gene encoding for the lysosomal enzyme arysulfatase B (ARSB). Deficient ARSB activity leads to lysosomal accumulation of dermatan sulfate in a wide range of tissues and organs. There are various animal models of MPS VI that have been well characterized from a biochemical and morphological point of view. In this study, we report the sensory-motor characterization of MPS VI rats carrying homozygous null ARSB mutations. We show that adult MPS VI rats are specifically impaired in vertical activity and motor endurance. All together, these data are consistent with biochemical findings that show a major impairment in connective tissues, such as joints and bones. The behavioral abnormalities of MPS VI rats represent fundamental endpoints for studies aimed at testing the pre-clinical safety and efficacy of novel therapeutic approaches for MPS VI.

Structural, compositional, and biomechanical alterations of the lumbar spine in rats with mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome)

Mucopolysaccharidosis (MPS) VI is an inherited lysosomal storage disorder resulting from deficiency of N-acetylgalactosamine-4-sulfatase activity and subsequent accumulation of incompletely degraded dermatan sulfate (DS) containing glycosaminoglycans (GAGs). Painful spinal deformities are commonly found in MPS VI patients. We characterized lumbar spine structure, composition, and biomechanics in a naturally occurring rat MPS VI model and evaluated the role of MMP-13, ADAMTS-5 and TNF-α in modulating the observed changes. MPS VI rats had discs with large vacuolated cells and sizable nuclear defects. MPS spine segments also had structural and functional changes suggestive of spinal instability, including decreased nuclear pressurization, increased joint laxity and increased disc height index. These functional changes were at least partly associated with elevated ADAMTS-5, MMP-13, and TNF-α. Vertebral and endplate biomechanics were also affected by MPS VI with decreased failure load and stiffness. The discal and vertebral dysfunctions observed in MPS VI rats are likely to be associated with pathological spinal conditions, similar to those that afflict MPS patients. Our findings also suggest more broadly that abnormal accumulation of GAGs and the associated chronic pro-inflammatory and catabolic cascade may also be a source of spinal dysfunction.

Gene therapy for mucopolysaccharidosis type VI is effective in cats without pre-existing immunity to AAV8

Liver gene transfer with adeno-associated viral (AAV) 2/8 vectors is being considered for therapy of systemic diseases like mucopolysaccharidosis type VI (MPS VI), a lysosomal storage disease due to deficiency of arylsulfatase B (ARSB). We have previously reported that liver gene transfer with AAV2/8 results in sustained yet variable expression of ARSB. We hypothesized that the variability we observed could be due to pre-existing immunity to wild-type AAV8. To test this, we compared the levels of AAV2/8-mediated transduction in MPS VI cats with and without pre-existing immunity to AAV8. In addition, since levels of lysosomal enzymes as low as 5% of normal are expected to be therapeutic, we evaluated the impact of pre-existing immunity on MPS VI phenotypic rescue. AAV2/8 administration to MPS VI cats without pre-existing neutralizing antibodies to AAV8 resulted in consistent and dose-dependent expression of ARSB, urinary glycosaminoglycan (GAG) reduction, and femur length amelioration. Conversely, animals with pre-existing immunity to AAV8 showed low levels of ARSB expression and limited phenotypic improvement. Our data support the use of AAV2/8-mediated gene transfer for MPS VI and other systemic diseases, and highlight that pre-existing immunity to AAV8 should be considered in determining subject eligibility for therapy.

Anti-TNF-alpha therapy enhances the effects of enzyme replacement therapy in rats with mucopolysaccharidosis type VI

Background

Although enzyme replacement therapy (ERT) is available for several lysosomal storage disorders, the benefit of this treatment to the skeletal system is very limited. Our previous work has shown the importance of the Toll-like receptor 4/TNF-alpha inflammatory pathway in the skeletal pathology of the mucopolysaccharidoses (MPS), and we therefore undertook a study to examine the additive benefit of combining anti-TNF-alpha therapy with ERT in a rat model of MPS type VI.

Methodology/Principal Findings

MPS VI rats were treated for 8 months with Naglazyme® (recombinant human N-acetyl-galactosamine-4-sulfatase), or by a combined protocol using Naglazyme® and the rat-specific anti-TNF-alpha drug, CNTO1081. Both protocols led to markedly reduced serum levels of TNF-alpha and RANKL, although only the combined treatment reduced TNF-alpha in the articular cartilage. Analysis of cultured articular chondrocytes showed that the combination therapy also restored collagen IIA1 expression, and reduced expression of the apoptotic marker, PARP. Motor activity and mobility were improved by ERT, and these were significantly enhanced by combination treatment. Tracheal deformities in the MPS VI animals were only improved by combination therapy, and there was a modest improvement in bone length. Ceramide levels in the trachea also were markedly reduced. MicroCT analysis did not demonstrate any significant positive effects on bone microarchitecture from either treatment, nor was there histological improvement in the bone growth plates.

Conclusions/Significance

The results demonstrate that combining ERT with anti-TNF- alpha therapy improved the treatment outcome and led to significant clinical benefit. They also further validate the usefulness of TNF-alpha, RANKL and other inflammatory molecules as biomarkers for the MPS disorders. Further evaluation of this combination approach in other MPS animal models and patients is warranted.

Long-term amelioration of feline Mucopolysaccharidosis VI after AAV-mediated liver gene transfer

Mucopolysaccharidosis VI (MPS VI) is caused by deficient arylsulfatase B (ARSB) activity resulting in lysosomal storage of glycosaminoglycans (GAGs). MPS VI is characterized by dysostosis multiplex, organomegaly, corneal clouding, and heart valve thickening. Gene transfer to a factory organ like liver may provide a lifetime source of secreted ARSB. We show that intravascular administration of adeno-associated viral vectors (AAV) 2/8-TBG-felineARSB in MPS VI cats resulted in ARSB expression up to 1 year, the last time point of the study. In newborn cats, normal circulating ARSB activity was achieved following delivery of high vector doses (6 × 10(13) genome copies (gc)/kg) whereas delivery of AAV2/8 vector doses as low as 2 × 10(12) gc/kg resulted in higher than normal serum ARSB levels in juvenile MPS VI cats. In MPS VI cats showing high serum ARSB levels, independent of the age at treatment, we observed: (i) clearance of GAG storage, (ii) improvement of long bone length, (iii) reduction of heart valve thickness, and (iv) improvement in spontaneous mobility. Thus, AAV2/ 8-mediated liver gene transfer represents a promising therapeutic strategy for MPS VI patients.

Involvement of the Toll-like receptor 4 pathway and use of TNF-alpha antagonists for treatment of the mucopolysaccharidoses

Enzyme replacement therapy is currently available for three of the mucopolysaccharidoses (MPSs) but has limited effects on the skeletal lesions. We investigated the involvement of the Toll-like receptor 4 (TLR4) signaling pathway in the pathogenesis of MPS bone and joint disease, and the use of the anti-TNF-alpha drug, Remicade (Centocor, Inc.), for treatment. TLR4 KO (TLR4(lps-/-)) mice were interbred with MPS VII mice to produce double-KO (DKO) animals. The DKO mice had longer and thinner faces and longer femora as revealed by micro-computed tomography analysis compared with MPS VII mice. Histological analyses also revealed more organized and thinner growth plates. The serum levels of TNF-alpha were normalized in the DKO animals, and the levels of phosphorylated STAT1 and STAT3 in articular chondrocytes were corrected. These findings led us to evaluate the effects of Remicade in MPS VI rats. When initiated at 1 month of age, i.v. treatment prevented the elevation of TNF-alpha, receptor activator of NF-kappaB, and other inflammatory molecules not only in the blood but in articular chondrocytes and fibroblast-like synoviocytes (FLSs). Treatment of 6-month-old animals also reduced the levels of these molecules to normal. The number of apoptotic articular chondrocytes in MPS VI rats was similarly reduced, with less infiltration of synovial tissue into the underlying bone. These studies revealed the important role of TLR4 signaling in MPS bone and joint disease and suggest that targeting TNF-alpha may have positive therapeutic effects.

Hippocampal atrophy as a quantitative trait in a genome-wide association study identifying novel susceptibility genes for Alzheimer's disease

Background

With the exception of APOE ε4 allele, the common genetic risk factors for sporadic Alzheimer's Disease (AD) are unknown.

Methods and Findings

We completed a genome-wide association study on 381 participants in the ADNI (Alzheimer's Disease Neuroimaging Initiative) study. Samples were genotyped using the Illumina Human610-Quad BeadChip. 516,645 unique Single Nucleotide Polymorphisms (SNPs) were included in the analysis following quality control measures. The genotype data and raw genetic data are freely available for download (LONI, http://www.loni.ucla.edu/ADNI/Data/). Two analyses were completed: a standard case-control analysis, and a novel approach using hippocampal atrophy measured on MRI as an objectively defined, quantitative phenotype. A General Linear Model was applied to identify SNPs for which there was an interaction between the genotype and diagnosis on the quantitative trait. The case-control analysis identified APOE and a new risk gene, TOMM40 (translocase of outer mitochondrial membrane 40), at a genome-wide significance level of≤10⁻⁶ (10⁻¹¹ for a haplotype). TOMM40 risk alleles were approximately twice as frequent in AD subjects as controls. The quantitative trait analysis identified 21 genes or chromosomal areas with at least one SNP with a p-value≤10⁻⁶, which can be considered potential “new” candidate loci to explore in the etiology of sporadic AD. These candidates included EFNA5, CAND1, MAGI2, ARSB, and PRUNE2, genes involved in the regulation of protein degradation, apoptosis, neuronal loss and neurodevelopment. Thus, we identified common genetic variants associated with the increased risk of developing AD in the ADNI cohort, and present publicly available genome-wide data. Supportive evidence based on case-control studies and biological plausibility by gene annotation is provided. Currently no available sample with both imaging and genetic data is available for replication.

Conclusions

Using hippocampal atrophy as a quantitative phenotype in a genome-wide scan, we have identified candidate risk genes for sporadic Alzheimer's disease that merit further investigation.

Cell-surface arylsulfatase A and B on sinusoidal endothelial cells, hepatocytes, and Kupffer cells in mammalian livers

Arylsulfatase A (ARSA) and B (ARSB) have been regarded as lysosomal enzymes because of their hydrolytic activity on synthetic aromatic substrates and the lysosomal localization of their enzymatic activity. Using sea urchin embryos, we previously demonstrated that the bulk of ARS is located on the cell surface of the epithelium, colocalizing with sulfated polysaccharides, and that it does not exhibit enzymatic activity. To examine whether ARSA and ARSB exist on the cell surface in mammalian tissues, we raised antibodies against ARSA and ARSB and examined immunohistochemically their localization in the liver using light and electron microscopy. Here we show that mammalian ARSA and ARSB exist on the cell surface of sinusoidal endothelial cells, hepatocytes, and sinusoidal macrophages (Kupffer cells), as well as in the lysosome. They are also colocalized with heparan sulfate proteoglycan. These results suggest that ARSA and ARSB also may function in the cell surface of mammals. This is the first report to show cell-surface localization of ARS in mammalian somatic cells. The extracellular localization of ARS will provide new insight for human ARS deficiency disorders, such as metachromatic leukodystrophy and mucopolysaccharidosis VI.

Abnormal autophagy, ubiquitination, inflammation and apoptosis are dependent upon lysosomal storage and are useful biomarkers of mucopolysaccharidosis VI

Background

Lysosomal storage diseases are characterized by intracellular accumulation of metabolites within lysosomes. Recent evidence suggests that lysosomal storage impairs autophagy resulting in accumulation of polyubiquitinated proteins and dysfunctional mitochondria, ultimately leading to apoptosis. We studied the relationship between lysosome storage and impairment of different intracellular pathways and organelle function in mucopolysaccharidosis VI, which is characterized by accumulation of dermatan sulfate and signs of visceral and skeletal but not cerebral involvement.

Results

We show lysosomal storage, impaired autophagy, accumulation of polyubiquitinated proteins, and mitochondrial dysfunction in fibroblasts from mucopolysaccharidosis VI patients. We observe similar anomalies, along with inflammation and cell death, in association with dermatan sulfate storage in the visceral organs of mucopolysaccharidosis VI rats, but not in their central nervous system where dermatan sulfate storage is absent. Importantly, we show that prevention of dermatan sulfate storage in the mucopolysaccharidosis VI rat visceral organs by gene transfer results in correction of abnormal autophagy, inflammation, and apoptosis, suggesting that dermatan sulfate accumulation impairs lysosomal ability to receive and degrade molecules and organelles from the autophagic pathway, thus leading to cell toxicity.

Conclusion

These results indicate that the non-lysosomal degradation pathways we found activated in mucopolysaccharidosis VI can be both targets of new experimental therapies and biomarkers for follow-up of existing treatments.

Lentiviral-mediated correction of MPS VI cells and gene transfer to joint tissues

Joint disease in mucopolysaccharidosis type VI (MPS VI) remains difficult to treat despite the success of enzyme replacement therapy in treating other symptoms. In this study, the efficacy of a lentiviral vector to transduce joint tissues and express N-acetylgalactosamine-4-sulphatase (4S), the enzyme deficient in MPS VI, was evaluated in vitro and the expression of beta-galactosidase was used to evaluate transduction in vivo. High viral copy number was achieved in MPS VI fibroblasts and 4-sulphatase activity reached 12 times the normal level. Storage of accumulated glycosaminoglycan was reduced in a dose dependent manner in both MPS VI skin fibroblasts and chondrocytes. Enzyme expression was maintained in skin fibroblasts for up to 41 days. Comparison of two promoters; the murine phosphoglycerate kinase gene promoter (pgk) and the myeloproliferative sarcoma virus long terminal repeat promoter (mpsv), demonstrated a higher level of marker gene expression driven by the mpsv promoter in both chondrocytes and synoviocytes in vitro. When injected into the rat knee, the expression of beta-galactosidase from the mpsv promoter was widespread across the synovial membrane and the fascia covering the cruciate ligaments and meniscus. No transduction of chondrocytes or ligament cells was observed. Transduction was maintained for at least 8 weeks after injection. These results indicate that the lentiviral vector can be used to deliver 4S to a range of joint tissues in vitro and efficiently transduce synovial cells and express beta-galactosidase in vivo.

Mechanism of glycosaminoglycan-mediated bone and joint disease: implications for the mucopolysaccharidoses and other connective tissue diseases

We have previously shown that glycosaminoglycan (GAG) storage in animal models of the mucopolysaccharidoses (MPS) leads to inflammation and apoptosis within cartilage. We have now extended these findings to synovial tissue and further explored the mechanism underlying GAG-mediated disease. Analysis of MPS rats, cats, and/or dogs revealed that MPS synovial fibroblasts and fluid displayed elevated expression of numerous inflammatory molecules, including several proteins important for lipopolysaccharide signaling (eg, Toll-like receptor 4 and lipoprotein-binding protein). The expression of tumor necrosis factor, in particular, was elevated up to 50-fold, leading to up-regulation of the osteoclast survival factor, receptor activator of nuclear factor-kappaB ligand, and the appearance of multinucleated osteoclast-like cells in the MPS bone marrow. Treatment of normal synovial fibroblasts with GAGs also led to production of the prosurvival lipid sphingosine-1-phosphate, resulting in enhanced cell proliferation, consistent with the hyperplastic synovial tissue observed in MPS patients. In contrast, GAG treatment of normal chondrocytes led to production of the proapoptotic lipid ceramide, confirming the enhanced cell death we had previously observed in MPS cartilage. These findings have important implications for the pathogenesis and treatment of MPS and have further defined the mechanism of GAG-stimulated disease.

Biochemical, pathological, and skeletal improvement of mucopolysaccharidosis VI after gene transfer to liver but not to muscle

Mucopolysaccharidosis VI (MPS VI) is caused by deficient activity of arylsulfatase B (ARSB), resulting in intralysosomal storage of dermatan sulfate (DS) and multisystem disease without central nervous system involvement. After gene transfer, muscle or liver can theoretically be converted into factories for systemic ARSB secretion, leading to uptake by non-transduced cells. We have injected newborn MPS VI rats and cats with adeno-associated viral (AAV) vectors expressing ARSB under the control of liver-specific, muscle-specific, or universally active promoters. After systemic or intramuscular (IM) administration of AAV, therapeutic levels of circulating ARSB are achieved, resulting in skeletal improvements and significant decrease in glycosaminoglycan (GAG) storage, inflammation and apoptosis (despite a neutralizing immune response to ARSB in MPS VI rats). In addition, we have observed wide-spread dissemination of vector after IM AAV administration. This results in secretion of therapeutic levels of ARSB when the universally active cytomegalovirus (CMV) but not the muscle-specific muscle creatine kinase (MCK) promoter is used, suggesting that transduction of extramuscular sites rather than enzyme secretion from muscle occurs after muscle ARSB gene transfer. We conclude that AAV-mediated expression of ARSB from liver represents a feasible therapeutic strategy for MPS VI, potentially avoiding multiple infusions of costly recombinant enzyme associated with enzyme replacement therapy.

Animal models for mucopolysaccharidosis disorders and their clinical relevance

Progress in understanding how a particular genotype produces the phenotype of an inborn error of metabolism, such as a mucopolysaccharidosis, in human patients has been facilitated by the study of animals with mutations in the orthologous genes. These are not just animal models, but true orthologues of the human genetic disease, with defects involving the same evolutionarily conserved genes and the same molecular, biochemical, and anatomic lesions as in human patients. These animals are often domestic species because of the individual medical attention paid to them, particularly dogs and cats. In addition, naturally occurring mouse models have also been found in breeding colonies. Within the last several decades, advances in molecular biology have allowed the production of knockout mouse models of human genetic disease, including the lysosomal storage diseases. The ability to use both inbred strains of a small, prolific species together with larger out-bred animals found because of their disease phenotype provides a powerful combination with which to investigate pathogenesis, develop approaches to therapy, and define biomarkers to evaluate therapeutic success. This has been true for the inborn errors of metabolism and, in particular, the mucopolysaccharidoses.

CONCLUSION

Animal models of human genetic disease continue to play an important role in understanding the molecular and physiological consequences of lysosomal storage diseases and to provide an opportunity to evaluate the efficacy and safety of therapeutic interventions.

Sulfatases and human disease

Sulfatases are a highly conserved family of proteins that cleave sulfate esters from a wide range of substrates. The importance of sulfatases in human metabolism is underscored by the presence of at least eight human monogenic diseases caused by the deficiency of individual sulfatases. Sulfatase activity requires a unique posttranslational modification, which is impaired in patients with multiple sulfatase deficiency (MSD) due to a mutation of the sulfatase modifying factor 1 (SUMF1). Here we review current knowledge and future perspectives on the evolution of the sulfatase gene family, on the role of these enzymes in human metabolism, and on new developments in the therapy of sulfatase deficiencies.

Abnormal neuronal metabolism and storage in mucopolysaccharidosis type VI (Maroteaux-Lamy) disease

Mucopolysaccharidosis (MPS) type VI, also known as Maroteaux-Lamy disease, is an inherited disorder of glycosaminoglycan catabolism caused by deficient activity of the lysosomal hydrolase, N-acetylgalactosamine 4-sulphatase (4S). A variety of prominent visceral and skeletal defects are characteristic, but primary neurological involvement has generally been considered absent. We report here that the feline model of MPS VI exhibits abnormal lysosomal storage in occasional neurones and glia distributed throughout the cerebral cortex. Abnormal lysosomal inclusions were pleiomorphic with some resembling zebra bodies and dense core inclusions typical of other MPS diseases or the membranous storage bodies characteristic of the gangliosidoses. Pyramidal neurones were shown to contain abnormal amounts of GM2 and GM3 gangliosides by immunocytochemical staining and unesterified cholesterol by histochemical (filipin) staining. Further, Golgi staining of pyramidal neurones revealed that some possessed ectopic axon hillock neurites and meganeurites similar to those described in Tay-Sachs and other neuronal storage diseases with ganglioside storage. Some animals evaluated in this study also received allogeneic bone marrow transplants, but no significant differences in neuronal storage were noted between treated and untreated individuals. These studies demonstrate that deficiency of 4S activity can lead to metabolic abnormalities in the neurones of central nervous system in cats, and that these changes may not be readily amenable to correction by bone marrow transplantation. Given the close pathological and biochemical similarities between feline and human MPS VI, it is conceivable that children with this disease have similar neuronal involvement.

Joint and bone disease in mucopolysaccharidoses VI and VII: identification of new therapeutic targets and biomarkers using animal models

The mucopolysaccharidoses (MPS) are inherited metabolic disorders resulting from the defective catabolism of glycosaminoglycans. In this report, we find that the stimulation of MPS connective tissue cells by the inflammatory cytokines causes enhanced secretion of several matrix-degrading metalloproteinases (MMPs). In addition, expression of tissue inhibitor of metalloproteinase-1 was elevated, consistent with the enhanced MMP activity. These findings were not restricted to one particular MPS disorder or species, and are consistent with previous observations in animal models with chemically induced arthritis. Bromodeoxyuridine incorporation studies also revealed that MPS chondrocytes proliferated up to 5-fold faster than normal chondrocytes, and released elevated levels of transforming growth factor-beta, presumably to counteract the marked chondrocyte apoptosis and matrix degradation associated with MMP expression. Despite this compensatory mechanism, studies of endochondral ossification revealed a reduction in chondro-differentiation in the growth plates. Thus, although MPS chondrocytes grew faster, most of the newly formed cells were immature and could not mineralize into bone. Our studies suggest that altered MMP expression, most likely stimulated by inflammatory cytokines and nitric oxide, is an important feature of the MPS disorders. These data also identify several proinflammatory cytokines, nitric oxide, and MMPs as novel therapeutic targets and/or biomarkers of MPS joint and bone disease. This information should aid in the evaluation of existing therapies for these disorders, such as enzyme replacement therapy and bone marrow transplantation, and may lead to the development of new therapeutic approaches.

Cardiac and ocular pathologies in a mouse model of mucopolysaccharidosis type VI

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disease caused by a deficiency of arylsulfatase B (ASB) which has its function in the sequential degradation of glycosaminoglycans (GAG). Targeted disruption of the ASB gene resulted in a mouse model of MPS VI that has been closely investigated for skeletal and chondral dysplasia. As ocular and cardiac impairment are also clinically important manifestations of the MPS VI syndrome, the present study was initiated for detailed biochemical, histologic and functional analysis of cornea, optic nerve and heart in ASB-deficient mice. Biochemical evidence for GAG-storage could be obtained for liver, kidney, spleen and myocardium as well as for heart valves, cornea and optic nerve from ASB-deficient mice. In MPS VI mice, histology revealed structural impairment of corneal stroma and epithelium as well as a thickening of the heart valves. According to histologic investigations, the optic nerve appeared not to be altered. However, GAG-storage in the dura mater could be demonstrated in MPS VI mice. Heart function was assessed by echocardiography. While the dimensions of MPS VI hearts were not altered, these hearts clearly showed decreased myocardial contraction and a 50% reduction of cardiac output. In addition, insufficiencies in the mitral and aortic valves were detected. Thus, ASB-deficient mice resemble the phenotype of human MPS VI not only in the skeletal but also in the ocular and cardiac symptoms. To our knowledge, these in vivo evaluations of heart function represent the first respective investigation of a MPS VI animal model and should provide a valuable measure for therapy studies in the MPS VI mouse.

Animal models for mucopolysaccharidoses and their clinical relevance

The mucopolysaccharidoses (MPS) are characterized by the accumulation of glycosaminoglycans (GAG) and result from the impaired function of one of 11 enzymes required for normal GAG degradation. MPS II was the first MPS to be defined clinically in humans and is caused by deficient activity of the enzyme iduronate-2-sulphatase. MPS VI was the first MPS recognized in an animal; since then, all but MPS IIIC and IX have been described as naturally occurring in animals or made by knock-out technology. As in humans, all are inherited as autosomal recessive traits, except for MPS II, which is X-linked. Most animal colonies have been established from single related heterozygous animals, making the affected offspring homozygous for the same mutant allele. Importantly, these models have disease pathology that is similar to that seen in humans, making the animals extremely valuable for the investigation of disease pathogenesis and the testing of therapies. Large animal homologues are similar to humans in natural genetic diversity, approaches to therapy and care, and the possibility of evaluating long-term effects of treatment. Therapeutic strategies for MPS include enzyme replacement therapy, heterologous bone marrow transplantation, and somatic cell gene transfer, all of which have been tested in animals with some success.

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.

Articular chondrocytes from animals with a dermatan sulfate storage disease undergo a high rate of apoptosis and release nitric oxide and inflammatory cytokines: a possible mechanism underlying degenerative joint disease in the mucopolysaccharidoses

Mucopolysaccharidosis (MPS) Type VI (Maroteaux-Lamy Disease) is the lysosomal storage disease characterized by deficient arylsulfatase B activity and the resultant accumulation of dermatan sulfate-containing glycosaminoglycans (GAGs). A major feature of this and other MPS disorders is abnormal cartilage and bone development leading to short stature, dysostosis multiplex, and degenerative joint disease. To investigate the underlying cause(s) of degenerative joint disease in the MPS disorders, articular cartilage and cultured articular chondrocytes were examined from rats and cats with MPS VI. An age-progressive increase in the number of apoptotic chondrocytes was identified in the MPS animals by terminal transferase nick-end translation (TUNEL) staining and by immunohistochemical staining with anti-poly (ADP-ribose) polymerase (PARP) antibodies. Articular chondrocytes grown from these animals also released more nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha) into the culture media than did control chondrocytes. Notably, dermatan sulfate, the GAG that accumulates in MPS VI cells, induced NO release from normal chondrocytes, suggesting that GAG accumulation was responsible, in part, for the enhanced cell death in the MPS cells. Coculture of normal chondrocytes with MPS VI cells reduced the amount of NO release, presumably because of the release of arylsulfatase B by the normal cells and reuptake by the mutant cells. As a result of the enhanced chondrocyte death, marked proteoglycan and collagen depletion was observed in the MPS articular cartilage matrix. These results demonstrate that MPS VI articular chondrocytes undergo cell death at a higher rate than normal cells, because of either increased levels of dermatan sulfate and/or the presence of inflammatory cytokines in the MPS joints. In turn, this leads to abnormal cartilage matrix homeostasis in the MPS individuals, which further exacerbates the joint deformities characteristic of these disorders.

Short-term enzyme replacement in the murine model of Sanfilippo syndrome type B

The Sanfilippo syndrome type B (MPS III B) is an autosomal recessive disease caused by deficiency of alpha-N-acetylglucosaminidase (EC 3. 2.1.50), one of the lysosomal enzymes required for the degradation of heparan sulfate. The disease is characterized by profound neurodegeneration but relatively mild somatic manifestations, and is usually fatal in the second decade. A mouse model had been generated by disruption of the Naglu gene in order to facilitate the study of pathogenesis and the development of therapy for this currently untreatable disease. Recombinant human alpha-N-acetylglucosaminidase (rhNAGLU) was prepared from secretions of Lec1 mutant Chinese hamster ovary cells. The enzyme, which has only unphosphorylated high-mannose carbohydrate chains, was endocytosed by mouse peritoneal macrophages via mannose receptors, with half-maximal uptake at ca. 10(-7) M. When administered intravenously to 3 month-old mice, rhNAGLU was taken up avidly by liver and spleen but marginally if at all by thymus, lung, kidney, heart, and brain (in order of diminishing uptake). The half-life of the enzyme was 2.5 days in liver and spleen. Immunohistochemistry and electron microscopy showed that only macrophages were involved in enzyme uptake and correction in these two organs, yet the storage of glycosaminoglycan was reduced to almost normal levels. The results show that the macrophage-targeted rhNAGLU can substantially reduce the body burden of glycosaminoglycan storage in the mouse model of Sanfilippo syndrome III B.

Changes in glycosylation of rat liver arylsulfatase B in relation to age

The aim of this study was to determine how glycosylation of the rat liver arylsulfatase B was influenced by the age of the animal. The enzyme was purified from a liver lysosomal fraction obtained from male Wistar rats aged 18 days of gestation, 1 week, and 1, 1.5, 3 and 18 months by an affinity chromatography. Examination of the carbohydrate structures was performed after electrophoresis and blotting, followed by a very sensitive detection system with a set of six highly specific digoxygenin-labelled lectins. After densitometric measurement of the intensity of a digoxigenin-labelled lectin binding to arylsulfatase B, it could be stated that, at least, changes in sialylation are related to the growth and development of rats. Sialylation increases while fucosylation slightly decreases with age of the animal.

The up-regulation of endosomal-lysosomal components in amyloid beta-resistant cells

The abundance of amyloid beta peptide (A beta) and the selective loss of neurons are characteristics of Alzheimer's disease. However, subpopulations of brain cells survive, including neurons near A beta-rich plaques. The surviving neurons may have gene expression profiles that allow them to be resistant to A beta toxicity. Here we use the differential display technique to compare the profiles of gene expression in an A beta-resistant cell line with its parental cells. Prominent among the changes are two components of the endosomal-lysosomal system, insulin growth factor II receptor/mannose-6-phosphate receptor and arylsulfatase B. Both are more highly expressed in the A beta-resistant clone, and arylsulfatase is inducible by A beta and hydrogen peroxide. Another lysosomal enzyme, beta-glucuronidase, is also up-regulated in A beta-resistant cells. These results are consistent with the observation that the endosomal-lysosomal system is highly activated in Alzheimer's disease brains, and they raise the possibility that the high expression of endosomal-lysosomal components is important for neuronal survival in the presence of A beta.

Autologous transplantation of retrovirally transduced bone marrow or neonatal blood cells into cats can lead to long-term engraftment in the absence of myeloablation

Autologous transplantation of retrovirally transduced bone marrow (BM) or neonatal blood cells was carried out on eight cats (ranging in age from 2 weeks to 12 months) with mucopolysaccharidosis type VI (MPS VI). The transducing vector contained the full-length cDNA encoding human arylsulfatase B (hASB), the enzymatic activity deficient in this lysosomal storage disorder. Following transplantation, the persistence of transduced cells and enzymatic expression were monitored for more than 2 years. Five of the cats received no myeloablative preconditioning, two cats received 370-390 cGy of total body irradiation (TBI), and one cat received 190 cGy TBI. Evidence of transduced cells, as judged by enzymatic activity and PCR detection of the provirus, was demonstrated in granulocytes, lymphocytes, or BM cells of the treated animals up to 31 months after transplantation. Radiation preconditioning was not required to achieve these results, nor were they dependent on the recipient's age. However, despite the long-term persistence of transduced cells, the levels of ASB activity in the transplanted animals was low, and no clinical improvements were detected. These data provide evidence for the long-term persistence of retrovirally transduced feline hematopoietic cells, and further documentation that engraftment of transduced cells can be achieved in the absence of myeloablation. Consistent with previous bone marrow transplantation studies, these results also suggest that to achieve clinical improvement of MPS VI, particularly in the skeletal system, high-level expression of ASB must be achieved in the treated animals and improved techniques for targeting the expressed enzyme to specific sites of pathology (e.g. chondrocytes) must be developed.

Murine mucopolysaccharidosis type VII: the impact of therapies on the clinical course and pathology in a murine model of lysosomal storage disease

Murine mucopolysaccharidosis type VII (MPS VII) is a lysosomal storage disease caused by a recessively inherited deficiency of the lysosomal enzyme beta-glucuronidase. Affected mice have clinical, biochemical and pathological findings similar to those seen in humans with MPS VII (Sly syndrome), including growth retardation, facial dysmorphism, deafness, behavioural deficits and widespread glycosaminoglycan storage in lysosomes in the viscera, skeleton and brain. This mouse model is a useful tool for the evaluation of the effectiveness and experimental therapies for the MPS disorders. Syngeneic bone marrow transplantation performed in newborn MPS VII animals--before clinical evidence of disease is pronounced--prolongs life, improves hearing and bone growth, and prevents lysosomal storage in many sites, but does not correct the central nervous system disease. Enzyme therapy with beta-glucuronidase from the first days of life does reduce lysosomal storage in the brain in murine MPS VII. The enzyme-replaced mice also have reduced visceral lysosomal storage, impressive normalization of their phenotype and an improved life span. The effectiveness of gene therapy for the treatment of lysosomal storage disease has also been tested using the MPS VII model. When transplanted into MPS VII mice, syngeneic haematopoietic stem cells or mouse skin fibroblasts infected with retrovirus expressing beta-glucuronidase decreased storage, but only in the liver and spleen. Injection of an adenovirus vector expressing beta-glucuronidase into the vitreous of the MPS VII mice reduced storage in the retinal pigment epithelium and corneal endothelium. Intravenous administration of the adenovirus vector transduced with the beta-glucuronidase gene reduced liver and spleen storage and, when instilled into the cerebral ventricles, this viral vector caused beta-glucuronidase production in epithelial cells lining the ventricles. Recently, retroviral vector-corrected MPS VII fibroblasts secreting high levels of beta-glucuronidase were engrafted directly into the brains of adult MPS VII mice with resultant reduction in storage in neurons and glia adjacent to the grafts. Future efforts aimed at prolonging expression of the beta-glucuronidase gene by viral vectors and more precisely directing the therapeutic effect to the skeleton and brain will be important in optimizing treatments for murine MPS VII and extending the results of such therapies to humans with MPS.

Lysosomal storage diseases of animals: an essay in comparative pathology

A wide variety of inherited lysosomal hydrolase deficiencies have been reported in animals and are characterized by accumulation of sphingolipids, glycolipids, oligosaccharides, or mucopolysaccharides within lysosomes. Inhibitors of a lysosomal hydrolase, e.g., swainsonine, may also induce storage disease. Another group of lysosomal storage diseases, the ceroid-lipofuscinoses, involve the accumulation of hydrophobic proteins, but their pathogenesis is unclear. Some of these diseases are of veterinary importance, and those caused by a hydrolase deficiency can be controlled by detection of heterozygotes through the gene dosage phenomenon or by molecular genetic techniques. Other of these diseases are important to biomedical research either as models of the analogous human disease and/or through their ability to help elucidate specific aspects of cell biology. Some of these models have been used to explore possible therapeutic strategies and to define their limitations and expectations.

Effect of enzyme replacement therapy on bone formation in a feline model of mucopolysaccharidosis type VI

A range of skeletal abnormalities are evident in mucopolysaccharidosis type VI (MPS VI, Maroteaux-Lamy syndrome) including short stature and dysostosis multiplex, resulting from a deficiency in the lysosomal hydrolase N-acetylgalactosamine-4-sulphatase (4S). In this article, bone pathology was assessed in a feline model of MPS VI to evaluate the efficacy of enzyme replacement therapy (ERT) as a treatment modality for this genetic disorder. Osteopenia is clearly evident in MPS VI animals, with bone mineral volume (BV/TV) falling well below that of normal animals (4.39% vs. 20.11%, respectively). Trabecular bone architecture was also affected in MPS VI with fewer, thinner, and more widely spaced trabeculae apparent. Bone formation rate (BFR/BS) was also lower in MPS VI animals than controls (0.0011 mm3/mm2 per day vs. 0.008 mm3/mm2 per day, respectively). Vertebral and tibial bone length in MPS VI animals progressively fell behind normal values with increasing age, as did cortical bone thickness. Vertebral body shape was also altered. ERT with recombinant human 4S (rh4S) resulted in a vertebral BV/TV of 8.23% in animals treated with an intravenous enzyme dose of 1 mg/kg and a BV/TV of 14.33% in animals treated with a dose of 5 mg/kg. BFR/BS also increased to 0.0034 mm3/mm2 per day in animals treated with enzyme doses of either 1.0 or 5.0 mg/kg rh4S. All other affected histomorphometric parameters also improved with ERT to a level intermediate between MPS VI untreated animals and normals. However, individual animals treated with 0.2 mg/kg rh4S intravenously or 1.0 mg/kg rh4S administered subcutaneously did not exhibit an improvement over untreated MPS VI animals. Vertebral and tibial bone lengths, tibial cortical bone thickness, and vertebral body shape also responded to ERT, with a trend away from the untreated group. Thus, ERT had a positive effect on bone development in MPS VI animals that was dependent upon the dose of enzyme administered and the route of administration.

Bone marrow transplantation in newborn rats with mucopolysaccharidosis type VI: biochemical, pathological, and clinical findings

BACKGROUND

Mucopolysaccharidosis type VI (MPS VI) is the lysosomal storage disorder caused by the deficient activity of arylsulfatase B (ASB). In this study, we evaluated bone marrow transplantation (BMT) for the treatment of MPS VI and the effects of irradiation on the survival and engraftment of bone marrow-transplanted neonatal rats.

METHODS

One- to 2-day-old MPS VI rats were injected with normal bone marrow after irradiation with 200, 400, or 800 cGy. Ninety percent of the animals receiving a single dose of 200 cGy (n=30) survived the procedure, whereas irradiation with 400 cGy (n=23) or 800 cGy (n=12) resulted in significant mortality (78% and 100%, respectively). Engraftment was monitored by determining ASB activities in peripheral white blood cells and by Y chromosome in situ hybridization analysis. Fifty-two percent of the animals from the 200-cGy group engrafted for up to 8 months after BMT; among the five animals that survived the 400-cGy dose, all engrafted. In comparison, only 20% of nonirradiated animals engrafted at low levels. Of the 24 engrafted animals that were monitored for 8 months after BMT, clinical and/or radiographic improvements were noted in only one (BMT animal 3). Enzymatic analysis revealed that the ASB activities in the reticuloendothelial organs of this animal, as well as two other engrafted but clinically unimproved animals (BMT animals 1 and 2), were normal or near normal; correspondingly, the glycosaminoglycan levels in these organs were significantly reduced. Consistent with the clinical and biochemical observations, light and electron microscopic findings were more improved in BMT animal 3 as compared with BMT animals 1 and 2, although a reduction of storage was evident in each of these transplant recipients, particularly in the trachea and aorta, two tissues that are characteristic sites of pathology in human patients.

CONCLUSIONS

These results indicate that BMT in newborn MPS VI patients may prevent many of the pathological and clinical findings in this disorder, but is likely to have very limited and unpredictable effects on the skeletal abnormalities.

Enzyme replacement therapy from birth in a feline model of mucopolysaccharidosis type VI

We report evidence of a dose responsive effect of enzyme replacement therapy in mucopolysaccharidosis type VI cats from birth, at the clinical, biochemical, and histopathological level. Cats treated with weekly, intravenous recombinant human N-acetylgalactosamine-4-sulfatase at 1 and 5 mg/kg, were heavier, more flexible, had greatly reduced or no spinal cord compression, and had almost normal urinary glycosaminoglycan levels. There was near normalization or complete reversal of lysosomal storage in heart valve, aorta, skin, dura, liver, and brain perivascular cells. No reduction in lysosomal vacuolation was observed in cartilage or cornea; however, articular cartilage was thinner and external ear pinnae were larger in some treated cats. Degenerative joint changes were not obviously delayed in treated cats. Skeletal pathology was reduced, with more normalized bone dimensions and with more uniform bone density and trabecular pattern clearly visible on radiographs by 5 to 6 mo; however, differences between 1 and 5 mg/kg dose rates were not clearly distinguishable. At a dose of 0.2 mg/kg, disease was not significantly altered in the majority of parameters examined. Lysosomal storage was present in all tissues examined in the midterm mucopolysaccharidosis type VI fetus and increased rapidly in extent and severity from birth.

Targeted disruption of the arylsulfatase B gene results in mice resembling the phenotype of mucopolysaccharidosis VI

Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease with autosomal recessive inheritance caused by a deficiency of the enzyme arylsulfatase B (ASB), which is involved in degradation of dermatan sulfate and chondroitin 4-sulfate. A MPS VI mouse model was generated by targeted disruption of the ASB gene. Homozygous mutant animals exhibit ASB enzyme deficiency and elevated urinary secretion of dermatan sulfate. They develop progressive symptoms resembling those of MPS VI in humans. Around 4 weeks of age facial dysmorphia becomes overt, long bones are shortened, and pelvic and costal abnormalities are observed. Major alterations in bone formation with perturbed cartilaginous tissues in newborns and widened, perturbed, and persisting growth plates in adult animals are seen. All major parenchymal organs show storage of glycosaminoglycans preferentially in interstitial cells and macrophages. Affected mice are fertile and mortality is not elevated up to 15 months of age. This mouse model will be a valuable tool for studying pathogenesis of MPS VI and may help to evaluate therapeutical approaches for lysosomal storage diseases.

Arylsulfatase B activities and glycosaminoglycan levels in retrovirally transduced mucopolysaccharidosis type VI cells. Prospects for gene therapy

Mucopolysacchariodosis type VI (MPS VI) is the lysosomal storage disorder caused by the deficient activity of arylsulfatase B (ASB; N-acetylgalactosamine 4-sulfatase) and the subsequent accumulation of the glycosaminoglycan (GAG), dermatan sulfate. In this study, a retroviral vector containing the full-length human ASB cDNA was constructed and used to transduce skin fibroblasts, chondrocytes, and bone marrow cells from human patients, cats, or rats with MPS VI. The ASB vector expressed high levels of enzymatic activity in each of the cell types tested and, in the case of cat and rat cells, enzymatic expression led to complete normalization of 35SO4 incorporation. In contrast, overexpression of ASB in human MPS VI skin fibroblasts did not lead to metabolic correction. High-level ASB expression was detected for up to eight weeks in transduced MPS VI cat and rat bone marrow cultures, and PCR analysis demonstrated retroviral-mediated gene transfer to approximately 30-50% of the CFU GM-derived colonies. Notably, overexpression of ASB in bone marrow cells led to release of the enzyme into the media and uptake by MPS VI cat and rat skin fibroblasts and/or chondrocytes via the mannose-6-phosphate receptor system, leading to metabolic correction. Thus, these studies provide important rationale for the development of gene therapy for this disorder and lay the frame-work for future in vivo studies in the animal model systems.

Enzyme replacement therapy in a feline model of Maroteaux-Lamy syndrome

We report studies that suggest enzyme replacement therapy will result in a significant reduction in disease progression and tissue pathology in patients with Maroteaux-Lamy syndrome (Mucopolysaccharidosis type VI, MPS VI). A feline model for MPS VI was used to evaluate tissue distribution and clinical efficacy of three forms of recombinant human N-acetylgalactosamine-4-sulfatase (rh4S, EC 3.1.6.1). Intravenously administered rh4S was rapidly cleared from circulation. The majority of rh4S was distributed to liver, but was also detected in most other tissues. Tissue half-life was approximately 2-4 d. Three MPS VI cats given regular intravenous infusions of rh4S for up to 20 mo showed variable reduction of storage vacuoles in Kupffer cells and connective tissues, however cartilage chondrocytes remained vacuolated. Vertebral bone mineral volume was improved in two MPS VI cats in which therapy was initiated before skeletal maturity, and increased bone volume appeared to correlate with earlier age of onset of therapy. One cat showed greater mobility in response to therapy.