Enzyme, cell and gene-based therapies for metachromatic leukodystrophy

Insight into adult-onset metachromatic leukodystrophy with optic atrophy: A comprehensive case report

This abstract provides an overview of metachromatic leukodystrophy (MLD), an autosomal recessive disorder stemming from arylsulfatase A deficiency. MLD leads to cerebroside sulfate accumulation, causing central and peripheral demyelination. Clinical manifestations vary by age group: late-infantile (rapid progression), juvenile (slower progression), and adult-onset (psychiatric symptoms). A case study details a 23-year-old with progressive vision impairment, motor weakness, and cognitive changes. Examination and MRI findings led to suspicion of MLD, later confirmed by enzyme testing. Optic nerve involvement is emphasized, along with diagnostic criteria involving enzyme assays, imaging, and urinary sulfatide excretion tests. While no cure exists, symptomatic and supportive care, including hematopoietic stem cell transplantation, remains key in MLD management.

First insights into region-specific lipidome alterations of prefrontal cortex and hippocampus of mice exposed chronically to microcystins

Microcystins (MCs), a group of most widespread freshwater cyanotoxins that possess strong neurotoxicity, can adversely affect brain structures and functions and are linked to neurodegenerative diseases. Despite the essential role of lipids in brain structures and functions, the brain lipidome profile of mammals exposed to MCs remains unexplored, hindering a clear understanding of the neurotoxic effects of MCs and underlying mechanisms. In this study, we performed untargeted lipidomic profiling using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) on the prefrontal cortex and hippocampus of mice orally exposed to 30 and 300 μg/kg body mass/day of microcystin-leucine arginine (MC-LR) for 180 days to evaluate the impacts of MC-LR on the brain lipidome profile and functions. Our results show that MC-LR resulted in a decline in cognitive parameters, as assessed by the Morris water maze test. Interestingly, apparent neurodegenerative changes were observed in the prefrontal cortex, but not in the hippocampus. Comprehensive lipidomic analyses uncovered profound, region-specific changes in the phospholipid and sphingolipid profile at the levels of lipid subclasses, lipid species, and fatty acyl composition. These changes showed overall decrease trends of lipid content in the prefrontal cortex yet increasing trends in the hippocampus. We identified distinct transcriptional regulations of lipid metabolism and apoptosis by MC-LR in the two regions, which appeared to underlie the neurodegenerative changes. Collectively, this study uncovers region-specific changes in the brain lipidome profile and functions induced by MCs, shedding light on the role of lipid dysfunction in neurotoxicity mechanism of MCs.

The endo-lysosomal regulatory protein BLOC1S1 modulates hepatic lysosomal content and lysosomal lipolysis

BLOC1S1 is a common component of BLOC and BORC multiprotein complexes which play distinct roles in endosome and lysosome biology. Recent human mutations in BLOC1S1 associate with juvenile leukodystrophy. As leukodystrophy is linked to perturbed lysosomal lipid storage we explored whether BLOC1S1 itself modulates this biology. Given the central role of the liver in lipid storage, our investigations were performed in hepatocyte specific liver bloc1s1 knockout (LKO) mice and in human hepatocyte-like lines (HLCs) derived from inducible pluripotential stem cells (iPSCs) from a juvenile leukodystrophy subject's with bloc1s1 mutations and from isogenic corrected iPSCs. Here we show that hepatocyte lipid stores are diminished in parallel with increased lysosomal content, increased lysosomal lipid uptake and lipolysis in LKO mice. The lysosomal lipolysis program was independent of macro- and chaperone-mediated lipophagy but dependent on cellular lysosome content. In parallel, genetic induction of lysosomal biogenesis in a transformed hepatocyte cell line replicated depletion of intracellular lipid stores. Interestingly bloc1s1 mutant and isogenic corrected HLCs both showed normal lysosomal enzyme activity. However, relative to the isogenic corrected HLCs, mutant bloc1s1 HLCs showed reduced lysosomal content and increased lipid storage. Together these data show distinct phenotypes in human mutant HLCs compared to murine knockout cells. At the same time, human blcs1s1 mutation and murine hepatocyte bloc1s1 depletion disrupt lysosome content and the cellular lipid storage. These data support that BLOC1S1 modulates lysosome content and lipid handling independent of autophagy and show that lysosomal lipolysis is dependent on the cellular content of functional lysosomes.

The importance of early diagnosis and views on newborn screening in metachromatic leukodystrophy: results of a Caregiver Survey in the UK and Republic of Ireland

Metachromatic Leukodystrophy (MLD) is a rare, autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme arylsulfatase A (ARSA). MLD causes progressive loss of motor function and severe decline in cognitive function, leading to premature death. Early diagnosis of MLD provides the opportunity to begin treatment before the disease progresses and causes severe disability. MLD is not currently included in newborn screening (NBS) in the UK.

This study consisted of an online survey, and follow-up semi-structured interviews open to MLD patients or caregivers, aged 18 years and over. The aims of the study were to understand the importance of early diagnosis and to establish the views of families and caregivers of patients with MLD on NBS.

A total of 24 patients took part in the survey, representing 20 families (two families had two children with MLD, one family had three children with MLD). Following on from the survey, six parents participated in the interviews. Our data showed diagnostic delay from first symptoms was between 0 and 3 years, with a median of 1 year (n = 18); during this time deterioration was rapid, especially in earlier onset MLD. In patients with late infantile MLD (n = 10), 50% were wheelchair dependent, 30% were unable to speak, and 50% were tube fed when a diagnosis of MLD was confirmed. In patients with early juvenile MLD (n = 5), over half used a wheelchair some of the time, had uncontrollable crying, and difficulty speaking (all 60%) before or at the time of diagnosis. A high degree of support was expressed for NBS among caregivers, 95% described it as very or extremely important and 86% believed detection of MLD at birth would have changed their child’s future. One parent expressed their gratitude for an early diagnosis as a result of familial MLD screening offered at birth and how it had changed their child’s future: “It did and it absolutely has I will be forever grateful for his early diagnosis thanks to his older sister.”

The rapid rate of deterioration in MLD makes it an essential candidate for NBS, particularly now the first gene therapy (Libmeldy™) has been approved by the European Medicines Agency. Libmeldy™ has also been recommended as a treatment option in England and Wales by the National Institute for Health and Care Excellence (NICE) and is being made available to patients in Scotland via the Scottish Medicines Consortium’s ultra-orphan pathway.

Emerging cellular themes in leukodystrophies

Leukodystrophies are a broad spectrum of neurological disorders that are characterized primarily by deficiencies in myelin formation. Clinical manifestations of leukodystrophies usually appear during childhood and common symptoms include lack of motor coordination, difficulty with or loss of ambulation, issues with vision and/or hearing, cognitive decline, regression in speech skills, and even seizures. Many cases of leukodystrophy can be attributed to genetic mutations, but they have diverse inheritance patterns (e.g., autosomal recessive, autosomal dominant, or X-linked) and some arise from de novo mutations. In this review, we provide an updated overview of 35 types of leukodystrophies and focus on cellular mechanisms that may underlie these disorders. We find common themes in specialized functions in oligodendrocytes, which are specialized producers of membranes and myelin lipids. These mechanisms include myelin protein defects, lipid processing and peroxisome dysfunction, transcriptional and translational dysregulation, disruptions in cytoskeletal organization, and cell junction defects. In addition, non-cell-autonomous factors in astrocytes and microglia, such as autoimmune reactivity, and intercellular communication, may also play a role in leukodystrophy onset. We hope that highlighting these themes in cellular dysfunction in leukodystrophies may yield conceptual insights on future therapeutic approaches.

Plasma arylsulfatase A levels are associated with cognitive function in Parkinson’s disease

Background

Arylsulfatase A (ARSA), a lysosomal enzyme, has been shown to inhibit the aggregation and propagation of α-synuclein (α-syn) through its molecular chaperone function. The relationship between ARSA levels and Parkinson’s disease (PD) in the Chinese Han population remains controversial, and few quantitative research studies have investigated the relationship between plasma ARSA levels and PD.

Objectives

The purpose of this study was to investigate the relationships between ARSA levels and cognitive function in PD patients and to evaluate the association of ARSA and α-syn levels with nonmotor symptoms.

Methods

Enzyme-linked immunosorbent assay (ELISA) was used to measure the plasma ARSA and α-syn levels in 50 healthy controls, 120 PD patients (61 PD patients with no cognitive impairment (PD-NCI) and 59 PD patients with cognitive impairment (PD-CI)). Motor symptoms and nonmotor symptoms (cognitive function, Unified Parkinson’s Disease Rating Scale (UPDRS) score, depression, anxiety, constipation, olfactory dysfunction, sleep disruption, and other symptoms) were assessed with the relevant scales. The Kruskal–Wallis H test was used for comparison between groups, and Pearson/Spearman analysis was used for correlation analysis.

Results

The plasma ARSA concentrations were lower in the PD-CI group than in the PD-NCI group. The plasma α-syn levels in the PD-CI group were higher than those in the healthy control group, and the plasma ARSA levels were correlated with the Mini-Mental State Examination (MMSE scores) and Hoehn and Yahr (H-Y) stage.

Conclusion

We used a quantitative assessment method to show that low plasma ARSA levels and high α-syn levels are related to cognitive impairment in PD patients. Plasma ARSA levels gradually decrease with PD progression.

A model of metformin mitochondrial metabolism in metachromatic leukodystrophy: first description of human Schwann cells transfected with CRISPR-Cas9

Metachromatic leukodystrophy is a neurological lysosomal deposit disease that affects public health despite its low incidence in the population. Currently, few reports are available on pathophysiological events related to enzyme deficiencies and subsequent sulfatide accumulation. This research aims to examine the use of metformin as an alternative treatment to counteract these effects. This was evaluated in human Schwann cells (HSCs) transfected or non-transfected with CRISPR-Cas9, and later treated with sulfatides and metformin. This resulted in transfected HSCs showing a significant increase in cell reactive oxygen species (ROS) production when exposed to 100 µM sulfatides (p = 0.0007), compared to non-transfected HSCs. Sulfatides at concentrations of 10 to 100 µM affected mitochondrial bioenergetics in transfected HSCs. Moreover, these analyses showed that transfected cells showed a decrease in basal and maximal respiration rates after exposure to 100 µM sulfatide. However, maximal and normal mitochondrial respiratory capacity decreased in cells treated with both sulfatide and metformin. This study has provided valuable insights into bioenergetic and mitochondrial effects of sulfatides in HSCs for the first time. Treatment with metformin (500 µM) restored the metabolic activity of these cells and decreased ROS production.

Gene Therapy for Pediatric Neurologic Disease

Pediatric lysosomal and peroxisomal storage disorders, leukodystrophies, and motor neuron diseases can have devastating neurologic manifestations. Despite efforts to exploit cross-correction to treat these monogenic disorders for several decades, definitive treatment has yet to be identified. This review explores recent attempts to transduce autologous hematopoietic stem cells with functional gene or provide therapeutic gene in vivo. Specifically, we discuss the rationale behind efforts to treat pediatric neurologic disorders with gene therapy, outline the specific disorders that have been targeted at this time, and review recent and current clinical investigations with attention to the future direction of therapy efforts.

Treatment of adult metachromatic leukodystrophy model mice using intrathecal administration of type 9 AAV vector encoding arylsulfatase A

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by an arylsulfatase A (ARSA) deficiency and characterized by severe neurological symptoms resulting from demyelination within the central and peripheral nervous systems. We investigated the feasibility and efficacy of intrathecal administration of a type 9 adeno-associated viral vector encoding ARSA (AAV9/ARSA) for the treatment of 6-week-old MLD model mice, which are presymptomatic, and 1-year-old mice, which exhibit neurological abnormalities. Immunohistochemical analysis following AAV9/ARSA administration showed ARSA expression within the brain, with highest activities in the cerebellum and olfactory bulbs. In mice treated at 1 year, alcian blue staining and quantitative analysis revealed significant decreases in stored sulfatide. Behaviorally, mice treated at 1 year showed no improvement in their ability to traverse narrow balance beams as compared to untreated mice. By contrast, MLD mice treated at 6 weeks showed significant decreases in stored sulfatide throughout the entire brain and improved ability to traverse narrow balance beams. These findings suggest intrathecal administration of an AAV9/ARSA vector is a promising approach to treating genetic diseases of the central nervous system, including MLD, though it may be essential to begin therapy before the onset of neurological symptoms.

Leukodystrophies in Children: Diagnosis, Care, and Treatment

Leukodystrophies are a group of genetically determined disorders that affect development or maintenance of central nervous system myelin. Leukodystrophies have an incidence of at least 1 in 4700 live births and significant morbidity and elevated risk of early death. This report includes a discussion of the types of leukodystrophies; their prevalence, clinical presentation, symptoms, and diagnosis; and current and future treatments. Leukodystrophies can present at any age from infancy to adulthood, with variability in disease progression and clinical presentation, ranging from developmental delay to seizures to spasticity. Diagnosis is based on a combination of history, examination, and radiologic and laboratory findings, including genetic testing. Although there are few cures, there are significant opportunities for care and improvements in patient well-being. Rapid advances in imaging and diagnosis, the emergence of and requirement for timely treatments, and the addition of leukodystrophy screening to newborn screening, make an understanding of the leukodystrophies necessary for pediatricians and other care providers for children.

Genetic diseases mimicking multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disorder manifesting as gradual or progressive loss of neurological functions. Most patients present with relapsing-remitting disease courses. Extensive research over recent decades has expounded our insights into the presentations and diagnostic features of MS. Groups of genetic diseases, CADASIL and leukodystrophies, for example, have been frequently misdiagnosed with MS due to some overlapping clinical and radiological features. The delayed identification of these diseases in late adulthood can lead to severe neurological complications. Herein we discuss genetic diseases that have the potential to mimic multiple sclerosis, with highlights on clinical identification and practicing pearls that may aid physicians in recognizing MS-mimics with genetic background in clinical settings.

Safety of Direct Intraparenchymal AAVrh.10-Mediated Central Nervous System Gene Therapy for Metachromatic Leukodystrophy

Metachromatic leukodystrophy, a fatal pediatric neurodegenerative lysosomal storage disease caused by mutations in the arylsulfatase A (ARSA) gene, is characterized by intracellular accumulation of sulfatides in the lysosomes of cells of the central nervous system (CNS). In previous studies, we have demonstrated efficacy of AAVrh.10hARSA, an adeno-associated virus (AAV) serotype rh.10 vector coding for the human ARSA gene to the CNS of a mouse model of the disease, and that catheter-based intraparenchymal administration of AAVrh.10hARSA to the CNS of nonhuman primates (NHPs) white matter results in widespread expression of ARSA. As a formal dose-escalating safety/toxicology study, we assessed the safety of intraparenchymal delivery of AAVrh.10hARSA vector to 12 sites in the white matter of the CNS of NHPs at 2.85 × 10¹⁰ (total low dose, 2.4 × 10⁹ genome copies [gc]/site) and 1.5 × 10¹² (total high dose, 1.3 × 10¹¹ gc/site) gc, compared to AAVrh.10Null (1.5 × 10¹² gc total, 1.3 × 10¹¹ gc/site) as a vector control, and phosphate buffered saline for a sham surgical control. No significant adverse effects were observed in animals treated with low dose AAVrh.10hARSA. However, animals treated with the high dose AAVrh.10ARSA and the high dose Null vector had highly localized CNS abnormalities on magnetic resonance imaging scans at the sites of catheter infusions, and histopathology demonstrated that these sites were associated with infiltrates of T cells, B cells, microglial cells, and/or macrophages. Although these findings had no clinical consequences, these safety data contribute to understanding the dose limits for CNS white matter direct intraparenchymal administration of AAVrh.10 vectors for treatment of CNS disorders.

Changes in plasma arylsulfatase A level as a compensatory biomarker of early Parkinson's disease

Lysosomal dysfunction has been associated with Parkinson's disease (PD). However, the activity of lysosomal enzymes is heterogeneously observed in PD. We investigated whether arylsulfatase A (ARSA) level can be used as a fluid biomarker of PD and can reflect disease progression. Plasma ARSA level was measured in 55 patients with early and drug-naïve PD, 13 patients with late PD, and 14 healthy controls. We compared the plasma ARSA level among the groups and assessed its correlation to clinical parameters and striatal dopamine transporter (DAT) activity. Plasma ARSA level was not correlated with age. The early PD group had higher plasma ARSA level than the control and late PD groups. In a generalized additive model including all patients with PD, the plasma ARSA level showed an inverted U-shape according to disease duration, peaking at 2.19 years. In patients with early PD, plasma ARSA level was positively correlated to parkinsonian motor score and negatively to striatal DAT activity. In summary, plasma ARSA level was elevated in early stage of PD, and elevated plasma ARSA level was correlated to the clinical and imaging markers of nigrostriatal degeneration. These results suggest that ARSA level is a potential biomarker of compensation in early PD.

Advances in the Treatment of Neuronal Ceroid Lipofuscinosis

Neuronal ceroid lipofuscinoses (NCL) represent a class of neurodegenerative disorders involving defective lysosomal processing enzymes or receptors, leading to lysosomal storage disorders, typically characterized by observation of cognitive and visual impairments, epileptic seizures, ataxia, and deterioration of motor skills. Recent success of a biologic (Brineura®) for the treatment of neurologic manifestations of the central nervous system (CNS) has led to renewed interest in therapeutics for NCL, with the goal of ablating or reversing the impact of these devastating disorders. Despite complex challenges associated with CNS therapy, many treatment modalities have been evaluated, including enzyme replacement therapy, gene therapy, stem cell therapy, and small molecule pharmacotherapy. Because the clinical endpoints for the evaluation of candidate therapies are complex and often reliant on subjective clinical scales, the development of quantitative biomarkers for NCLs has become an apparent necessity for the validation of potential treatments. We will discuss the latest findings in the search for relevant biomarkers for assessing disease progression. For this review, we will focus primarily on recent pre-clinical and clinical developments for treatments to halt or cure these NCL diseases. Continued development of current therapies and discovery of newer modalities will be essential for successful therapeutics for NCL.

AREAS COVERED

The reader will be introduced to the NCL subtypes, natural histories, experimental animal models, and biomarkers for NCL progression; challenges and different therapeutic approaches, and the latest pre-clinical and clinical research for therapeutic development for the various NCLs. This review corresponds to the literatures covering the years from 1968 to mid-2019, but primarily addresses pre-clinical and clinical developments for the treatment of NCL disease in the last decade and as a follow-up to our 2013 review of the same topic in this journal.

EXPERT OPINION

Much progress has been made in the treatment of neurologic diseases, such as the NCLs, including better animal models and improved therapeutics with better survival outcomes. Encouraging results are being reported at symposiums and in the literature, with multiple therapeutics reaching the clinical trial stage for the NCLs. The potential for a cure could be at hand after many years of trial and error in the preclinical studies. The clinical development of enzyme replacement therapy (Brineura® for CLN2), immunosuppression (CellCept® for CLN3), and gene therapy vectors (for CLN1, CLN2, CLN3, and CLN6) are providing encouragement to families that have a child afflicted with NCL. We believe that successful therapies in the future may involve the combination of two or more therapeutic modalities to provide therapeutic benefit especially as the patients grow older.

Measurement of recombinant human arylsulfatase A and leukocyte sulfatase activities by analytical isotachophoresis

Metachromatic Leukodystrophy (MLD) and Multiple Sulfatase Deficiency (MSD) are rare and ultra-rare lysosomal storage diseases. Due to enzyme defects, patients are unable to split the sulfategroup from the respective substrates. In MSD all sulfatases are affected due to a defect of the Sulfatase Modifying Factor 1 (SUMF1) gene coding for the formylglycine generating enzyme (FGE) necessary for the modification of the active site of sulfatases. In MLD mutations in the arylsulfatase A (ARSA) gene cause ARSA deficiency with subsequent accumulation of 3-sulfogalactocerebroside especially in oligodendrocytes. The clinical consequence is demyelination and a devastating neurological disease. Enzyme replacement therapy (ERT) with recombinant human arylsulfatase A (rhARSA), gene therapy, and stem cell transplantation are suggested as new therapeutic options. The aim of our study was to characterize rhARSA concerning its substrate specificity using analytical isotachophoresis (ITP). Substrate specificity could be demonstrated by sulfate splitting from the natural substrates 3-sulfogalactocerebroside and ascorbyl-2-sulfate and the artificial substrate p-nitrocatecholsulfate, whereas galactose-6-sulfate, a substrate of galactose-6‑sulfurylase, was totally resistant. In contrast, leukocyte extracts of healthy donors were able to split sulfate also from galactose-6-sulfate. The ITP method allows therefore a rapid and simple differentiation between samples of MLD and MSD patients and healthy donors. Therefore, the isotachophoretic diagnostic assay from leukocyte extracts described here provides a fast and efficient way for the diagnosis of MLD and MSD patients and an elegant system to differentiate between these diseases in one assay.

AAVrh.10-Mediated APOE2 Central Nervous System Gene Therapy for APOE4-Associated Alzheimer's Disease

Alzheimer's disease (AD) is a progressive degenerative neurological disorder affecting nearly one in nine elderly people in the United States. Population studies have shown that an inheritance of the apolipoprotein E (APOE) variant APOE4 allele increases the risk of developing AD, whereas APOE2 homozygotes are protected from late-onset AD. It was hypothesized that expression of the "protective" APOE2 variant by genetic modification of the central nervous system (CNS) of APOE4 homozygotes could reverse or prevent progressive neurologic damage. To assess the CNS distribution and safety of APOE2 gene therapy for AD in a large-animal model, intraparenchymal, intracisternal, and intraventricular routes of delivery to the CNS of nonhuman primates of AAVrh.10hAPOE2-HA, an AAVrh.10 serotype coding for an HA-tagged human APOE2 cDNA sequence, were evaluated. To evaluate the route of delivery that achieves the widest extent of APOE2 expression in the CNS, the expression of APOE2 in the CNS was evaluated 2 months following vector administration for APOE2 DNA, mRNA, and protein. Finally, using conventional toxicology assays, the safety of the best route of delivery was assessed. The data demonstrated that while all three routes are capable of mediating ApoE2 expression in AD relevant regions, intracisternal delivery of AAVrh.10hAPOE2-HA safely mediated wide distribution of ApoE2 with the least invasive surgical intervention, thus providing the optimal strategy to deliver vector-mediated human APOE2 to the CNS.

Gene therapy for metachromatic leukodystrophy

Leukodystrophies (LDs) are rare, often devastating genetic disorders with neurologic symptoms. There are currently no disease-specific therapeutic approaches for these diseases. In this review we use metachromatic leukodystrophy as an example to outline in the brief the therapeutic approaches to MLD that have been tested in animal models and in clinical trials, such as enzyme-replacement therapy, bone marrow/umbilical cord blood transplants, ex vivo transplantation of genetically modified hematopoietic stem cells, and gene therapy. These studies suggest that to be successful the ideal therapy for MLD must provide persistent and high level expression of the deficient gene, arylsulfatase A in the CNS. Gene therapy using adeno-associated viruses is therefore the ideal choice for clinical development as it provides the best balance of potential for efficacy with reduced safety risk. Here we have summarized the published preclinical data from our group and from others that support the use of a gene therapy with AAVrh.10 serotype for clinical development as a treatment for MLD, and as an example of the potential of gene therapy for LDs especially for Krabbe disease, which is the focus of this special issue. © 2016 Wiley Periodicals, Inc.

Four novel ARSA gene mutations with pathogenic impacts on metachromatic leukodystrophy: a bioinformatics approach to predict pathogenic mutations

Metachromatic leukodystrophy (MLD) disorder is a rare lysosomal storage disorder that leads to severe neurological symptoms and an early death. MLD occurs due to the deficiency of enzyme arylsulfatase A (ARSA) in leukocytes, and patients with MLD excrete sulfatide in their urine. In this study, the ARSA gene in 12 non-consanguineous MLD patients and 40 healthy individuals was examined using polymerase chain reaction sequencing. Furthermore, the structural and functional effects of new mutations on ARSA were analyzed using SIFT (sorting intolerant from tolerant), I-Mutant 2, and PolyPhen bioinformatics software. Here, 4 new pathogenic homozygous mutations c.585G>T, c.661T>A, c.849C>G, and c.911A>G were detected. The consequence of this study has extended the genotypic spectrum of MLD patients, paving way to a more effective method for carrier detection and genetic counseling.

Childhood leukodystrophies: A literature review of updates on new definitions, classification, diagnostic approach and management

Childhood leukodystrophies are a growing category of neurological disorders in pediatric neurology practice. With the help of new advanced genetic studies such as whole exome sequencing (WES) and whole genome sequencing (WGS), the list of childhood heritable white matter disorders has been increased to more than one hundred disorders. During the last three decades, the basic concepts and definitions, classification, diagnostic approach and medical management of these disorders much have changed. Pattern recognition based on brain magnetic resonance imaging (MRI), has played an important role in this process. We reviewed the last Global Leukodystrophy Initiative (GLIA) expert opinions in definition, new classification, diagnostic approach and medical management including emerging treatments for pediatric leukodystrophies.

Current Perspective of Stem Cell Therapy in Neurodegenerative and Metabolic Diseases

Neurodegenerative diseases have been an unsolved riddle for quite a while; to date, there are no proper and effective curative treatments and only palliative and symptomatic treatments are available to treat these illnesses. The absence of therapeutic treatments for neurodegenerative ailments has huge economic hit and strain on the society. Pharmacotherapies and various surgical procedures like deep brain stimulation are being given to the patient, but they are only effective for the symptoms and not for the diseases. This paper reviews the recent studies and development of stem cell therapy for neurodegenerative disorders. Stem cell-based treatment is a promising new way to deal with neurodegenerative diseases. Stem cell transplantation can advance useful recuperation by delivering trophic elements that impel survival and recovery of host neurons in animal models and patients with neurodegenerative maladies. Several mechanisms, for example, substitution of lost cells, cell combination, release of neurotrophic factor, proliferation of endogenous stem cell, and transdifferentiation, may clarify positive remedial results. With the current advancements in the stem cell therapies, a new hope for the cure has come out since they have potential to be a cure for the same. This review compiles stem cell therapy recent conceptions in neurodegenerative and neurometabolic diseases and updates in this field. Graphical Absract ᅟ.

The spectrum of leukodystrophies in children: Experience at a tertiary care centre from North India

Objective:

The objective of this study is to retrospectively collect and then describe the clinico-radiographical profile of confirmed cases of leukodystrophy who presented over a 5-year period to a tertiary care teaching hospital in North India.

Materials and Methods:

The case records of 80 confirmed cases of leukodystrophy were reviewed and the cases have been described in terms of their clinical presentation and neuroimaging findings.

Results:

The cases have been grouped into five categories: Hypomyelinating, demyelinating, disorders with vacuolization, cystic, and miscellaneous. The commonest leukodystrophies are megalencephalic leukoencephalopathy with subcortical cysts (MLC), Pelizaeus-Merzbacher disease (PMD), and metachromatic leukodystrophy (MLD). A notable proportion of hypomyelinating disorders were uncharacterized.

Conclusions:

Leukodystrophies at this point of time have no definite cure. They have a progressively downhill clinical course. Early diagnosis is imperative for appropriate genetic counseling. A simplified approach to diagnose common leukodystrophies has also been provided. It is important to develop a registry, which can provide valuable epidemiological data to prioritize research in this field, which has many unanswered questions.

Emerging treatments for pediatric leukodystrophies

The leukodystrophies are a heterogeneous group of inherited disorders with broad clinical manifestations and variable pathologic mechanisms. Improved diagnostic methods have allowed identification of the underlying cause of these diseases, facilitating identification of their pathologic mechanisms. Clinicians are now able to prioritize treatment strategies and advance research in therapies for specific disorders. Although only a few of these disorders have well-established treatments or therapies, a number are on the verge of clinical trials. As investigators are able to shift care from symptomatic management of disorders to targeted therapeutics, the unmet therapeutic needs could be reduced for these patients.

Disease specific therapies in leukodystrophies and leukoencephalopathies

Leukodystrophies are a heterogeneous, often progressive group of disorders manifesting a wide range of symptoms and complications. Most of these disorders have historically had no etiologic or disease specific therapeutic approaches. Recently, a greater understanding of the pathologic mechanisms associated with leukodystrophies has allowed clinicians and researchers to prioritize treatment strategies and advance research in therapies for specific disorders, some of which are on the verge of pilot or Phase I/II clinical trials. This shifts the care of leukodystrophy patients from the management of the complex array of symptoms and sequelae alone to targeted therapeutics. The unmet needs of leukodystrophy patients still remain an overwhelming burden. While the overwhelming consensus is that these disorders collectively are symptomatically treatable, leukodystrophy patients are in need of advanced therapies and if possible, a cure.

Sulfatide levels correlate with severity of neuropathy in metachromatic leukodystrophy

Objective

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disorder due to deficient activity of arylsulfatase A (ASA) that causes accumulation of sulfatide and lysosulfatide. The disorder is associated with demyelination and axonal loss in the central and peripheral nervous systems. The late infantile form has an early-onset, rapidly progressive course with severe sensorimotor dysfunction. The relationship between the degree of nerve damage and (lyso)sulfatide accumulation is, however, not established.

Methods

In 13 children aged 2–5 years with severe motor impairment, markedly elevated cerebrospinal fluid (CSF) and sural nerve sulfatide and lysosulfatide levels, genotype, ASA mRNA levels, residual ASA, and protein cross-reactive immunological material (CRIM) confirmed the diagnosis. We studied the relationship between (lyso)sulfatide levels and (1) the clinical deficit in gross motor function (GMFM-88), (2) median and peroneal nerve motor and median and sural nerve sensory conduction studies (NCS), (3) median and tibial nerve somatosensory evoked potentials (SSEPs), (4) sural nerve histopathology, and (5) brain MR spectroscopy.

Results

Eleven patients had a sensory-motor demyelinating neuropathy on electrophysiological testing, whereas two patients had normal studies. Sural nerve and CSF (lyso)sulfatide levels strongly correlated with abnormalities in electrophysiological parameters and large myelinated fiber loss in the sural nerve, but there were no associations between (lyso)sulfatide levels and measures of central nervous system (CNS) involvement (GMFM-88 score, SSEP, and MR spectroscopy).

Interpretation

Nerve and CSF sulfatide and lysosulfatide accumulation provides a marker of disease severity in the PNS only; it does not reflect the extent of CNS involvement by the disease process. The magnitude of the biochemical disturbance produces a continuously graded spectrum of impairments in neurophysiological function and sural nerve histopathology.

Metachromatic leukodystrophy: Disease spectrum and approaches for treatment

Metachromatic leukodystrophy is an inherited lysosomal disorder caused by recessive mutations in ARSA encoding arylsulfatase A. Low activity of arylsulfatase A results in the accumulation of sulfatides in the central and peripheral nervous system leading to demyelination. The disease is classified in a late-infantile, juvenile and adult onset type based on the age of onset, all characterized by a variety of neurological symptoms, which eventually lead to death if untreated. There is no curative treatment for all types and stages. This review discusses diagnostic process and efficacy of current and possible future therapies such as hematopoietic stem cell transplantation, enzyme replacement therapy and gene therapy. A systematic evaluation regarding the efficacy of hematopoietic stem cell transplantation and a longer follow up period for gene therapy are needed to come to a general conclusion and improve treatment options for metachromatic leukodystrophy.

Lentivector integration sites in ependymal cells from a model of metachromatic leukodystrophy: non-B DNA as a new factor influencing integration

The blood–brain barrier controls the passage of molecules from the blood into the central nervous system (CNS) and is a major challenge for treatment of neurological diseases. Metachromatic leukodystrophy is a neurodegenerative lysosomal storage disease caused by loss of arylsulfatase A (ARSA) activity. Gene therapy via intraventricular injection of a lentiviral vector is a potential approach to rapidly and permanently deliver therapeutic levels of ARSA to the CNS. We present the distribution of integration sites of a lentiviral vector encoding human ARSA (LV-ARSA) in murine brain choroid plexus and ependymal cells, administered via a single intracranial injection into the CNS. LV-ARSA did not exhibit a strong preference for integration in or near actively transcribed genes, but exhibited a strong preference for integration in or near satellite DNA. We identified several genomic hotspots for LV-ARSA integration and identified a consensus target site sequence characterized by two G-quadruplex-forming motifs flanking the integration site. In addition, our analysis identified several other non-B DNA motifs as new factors that potentially influence lentivirus integration, including human immunodeficiency virus type-1 in human cells. Together, our data demonstrate a clinically favorable integration site profile in the murine brain and identify non-B DNA as a potential new host factor that influences lentiviral integration in murine and human cells.

National variation in costs and mortality for leukodystrophy patients in US children's hospitals

BACKGROUND

Inherited leukodystrophies are progressive, debilitating neurological disorders with few treatment options and high mortality rates. Our objective was to determine national variation in the costs for leukodystrophy patients and to evaluate differences in their care.

METHODS

We developed an algorithm to identify inherited leukodystrophy patients in deidentified data sets using a recursive tree model based on International Classification of Disease, 9th Edition, Clinical Modification, diagnosis and procedure charge codes. Validation of the algorithm was performed independently at two institutions, and with data from the Pediatric Health Information System (PHIS) of 43 US children's hospitals, for a 7-year period between 2004 and 2010.

RESULTS

A recursive algorithm was developed and validated, based on six International Classification of Disease, 9th Edition, Clinical Modification, codes and one procedure code that had a sensitivity up to 90% (range 61-90%) and a specificity up to 99% (range 53-99%) for identifying inherited leukodystrophy patients. Inherited leukodystrophy patients comprise 0.4% of admissions to children's hospitals and 0.7% of costs. During 7 years, these patients required $411 million of hospital care, or $131,000/patient. Hospital costs for leukodystrophy patients varied at different institutions, ranging from two to 15 times more than the average pediatric patient. There was a statistically significant correlation between higher volume and increased cost efficiency. Increased mortality rates had an inverse relationship with increased patient volume that was not statistically significant.

CONCLUSIONS

We developed and validated a code-based algorithm for identifying leukodystrophy patients in deidentified national datasets. Leukodystrophy patients account for $59 million of costs yearly at children's hospitals. Our data highlight potential to reduce unwarranted variability and improve patient care.

Direct tandem mass spectrometric profiling of sulfatides in dry urinary samples for screening of metachromatic leukodystrophy

BACKGROUND

Prediagnostic steps in suspected metachromatic leukodystrophy (MLD) rely on clinical chemical methods other than enzyme assays. We report a new diagnostic method which evaluates changes in the spectrum of molecular types of sulfatides (3-O-sulfogalactosyl ceramides) in MLD urine.

METHODS

The procedure allows isolation of urinary sulfatides by solid-phase extraction on DEAE-cellulose membranes, transportation of a dry membrane followed by elution and tandem mass spectrometry (MS/MS) analysis in the clinical laboratory. Major sulfatide isoforms are normalized to the least variable component of the spectrum, which is the indigenous C18:0 isoform. This procedure does not require the use of specific internal standards and minimizes errors caused by sample preparation and measurement.

RESULTS

Urinary sulfatides were analyzed in a set of 21 samples from patients affected by sulfatidosis. The combined abundance of the five most elevated isoforms, C22:0, C22:0-OH, C24:0, C24:1-OH, and C24:0-OH sulfatides, was found to give the greatest distinction between MLD-affected patients and a control group.

CONCLUSIONS

The method avoids transportation of liquid urine samples and generates stable membrane-bound sulfatide samples that can be stored at ambient temperature. MS/MS sulfatide profiling targeted on the most MLD-representative isoforms is simple with robust results and is suitable for screening.

Role of sulfatide in normal and pathological cells and tissues

Sulfatide is 3-O-sulfogalactosylceramide that is synthesized by two transferases (ceramide galactosyltransferase and cerebroside sulfotransferase) from ceramide and is specifically degraded by a sulfatase (arylsulfatase A). Sulfatide is a multifunctional molecule for various biological fields including the nervous system, insulin secretion, immune system, hemostasis/thrombosis, bacterial infection, and virus infection. Therefore, abnormal metabolism or expression change of sulfatide could cause various diseases. Here, we discuss the important biological roles of sulfatide in the nervous system, insulin secretion, immune system, hemostasis/thrombosis, cancer, and microbial infections including human immunodeficiency virus and influenza A virus. Our review will be helpful to achieve a comprehensive understanding of sulfatide, which serves as a fundamental target of prevention of and therapy for nervous disorders, diabetes mellitus, immunological diseases, cancer, and infectious diseases.

Developing treatment options for metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) represents a devastating lysosomal storage disease characterized by intralysosomal accumulation of the sphingolipid sulfatide in various tissues. Three types of the disease are currently distinguished: the late-infantile, which is the most commonly observed, the juvenile and the adult type. Demyelination represents the main histopathological feature of the disorder, leading to neurological impairment with no curative treatment currently available. Nevertheless, the increased scientific interest on the disease has led to the experimental use of innovative therapeutic approaches in animal models, aiming to provide an effective therapeutic regimen for human patients, as well. This paper provides an overview of developing treatment options among patients with MLD. Apart from hematopoietic stem cell transplantation, already in use for decades, other recent data discussed includes umbilical cord blood and stem cell transplantation, enzyme replacement therapy, gene therapy and autologous hematopoietic transplantation of genetically modified stem cells. Gene therapy with oligodedroglial, neural progenitor, embryonic and microencapsulated recombinant cells represents add-on treatment options still on experimental level.

The natural course of gross motor deterioration in metachromatic leukodystrophy

AIM

Motor deterioration is a key feature in metachromatic leukodystrophy (MLD). The lack of data about its natural course impedes evaluation of therapeutic interventions. This study aimed to provide data about motor decline in MLD.

METHOD

Fifty-nine patients (27 males, 32 females) with MLD (21 with late-infantile MLD and 38 with juvenile MLD) were recruited within a nationwide survey (the German LEUKONET). Median (range) age at onset was 17 months (9-27) for the group with late-infantile MLD and 6 years 2 months (2y 11mo-14y) for the group with juvenile MLD. Gross motor function was assessed using the Gross Motor Function Classification for MLD.

RESULTS

In late-infantile MLD, all patients showed loss of all gross motor function until 3 years 4 months of age. Patients with juvenile MLD showed a more variable and significantly longer motor decline (p<0.001). For a patient with the juvenile form showing first gait disturbances, the probability of remaining stable for more than 1 year was 84%, and 51% for more than 2 years. Having lost independent walking, subsequent motor decline was as steep as in the late-infantile form (median 5 mo, interquartile range 3-22).

INTERPRETATION

The course of motor disease was more variable in juvenile MLD with respect to onset and dynamics. However, the motor decline after the loss of independent walking was similarly steep in both forms. These data can serve as a reference for clinical studies that are topics of current research and allow definition of inclusion/exclusion criteria.

Development and reliability of a classification system for gross motor function in children with metachromatic leucodystrophy

AIM

Motor deterioration is a key feature of late infantile and juvenile metachromatic leucodystrophy (MLD). Assessment of the disease course implies the need for a standardized description of motor decline. The aim of this study was to establish a classification system for gross motor function in MLD and to assess its interrater reliability.

METHOD

The Gross Motor Function Classification in MLD (GMFC-MLD) was modelled analogous to the Gross Motor Function Classification System in cerebral palsy. Motor data from 59 individuals (27 male; 32 female) with MLD (21 late infantile; 38 juvenile) born between 1970 and 2007 were gathered from a nationwide survey and classified by six independent raters. Median age at onset was 17 months (range 9-27 mo) for the late infantile group and 74 months (35-168 mo) for the juvenile group.

RESULTS

The GMFC-MLD consists of seven levels and is applicable from the age of 18 months. It represents all clinically relevant stages from normal (level 0) to loss of all gross motor function (level 6). The kappa coefficient was 0.90 for overall rater agreement. There were no significant differences between level-specific kappa coefficients.

INTERPRETATION

The GMFC-MLD is a highly reliable, feasible tool for standardized assessment of gross motor function in MLD which can be used for the description of the natural course of the disease and for evaluation of therapeutic options such as stem cell transplantation and enzyme replacement, both of which are topics of current research.

Haematopoietic stem cell transplantation does not retard disease progression in the psycho-cognitive variant of late-onset metachromatic leukodystrophy

Haematopoietic stem cell transplantation has an unproven role in the management of late-onset metachromatic leukodystrophy: theoretically justified through the engraftment of enzyme-replete haematopoietic progenitors and restoration of capacity for sulphatide catabolism in neural tissue through enzyme recapture, the long-term outcome is unknown. The rarity of the psycho-cognitive variant and slow progression of late-onset disease impairs evaluation of treatment. We report detailed clinical and neuropsychological assessments after haematopoietic stem-cell transplantation in a patient with a late-onset psycho-cognitive form of metachromatic leukodystrophy. Cognitive decline, indistinguishable from the natural course of the disease, was serially documented over 11 years despite complete donor chimaerism and correction of leukocyte arylsulphatase A to wild type values; subtle motor deterioration was similarly noted and progressive cerebral volume loss was evident upon magnetic resonance imaging. Sensory nerve conduction deteriorated 17 months post-transplantation with apparent stabilisation at 11-year review. Haematopoietic stem-cell transplantation was ineffective for this rare attenuated variant of metachromatic leukodystrophy. In the few patients identified pre-symptomatically or with early-phase disease, clear recommendations are lacking; when transplantation is considered, umbilical cord blood grafts from enzyme-replete donors with adjunctive mesenchymal stem cell infusions from the same source may be preferable. Improved outcomes will depend on enhanced awareness and early diagnosis of the disease, so that promising interventions such as genetically modified, autologous stem cell transplantation have the best opportunity of success.

Adult metachromatic leukodystrophy treated by allo-SCT and a review of the literature

Five patients with adult-onset metachromatic leukodystrophy (MLD) underwent allo-SCT. Conditioning was reduced in intensity and grafts were obtained from voluntary unrelated donors. All but one graft were depleted of T-lymphocytes. Patient age at transplantation varied from 18 to 29 (median, 27) years. Two patients rejected their graft and MLD progressed. The recipient of the unmanipulated graft converted to complete donor chimerism with normalization of arylsulphatase A (ARSA) levels. Despite ARSA normalization, he deteriorated. Another patient was a mixed chimera. Following escalated doses of donor lymphocyte infusions he converted to complete donor chimerism. His levels of ARSA correlated positively with the percentage of donor cells and MLD was not progressive. The fifth patient died after 35 days from complications associated with GVHD. We conclude that results of allo-SCT in symptomatic MLD patients are poor. However, allo-SCT may stop progression of MLD in selected patients.

Metachromatic leukodystrophy: a case of triplets with the late infantile variant and a systematic review of the literature

Metachromatic leukodystrophy is a rare disorder with great clinical variability. We report the first case of triplets with the late infantile form of the disease and their systematic progression of symptoms. We reviewed the literature and identified all human studies that reported new cases since 1921. We analyzed survival by decade to assess the impact of historical changes in the management of care. Mean age at death and the 5-year survival from onset of symptoms for late infantile, juvenile, and adult phenotypes were 4.2 years and 24.9%, 17.4 years and 70.3%, and 43.1 years and 88.6%, respectively. The 5-year survival of cases reported after 1990 was significantly better than cases reported before 1970 in all subtypes of metachromatic leukodystrophy (late infantile: 52% vs 14%, juvenile: 100% vs 46%, adult: 95% vs 67%). Survival in the late infantile subtype was worse than that in other subtypes. Survival significantly improved over time in all subtypes.

Efficient intracerebral delivery of AAV5 vector encoding human ARSA in non-human primate

Metachromatic leukodystrophy (MLD) is a lethal neurodegenerative disease caused by a deficiency in the lysosomal arylsulfatase A (ARSA) enzyme leading to the accumulation of sulfatides in glial and neuronal cells. We previously demonstrated in ARSA-deficient mice that intracerebral injection of a serotype 5 adeno-associated vector (AAV) encoding human ARSA corrects the biochemical, neuropathological and behavioral abnormalities. However, before considering a potential clinical application, scaling-up issues should be addressed in large animals. Therefore, we performed intracerebral injection of the same AAV vector (total dose of 3.8 x 10(11) or 1.9 x 10(12) vector genome, three sites of injection in the right hemisphere, two deposits per site of injection) into three selected areas of the centrum semiovale white matter, or in the deep gray matter nuclei (caudate nucleus, putamen, thalamus) of six non-human primates to evaluate vector distribution, as well as expression and activity of human ARSA. The procedure was perfectly tolerated, without any adverse effect or change in neurobehavioral examination. AAV vector was detected in a brain volume of 12-15 cm(3) that corresponded to 37-46% of the injected hemisphere. ARSA enzyme was expressed in multiple interconnected brain areas over a distance of 22-33 mm. ARSA activity was increased by 12-38% in a brain volume that corresponded to 50-65% of injected hemisphere. These data provide substantial evidence for potential benefits of brain gene therapy in patients with MLD.

Inherited metabolic disorders involving the eye: a clinico-biochemical perspective

The diagnosis of inborn errors of metabolism is challenging for most physicians. Improvements in medical technology and greater knowledge of the human genome are resulting in significant changes in the diagnosis, classification, and treatment of inherited metabolic disorders (IMDs). Many known inborn errors of metabolism will be recognised earlier or treated differently because of these changes. It is important that physicians recognise the clinical signs of IMDs and know when to propose advanced laboratory testing or referral to a higher centre for better patient management. Ocular manifestations occur in various metabolic disorders. Although there is an extensive understanding of many inborn errors of metabolism at the biochemical, molecular, and metabolic levels, little is known about their pathogenesis. In particular, how systemic metabolic disease contributes to ocular defects remains to be elucidated in IMDs. The occurrence of eye abnormalities could be due to direct toxic mechanisms of abnormal metabolic products or accumulation of normal metabolites by errors of synthetic pathways or by deficient energy metabolism. A detailed ophthalmological assessment is essential. Definitive diagnosis and management of patients with IMDs is ideally carried out by a combination of specialists, including an ophthalmologist, paediatrician, biochemist, and medical geneticist. Recent advances in the diagnosis and treatment of IMDs have substantially improved the prognosis for many of these conditions.

Metachromatic leukodystrophy: genetics, pathogenesis and therapeutic options

Metachromatic leukodystrophy is a lysosomal storage disease caused by the deficiency of arylsulphatase A (ASA). This leads to storage of the membrane lipid sulphatide, which is abundant in myelin. A pathological hallmark of the disease is demyelination, causing various and ultimately lethal neurological symptoms. Today more than 110 mutations in the ASA gene have been identified, of which only three are frequent. Patients homozygous for alleles, which do not allow for the synthesis of functional ASA always suffer from the severe form of the disease, whereas alleles allowing the expression of residual enzyme activity are associated with the later onset juvenile or adult forms of metachromatic leukodystrophy. In addition, there are other as yet unknown genetic or epigenetic factors modifying the phenotype substantially. ASA-deficient mice have been generated as a model of metachromatic leukodystrophy. These mice store sulphatide and show progressive neurological symptoms, but do not demyelinate. This animal model was recently improved using a transgenic approach, which generated mice in which sulphatide synthesis in myelin-producing cells is enhanced. This new animal model reflects the pathological characteristics of the human disease. ASA-deficient mice have been used in various therapeutic trials involving enzyme replacement, haematopoietic stem-cell-based gene therapy and direct injections of ASA-expressing viral vectors into the brain. These animal studies have paved the way for future clinical studies of enzyme replacement and gene therapy.

CONCLUSION

For many years this devastating disorder was considered untreatable and the outlook for patients was poor. Within a comparatively short period of time since the ASA gene was cloned in 1989, genetic and biochemical studies and data generated from newly developed animal models have led to the first clinical trials. It is hoped that these developments will prove beneficial for patients.

Induction of tolerance to human arylsulfatase A in a mouse model of metachromatic leukodystrophy

A deficiency of arylsulfatase A (ASA) causes metachromatic leukodystrophy (MLD), a lysosomal storage disorder characterized by accumulation of sulfatide, a severe neurological phenotype and early death. The efficacy of enzyme replacement therapy (ERT) has previously been determined in ASA knockout (ASA-/-) mice representing the only available animal model for MLD. Repeated intravenous injection of human ASA (hASA) improved the nervous system pathology and function, but also elicited a progressive humoral immune response leading to treatment resistance, anaphylactic reactions, and high mortality. In contrast to ASA-/- mice, most MLD patients express mutant hASA which may entail immunological tolerance to substituted wildtype hASA and thus protect from immunological complications. To test this notion, a cysteine-to-serine substitution was introduced into the active site of the hASA and the resulting inactive hASA-C69S variant was constitutively expressed in ASA-/- mice. Mice with sub-to supranormal levels of mutant hASA expression were analyzed. All mice, including those showing transgene expression below the limit of detection, were immunologically unresponsive to injected hASA. More than 100-fold overexpression did not induce an overt new phenotype except occasional intralysosomal deposition of minor amounts of glycogen in hepatocytes. Furthermore, long-term, low-dose ERT reduced sulfatide storage in peripheral tissues and the central nervous system indicating that high levels of extracellular mutant hASA do not prevent cellular uptake and lysosomal targeting of substituted wildtype hASA. Due to the tolerance to hASA and maintenance of the MLD-like phenotype, the novel transgenic strain may be particularly advantageous to assess the benefit and risk of long-term ERT.

Metabolic responses of sulfatide and related glycolipids in Madin-Darby canine kidney (MDCK) cells under osmotic stresses

Incorporation of (35)S-sulfate into the polar molecular species of sulfoglycolipids (SM4s) in Madin-Darby canine kidney cells increased in a hypertonic medium (500 mOsm/L) supplemented with sodium chloride. The unknown sulfoglycolipid (SX) was identified as GlcCer sulfate based on the results of TLC, GLC, and mass spectra. The synthesis of SX increased in the hypotonic medium unlike that of SM4s and SM3. TLC showed that hypertonic stress induced the accumulation of GalCer as a precursor of SM4s, whereas hypotonic stress increased GlcCer as a precursor of GlcCer sulfate. The level of ceramide as a precursor of both GalCer and GlcCer increased under hypertonic stress and decreased under hypotonic stress. Cerebroside sulfotransferase mRNA was shown to be elevated in the hyperosmotic condition but not in the hypotonic condition. The increase in SM4s under hypertonic stress was induced by the activation of both the ceramide galactosyltransferase and the cerebroside sulfotransferase genes, whereas the increase in GlcCer sulfate under hypotonic stress was caused by the accumulation of GlcCer as the result of activation of ceramide glucosyltransferase.