Neuroprotection of host cells by human central nervous system stem cells in a mouse model of infantile neuronal ceroid lipofuscinosis

Generation and characterization of an immunodeficient mouse model of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (Hunter syndrome, MPS II) is an inherited X-linked recessive disease caused by deficiency of iduronate-2-sulfatase (IDS), resulting in the accumulation of the glycosaminoglycans (GAG) heparan and dermatan sulfates. Mouse models of MPS II have been used in several reports to study disease pathology and to conduct preclinical studies for current and next generation therapies. Here, we report the generation and characterization of an immunodeficient mouse model of MPS II, where CRISPR/Cas9 was employed to knock out a portion of the murine IDS gene on the NOD/SCID/Il2rγ (NSG) immunodeficient background. IDS-/- NSG mice lacked detectable IDS activity in plasma and all analyzed tissues and exhibited elevated levels of GAGs in those same tissues and in the urine. Histopathology revealed vacuolized cells in both the periphery and CNS of NSG-MPS II mice. This model recapitulates skeletal disease manifestations, such as increased zygomatic arch diameter and decreased femur length. Neurocognitive deficits in spatial memory and learning were also observed in the NSG-MPS II model. We anticipate that this new immunodeficient model will be appropriate for preclinical studies involving xenotransplantation of human cell products intended for the treatment of MPS II.

Purification and characterization of human neural stem and progenitor cells

The human brain undergoes rapid development at mid-gestation from a pool of neural stem and progenitor cells (NSPCs) that give rise to the neurons, oligodendrocytes, and astrocytes of the mature brain. Functional study of these cell types has been hampered by a lack of precise purification methods. We describe a method for prospectively isolating ten distinct NSPC types from the developing human brain using cell-surface markers. CD24-THY1-/lo cells were enriched for radial glia, which robustly engrafted and differentiated into all three neural lineages in the mouse brain. THY1hi cells marked unipotent oligodendrocyte precursors committed to an oligodendroglial fate, and CD24+THY1-/lo cells marked committed excitatory and inhibitory neuronal lineages. Notably, we identify and functionally characterize a transcriptomically distinct THY1hiEGFRhiPDGFRA- bipotent glial progenitor cell (GPC), which is lineage-restricted to astrocytes and oligodendrocytes, but not to neurons. Our study provides a framework for the functional study of distinct cell types in human neurodevelopment.

Intravitreal gene therapy restores the autophagy-lysosomal pathway and attenuates retinal degeneration in cathepsin D-deficient mice

Loss of vision due to progressive retinal degeneration is a hallmark of neuronal ceroid lipofuscinoses (NCL), a group of fatal neurodegenerative lysosomal storage diseases. Enzyme substitution therapies represent promising treatment options for NCLs caused by dysfunctions of soluble lysosomal enzymes. Here, we compared the efficacy of a cell-based enzyme substitution strategy and a gene therapy approach to attenuate the retinal pathology in cathepsin D- (CTSD) deficient mice, an animal model of CLN10 disease. Levels of enzymatically active CTSD in mutant retinas were significantly higher after an adeno-associated virus vector-mediated CTSD transfer to retinal glial cells and retinal pigment epithelial cells than after intravitreal transplantations of a CTSD overexpressing clonal neural stem cell line. In line with this finding, the gene therapy treatment restored the disrupted autophagy-lysosomal pathway more effectively than the cell-based approach, as indicated by a complete clearance of storage, significant attenuation of lysosomal hypertrophy, and normalized levels of the autophagy marker sequestosome 1/p62 and microtubule-associated protein 1 light chain 3-II. While the cell-based treatment did not prevent the rapidly progressing loss of various retinal cell types, the gene therapy approach markedly attenuated retinal degeneration as demonstrated by a pronounced rescue of photoreceptor cells and rod bipolar cells.

Stem Cell Research Tools in Human Metabolic Disorders: An Overview

Metabolic disorders are very common in the population worldwide and are among the diseases with the highest health utilization and costs per person. Despite the ongoing efforts to develop new treatments, currently, for many of these disorders, there are no approved therapies, resulting in a huge economic hit and tension for society. In this review, we recapitulate the recent advancements in stem cell (gene) therapy as potential tools for the long-term treatment of both inherited (lysosomal storage diseases) and acquired (diabetes mellitus, obesity) metabolic disorders, focusing on the main promising results observed in human patients and discussing the critical hurdles preventing the definitive jump of this approach from the bench to the clinic.

Ocular Manifestations of Neuronal Ceroid Lipofuscinoses

Neuronal ceroid lipofuscinoses (NCLs) are a group of rare neurodegenerative storage disorders associated with devastating visual prognosis, with an incidence of 1/1,000,000 in the United States and comparatively higher incidence in European countries. The pathophysiological mechanisms causing NCLs occur due to enzymatic or transmembrane defects in various sub-cellular organelles including lysosomes, endoplasmic reticulum, and cytoplasmic vesicles. NCLs are categorized into different types depending upon the underlying cause i.e., soluble lysosomal enzyme deficiencies or non-enzymatic deficiencies (functions of identified proteins), which are sub-divided based on an axial classification system. In this review, we have evaluated the current evidence in the literature and reported the incidence rates, underlying mechanisms and currently available management protocols for these rare set of neuroophthalmological disorders. Additionally, we also highlighted the potential therapies under development that can expand the treatment of these rare disorders beyond symptomatic relief.

Human Glial Progenitor Cells Effectively Remyelinate the Demyelinated Adult Brain

Neonatally transplanted human glial progenitor cells (hGPCs) can myelinate the brains of myelin-deficient shiverer mice, rescuing their phenotype and survival. Yet, it has been unclear whether implanted hGPCs are similarly able to remyelinate the diffusely demyelinated adult CNS. We, therefore, ask if hGPCs could remyelinate both congenitally hypomyelinated adult shiverers and normal adult mice after cuprizone demyelination. In adult shiverers, hGPCs broadly disperse and differentiate as myelinating oligodendrocytes after subcortical injection, improving both host callosal conduction and ambulation. Implanted hGPCs similarly remyelinate denuded axons after cuprizone demyelination, whether delivered before or after demyelination. RNA sequencing (RNA-seq) of hGPCs back from cuprizone-demyelinated brains reveals their transcriptional activation of oligodendrocyte differentiation programs, while distinguishing them from hGPCs not previously exposed to demyelination. These data indicate the ability of transplanted hGPCs to disperse throughout the adult CNS, to broadly myelinate regions of dysmyelination, and also to be recruited as myelinogenic oligodendrocytes later in life, upon demyelination-associated demand.

Human INCL fibroblasts display abnormal mitochondrial and lysosomal networks and heightened susceptibility to ROS-induced cell death

Infantile Neuronal Ceroid Lipofuscinosis (INCL) is a pediatric neurodegenerative disorder characterized by progressive retinal and central nervous system deterioration during infancy. This lysosomal storage disorder results from a deficiency in the Palmitoyl Protein Thioesterase 1 (PPT1) enzyme—a lysosomal hydrolase which cleaves fatty acid chains such as palmitate from lipid-modified proteins. In the absence of PPT1 activity, these proteins fail to be degraded, leading to the accumulation of autofluorescence storage material in the lysosome. The underlying molecular mechanisms leading to INCL pathology remain poorly understood. A role for oxidative stress has been postulated, yet little evidence has been reported to support this possibility. Here we present a comprehensive cellular characterization of human PPT1-deficient fibroblast cells harboring Met1Ile and Tyr247His compound heterozygous mutations. We detected autofluorescence storage material and observed distinct organellar abnormalities of the lysosomal and mitochondrial structures, which supported previous postulations about the role of ER, mitochondria and oxidative stress in INCL. An increase in the number of lysosomal structures was found in INCL patient fibroblasts, which suggested an upregulation of lysosomal biogenesis, and an association with endoplasmic reticulum stress response. The mitochondrial network also displayed abnormal spherical punctate morphology instead of normal elongated tubules with extensive branching, supporting the involvement of mitochondrial and oxidative stress in INCL cell death. Autofluorescence accumulation and lysosomal pathologies can be mitigated in the presence of conditioned wild type media suggesting that a partial restoration via passive introduction of the enzyme into the cellular environment may be possible. We also demonstrated, for the first time, that human INCL fibroblasts have a heightened susceptibility to exogenous reactive oxygen species (ROS)-induced cell death, which suggested an elevated basal level of endogenous ROS in the mutant cell. Collectively, these findings support the role of intracellular organellar networks in INCL pathology, possibly due to oxidative stress.

Neuronal Ceroid Lipofuscinosis: Potential for Targeted Therapy

Neuronal ceroid lipofuscinosis (NCLs) is a group of inherited neurodegenerative lysosomal storage diseases that together represent the most common cause of dementia in children. Phenotypically, patients have visual impairment, cognitive and motor decline, epilepsy, and premature death. A primary challenge is to halt and/or reverse these diseases, towards which developments in potential effective therapies are encouraging. Many treatments, including enzyme replacement therapy (for CLN1 and CLN2 diseases), stem-cell therapy (for CLN1, CLN2, and CLN8 diseases), gene therapy vector (for CLN1, CLN2, CLN3, CLN5, CLN6, CLN7, CLN10, and CLN11 diseases), and pharmacological drugs (for CLN1, CLN2, CLN3, and CLN6 diseases) have been evaluated for safety and efficacy in pre-clinical and clinical studies. Currently, cerliponase alpha for CLN2 disease is the only approved therapy for NCL. Lacking is any study of potential treatments for CLN4, CLN9, CLN12, CLN13 or CLN14 diseases. This review provides an overview of genetics for each CLN disease, and we discuss the current understanding from pre-clinical and clinical study of potential therapeutics. Various therapeutic interventions have been studied in many experimental animal models. Combination of treatments may be useful to slow or even halt disease progression; however, few therapies are unlikely to even partially reverse the disease and a complete reversal is currently improbable. Early diagnosis to allow initiation of therapy, when indicated, during asymptomatic stages is more important than ever.

CNS-Targeting Therapies for Lysosomal Storage Diseases: Current Advances and Challenges

During the past decades, several therapeutic approaches have been developed and made rapidly available for many patients afflicted with lysosomal storage disorders (LSDs), inborn organelle disorders with broad clinical manifestations secondary to the progressive accumulation of undegraded macromolecules within lysosomes. These conditions are individually rare, but, collectively, their incidence ranges from 1 in 2,315 to 7,700 live-births. Most LSDs are manifested by neurological symptoms or signs, including developmental delay, seizures, acroparesthesia, motor weakness, and extrapyramidal signs. The chronic and later-onset clinical forms are at one end of the continuum spectrum and are characterized by a subtle and slow progression of neurological symptoms. Due to its inherent physiological properties, unfortunately, the blood-brain barrier (BBB) constitutes a significant obstacle for current and upcoming therapies to achieve the central nervous system (CNS) and treat neurological problems so prevalent in these conditions. To circumvent this limitation, several strategies have been developed to make the therapeutic agent achieve the CNS. This narrative will provide an overview of current therapeutic strategies under development to permeate the BBB, and address and unmet need for treatment of the progressive neurological manifestations, which are so prevalent in these inherited lysosomal disorders.

Emerging treatments for progressive myoclonus epilepsies

Introduction: Progressive myoclonus epilepsies (PMEs) are a group of neurodegenerative diseases, invariably leading to severe disability or fatal outcome in a few years or decades. Nowadays, PMEs treatment remains challenging with a significant burden of disability for patients. Pharmacotherapy is primarily used to treat seizures, which impact patients' quality of life. However, new approaches have emerged in the last few years, which try to curb the neurological deterioration of PMEs through a better knowledge of the pathogenetic process. This is a review on the newest therapeutic options for the treatment of PMEs.Areas covered: Experimental and clinical results on novel therapeutic approaches for the different forms of PME are reviewed and discussed. Special attention is primarily focused on the efficacy and tolerability outcomes, trying to infer the role novel approaches may have in the future.Expert opinion: The large heterogeneity of disease-causing mechanisms prevents researchers from identifying a single approach to treat PMEs. Understanding of pathophysiologic processes is leading the way to targeted therapies, which, through enzyme replacement or underlying gene defect correction have already proved to potentially strike on neurodegeneration.

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.

CRISPR/Cas9 Genome Engineering in Engraftable Human Brain-Derived Neural Stem Cells

Human neural stem cells (NSCs) offer therapeutic potential for neurodegenerative diseases, such as inherited monogenic nervous system disorders, and neural injuries. Gene editing in NSCs (GE-NSCs) could enhance their therapeutic potential. We show that NSCs are amenable to gene targeting at multiple loci using Cas9 mRNA with synthetic chemically modified guide RNAs along with DNA donor templates. Transplantation of GE-NSC into oligodendrocyte mutant shiverer-immunodeficient mice showed that GE-NSCs migrate and differentiate into astrocytes, neurons, and myelin-producing oligodendrocytes, highlighting the fact that GE-NSCs retain their NSC characteristics of self-renewal and site-specific global migration and differentiation. To show the therapeutic potential of GE-NSCs, we generated GALC lysosomal enzyme overexpressing GE-NSCs that are able to cross-correct GALC enzyme activity through the mannose-6-phosphate receptor pathway. These GE-NSCs have the potential to be an investigational cell and gene therapy for a range of neurodegenerative disorders and injuries of the central nervous system, including lysosomal storage disorders.

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Human neural stem cells are amenable to CRISPR-Cas9-mediated gene targeting

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Truncated CD19 surface marker allows for enrichment of gene-targeted NSCs to >90%

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Gene-targeted NSCs engraft, migrate, and differentiate in immunodeficient mice

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GALC-engineered overexpressing NSCs cross-correct Krabbe disease fibroblasts in vitro

A mixed breed dog with neuronal ceroid lipofuscinosis is homozygous for a CLN5 nonsense mutation previously identified in Border Collies and Australian Cattle Dogs

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by progressive declines in neurological functions following normal development. The NCLs are distinguished from similar disorders by the accumulation of autofluorescent lysosomal storage bodies in neurons and many other cell types, and are classified as lysosomal storage diseases. At least 13 genes contain pathogenic sequence variants that underlie different forms of NCL. Naturally occurring canine NCLs can serve as models to develop better understanding of the disease pathologies and for preclinical evaluation of therapeutic interventions for these disorders. To date 14 sequence variants in 8 canine orthologs of human NCL genes have been found to cause progressive neurological disorders similar to human NCLs in 12 different dog breeds. A mixed breed dog with parents of uncertain breed background developed progressive neurological signs consistent with NCL starting at approximately 11 to 12 months of age, and when evaluated with magnetic resonance imaging at 21 months of age exhibited diffuse brain atrophy. Due to the severity of neurological decline the dog was euthanized at 23 months of age. Cerebellar and cerebral cortical neurons contained massive accumulations of autofluorescent storage bodies the contents of which had the appearance of tightly packed membranes. A whole genome sequence, generated with DNA from the affected dog contained a homozygous C-to-T transition at position 30,574,637 on chromosome 22 which is reflected in the mature CLN5 transcript (CLN5: c.619C > T) and converts a glutamine codon to a termination codon (p.Gln207Ter). The identical nonsense mutation has been previously associated with NCL in Border Collies, Australian Cattle Dogs, and a German Shepherd-Australian Cattle Dog mix. The current whole genome sequence and a previously generated whole genome sequence for an Australian Cattle Dog with NCL share a rare homozygous haplotype that extends for 87 kb surrounding 22: 30, 574, 637 and includes 21 polymorphic sites. When genotyped at 7 of these polymorphic sites, DNA samples from the German Shepherd-Australian Cattle Dog mix and from 5 Border Collies with NCL that were homozygous for the CLN5: c.619 T allele also shared this homozygous haplotype, suggesting that the NCL in all of these dogs stems from the same founding mutation event that may have predated the establishment of the modern dog breeds. If so, the CLN5 nonsence allele is probably segregating in other, as yet unidentified, breeds. Thus, dogs exhibiting similar NCL-like signs should be screened for this CLN5 nonsense allele regardless of breed.

Next-Generation Sequencing Analysis Reveals Novel Pathogenic Variants in Four Chinese Siblings With Late-Infantile Neuronal Ceroid Lipofuscinosis

Neuronal Ceroid Lipofuscinoses (NCLs) are progressive degenerative diseases mainly affect brain and retina. They are characterized by accumulation of autofluorescent storage material, mitochondrial ATPase subunit C, or sphingolipid activator proteins A and D in lysosomes of most cells. Heterogenous storage material in NCLs is not completely disease-specific. Most of CLN proteins and their natural substrates are not well-characterized. Studies have suggested variants of Late-Infantile NCLs (LINCLs) include the major type CLN2 and minor types CLN5, CLN6, CLN7, and CLN8. Therefore, combination of clinical and molecular analysis has become a more effective diagnosis method. We studied 4 late-infantile NCL siblings characterized by seizures, ataxia as early symptoms, followed by progressive regression in intelligence and behavior, but mutations are located in different genes. Symptoms and progression of 4 types of LINCLs are compared. Pathology of LINCLs is also discussed. We performed Nest-Generation Sequencing on these phenotypically similar families. Three novel variants c.1551+1insTGAT in TPP1, c.244G>T in CLN6, c.554-5A>G in MFSD8 were identified. Potential outcome of the mutations in structure and function of proteins are studied. In addition, we observed some common and unique clinical features of Chinese LINCL patient as compared with those of Western patients, which greatly improved our understanding of the LINCLs.

Therapeutic landscape for Batten disease: current treatments and future prospects

Batten disease (also known as neuronal ceroid lipofuscinoses) constitutes a family of devastating lysosomal storage disorders that collectively represent the most common inherited paediatric neurodegenerative disorders worldwide. Batten disease can result from mutations in 1 of 13 genes. These mutations lead to a group of diseases with loosely overlapping symptoms and pathology. Phenotypically, patients with Batten disease have visual impairment and blindness, cognitive and motor decline, seizures and premature death. Pathologically, Batten disease is characterized by lysosomal accumulation of autofluorescent storage material, glial reactivity and neuronal loss. Substantial progress has been made towards the development of effective therapies and treatments for the multiple forms of Batten disease. In 2017, cerliponase alfa (Brineura), a tripeptidyl peptidase enzyme replacement therapy, became the first globally approved treatment for CLN2 Batten disease. Here, we provide an overview of the promising therapeutic avenues for Batten disease, highlighting current FDA-approved clinical trials and prospective future treatments.

Current and Emerging Treatment Strategies for Neuronal Ceroid Lipofuscinoses

The neuronal ceroid lipofuscinoses comprise a group of neurodegenerative lysosomal storage disorders caused by mutations in at least 13 different genes and primarily affect the brain and the retina of children or young adults. The disorders are characterized by progressive neurological deterioration with dementia, epilepsy, loss of vision, motor disturbances, and early death. While various therapeutic strategies are currently being explored as treatment options for these fatal disorders, there is presently only one clinically approved drug that has been shown to effectively attenuate the progression of a specific form of neuronal ceroid lipofuscinosis, CLN2 disease (cerliponase alfa, a lysosomal enzyme infused into the brain ventricles of patients with CLN2 disease). Therapeutic approaches for the treatment of other forms of neuronal ceroid lipofuscinosis include the administration of immunosuppressive agents to antagonize neuroinflammation associated with neurodegeneration, the use of various small molecules, stem cell therapy, and gene therapy. An important aspect of future work aimed at developing therapies for neuronal ceroid lipofuscinoses is the need for treatments that effectively attenuate neurodegeneration in both the brain and the retina.

Clinical challenges and future therapeutic approaches for neuronal ceroid lipofuscinosis

Treatment of the neuronal ceroid lipofuscinoses, also known as Batten disease, is at the start of a new era because of diagnostic and therapeutic advances relevant to this group of inherited neurodegenerative and life-limiting disorders that affect children. Diagnosis has improved with the use of comprehensive DNA-based tests that simultaneously screen for many genes. The identification of disease-causing mutations in 13 genes provides a basis for understanding the molecular mechanisms underlying neuronal ceroid lipofuscinoses, and for the development of targeted therapies. These targeted therapies include enzyme replacement therapies, gene therapies targeting the brain and the eye, cell therapies, and pharmacological drugs that could modulate defective molecular pathways. Such therapeutic developments have the potential to enable earlier diagnosis and better targeted therapeutic management. The first approved treatment is an intracerebroventricularly administered enzyme for neuronal ceroid lipofuscinosis type 2 disease that delays symptom progression. Efforts are underway to make similar progress for other forms of the disorder.

Genetically Corrected iPSC-Derived Neural Stem Cell Grafts Deliver Enzyme Replacement to Affect CNS Disease in Sanfilippo B Mice

Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB [MPS IIIB]) is a lysosomal storage disorder primarily affecting the brain that is caused by a deficiency in the enzyme α-N-acetylglucosaminidase (NAGLU), leading to intralysosomal accumulation of heparan sulfate. There are currently no treatments for this disorder. Here we report that, ex vivo, lentiviral correction of Naglu-/- neural stem cells derived from Naglu-/- mice (iNSCs) corrected their lysosomal pathology and allowed them to secrete a functional NAGLU enzyme that could be taken up by deficient cells. Following long-term transplantation of these corrected iNSCs into Naglu-/- mice, we detected NAGLU activity in the majority of engrafted animals. Successfully transplanted Naglu-/- mice showed a significant decrease in storage material, a reduction in astrocyte activation, and complete prevention of microglial activation within the area of engrafted cells and neighboring regions, with beneficial effects extending partway along the rostrocaudal axis of the brain. Our results demonstrate long-term engraftment of iNSCs in the brain that are capable of cross-correcting pathology in Naglu-/- mice. Our findings suggest that genetically engineered iNSCs could potentially be used to deliver enzymes and treat MPS IIIB.

Progress in gene and cell therapies for the neuronal ceroid lipofuscinoses

INTRODUCTION

The neuronal ceroid lipofuscinoses (NCLs) are a subset of lysosomal storage diseases (LSDs) that cause myoclonic epilepsy, loss of cognitive and motor function, degeneration of the retina leading to blindness, and early death. Most are caused by loss-of-function mutations in either lysosomal proteins or transmembrane proteins. Current therapies are supportive in nature. NCLs involving lysosomal enzymes are amenable to therapies that provide an exogenous source of protein, as has been used for other LSDs. Those that involve transmembrane proteins, however, require new approaches.

AREAS COVERED

This review will discuss potential gene and cell therapy approaches that have been, are, or may be in development for these disorders and those that have entered clinical trials.

EXPERT OPINION

In animal models, gene therapy approaches have produced remarkable improvements in neurological function and lifespan. However, a complete cure has not been reached for any NCL, and a better understanding of the limits of the current crop of vectors is needed to more fully address these diseases. The prospects for gene therapy, particularly those that can be delivered systemically and treat both the brain and peripheral tissue, are high. The future is beginning to look bright for NCL patients and their families.

HuCNS-SC Human NSCs Fail to Differentiate, Form Ectopic Clusters, and Provide No Cognitive Benefits in a Transgenic Model of Alzheimer's Disease

Transplantation of neural stem cells (NSCs) can improve cognition in animal models of Alzheimer's disease (AD). However, AD is a protracted disorder, and prior studies have examined only short-term effects. We therefore used an immune-deficient model of AD (Rag-5xfAD mice) to examine long-term transplantation of human NSCs (StemCells Inc.; HuCNS-SCs). Five months after transplantation, HuCNS-SCs had engrafted and migrated throughout the hippocampus and exhibited no differences in survival or migration in response to β-amyloid pathology. Despite robust engraftment, HuCNS-SCs failed to terminally differentiate and over a quarter of the animals exhibited ectopic human cell clusters within the lateral ventricle. Unlike prior short-term experiments with research-grade HuCNS-SCs, we also found no evidence of improved cognition, no changes in brain-derived neurotrophic factor, and no increase in synaptic density. These data, while disappointing, reinforce the notion that individual human NSC lines need to be carefully assessed for efficacy and safety in appropriate long-term models.

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Human neural stem cells (HuCNS-SC) have been used in multiple human clinical trials

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HuCNS-SC originally derived under GMP conditions did not improve cognition in AD mice

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HuCNS-SC failed to differentiate, improve synaptic density, or increase BDNF levels

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HuCNS-SC formed ectopic ventricular clusters in a quarter of transplanted mice

Stem Cell Therapies for Reversing Vision Loss

Current clinical trials that evaluate human pluripotent stem cell (hPSC)-based therapies predominantly target treating macular degeneration of the eyes because the eye is an isolated tissue that is naturally weakly immunogenic. Here, we discuss current bioengineering approaches and biomaterial usage in combination with stem cell therapy for macular degeneration disease treatment. Retinal pigment epithelium (RPE) differentiated from hPSCs is typically used in most clinical trials for treating patients, whereas bone marrow mononuclear cells (BMNCs) or mesenchymal stem cells (MSCs) are intravitreally transplanted, undifferentiated, into patient eyes. We also discuss reported negative effects of stem cell therapy, such as patients becoming blind following transplantation of adipose-derived stem cells, which are increasingly used by 'stem-cell clinics'.

Synergistic effects of treating the spinal cord and brain in CLN1 disease

Infantile neuronal ceroid lipofuscinosis (INCL, or CLN1 disease) is an inherited neurodegenerative storage disorder caused by a deficiency of the lysosomal enzyme palmitoyl protein thioesterase 1 (PPT1). It was widely believed that the pathology associated with INCL was limited to the brain, but we have now found unexpectedly profound pathology in the human INCL spinal cord. Similar pathological changes also occur at every level of the spinal cord of PPT1-deficient (Ppt1^-/- ) mice before the onset of neuropathology in the brain. Various forebrain-directed gene therapy approaches have only had limited success in Ppt1^-/- mice. Targeting the spinal cord via intrathecal administration of an adeno-associated virus (AAV) gene transfer vector significantly prevented pathology and produced significant improvements in life span and motor function in Ppt1^-/- mice. Surprisingly, forebrain-directed gene therapy resulted in essentially no PPT1 activity in the spinal cord, and vice versa. This leads to a reciprocal pattern of histological correction in the respective tissues when comparing intracranial with intrathecal injections. However, the characteristic pathological features of INCL were almost completely absent in both the brain and spinal cord when intracranial and intrathecal injections of the same AAV vector were combined. Targeting both the brain and spinal cord also produced dramatic and synergistic improvements in motor function with an unprecedented increase in life span. These data show that spinal cord pathology significantly contributes to the clinical progression of INCL and can be effectively targeted therapeutically. This has important implications for the delivery of therapies in INCL, and potentially in other similar disorders.

Safety and potential efficacy of gemfibrozil as a supportive treatment for children with late infantile neuronal ceroid lipofuscinosis and other lipid storage disorders

Neuronal Ceroid Lipofuscinosis (NCL), also known as Batten disease, is a group of genetically distinct lysosomal disorders that mainly affect the central nervous system, resulting in progressive motor and cognitive decline primarily in children. Multiple distinct genes involved in the metabolism of lipids have been identified to date with various mutations in this family of diseases. There is no cure for these diseases but some new therapeutic approaches have been tested that offer more hope than the standard palliative care. Many of the therapeutic advances require invasive procedures but some progress in slowing the disease has been found and more options can be expected in the future. We also review the literature on children with disease/conditions other than NCL for the non-invasive use, safety, and tolerability of a lipid-lowering drug, gemfibrozil, as a potential treatment for NCLs. Gemfibrozil has shown efficacy in an animal model of NCL known as CLN2 (late infantile classic juvenile) and has been shown to be safe for lowering lipids in children. Among the 200 non-NCL children found in the published literature who were treated with gemfibrozil for NCL-related problems, only 3 experienced adverse events, including 2 with muscle pain and 1 with localized linear IgA bullous dermatitis. We conclude that gemfibrozil is safe for long-term use in children, causes minimal adverse events, is well tolerated, and may delay the progression of NCLs. Gemfibrozil may potentially be an alternative to more invasive therapeutic approaches currently under investigation and has the potential to be used in combination with other therapeutic approaches.

Neurogenin-2-transduced human neural progenitor cells attenuate neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic (HI) brain injury leads to high mortality and neurodevelopmental disabilities. Multipotent neural progenitor cells (NPCs) with self-renewing capacity have the potential to reduce neuronal loss and improve the compromised environment in the HI brain injury. However, the therapeutic efficacy of neuronal-committed progenitor cells and the underlying mechanisms of recovery are not yet fully understood. Therefore, this study investigated the regenerative ability and action mechanisms of neuronally committed human NPCs (hNPCs) transduced with neurogenin-2 (NEUROG2) in neonatal HI brain injury. NEUROG2- or green fluorescent protein (GFP)-encoding adenoviral vector-transduced hNPCs (NEUROG2- or GFP-NPCs) were transplanted into neonatal mouse brains with HI injury. Grafted NEUROG2-NPCs showed robust dispersion and engraftment, prolonged survival, and neuronal differentiation in HI brain injury. NEUROG2-NPCs significantly improved neurological behaviors, decreased cellular apoptosis, and increased the neurite outgrowth and axonal sprouting in HI brain injury. In contrast, GFP-NPC grafts moderately enhanced axonal extension with limited behavioral recovery. Notably, NEUROG2-NPCs showed increased secretion of multiple factors, such as nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NTF3), fibroblast growth factor 9 (FGF9), ciliary neurotrophic factor (CNTF), and thrombospondins 1 and 2 (THBS 1/2), which promoted SH-SY5Y neuroblastoma cell survival and neurite outgrowth. Thus, we postulate that NEUROG2-expressing human NPCs facilitate functional recovery after neonatal HI brain injury via their ability to secrete multiple factors that enhance neuronal survival and neuroplasticity.

Progenitor cell-based treatment of glial disease

Diseases of glia, including astrocytes and oligodendrocytes, are among the most prevalent and disabling, yet least appreciated, conditions in neurology. In recent years, it has become clear that besides the overtly glial disorders of oligodendrocyte loss and myelin failure, such as the leukodystrophies and inflammatory demyelinations, a number of neurodegenerative and psychiatric disorders may also be causally linked to glial dysfunction and derive from astrocytic as well as oligodendrocytic pathology. The relative contribution of glial dysfunction to many of these disorders may be so great as to allow their treatment by the delivery of allogeneic glial progenitor cells, the precursors to both astroglia and myelin-producing oligodendrocytes. Given the development of new methods for producing and isolating these cells from pluripotent stem cells, both the myelin disorders and appropriate glial-based neurodegenerative conditions may now be compelling targets for cell-based therapy. As such, glial cell-based therapies may offer potential benefit to a broader range of diseases than ever before contemplated, including disorders such as Huntington's disease and the motor neuron degeneration of amyotrophic lateral sclerosis, which have traditionally been considered neuronal in nature.

The CD24 surface antigen in neural development and disease

A cell's surface molecular signature enables its reciprocal interactions with the associated microenvironments in development, tissue homeostasis and pathological processes. The CD24 surface antigen (heat-stable antigen, nectadrin; small cell lung cancer antigen cluster-4) represents a prime example of a neural surface molecule that has long been known, but whose diverse molecular functions in intercellular communication we have only begun to unravel. Here, we briefly summarize the molecular fundamentals of CD24 structure and provide a comprehensive review of CD24 expression and functional studies in mammalian neural developmental systems and disease models (rodent, human). Striving for an integrated view of the intracellular signaling processes involved, we discuss the most pertinent routes of CD24-mediated signaling pathways and functional networks in neurobiology (neural migration, neurite extension, neurogenesis) and pathology (tumorigenesis, multiple sclerosis).

Clinical application of oligodendrocyte precursor cells for cell-based therapy

Oligodendrocyte precursor cells (OPCs), which give rise to mature oligodendrocytes (OLs), play important roles in maintaining white matter function. Even during the adulthood period, OPCs comprise roughly 5% of all cells in the forebrain and retain a capability to become myelinated OLs. Recently, OPCs have been proposed as a novel source for cell-based therapy. For the purpose, OPCs can be obtained from embryonic stem cells, induced pluripotent stem cells, and directly converted cells derived from patients. Here, we will provide a brief review of the potential of using OPCs as a cell-based therapy for treating various neurological diseases.

Generation of Human Induced Pluripotent Stem Cell-Derived Bona Fide Neural Stem Cells for Ex Vivo Gene Therapy of Metachromatic Leukodystrophy

Allogeneic fetal‐derived human neural stem cells (hfNSCs) that are under clinical evaluation for several neurodegenerative diseases display a favorable safety profile, but require immunosuppression upon transplantation in patients. Neural progenitors derived from patient‐specific induced pluripotent stem cells (iPSCs) may be relevant for autologous ex vivo gene‐therapy applications to treat genetic diseases with unmet medical need. In this scenario, obtaining iPSC‐derived neural stem cells (NSCs) showing a reliable “NSC signature” is mandatory. Here, we generated human iPSC (hiPSC) clones via reprogramming of skin fibroblasts derived from normal donors and patients affected by metachromatic leukodystrophy (MLD), a fatal neurodegenerative lysosomal storage disease caused by genetic defects of the arylsulfatase A (ARSA) enzyme. We differentiated hiPSCs into NSCs (hiPS‐NSCs) sharing molecular, phenotypic, and functional identity with hfNSCs, which we used as a “gold standard” in a side‐by‐side comparison when validating the phenotype of hiPS‐NSCs and predicting their performance after intracerebral transplantation. Using lentiviral vectors, we efficiently transduced MLD hiPSCs, achieving supraphysiological ARSA activity that further increased upon neural differentiation. Intracerebral transplantation of hiPS‐NSCs into neonatal and adult immunodeficient MLD mice stably restored ARSA activity in the whole central nervous system. Importantly, we observed a significant decrease of sulfatide storage when ARSA‐overexpressing cells were used, with a clear advantage in those mice receiving neonatal as compared with adult intervention. Thus, we generated a renewable source of ARSA‐overexpressing iPSC‐derived bona fide hNSCs with improved features compared with clinically approved hfNSCs. Patient‐specific ARSA‐overexpressing hiPS‐NSCs may be used in autologous ex vivo gene therapy protocols to provide long‐lasting enzymatic supply in MLD‐affected brains. Stem Cells Translational Medicine2017;6:352–368

Stem Cell Therapy for the Central Nervous System in Lysosomal Storage Diseases

Neurological diseases with genetic etiologies result in the loss or dysfunction of neural cells throughout the CNS. At present, few treatment options exist for the majority of neurogenetic diseases. Stem cell transplantation (SCT) into the CNS has the potential to be an effective treatment modality because progenitor cells may replace lost cells in the diseased brain, provide multiple trophic factors, or deliver missing proteins. This review focuses on the use of SCT in lysosomal storage diseases (LSDs), a large group of monogenic disorders with prominent CNS disease. In most patients the CNS disease results in intellectual disability that is refractory to current standard-of-care treatment. A large amount of preclinical work on brain-directed SCT has been performed in rodent LSD models. Cell types that have been used for direct delivery into the CNS include neural stem cells, embryonic and induced pluripotent stem cells, and mesenchymal stem cells. Hematopoietic stem cells have been an effective therapy for the CNS in a few LSDs and may be augmented by overexpression of the missing gene. Current barriers and potential strategies to improve SCT for translation into effective patient therapies are discussed.

Glial progenitor cell-based treatment of the childhood leukodystrophies

The childhood leukodystrophies comprise a group of hereditary disorders characterized by the absence, malformation or destruction of myelin. These disorders share common clinical, radiological and pathological features, despite their diverse molecular and genetic etiologies. Oligodendrocytes and astrocytes are the major affected cell populations, and are either structurally impaired or metabolically compromised through cell-intrinsic pathology, or are the victims of mis-accumulated toxic byproducts of metabolic derangement. In either case, glial cell replacement using implanted tissue or pluripotent stem cell-derived human neural or glial progenitor cells may comprise a promising strategy for both structural remyelination and metabolic rescue. A broad variety of pediatric white matter disorders, including the primary hypomyelinating disorders, the lysosomal storage disorders, and the broader group of non-lysosomal metabolic leukodystrophies, may all be appropriate candidates for glial progenitor cell-based treatment. Nonetheless, a variety of specific challenges remain before this therapeutic strategy can be applied to children. These include timely diagnosis, before irreparable neuronal injury has ensued; understanding the natural history of the targeted disease; defining the optimal cell phenotype for each disorder; achieving safe and scalable cellular compositions; designing age-appropriate controlled clinical trials; and for autologous therapy of genetic disorders, achieving the safe genetic editing of pluripotent stem cells. Yet these challenges notwithstanding, the promise of glial progenitor cell-based treatment of the childhood myelin disorders offers hope to the many victims of this otherwise largely untreatable class of disease.

Moving towards effective therapeutic strategies for Neuronal Ceroid Lipofuscinosis

The Neuronal Ceroid Lipofuscinoses (NCLs) are a family of autosomal recessive neurodegenerative disorders that annually affect 1:100,000 live births worldwide. This family of diseases results from mutations in one of 14 different genes that share common clinical and pathological etiologies. Clinically, the diseases are subcategorized into infantile, late-infantile, juvenile and adult forms based on their age of onset. Though the disease phenotypes may vary in their age and order of presentation, all typically include progressive visual deterioration and blindness, cognitive impairment, motor deficits and seizures. Pathological hallmarks of NCLs include the accumulation of storage material or ceroid in the lysosome, progressive neuronal degeneration and massive glial activation. Advances have been made in genetic diagnosis and counseling for families. However, comprehensive treatment programs that delay or halt disease progression have been elusive. Current disease management is primarily targeted at controlling the symptoms rather than "curing" the disease. Recognizing the growing need for transparency and synergistic efforts to move the field forward, this review will provide an overview of the therapeutic approaches currently being pursued in preclinical and clinical trials to treat different forms of NCL as well as provide insight to novel therapeutic approaches in development for the NCLs.

Human neural progenitor cells in central nervous system lesions

Various immature cells can be isolated from human embryonic and fetal central nervous system (CNS) residual tissue and potentially be used in cell therapy for a number of neurological diseases and CNS insults. Transplantation of neural stem and progenitor cells is essential for replacing lost cells, particularly in the CNS with very limited endogenous regenerative capacity. However, while dopamine released from transplanted cells can substitute the lost dopamine neurons in the experimental models of Parkinson's disease, stem and progenitor cells primarily have a neuroprotective effect, probably through the release of trophic factors. Understanding the therapeutic effects of transplanted cells is crucial to determine the design of clinical trials. During the last few years, a number of clinical trials for CNS diseases and insults such as amyotrophic lateral sclerosis (ALS), stroke, and spinal cord trauma using neural progenitor cells have been initiated. Data from these early studies will provide vital information on the safety of transplanting these cells, which still is a major concern. That the beneficial results observed in experimental models also can be repeated in the clinical setting is highly hoped for.

Immunohistochemical toolkit for tracking and quantifying xenotransplanted human stem cells

AIM

Biomarker-based tracking of human stem cells xenotransplanted into animal models is crucial for studying their fate in the field of cell therapy or tumor xenografting.

MATERIALS & METHODS

Using immunohistochemistry and in situ hybridization, we analyzed the expression of three human-specific biomarkers: Ku80, human mitochondria (hMito) and Alu.

RESULTS

We showed that Ku80, hMito and Alu biomarkers are broadly expressed in human tissues with no or low cross-reactivity toward rat, mouse or pig tissues. In vitro, we demonstrated that their expression is stable over time and does not change along the differentiation of human-derived induced pluripotent stem cells or human glial-restricted precursors. We tracked in vivo these cell populations after transplantation in rodent spinal cords using aforementioned biomarkers and human-specific antibodies detecting apoptotic, proliferating or neural-committed cells.

CONCLUSION

This study assesses the human-species specificity of Ku80, hMito and Alu, and proposes useful biomarkers for characterizing human stem cells in xenotransplantation paradigms.

Human neural stem cells alleviate Alzheimer-like pathology in a mouse model

Background

Alzheimer’s disease (AD) is an inexorable neurodegenerative disease that commonly occurs in the elderly. The cognitive impairment caused by AD is associated with abnormal accumulation of amyloid-β (Aβ) and hyperphosphorylated tau, which are accompanied by inflammation. Neural stem cells (NSCs) are self-renewing, multipotential cells that differentiate into distinct neural cells. When transplanted into a diseased brain, NSCs repair and replace injured tissues after migration toward and engraftment within lesions. We investigated the therapeutic effects in an AD mouse model of human NSCs (hNSCs) that derived from an aborted human fetal telencephalon at 13 weeks of gestation. Cells were transplanted into the cerebral lateral ventricles of neuron-specific enolase promoter-controlled APPsw-expressing (NSE/APPsw) transgenic mice at 13 months of age.

Results

Implanted cells extensively migrated and engrafted, and some differentiated into neuronal and glial cells, although most hNSCs remained immature. The hNSC transplantation improved spatial memory in these mice, which also showed decreased tau phosphorylation and Aβ42 levels and attenuated microgliosis and astrogliosis. The hNSC transplantation reduced tau phosphorylation via Trk-dependent Akt/GSK3β signaling, down-regulated Aβ production through an Akt/GSK3β signaling-mediated decrease in BACE1, and decreased expression of inflammatory mediators through deactivation of microglia that was mediated by cell-to-cell contact, secretion of anti-inflammatory factors generated from hNSCs, or both. The hNSC transplantation also facilitated synaptic plasticity and anti-apoptotic function via trophic supplies. Furthermore, the safety and feasibility of hNSC transplantation are supported.

Conclusions

These findings demonstrate the hNSC transplantation modulates diverse AD pathologies and rescue impaired memory via multiple mechanisms in an AD model. Thus, our data provide tangible preclinical evidence that human NSC transplantation could be a safe and versatile approach for treating AD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-015-0035-6) contains supplementary material, which is available to authorized users.

Moving stem cells to the clinic: potential and limitations for brain repair

Stem cell-based therapies hold considerable promise for many currently devastating neurological disorders. Substantial progress has been made in the derivation of disease-relevant human donor cell populations. Behavioral data in relevant animal models of disease have demonstrated therapeutic efficacy for several cell-based approaches. Consequently, cGMP grade cell products are currently being developed for first in human clinical trials in select disorders. Despite the therapeutic promise, the presumed mechanism of action of donor cell populations often remains insufficiently validated. It depends greatly on the properties of the transplanted cell type and the underlying host pathology. Several new technologies have become available to probe mechanisms of action in real time and to manipulate in vivo cell function and integration to enhance therapeutic efficacy. Results from such studies generate crucial insight into the nature of brain repair that can be achieved today and push the boundaries of what may be possible in the future.

Towards a new understanding of NCL pathogenesis

The Neuronal Ceroid Lipofuscinoses (NCLs, Batten disease) are a group of inherited neurodegenerative disorders that have been traditionally grouped together on the basis of certain shared clinical and pathological features. However, as the number of genes that appear to cause new forms of NCL continues to grow, it is timely to reassess our understanding of the pathogenesis of these disorders and what groups them together. The various NCL subtypes do indeed share features of a build-up of autofluorescent storage material, progressive neuron loss and activation of the innate immune system. The characterisation of animal models has highlighted the selective nature of neuron loss and its intimate relationship with glial activation, rather than the generalised build-up of storage material. More recent data provide evidence for the pathway-dependent nature of pathology, the contribution of glial dysfunction, and the involvement of new brain regions previously thought to be unaffected, and it is becoming apparent that pathology extends beyond the brain. These data have important implications, not just for therapy, but also for our understanding of these disorders. However, looking beneath these broadly similar pathological themes evidence emerges for marked differences in the nature and extent of these events in different forms of NCL. Indeed, given the widely different nature of the mutated gene products it is perhaps more surprising that these disorders resemble each other as much as they do. Such data raise the question whether we should rethink the collective grouping of these gene deficiencies together, or whether it would be better to consider them as separate entities. This article is part of a Special Issue entitled: Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease).

Glia Disease and Repair-Remyelination

The inability of the mammalian central nervous system (CNS) to undergo spontaneous regeneration has long been regarded as a central tenet of neurobiology. However, although this is largely true of the neuronal elements of the adult mammalian CNS, save for discrete populations of granular neurons, the same is not true of its glial elements. In particular, the loss of oligodendrocytes, which results in demyelination, triggers a spontaneous and often highly efficient regenerative response, remyelination, in which new oligodendrocytes are generated and myelin sheaths are restored to denuded axons. Yet, remyelination in humans is not without limitation, and a variety of demyelinating conditions are associated with sustained and disabling myelin loss. In this review, we will review the biology of remyelination, including the cells and signals involved; describe when remyelination occurs and when and why it fails and the consequences of its failure; and discuss approaches for therapeutically enhancing remyelination in demyelinating diseases of both children and adults, both by stimulating endogenous oligodendrocyte progenitor cells and by transplanting these cells into demyelinated brain.

Experimental therapies in the neuronal ceroid lipofuscinoses

The neuronal ceroid lipofuscinoses represent a group of severe childhood lysosomal storage diseases. With at least 13 identified variants they are the most common cause of inherited neurodegeneration in children. These diseases share common pathological characteristics including motor problems, vision loss, seizures, and cognitive decline, culminating in premature death. Currently, no form of the disease can be treated or cured, with only palliative care to minimise discomfort. This review focuses on current and potentially ground-breaking clinical trials, including small molecule, enzyme replacement, stem cell, and gene therapies, in the development of effective treatments for the various disease subtypes. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

The neuronal ceroid lipofuscinoses: Opportunities from model systems

The neuronal ceroid lipofuscinoses are a group of severe and progressive neurodegenerative disorders, generally with childhood onset. Despite the fact that these diseases remain fatal, significant breakthroughs have been made in our understanding of the genetics that underpin these conditions. This understanding has allowed the development of a broad range of models to study disease processes, and to develop new therapeutic approaches. Such models have contributed significantly to our knowledge of these conditions. In this review we will focus on the advantages of each individual model, describe some of the contributions the models have made to our understanding of the broader disease biology and highlight new techniques and approaches relevant to the study and potential treatment of the neuronal ceroid lipofuscinoses. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

Delivering drugs to the central nervous system: an overview

Developing therapies for the brain is perhaps the greatest challenge facing modern medicine today. While a great many potential therapies show promise in animal models, precious few make it to approval or are even studied in human patients. The particular challenges to the translation of neurotherapeutics to the clinic are many, but a major barrier is difficulty in delivering therapeutics into the brain. The goal of this workshop was to present ways to deliver therapeutics to the brain, including the limitations of each method, and describe ways to track their delivery, safety, and efficacy. Solving the problem of delivery will aid translation of therapeutics for patients suffering from neurodegeneration and other disorders of the brain.

Combined gene/cell therapies provide long-term and pervasive rescue of multiple pathological symptoms in a murine model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD) is a lysosomal storage disease caused by deficient activity of β-galactocerebrosidase (GALC). The infantile forms manifest with rapid and progressive central and peripheral demyelination, which represent a major hurdle for any treatment approach. We demonstrate here that neonatal lentiviral vector-mediated intracerebral gene therapy (IC GT) or transplantation of GALC-overexpressing neural stem cells (NSC) synergize with bone marrow transplant (BMT) providing dramatic extension of lifespan and global clinical–pathological rescue in a relevant GLD murine model. We show that timely and long-lasting delivery of functional GALC in affected tissues ensured by the exclusive complementary mode of action of the treatments underlies the outstanding benefit. In particular, the contribution of neural stem cell transplantation and IC GT during the early asymptomatic stage of the disease is instrumental to enhance long-term advantage upon BMT. We clarify the input of central nervous system, peripheral nervous system and periphery to the disease, and the relative contribution of treatments to the final therapeutic outcome, with important implications for treatment strategies to be tried in human patients. This study gives proof-of-concept of efficacy, tolerability and clinical relevance of the combined gene/cell therapies proposed here, which may constitute a feasible and effective therapeutic opportunity for children affected by GLD.

Stem cell therapy in neurodegenerative diseases: From principles to practice

The lack of curative therapies for neurodegenerative diseases has high economic impact and places huge burden on the society. The contribution of stem cells to cure neurodegenerative diseases has been unraveled and explored extensively over the past few years. Beyond substitution of the lost neurons, stem cells act as immunomodulators and neuroprotectors. A large number of preclinical and a small number of clinical studies have shown beneficial outcomes in this context. In this review, we have summarized the current concepts of stem cell therapy in neurodegenerative diseases and the recent advances in this field, particularly between 2010 and 2012. Further studies should be encouraged to resolve the clinical issues and vague translational findings for maximum optimization of the efficacy of stem cell therapy in neurodegenerative diseases.

Fetal stem cell transplantation: Past, present, and future

Since 1928, human fetal tissues and stem cells have been used worldwide to treat various conditions. Although the transplantation of the fetal midbrain substantia nigra and dopaminergic neurons in patients suffering from Parkinson’s disease is particularly noteworthy, the history of other types of grafts, such as those of the fetal liver, thymus, and pancreas, should be addressed as there are many lessons to be learnt for future stem cell transplantation. This report describes previous practices and complications that led to current clinical trials of isolated fetal stem cells and embryonic stem (ES) cells. Moreover, strategies for transplantation are considered, with a particular focus on donor cells, cell processing, and the therapeutic cell niche, in addition to ethical issues associated with fetal origin. With the advent of autologous induced pluripotent stem cells and ES cells, clinical dependence on fetal transplantation is expected to gradually decline due to lasting ethical controversies, despite landmark achievements.