Fluoxetine ameliorates mucopolysaccharidosis type IIIA.

Mucopolysaccharidosis type IIIA (MPS-IIIA) is an autosomal recessive disorder caused by mutations in SGSH involved in the degradation of heparan sulfate. MPS-IIIA presents severe neurological symptoms such as progressive developmental delay and cognitive decline, for which there is currently no treatment. Brain targeting represents the main challenge for therapeutics to treat MPS-IIIA, and the development of small-molecule-based treatments able to reach the CNS could be a relevant advance for therapy. Using cell-based high content imaging to survey clinically approved drugs in MPS-IIIA cells, we identified fluoxetine, a selective serotonin reuptake inhibitor. Fluoxetine increases lysosomal and autophagic functions via TFEB activation through a RagC-dependent mechanism. Mechanistically, fluoxetine increases lysosomal exocytosis in mouse embryonic fibroblasts from MPS-IIIA mice, suggesting that this process may be responsible for heparan sulfate clearance. In vivo, fluoxetine ameliorates somatic and brain pathology in a mouse model of MPS-IIIA by decreasing the accumulation of glycosaminoglycans and aggregated autophagic substrates, reducing inflammation, and slowing down cognitive deterioration. We repurposed fluoxetine for potential therapeutics to treat human MPS-IIIA disease.

Bayesian model of disease progression in mucopolysaccaridosis IIIA.

Mucopolysaccaridosis IIIA (MPS IIIA) is a rare genetic disease that afflicts children and leads to neurocognitive degeneration. We develop a Bayesian disease progression model (DPM) of MPS IIIA that characterizes the pattern of cognitive growth and decline in this disease. The DPM is a repeated measures model that incorporates a nonlinear developmental trajectory and shape-invariant random effects. This approach quantifies the pattern of cognitive development in MPS IIIA and addresses differences in biological age, length of follow-up, and clinical outcomes across natural history subjects. The DPM can be used in clinical trials to estimate the percent slowing in disease progression for treatment relative to natural history. Simulations demonstrate that the DPM provides substantial improvements in power relative to alternative analyses.

A phase 1/2 study of intrathecal heparan-N-sulfatase in patients with mucopolysaccharidosis IIIA.

OBJECTIVE: This was an open-label, phase 1/2 dose-escalation, safety trial of intrathecal recombinant human heparan-N-sulfatase (rhHNS) administered via intrathecal drug delivery device (IDDD) for treating mucopolysaccharidosis IIIA (NCT01155778). STUDY DESIGN: Twelve patients received 10, 45, or 90mg of rhHNS via IDDD once monthly for a total of 6 doses. Primary endpoints included adverse events (AEs) and anti-rhHNS antibodies. Secondary endpoints included standardized neurocognitive assessments, cortical gray matter volume, and pharmacokinetic/pharmacodynamic analyses. RESULTS: All patients experienced treatment-emergent AEs; most of mild-to-moderate severity. Seven patients reported a total of 10 serious AEs (SAEs), all but one due to hospitalization to revise a nonfunctioning IDDD. No SAEs were considered related to rhHNS. Anti-rhHNS antibodies were detected in the serum of 6 patients and in the cerebrospinal fluid (CSF) of 2 of these. CSF heparan sulfate levels were elevated at baseline and there were sustained declines in all tested patients following the first rhHNS dose. No impact of anti-rhHNS antibodies on any pharmacodynamic or safety parameters was evident. 4 of 12 patients showed a decline in developmental quotient, 6 were stable, and 2 patients had only a single data point. No dose group showed a clearly different response pattern. CONCLUSIONS: rhHNS administration via IDDD appeared generally safe and well tolerated. Treatment resulted in consistent declines in CSF heparan sulfate, suggesting in vivo activity in the relevant anatomical compartment. Results of this small study should be interpreted with caution. Future studies are required to assess the potential clinical benefits of rhHNS and to test improved IDDD models.

Determination of the role of injection site on the efficacy of intra-CSF enzyme replacement therapy in MPS IIIA mice.

MPS IIIA is an inherited neurodegenerative lysosomal storage disorder characterized by cognitive impairment, sleep-wake cycle disturbance, speech difficulties, eventual mental regression and early death. Neuropathological changes include accumulation of heparan sulfate and glycolipids, neuroinflammation and degeneration. Pre-clinical animal studies indicate that replacement of the deficient enzyme, sulfamidase, via intra-cerebrospinal fluid (CSF) injection is a clinically-relevant treatment approach, reducing neuropathological changes and improving symptoms. Given that there are several routes of administration of enzyme into the CSF (intrathecal lumbar, cisternal and ventricular), determining the effectiveness of each injection strategy is crucial in order to provide the best outcome for patients. We delivered recombinant human sulfamidase (rhSGSH) to a congenic mouse model of MPS IIIA via each of the three routes. Mice were euthanized 24h or one-week post-injection; the distribution of enzyme within the brain and spinal cord parenchyma was investigated, and the impact on primary substrate levels and other pathological lesions determined. Both ventricular and cisternal injection of rhSGSH enable enzyme delivery to brain and spinal cord regions, with the former mediating large, statistically significant decreases in substrate levels and reducing microglial activation. The single lumbar CSF infusion permitted more restricted enzyme delivery, with no reduction in substrate levels and little change in other disease-related lesions in brain tissue. While the ventricular route is the most invasive of the three methods, this strategy may enable the widest distribution of enzyme within the brain, and thus requires further exploration.

Human pathology in NCL.

In childhood the neuronal ceroid lipofuscinoses (NCL) are the most frequent lysosomal diseases and the most frequent neurodegenerative diseases but, in adulthood, they represent a small fraction among the neurodegenerative diseases. Their morphology is marked by: (i) loss of neurons, foremost in the cerebral and cerebellar cortices resulting in cerebral and cerebellar atrophy; (ii) an almost ubiquitous accumulation of lipopigments in nerve cells, but also in extracerebral tissues. Loss of cortical neurons is selective, indiscriminate depletion in early childhood forms occurring only at an advanced stage, whereas loss of neurons in subcortical grey-matter regions has not been quantitatively documented. Among the fourteen different forms of NCL described to date, CLN1 and CLN10 are marked by granular lipopigments, CLN2 by curvilinear profiles (CVPs), CLN3 by fingerprint profiles (FPPs), and other forms by a combination of these features. Among extracerebral tissues, lymphocytes, skin, rectum, skeletal muscle and, occasionally, conjunctiva are possible guiding targets for diagnostic identification, the precise type of NCL then requiring molecular analysis within the clinical and morphological context. Autosomal-recessive adult NCL has been linked molecularly to different childhood forms, i.e. CLN1, CLN5, and CLN6, whilst autosomal-dominant adult NCL, now designated as CLN4, is caused by a newly identified separate gene, DNAJC5. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.

Initiation of fluoxetine in a pediatric patient with Mucopolysaccharidosis IIIA: Early observations.

Fluoxetine has been identified as a potential treatment for mucopolysaccharidosis IIIA (MPS IIIA), a debilitating and progressive lysosomal storage disorder for which no treatments are approved. In the MPS IIIA mouse model, fluoxetine decreases the accumulation of glycosaminoglycans and aggregated autophagic substrates, reducing inflammation, and slowing cognitive deterioration. 1 We treated a single patient, 6 years old, under off-label prescription of fluoxetine, a selective serotonin reuptake inhibitor (SSRI). The primary endpoint was safety. Secondary exploratory assessments included urine quantitative heparan sulfate. Fluoxetine was well-tolerated in this patient and the patient continued treatment following the 12-month monitoring period. The patient experienced an increase in daytime somnolence which resolved with rescheduling fluoxetine administration to bedtime. Quantitative heparan sulfate levels remained elevated during treatment. Parents reported improved sleep latency time and less nighttime waking. These findings support general tolerability and further study of fluoxetine as a potential therapy for MPS IIIA.

Repetitive, non-invasive imaging of neurodegeneration, and prevention of it with gene replacement, in mice with Sanfilippo syndrome.

Hampering assessment of treatment outcomes in gene therapy and other clinical trials in patients with childhood dementia is the lack of an objective, non-invasive measure of neurodegeneration. Optical coherence tomography (OCT) is a widely available, rapid, non-invasive, and quantitative method for examining the integrity of the neuroretina. Profound brain and retinal dysfunction occur in patients and animal models of childhood dementia, including Sanfilippo syndrome and we recently revealed a correlation between the age of onset and rate of progression of retinal and brain degeneration in sulfamidase-deficient Sanfilippo mice. The aim of the current study was to use OCT to visualise the discrete changes in retinal structure that occur during disease progression. A progressive decline in retinal thickness was readily observable in Sanfilippo mice using OCT, with differences seen in affected animals from 10-weeks of age. OCT applied to i.v. AAV9-sulfamidase-treated Sanfilippo mice enabled visualisation of improved retinal anatomy in living animals, an outcome confirmed via histology. Importantly, brain disease lesions were also ameliorated in treated Sanfilippo mice. The findings highlight the sensitivity, ease of repetitive use and quantitative capacity of OCT for detection of discrete changes in retinal structure and their prevention with a therapeutic. Combined with the knowledge that retinal and brain degeneration are correlated in Sanfilippo syndrome, OCT provides a window to the brain in this and potentially other childhood dementias.

Understanding disease symptoms and impacts and producing qualitatively-derived severity stages for MPS IIIA: a mixed methods approach.

BACKGROUND: MPS IIIA is a rare, degenerative pediatric genetic disease characterized by symptoms impacting cognition, mobility and behavior; the mean age of death is around 15 years of age. Currently, there are no approved therapies for MPS IIIA. METHODS: A two-year, multi-center, prospective, descriptive cohort study was conducted to document the natural history course of MPS IIIA. In the context of this study, semi-structured interviews were performed with parents of children at study entry and one year later. Interview transcripts were analyzed using thematic analysis methods to identity concepts of interest to children and parents, identify what factors impacted parents' burden the most, and develop qualitatively-derived disease severity stages. Children were sorted into these stages according to the symptoms their parents described at the entry interview. This sorting was compared quantitatively to the sorting of children at baseline according to the child's calendar age and their BSID development quotient (DQ). RESULTS: 22 parents in France, Germany, the Netherlands and the UK were interviewed. Children ranged in age from 28 to 105 months (mean 61.4 months). The conceptual models for children's symptoms and impacts and parents' impacts provided a detailed and comprehensive picture of what it is like for children of various ages and their parents to live with MPS IIIA. Four factors were identified as mediating the burden perceived by parents: state support, family support, time since diagnosis, and parent coping strategy. Four disease stages were developed, accounting for both the presence and the severity of MPS IIIA symptoms. The comparison of children's sorting into these stages with the BSID DQ and the child's calendar age showed strong statistical associations. CONCLUSIONS: The findings of this qualitative research embedded in a natural history study add to the current understanding of MPS IIIA as a complex disease that impacts every aspect of the lives of children and their families. This study demonstrates the unique potential of mixed methods research in rare diseases to address some of the current limitations of more traditional quantitative approaches by providing an individualized, detailed understanding of the patient experience.

Increased Alveolar Heparan Sulphate and Reduced Pulmonary Surfactant Amount and Function in the Mucopolysaccharidosis IIIA Mouse.

Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry showed an increase in minimum and maximum surface tension and percent surface area compression, as well as a higher compressibility and hysteresis in MPS IIIA surfactant upon dynamic cycling. Collectively these biochemical and biophysical changes in alveolar surfactant are likely to be detrimental to lung function in MPS IIIA.

Impaired neural differentiation of MPS IIIA patient induced pluripotent stem cell-derived neural progenitor cells.

Mucopolysaccharidosis type IIIA (MPS IIIA) is characterised by a progressive neurological decline leading to early death. It is caused by bi-allelic loss-of-function mutations in SGSH encoding sulphamidase, a lysosomal enzyme required for heparan sulphate glycosaminoglycan (HS GAG) degradation, that results in the progressive build-up of HS GAGs in multiple tissues most notably the central nervous system (CNS). Skin fibroblasts from two MPS IIIA patients who presented with an intermediate and a severe clinical phenotype, respectively, were reprogrammed into induced pluripotent stem cells (iPSCs). The intermediate MPS IIIA iPSCs were then differentiated into neural progenitor cells (NPCs) and subsequently neurons. The patient derived fibroblasts, iPSCs, NPCs and neurons all displayed hallmark biochemical characteristics of MPS IIIA including reduced sulphamidase activity and increased accumulation of an MPS IIIA HS GAG biomarker. Proliferation of MPS IIIA iPSC-derived NPCs was reduced compared to control, but could be partially rescued by reintroducing functional sulphamidase enzyme, or by doubling the concentration of the mitogen fibroblast growth factor 2 (FGF2). Whilst both control heparin, and MPS IIIA HS GAGs had a similar binding affinity for FGF2, only the latter inhibited FGF signalling, suggesting accumulated MPS IIIA HS GAGs disrupt the FGF2:FGF2 receptor:HS signalling complex. Neuronal differentiation of MPS IIIA iPSC-derived NPCs was associated with a reduction in the expression of neuronal cell marker genes ßIII-TUBULIN, NF-H and NSE, revealing reduced neurogenesis compared to control. A similar result was achieved by adding MPS IIIA HS GAGs to the culture medium during neuronal differentiation of control iPSC-derived NPCs. This study demonstrates the generation of MPS IIIA iPSCs, and NPCs, the latter of which display reduced proliferation and neurogenic capacity. Reduced NPC proliferation can be explained by a model in which soluble MPS IIIA HS GAGs compete with cell surface HS for FGF2 binding. The mechanism driving reduced neurogenesis remains to be determined but appears downstream of MPS IIIA HS GAG accumulation.

Retinal Degeneration in MPS-IIIA Mouse Model.

Mucopolysaccharidosis type IIIA (MPS-IIIA, Sanfilippo A) is one of the most severe lysosomal storage disorder (LSD) caused by the inherited deficiency of sulfamidase, a lysosomal sulfatase enzyme involved in the stepwise degradation of heparan sulfates (HS). MPS-IIIA patients show multisystemic problems, including a strong impairment of central nervous system (CNS), mild somatic involvement, and ocular manifestations that result in significant visual impairment. Despite the CNS and somatic pathology have been well characterized, studies on visual system and function remain partially explored. Here, we characterized the retina morphology and functionality in MPS-IIIA mouse model and analyzed how the SGSH deficiency affects the autophagic flux. MPS-IIIA mice exhibited a progressive retinal dystrophy characterized by significant alterations in visual function. The photoreceptor degeneration was associated with HS accumulation and a block of autophagy pathway. These events caused a reactive microgliosis, and a development of apoptotic processes in MPS-IIIA mouse retina. Overall, this study provides the first phenotypic spectrum of retinal disorders in MPS-IIIA and significantly contributes for diagnosis, counseling, and potential therapies development.

Hematopoietic stem cell transplantation in mucopolysaccharidosis type IIIA: A case description and comparison with a genotype-matched control group.

BACKGROUND: Mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo A syndrome) is a chronic progressive neurodegenerative storage disorder caused by a deficiency of lysosomal sulfamidase. The clinical hallmarks are sleep disturbances, behavioral abnormalities and loss of cognitive, speech and motor abilities. Affected children show developmental slowing from the second year of life, dementia occurs by the age of 5 years followed by death in the second decade of life. Only a few studies concerning HSCT in MPS IIIA have been published and do not document a clear benefit of treatment. METHODS: The present study summarizes the clinical outcome of a girl with MPS IIIA who received HSCT at the age of 2.5 years. Her clinical course was compared with the natural history of six untreated MPS IIIA patients carrying the same mutations (p.R74C and p. R245H) in the SGSH-gene. RESULTS: Eight years after successful HSCT, the patient showed a global developmental delay. However, cognitive abilities continued to develop, albeit very slowly. There was no sign of regression. She could talk in short sentences, had good motor abilities and performed basic daily living activities by herself. She did not present with sleeping problems, but behavioral abnormalities were profound. In contrast, the six untreated patients with identical mutations in the SGSH-gene showed the typical progressive course of disease with early and continuous loss of abilities. CONCLUSIONS: The present data suggest a beneficial effect of HSCT performed at an early stage of MPS IIIA on cognitive skills, motor function and quality of life.

Impact of chemical modification of sulfamidase on distribution to brain interstitial fluid and to CSF after an intravenous administration in awake, freely-moving rats.

Mucopolysaccharidosis III A (MPS IIIA) is an autosomal recessive lysosomal storage disorder caused by deficiency of the enzyme sulfamidase. The disorder results in accumulation of heparan sulfate, lysosomal enlargement and cellular and organ dysfunction. Patients exhibit progressive neurodegeneration and behavioral problems and no treatment is currently available. Enzyme replacement therapy is explored as potential treatment strategy for MPS IIIA patients and to modify the disease, sulfamidase must reach the brain. The glycans of recombinant human sulfamidase (rhSulfamidase) can be chemically modified to generate CM-rhSulfamidase. The chemical modification reduced the affinity to the cation-independent mannose-6-phosphate receptor with the aim a prolonged higher concentration in circulation and thus at the blood brain barrier. The pharmacokinetic properties in serum and the distribution to brain and to cerebrospinal fluid (CSF) of chemically modified recombinant human sulfamidase (CM-rhSulfamidase) were studied and compared to those of rhSulfamidase, after a single intravenous (i.v.) 30 mg/kg dose in awake, freely-moving male Sprague Dawley rats. Distribution to brain was studied by microdialysis of the interstitial fluid in prefrontal cortex and by repeated intra-individual CSF sampling from the cisterna magna. Push-pull microdialysis facilitated sampling of brain interstitial fluid to determine large molecule concentrations in awake, freely-moving male Sprague Dawley rats. Together with repeated serum and CSF sampling, push-pull microdialysis facilitated determination of CM-rhSulfamidase and rhSulfamidase kinetics after i.v. administration by non-compartments analysis and by a population modelling approach. Chemical modification increased the area under the concentration versus time in serum, CSF and brain interstitial fluid at least 7-fold. The results and the outcome of a population modelling approach of the concentration versus time data indicated that both compounds pass the BBB with an equilibrium established fairly rapid after administration. We suggest that prolonged high serum concentrations facilitated high brain interstitial fluid concentrations, which could be favorable to reach various target cells in the brain.

Synthetic Disaccharide Standards Enable Quantitative Analysis of Stored Heparan Sulfate in MPS IIIA Murine Brain Regions.

Heparan sulfate (HS) is a complex polysaccharide from the glycosaminoglycan (GAG) family that accumulates in tissues in several neurological lysosomal storage diseases known as mucopolysaccharidosis (MPS) disorders. The quantitation of HS in biological samples is important for studying MPS disorders but is very challenging because of its high molecular weight and heterogeneity. Recently, acid-catalyzed butanolysis followed by LC-MS/MS analysis has emerged as a promising method for the determination of HS. Butanolysis of HS produces fully desulfated disaccharide cleavage products which are detected by LC-MS/MS. Herein we describe the synthesis of butylated HS disaccharide standards and their use for determining the identity of major product peaks in LC-MS chromatograms from butanolysis of HS as well as the related GAGs heparin and heparosan. Furthermore, synthesis of a d9-labeled disaccharide internal standard enabled the development of a quantitative LC-MS/MS assay for HS. The assay was utilized for the analysis of MPS IIIA mouse brain tissues, revealing significant differences in abundance and in the regional accumulation of the various HS disaccharides in affected mice.

Assessing the impact on caregivers caring for patients with rare pediatric lysosomal storage diseases: development of the Caregiver Impact Questionnaire.

BACKGROUND: Capturing the impact of caring for patients with debilitating rare disease is important for understanding disease burden. We aimed to develop and validate an instrument to measure the impact on caregivers of caring for children with three lysosomal storage diseases (LSDs): metachromatic leukodystrophy (MLD), neuronopathic mucopolysaccharidosis type II (MPS II) and mucopolysaccharidosis type IIIA (MPS IIIA). METHODS: A draft instrument was developed based on targeted literature searches and revised through sequential qualitative interviews with caregivers of patients first with MLD (n = 16), then with MPS II (n = 22), and finally with MPS IIIA (n = 8). The instrument, which covered domains of physical, emotional, social and economic burden, was refined at each stage of development based on caregiver feedback. Saturation of major concepts was reached during concept elicitation (MLD and MPS II). RESULTS: It was confirmed that caring for a patient with an LSD impacts social functioning, emotional/psychological functioning, physical functioning, daily activities, and finances/work productivity. Results from cognitive debriefing of the draft questionnaires were considered during each round of interviews, resulting in a final set of items that caregivers found clear and easy to understand. The Caregiver Impact Questionnaire (CIQ) has 30 items in five domains: (1) social functioning (7 items); (2) impact on daily activities (5 items); (3) emotional/psychological functioning (10 items); (4) physical functioning (6 items); and (5) financial impact (2 items). CONCLUSIONS: These findings demonstrate that the content of the CIQ is relevant for determining the impact of caring on caregivers of patients with MLD, MPS II and MPS IIIA.

Intravenous delivery of a chemically modified sulfamidase efficiently reduces heparan sulfate storage and brain pathology in mucopolysaccharidosis IIIA mice.

Mucopolysaccharidosis type IIIA (MPS IIIA) is a lysosomal storage disorder (LSD) characterized by severe central nervous system (CNS) degeneration. The disease is caused by mutations in the SGSH gene coding for the lysosomal enzyme sulfamidase. Sulfamidase deficiency leads to accumulation of heparan sulfate (HS), which triggers aberrant cellular function, inflammation and eventually cell death. There is currently no available treatment against MPS IIIA. In the present study, a chemically modified recombinant human sulfamidase (CM-rhSulfamidase) with disrupted glycans showed reduced glycan receptor mediated endocytosis, indicating a non-receptor mediated uptake in MPS IIIA patient fibroblasts. Intracellular enzymatic activity and stability was not affected by chemical modification. After intravenous (i.v.) administration in mice, CM-rhSulfamidase showed a prolonged exposure in plasma and distributed to the brain, present both in vascular profiles and in brain parenchyma. Repeated weekly i.v. administration resulted in a dose- and time-dependent reduction of HS in CNS compartments in a mouse model of MPS IIIA. The reduction in HS was paralleled by improvements in lysosomal pathology and neuroinflammation. Behavioral deficits in the MPS IIIA mouse model were apparent in the domains of exploratory behavior, neuromuscular function, social- and learning abilities. CM-rhSulfamidase treatment improved activity in the open field test, endurance in the wire hanging test, sociability in the three-chamber test, whereas other test parameters trended towards improvements. The unique properties of CM-rhSulfamidase described here strongly support the normalization of clinical symptoms, and this candidate drug is therefore currently undergoing clinical studies evaluating safety and efficacy in patients with MPS IIIA.

Application of MALDI-TOF Mass Spectrometry for Non-invasive Diagnostics of Mucopolysaccharidosis IIIA

Abstract Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disorder (LSD) caused by deficiency of lysosomal N-sulphoglucosamine sulphohydrolase, which is one of four enzymes involved in heparan sulfate degradation. Traditional methods used for MPS IIIA diagnostics usually constitute of selective screening, based on the analysis of urinary glycosaminoglycans, further enzymatic assays in leukocytes, and mutation analysis. Nowadays, some LSDs, including mucopolysaccharidoses, can be precisely diagnosed by mass spectrometry-based techniques. Up to this date, there are no comprehensive studies of MPS IIIA diagnostics by MALDI-TOF analysis of free oligosaccharides in urine published. In the presented work, MALDI-TOF/TOF analysis of permethylated oligosaccharides was performed to obtain the set of glyco-biomarkers that together form the specific fingerprint of this disease. Early and accurate diagnostics of MPS IIIA is crucial to stabilize the progressive cellular damage and improve the overall well-being of patients.

Low-dose, continual enzyme delivery ameliorates some aspects of established brain disease in a mouse model of a childhood-onset neurodegenerative disorder.

AIM: To determine the capacity of continual low-dose lysosomal enzyme infusion into the cerebrospinal fluid of mucopolysaccharidosis type IIIA (MPS IIIA) mice to reverse established neurodegenerative disease. The rationale behind the study is that there is only limited animal model-derived evidence supporting treatment of symptomatic patients, principally because few studies have been designed to examine disease reversibility. METHODS: Twelve-week old MPS IIIA mice were implanted with indwelling unilateral intra-ventricular cannulae. These were connected to subcutaneous mini-osmotic pumps infusing recombinant human sulphamidase. Pump replacement was carried out in some mice at 16-weeks of age, enabling treatment to continue for a further month. Control affected/unaffected mice received vehicle via the same method. Behavioural, neuropathological and biochemical parameters of disease were assessed. RESULTS: Improvement in some, but not all, behavioural parameters occurred. Sulphamidase infusion mediated a statistically significant reduction in primary (heparan sulphate) and secondary (gangliosides GM2, GM3) substrate accumulation in the brain, with small reductions in micro- but not astro-gliosis. There was no change in axonal spheroid number. All mice developed a humoural response, however the antibodies were non-neutralising and no adverse clinical effects were observed. CONCLUSIONS: Continual infusion of replacement enzyme partially ameliorates clinical, histological and biochemical aspects of MPS IIIA mice, when treatment begins at an early symptomatic stage.