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Human iPSC-based models highlight defective glial and neuronal differentiation from neural progenitor cells in metachromatic leukodystrophy.

ABSTRACT: The pathological cascade leading from primary storage to neural cell dysfunction and death in metachromatic leukodystrophy (MLD) has been poorly elucidated in human-derived neural cell systems. In the present study, we have modeled the progression of pathological events during the differentiation of patient-specific iPSCs to neuroepithelial progenitor cells (iPSC-NPCs) and mature neurons, astrocytes, and oligodendrocytes at the morphological, molecular, and biochemical level. We showed significant sulfatide accumulation and altered sulfatide composition during the differentiation of MLD iPSC-NPCs into neuronal and glial cells. Changes in sulfatide levels and composition were accompanied by the expansion of the lysosomal compartment, oxidative stress, and apoptosis. The neuronal and glial differentiation capacity of MLD iPSC-NPCs was significantly impaired. We showed delayed appearance and/or reduced levels of oligodendroglial and astroglial markers as well as reduced number of neurons and disorganized neuronal network. Restoration of a functional Arylsulfatase A (ARSA) enzyme in MLD cells using lentiviral-mediated gene transfer normalized sulfatide levels and composition, globally rescuing the pathological phenotype. Our study points to MLD iPSC-derived neural progeny as a useful in vitro model to assess the impact of ARSA deficiency along NPC differentiation into neurons and glial cells. In addition, iPSC-derived neural cultures allowed testing the impact of ARSA reconstitution/overexpression on disease correction and, importantly, on the biology and functional features of human NPCs, with important therapeutic implications.

SUBMITTER: Frati G

PROVIDER: S-EPMC5997994 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Lymphotoxin (LT) is a lymphokine mainly expressed in lymphocytes. LT? binds one or two membrane-associated LT? to form LT?2?1 or LT?1?2 heterotrimers. The predominant LT?1?2 binds to LT? receptor (LT?R) primarily expressed in epithelial and stromal cells. Most studies on LT?R signaling have focused on the organization, development, and maintenance of lymphoid tissues. However, the roles of LT?R signaling in the nervous system, particularly in neurogenesis, remain unknown. Here, we investigated the role of LT?R-mediated NF?B signaling in regulating neural lineage differentiation. METHODS:The C57BL/6J wild-type and GFAP-dnI?B? transgenic mice were used. Serum-free embryoid bodies were cultured from mouse embryonic stem cells and further induced into neural stem/progenitor cells (NSCs/NPCs). Primary neurospheres were cultured from embryonic and adult mouse brains followed by monolayer culture for amplification/passage. NF?B activation was determined by adenovirus-mediated NF?B-firefly-luciferase reporter assay and p65/RelB/p52 nuclear translocation assay. LT?R mRNA expression was evaluated by quantitative RT-PCR and LT?R protein expression was determined by immunohistochemistry and Western blot analysis. Multilabeled immunocytochemistry or immunohistochemistry followed by fluorescent confocal microscopy and quantitative analysis of neural lineage differentiation were performed. Graphing and statistical analysis were performed with GraphPad Prism software. RESULTS:In cultured NSCs/NPCs, LT?1?2 stimulation induced an activation of classical and non-classical NF?B signaling. The expression of LT?R-like immunoreactivity in GFAP+/Sox2+ NSCs was identified in well-established neurogenic zones of adult mouse brain. Quantitative RT-PCR and Western blot analysis validated the expression of LT?R in cultured NSCs/NPCs and brain neurogenic regions. LT?R expression was significantly increased during neural induction. LT?1?2 stimulation in cultured NSCs/NPCs promoted astroglial and oligodendrocytic lineage differentiation, but inhibited neuronal lineage differentiation. Astroglial NF?B inactivation in GFAP-dnI?B? transgenic mice rescued LT?R-mediated abnormal phenotypes of cultured NSCs/NPCs. CONCLUSION:This study provides the first evidence for the expression and function of LT?R signaling in NSCs/NPCs. Activation of LT?R signaling promotes glial lineage differentiation. Our results suggest that neurogenesis is regulated by the adaptive immunity and inflammatory responses.

Project description:Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal disorder caused by the deficiency of arylsulfatase A (ASA), resulting in impaired degradation of sulfatide, an essential sphingolipid of myelin. The clinical manifestations of MLD are characterized by progressive demyelination and subsequent neurological symptoms resulting in severe debilitation. The availability of therapeutic options for treating MLD is limited but expanding with a number of early stage clinical trials already in progress. In the development of therapeutic approaches for MLD, scientists have been facing a number of challenges including blood-brain barrier (BBB) penetration, safety issues concerning therapies targeting the central nervous system, uncertainty regarding the ideal timing for intervention in the disease course, and the lack of more in-depth understanding of the molecular pathogenesis of MLD. Here, we discuss the current status of the different approaches to developing therapies for MLD. Hematopoietic stem cell transplantation has been used to treat MLD patients, utilizing both umbilical cord blood and bone marrow sources. Intrathecal enzyme replacement therapy and gene therapies, administered locally into the brain or by generating genetically modified hematopoietic stem cells, are emerging as novel strategies. In pre-clinical studies, different cell delivery systems including microencapsulated cells or selectively neural cells have shown encouraging results. Small molecules that are more likely to cross the BBB can be used as enzyme enhancers of diverse ASA mutants, either as pharmacological chaperones, or proteostasis regulators. Specific small molecules may also be used to reduce the biosynthesis of sulfatides, or target different affected downstream pathways secondary to the primary ASA deficiency. Given the progressive neurodegenerative aspects of MLD, also seen in other lysosomal diseases, current and future therapeutic strategies will be complementary, whether used in combination or separately at specific stages of the disease course, to produce better outcomes for patients afflicted with this devastating inherited disorder.

Project description:ObjectiveWe aimed to gain more insight into the pathomechanisms of metachromatic leukodystrophy (MLD), by comparing magnitude and direction of diffusion between patients and controls at diagnosis and during follow-up.MethodsFour late-infantile, 16 juvenile and 8 adult onset MLD patients [of which 13 considered eligible for hematopoietic cell transplantation (HCT)] and 47 controls were examined using diffusion tensor imaging. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were quantified and compared between groups using tract-based spatial statistics (TBSS). Diffusion measures were determined for normal-appearing white matter (NAWM), corpus callosum, thalamus (all based on subject-wise segmentation), and pyramidal tracts, determined with probabilistic tractography. Measures were compared between HCT-eligible patients, non-eligible patients and controls using general linear model and nonparametric permutation analyses (randomise) for TBSS data, considering family-wise error corrected p < 0.05 significant.ResultsThroughout white matter (WM), FA was decreased and MD and RD increased in both patient groups compared to controls, while AD was decreased in NAWM and corpus callosum. In the thalamus, no differences in FA were observed, but all diffusivities were increased in both patient groups. Differences were most pronounced between controls and patients non-eligible for HCT. Longitudinally (median follow-up 3.9 years), diffusion measures remained relatively stable for HCT-treated patients, but were progressively abnormal for non-eligible patients.InterpretationThe observed diffusion measures confirm that brain microstructure is changed in MLD, reflecting different pathological processes including loss of myelin and sulfatide accumulation. The observation of both increased and decreased AD probably reflects a balance between myelin and axonal loss vs. intracellular sulfatide storage in macrophages, depending on region and disease stage.

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Human iPSC-based models highlight defective glial and neuronal differentiation from neural progenitor cells in metachromatic leukodystrophy.

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