Single Systemic Administration of a Gene Therapy Leading to Disease Treatment in Metachromatic Leukodystrophy Arsa Knock-Out Mice.

Metachromatic leukodystrophy (MLD) is a rare, inherited, demyelinating lysosomal storage disorder caused by mutations in the arylsulfatase-A gene (ARSA). In patients, levels of functional ARSA enzyme are diminished and lead to deleterious accumulation of sulfatides. Herein, we demonstrate that intravenous administration of HSC15/ARSA restored the endogenous murine biodistribution of the corresponding enzyme, and overexpression of ARSA corrected disease biomarkers and ameliorated motor deficits in Arsa KO mice of either sex. In treated Arsa KO mice, when compared with intravenously administered AAV9/ARSA, significant increases in brain ARSA activity, transcript levels, and vector genomes were observed with HSC15/ARSA Durability of transgene expression was established in neonate and adult mice out to 12 and 52 weeks, respectively. Levels and correlation between changes in biomarkers and ARSA activity required to achieve functional motor benefit was also defined. Finally, we demonstrated blood-nerve, blood-spinal and blood-brain barrier crossing as well as the presence of circulating ARSA enzyme activity in the serum of healthy nonhuman primates of either sex. Together, these findings support the use of intravenous delivery of HSC15/ARSA-mediated gene therapy for the treatment of MLD.SIGNIFICANCE STATEMENT Herein, we describe the method of gene therapy adeno-associated virus (AAV) capsid and route of administration selection leading to an efficacious gene therapy in a mouse model of metachromatic leukodystrophy. We demonstrate the therapeutic outcome of a new naturally derived clade F AAV capsid (AAVHSC15) in a disease model and the importance of triangulating multiple end points to increase the translation into higher species via ARSA enzyme activity and biodistribution profile (with a focus on the CNS) with that of a key clinically relevant biomarker.

Neurodevelopmental Outcome after Hematopoietic Cell Transplantation in Inborn Errors of Metabolism: Current Considerations and Future Perspectives.

Inborn errors of metabolism (IEM) comprise an assorted group of inherited diseases, some of which are due to disordered lysosomal or peroxisomal function and some of which might be improved following hematopoietic cell transplantation (HCT). In these disorders the onset in infancy or early childhood is typically accompanied by rapid deterioration, resulting in early death in the more severe phenotypes. Timely diagnosis and immediate referral to an IEM specialist are essential steps in optimal management. Treatment recommendations are based on the diagnosis, its phenotype, rate of progression, prior extent of disease, family values, and expectations, and the risks and benefits associated with available therapies, including HCT. International collaborative efforts are of utmost importance in determining outcomes of therapy for these rare diseases, and have improved those outcomes significantly over the last decades. In this review, we will focus on the neurodevelopmental outcomes after HCT in IEM, providing an international perspective on progress, limitations, and future directions.

Neurodevelopmental outcomes of umbilical cord blood transplantation in metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is an inherited demyelinating disease that causes progressive neurologic deterioration, leading to severe motor disability, developmental regression, seizures, blindness, deafness, and death. The disease presents as a late-infantile, juvenile, or adult form. Hematopoietic stem cell transplantation has been shown to slow disease progression. The purpose of this longitudinal study was to evaluate long-term treatment outcomes after unrelated donor umbilical cord blood (UCB) transplantation in pediatric patients according to disease burden and age at onset (ie, late-infantile versus juvenile). Engraftment, survival, treatment-related toxicity, graft-versus-host disease, neurophysiologic measures, and neurodevelopmental function were assessed. To evaluate whether signal intensity abnormalities on magnetic resonance imaging (ie, modified Loes scores) predict post-transplant cognitive and gross motor development, a general linear mixed model was fit to the data. Twenty-seven patients underwent transplantation after myeloablative chemotherapy; 24 patients engrafted after the initial transplantation. Seven patients died of infection, regimen-related toxicity, or disease progression. Twenty patients (6 with late-infantile onset and 14 with juvenile onset) were followed for a median of 5.1 years (range, 2.4 to 14.7). We found that patients with motor function symptoms at the time of transplant did not improve after transplantation. Brainstem auditory evoked responses, visual evoked potentials, electroencephalogram, and/or peripheral nerve conduction velocities stabilized or improved in juvenile patients but continued to worsen in most patients with the late-infantile presentation. Pretransplant modified Loes scores were highly correlated with developmental outcomes and predictive of cognitive and motor function. Children who were asymptomatic at the time of transplantation benefited most from the procedure. Children with juvenile onset and minimal symptoms showed stabilization or deterioration of motor skills but maintained cognitive skills. Overall, children with juvenile onset had better outcomes than those with late-infantile onset. As in other leukodystrophies, early intervention correlated with optimal outcomes. We conclude that UCB transplantation benefits children with presymptomatic late-infantile MLD or minimally symptomatic juvenile MLD.

Unrelated umbilical cord blood transplant for juvenile metachromatic leukodystrophy: a 5-year follow-up in three affected siblings.

Unrelated umbilical cord blood transplantation (UCBT) was used to treat three siblings with juvenile metachromatic leukodystrophy (jMLD). The efficacy of this therapy was measured over a 5-year period with serial neurological examinations, neuroimaging, nerve conduction studies (NCS), and neuropsychological evaluations (NPE). Outcomes were a function of disease stage at time of UCBT with alteration of disease course occurring in the first 2 years after UCBT and then subsequent halting of progression and stabilization of symptoms and disease.

Metachromatic leukodystrophy: natural course of cerebral MRI changes in relation to clinical course.

OBJECTIVE: Metachromatic Leukodystrophy (MLD) is a rare disorder leading to demyelination and neurological impairment. A natural history study within the German leukodystrophy network analyzed MRI changes with respect to the clinical course. METHODS: 113 MR images of 68 patients (33 late-infantile, 35 juvenile) were studied cross-sectionally and longitudinally. MRI and motor deterioration were assessed using standardized scoring systems. RESULTS: The temporal and spatial patterns of MR severity scores differed between the late-infantile and juvenile form. Although early (involving central white matter, corpus callosum) and late signs (involving pons, cerebellum, cerebral atrophy) were similar, high MRI scores (mean 18, SD 1.2, p < 0.001) were evident in the juvenile form already at the onset of first symptoms and even in presymptomatic patients. The progression rate of the MRI score was clearly higher and more uniform in the late-infantile (on average 8 per year, p < 0.0001) than in the juvenile patients (on average 0.4 per year, p < 0.08). In late-infantile patients, MRI changes correlated highly with motor deterioration (rho = 0.73, p < 0.001), this was less remarkable in the juvenile form (rho = 0.50, p < 0.01). Severe motor dysfunction was associated with U-fiber involvement and cerebellar changes (p < 0.05). CONCLUSIONS: MRI showed a typical spatial pattern, which evolved gradually and uniformly during disease progression in late-infantile MLD. In juvenile MLD MRI changes were already observed at disease onset and temporal patterns were more variable. As therapeutic options for MLD are evolving, these findings are not only important for patient counseling but also for the evaluation of therapeutic interventions.

Gallbladder cancer with ascites in a child with metachromatic leukodystrophy.

INTRODUCTION: Metachromatic leukodystrophy (MLD) refers to leukodystrophy caused by the accumulation of sulfatide from arylsulfatase A (ARSA) gene mutations. Sulfatide also accumulates in various organs, including the peripheral nerves, kidney, and gallbladder. Proliferative changes in the gallbladder have been reported in several patients, while gallbladder cancer is reported in only two adult MLD cases. We report what is likely the first pediatric case of MLD with gallbladder cancer. CASE REPORT: The patient was a 5-year-old girl diagnosed with MLD using head magnetic resonance imaging and detecting a homozygous mutation of c.302G>A (p.Gly101Asp) in ARSA. Abdominal bloating was observed at the age of 4 years; CT revealed a giant tumor in the gallbladder and massive ascites. Cholecystectomy was performed and pathological examination revealed adenocarcinoma. Measurement of serum sulfatide revealed increased levels compared to the average healthy range. DISCUSSION: Rapidly increased ascites and large polyps which are reported as risk factors for cancer were characteristic in our MLD case. When such lesions are detected, they should be removed immediately because of the possibility of cancer, even in a pediatric patient.

Leukodystrophies with late disease onset: an update.

PURPOSE OF REVIEW: Knowledge of the metabolic and genetic basis of known and previously unknown leukodystrophies is constantly increasing, opening new treatment options such as enzyme replacement or cell-based therapies. This brief review highlights some recent work, particularly emphasizing results from studies in adulthood leukodystrophies. RECENT FINDINGS: Evidence from recent studies suggests increasing importance of metabolic dysfunctions, for example, in peroxisomal lipid metabolism or energy homeostasis, influencing axonal integrity and oligodendrocyte function and leading to white matter demyelination. In addition, diagnostic and therapeutic progress in metachromatic leukodystrophy, X-linked adrenoleukodystrophy, Krabbe diseases and other rare leukodystrophies with late onset are summarized. SUMMARY: Better understanding of leukodystrophies in neurological routine practice is of crucial importance for differentiating between other white matter diseases such as toxic, inflammatory or vascular leukoencephalopathies. Many leukodystrophies are particularly important to recognize because specific treatments already exist or are currently under investigation. The article also provides an overview of currently known leukodystrophies in adulthood.

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.

Metachromatic leukodystrophy--an update.

Metachromatic leukodystrophy (MLD) is a rare lysosomal sphingolipid storage disorder, caused by a deficiency of arylsulfatase A (ASA). It is inherited in an autosomal recessive way, among Caucasians three causing alleles are frequent. Demyelination is the hallmark of MLD. Interest in the disease has increased as therapeutic options such as stem cell transplantation, enzyme replacement and gene therapy are topics of current research. A late-infantile (onset before 3 years of age), a juvenile form (onset before 16 years) and an adult form are usually distinguished. Rapid motor decline is typical for the first and also the second forms, the second may be preceded by cognitive and behavioural problems, which mainly characterize the adult form. There is evidence for a genotype-phenotype correlation: patients homozygous for alleles which do not allow the expression of any enzyme activity (null-allele) suffer from the late infantile form; heterozygosity for a null allele and a non-null allele are more associated with the juvenile form and homozygosity for non-null alleles is more frequent in the most attenuated adult onset form.

Umbilical cord blood transplantation for juvenile metachromatic leukodystrophy.

Three siblings with metachromatic leukodystrophy underwent umbilical cord blood transplantation at different stages of disease. Neuroimaging, nerve conduction studies, neurological examinations, and neuropsychological examinations were used to measure outcome over 2 years. After transplant, the oldest sibling experienced disease progression. His two siblings had near or total resolution of signal abnormalities on neuroimaging. Their neuropsychological testing remained stable, and nerve conduction studies have shown improvement. These results indicate pretransplantation neurological examinations may be the most significant predictor of outcome after transplant. To our knowledge, this report is the first to document neurological outcome of metachromatic leukodystrophy treated by umbilical cord blood transplantation.

Enhancing cranial nerves and cauda equina: an emerging magnetic resonance imaging pattern in metachromatic leukodystrophy and krabbe disease.

We report on three cases of infantile Krabbe disease and one case of infantile metachromatic leukodystrophy showing magnetic resonance (MR) imaging findings of diffuse and coexistent cranial nerve and cauda equina nerve roots enhancement. Such findings may be simultaneous, or even precede, typical white matter abnormalities and, in the appropriate clinical context, may facilitate an earlier diagnosis. There is a rational for the use of contrast agents and craniospinal MR imaging during the first imaging of children with a history of psychomotor regression and clinical evidence of peripheral nerve involvement to exclude differential diagnoses.

Lipidomics in diagnosis of lipidoses.

A review is presented of the major clinical features of a number of glycolipidoses including Fabry, Gaucher, Tay-Sachs, metachromatic leukodystrophy as well as CeroidLipofucinosis and Sjogren-Larsson syndrome. The possibilities offered by lipidomics for diagnosis and follow-up after enzyme replacement therapy are presented from a practical perspective. The contribution of HPLC coupled with tandem mass spectrometry has considerably simplified the detection and assay of abnormal metabolites. Corresponding internal standards consisting of weighed mixtures of the stable-isotope labeled metabolites required to calibrate and quantitate lipid components of these orphan diseases standards have yet to become commercially available. A lipidomics approach has been found to compare favorably with DNA-sequence analysis for the rapid diagnosis of pre-birth syndromes resulting from these multiple gene defects. The method also seems to be suitable for screening applications in terms of a high throughput combined with a low rate of false diagnoses based on the wide differences in metabolite concentrations found in affected patients as compared with normal subjects. The practical advantages of handling samples for lipidomic diagnoses as compared to enzyme assay are presented for application to diagnosis during pregnancy.

Leukodystrophy caused by plasmalogen deficiency rescued by glyceryl 1-myristyl ether treatment.

Plasmalogens are the most abundant form of ether phospholipids in myelin and their deficiency causes Rhizomelic Chondrodysplasia Punctata (RCDP), a severe developmental disorder. Using the Gnpat-knockout (KO) mouse as a model of RCDP, we determined the consequences of a plasmalogen deficiency during myelination and myelin homeostasis in the central nervous system (CNS). We unraveled that the lack of plasmalogens causes a generalized hypomyelination in several CNS regions including the optic nerve, corpus callosum and spinal cord. The defect in myelin content evolved to a progressive demyelination concomitant with generalized astrocytosis and white matter-selective microgliosis. Oligodendrocyte precursor cells (OPC) and mature oligodendrocytes were abundant in the CNS of Gnpat KO mice during the active period of demyelination. Axonal loss was minimal in plasmalogen-deficient mice, although axonal damage was observed in spinal cords from aged Gnpat KO mice. Characterization of the plasmalogen-deficient myelin identified myelin basic protein and septin 7 as early markers of dysmyelination, whereas myelin-associated glycoprotein was associated with the active demyelination phase. Using in vitro myelination assays, we unraveled that the intrinsic capacity of oligodendrocytes to ensheath and initiate membrane wrapping requires plasmalogens. The defect in plasmalogens was rescued with glyceryl 1-myristyl ether [1-O-tetradecyl glycerol (1-O-TDG)], a novel alternative precursor in the plasmalogen biosynthesis pathway. 1-O-TDG treatment rescued myelination in plasmalogen-deficient oligodendrocytes and in mutant mice. Our results demonstrate the importance of plasmalogens for oligodendrocyte function and myelin assembly, and identified a novel strategy to promote myelination in nervous tissue.

Multipotential neural precursors transplanted into the metachromatic leukodystrophy brain fail to generate oligodendrocytes but contribute to limit brain dysfunction.

Neural stem cells appear to be best suited for regenerative therapy in neurological diseases. However, the effects of high levels of potentially toxic substances such as sulfatides--which accumulate in metachromatic leukodystrophy (MLD)--on this regenerative ability are still largely unclear. To start addressing this question, in vitro and in vivo experiments were used to examine the behavior of multipotential neural precursors exposed to abnormally high levels of sulfatides. Following transplantation of dissociated neurospheres into the brain of presymptomatic MLD pups, the majority of donor-derived cells were distributed in a caudal to rostral direction, with higher numbers in the cortex. Most if not all of the donor cells acquired an astroglial phenotype. We found no evidence of oligodendrocyte or neuronal commitment of transplanted cells in long-term-treated MLD mice (e.g. up to 1.5 years of age). This was in line with our in vitro findings of sulfatides blocking oligodendrocyte formation after induction of differentiation in sulfatide-treated epidermal growth factor/fibroblast growth factor responsive neurospheres. Transplanted MLD mice showed an improved arylsulfatase A (ARSA) activity and a significant amelioration of sulfatide metabolism, neurodegeneration and motor-learning/memory deficits. Furthermore, transplanted cells were shown to act as a source of ARSA enzyme that accumulated in endogenous brain cells, indicating the occurrence of enzyme cross-correction between transplanted and host cells. These results provide a first insight into the effect of sulfatides on the stemness properties of neural stem cells and on the effects of the MLD environment on the in vivo expectations of using neural stem cells in cell therapy.

Early signs of neurolipidosis-related behavioural alterations in a murine model of metachromatic leukodystrophy.

Arylsulfatase A (ASA)-deficient mice represent an animal model for the lysosomal storage disorder metachromatic leukodystrophy (MLD). Although the model has been applied in pathophysiological and therapeutic studies, the behavioural phenotype of ASA(-/-) mice is only partially characterized, and the most decisive outcome measures for therapy evaluation only emerge beyond 1 year of age. Presently, ASA(-/-) mice and ASA(+/-) control mice were studied at 6 and 12 months of age on an extensive battery including tests of neuromotor ability, exploratory behaviour, and learning and memory. Overt signs of ataxia were not observed in 6-month-old ASA(-/-) mice, but quantitative gait analysis during open-field exploration revealed that ASA(-/-) mice displayed increased hind base width and increased stride lengths for all paws. Their covert motor incoordination was evident in a correlation analysis which unveiled decreased harmonisation of concurrent gait parameters. For example, while ASA(+/-) controls demonstrated substantial convergence of front and hind base width (r=0.54), these variables actually diverged in ASA(-/-) mice (r=-0.37). Furthermore, various behavioural observations indicated emotional alterations in ASA(-/-) mice. Six-month-old ASA(-/-) mice also showed decreased response rates in scheduled operant responding. The present findings could provide relevant behavioural outcome measures for further use of this murine MLD model in preclinical studies.

Polymorphisms in genes encoding the serotonin and dopamine pathways in two sisters with metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a metabolic disease that has recently been investigated as a model for the study of psychosis. We report on two sisters with adult-type MLD who developed psychiatric symptomatology, but differed in their expression of psychotic and depressive symptoms. Association studies have indicated that polymorphisms in genes encoding the serotonin and dopamine transporters and receptors are related to the symptomatology of schizophrenia and/or depression; hence both sisters were genotyped for some of these candidate genes. The sisters shared dopamine receptor D(2) (DRD(2)) c.1047GG (p.311Ser/Ser) and c.-141Cins/ins polymorphisms, which are significantly associated with schizophrenia, but differed in the serotonin transporter gene-linked polymorphic region and serotonin receptor 1A (5-HT(1A)) c.-1019C to G polymorphisms, which may have increased the elder sister's susceptibility to depressive symptoms. Much bigger samples would be needed to gain enough statistical power to develop any hypotheses. This is the first report on genotyping MLD patients for candidate genes for psychiatric disorders, although MLD has been proposed as a model for schizophrenia.

Enzyme, cell and gene-based therapies for metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a demyelinating storage disease caused by deficiency of the lysosomal enzyme arylsulfatase A (ARSA). Lack of ARSA activity leads to the accumulation of galactosylceramide-3-O-sulfate (sulfatide) in the central and peripheral nervous systems. Based on the age at onset, the disease is usually classified into three forms: the late-infantile form, which manifests in the second year of life; the juvenile variants (onset between 4 and 12 years), which are subdivided into early-juvenile (EJ, onset before 6 years) and late-juvenile (LJ, onset after 6 years); and the adult form (onset after 12 years of age). Currently, there is no efficient therapy for the late-infantile form of MLD (50% of the patients), death occurring within a few years after onset of neurological symptoms. Allogeneic haematopoietic cell transplantation (HCT), when performed at a very early stage of the disease, may improve selected patients with juvenile or adult forms of MLD. As with other lysosomal storage diseases, the physiopathology of MLD is poorly understood. Demyelination is the main pathological finding, but substantial storage of sulfatides in neurons also occurs, and may contribute to the clinical phenotype. The physiopathological process leading to neuronal and glial cell degeneration and apoptosis involves accumulation of undegraded sulfatides but also secondary abnormalities (storage/mislocalization of unrelated lipids, inflammatory processes). This review summarizes the recent advances in the understanding of the physiopathology of MLD and the new therapeutic perspectives currently under preclinical investigation, including enzyme replacement therapy, gene therapy and cell therapy.

Stabilization of juvenile metachromatic leukodystrophy after bone marrow transplantation: a 13-year follow-up.

A 29-year-old female patient with juvenile metachromatic leukodystrophy diagnosed at age 14 years received a bone marrow transplant at age 16 years. A report was published 6 years after bone marrow transplantation concluding that the disease had slowly progressed in the 2 years following bone marrow transplantation. We now report on a further 7-year follow-up, typified by a steady state of spastic paraplegia and mild dementia. Neurophysiological, neuroradiological, and psychological status also remained stable. In the patient's leukocytes, the activity of arylsulfatase A, the enzyme deficient in untreated metachromatic leukodystrophy, was within the normal range whereas urinary sulfatides remained elevated. Data on the natural course of juvenile metachromatic leukodystrophy are rare, so in the present case it is difficult to establish whether the rather favorable course can be attributed with certainty to bone marrow transplantation. The long-term stabilization in this patient, however, suggested that bone marrow transplantation may halt the progression of juvenile metachromatic leukodystrophy.

[Metachromatic Leukodystrophy. Case Presentation]. / Leucodistrofia metacromática. Presentación de caso.

Metachromatic leukodystrophy (MLD) is a rare demyelinating disease (prevalence 1:40 000), also called arylsulfatase A deficiency (ARS-A), which may present with neurological and psychiatric symptoms. Clinical assessment may be difficult, due to unspecific signs and symptoms. A case is presented of a 16 year-old female patient seen in psychiatry due to behavioural changes, psychosis, and with impaired overall performance. She was initially diagnosed with schizophrenia, but the Nuclear Magnetic Resonance (NMR) scan and laboratory tests lead to the diagnosis of MLD.