Non-immortalized human neural stem (NS) cells as a scalable platform for cellular assays

Discovery of a Novel Benzothiadiazine-Based Selective Aldose Reductase Inhibitor as Potential Therapy for Diabetic Peripheral Neuropathy

Aldose reductase 2 (ALR2), an activated enzyme in the polyol pathway by hyperglycemia, has long been recognized as one of the most promising targets for complications of diabetes, especially in diabetic peripheral neuropathy (DPN). However, many of the ALR2 inhibitors have shown serious side effects due to poor selectivity over aldehyde reductase (ALR1). Herein, we describe the discovery of a series of benzothiadiazine acetic acid derivatives as potent and selective inhibitors against ALR2 and evaluation of their anti-DPN activities in vivo. Compound 15c, carrying a carbonyl group at the 3-position of the thiadiazine ring, showed high potent inhibition against ALR2 (IC50 = 33.19 nmol/L) and ∼16,109-fold selectivity for ALR2 over ALR1. Cytotoxicity assays ensured the primary biosafety of 15c. Further pharmacokinetic assay in rats indicated that 15c had a good pharmacokinetic feature (t1/2 = 5.60 h, area under the plasma concentration time curve [AUC(0-t)] = 598.57 ± 216.5 μg/mL * h), which was superior to epalrestat (t1/2 = 2.23 h, AUC[0-t] = 20.43 ± 3.7 μg/mL * h). Finally, in a streptozotocin-induced diabetic rat model, 15c significantly increased the nerve conduction velocities of impaired sensory and motor nerves, achieved potent inhibition of d-sorbitol production in the sciatic nerves, and significantly increased the paw withdrawal mechanical threshold. By combining the above investigations, we propose that 15c might represent a promising lead compound for the discovery of an antidiabetic peripheral neuropathy drug.

ARTICLE HIGHLIGHTS

Vasculature cells control neuroglial co-localization and synaptic connection in a central nervous system tissue mimic system

Despite the development of neural tissue differentiation methods using a wide variety of stem cells and compartments, there is no standardized strategy for establishing synapses. As the neuronal network is developed in parallel with blood vessel angiogenesis in the central nervous system (CNS) from the embryonic period, we examined neuron-astrocyte-vasculature interactions to understand the effect of the vasculature on the development and stabilization of neurological morphogenesis. We generated a cellular co-culture module targeting the CNS that was embedded in a collagen-based extracellular matrix (ECM) gel. Our neuron-astrocyte-vascular complex module identified the neurological co-localization effect by endothelial cells, as well as the pericyte-induced improvement of synaptic connections. Furthermore, it was suggested that the PDGF, BDNF, IGF, and WNT/BMP pathways were upregulated in synaptic connections enhanced conditions, which are composed of neurexin. These results suggest that the integrity of the vasculature cells in the CNS is important for the establishment of neuronal networks and for synapse connection.

Genome editing in stem cells for genetic neurodisorders

The recent advent of genome editing techniques and their rapid improvement paved the way in establishing innovative human neurological disease models and in developing new therapeutic opportunities. Human pluripotent (both induced or naive) stem cells and neural stem cells represent versatile tools to be applied to multiple research needs and, together with genomic snip and fix tools, have recently made possible the creation of unique platforms to directly investigate several human neural affections. In this chapter, we will discuss genome engineering tools, and their recent improvements, applied to the stem cell field, focusing on how these two technologies may be pivotal instruments to deeply unravel molecular mechanisms underlying development and function, as well as disorders, of the human brain. We will review how these frontier technologies may be exploited to investigate or treat severe neurodevelopmental disorders, such as microcephaly, autism spectrum disorder, schizophrenia, as well as neurodegenerative conditions, including Parkinson's disease, Huntington's disease, Alzheimer's disease, and spinal muscular atrophy.

Targeting metabolic plasticity in glioma stem cells in vitro and in vivo through specific inhibition of c-Src by TAT-Cx43266-283

Background

Glioblastoma is the most aggressive primary brain tumour and has a very poor prognosis. Inhibition of c-Src activity in glioblastoma stem cells (GSCs, responsible for glioblastoma lethality) and primary glioblastoma cells by the peptide TAT-Cx43_266–283 reduces tumorigenicity, and boosts survival in preclinical models. Because c-Src can modulate cell metabolism and several reports revealed poor clinical efficacy of various antitumoral drugs due to metabolic rewiring in cancer cells, here we explored the inhibition of advantageous GSC metabolic plasticity by the c-Src inhibitor TAT-Cx43_266-283.

Methods

Metabolic impairment induced by the c-Src inhibitor TAT-Cx43_266-283 in vitro was assessed by fluorometry, western blotting, immunofluorescence, qPCR, enzyme activity assays, electron microscopy, Seahorse analysis, time-lapse imaging, siRNA, and MTT assays. Protein expression in tumours from a xenograft orthotopic glioblastoma mouse model was evaluated by immunofluorescence.

Findings

TAT-Cx43_266–283 decreased glucose uptake in human GSCs and reduced oxidative phosphorylation without a compensatory increase in glycolysis, with no effect on brain cell metabolism, including rat neurons, human and rat astrocytes, and human neural stem cells. TAT-Cx43_266-283 impaired metabolic plasticity, reducing GSC growth and survival under different nutrient environments. Finally, GSCs intracranially implanted with TAT-Cx43_266–283 showed decreased levels of important metabolic targets for cancer therapy, such as hexokinase-2 and GLUT-3.

Interpretation

The reduced ability of TAT-Cx43_266-283–treated GSCs to survive in metabolically challenging settings, such as those with restricted nutrient availability or the ever-changing in vivo environment, allows us to conclude that the advantageous metabolic plasticity of GSCs can be therapeutically exploited through the specific and cell-selective inhibition of c-Src by TAT-Cx43_266-283.

Funding

Spanish Ministerio de Economía y Competitividad (FEDER BFU2015-70040-R and FEDER RTI2018-099873-B-I00), Fundación Ramón Areces. Fellowships from the Junta de Castilla y León, European Social Fund, Ministerio de Ciencia and Asociación Española Contra el Cáncer (AECC).

Human Neural Stem Cell Systems to Explore Pathogen-Related Neurodevelopmental and Neurodegenerative Disorders

Building and functioning of the human brain requires the precise orchestration and execution of myriad molecular and cellular processes, across a multitude of cell types and over an extended period of time. Dysregulation of these processes affects structure and function of the brain and can lead to neurodevelopmental, neurological, or psychiatric disorders. Multiple environmental stimuli affect neural stem cells (NSCs) at several levels, thus impairing the normal human neurodevelopmental program. In this review article, we will delineate the main mechanisms of infection adopted by several neurotropic pathogens, and the selective NSC vulnerability. In particular, TORCH agents, i.e., Toxoplasma gondii, others (including Zika virus and Coxsackie virus), Rubella virus, Cytomegalovirus, and Herpes simplex virus, will be considered for their devastating effects on NSC self-renewal with the consequent neural progenitor depletion, the cellular substrate of microcephaly. Moreover, new evidence suggests that some of these agents may also affect the NSC progeny, producing long-term effects in the neuronal lineage. This is evident in the paradigmatic example of the neurodegeneration occurring in Alzheimer's disease.

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

Human neuroepithelial stem cell regional specificity enables spinal cord repair through a relay circuit

Traumatic spinal cord injury results in persistent disability due to disconnection of surviving neural elements. Neural stem cell transplantation has been proposed as a therapeutic option, but optimal cell type and mechanistic aspects remain poorly defined. Here, we describe robust engraftment into lesioned immunodeficient mice of human neuroepithelial stem cells derived from the developing spinal cord and maintained in self-renewing adherent conditions for long periods. Extensive elongation of both graft and host axons occurs. Improved functional recovery after transplantation depends on neural relay function through the grafted neurons, requires the matching of neural identity to the anatomical site of injury, and is accompanied by expression of specific marker proteins. Thus, human neuroepithelial stem cells may provide an anatomically specific relay function for spinal cord injury recovery.

The optimal type or regional origin of stem cells for regenerative applications in the nervous system has not yet been established. Here the authors show that human neuroepithelial stem cells from the developing spinal cord, but not those from the developing cortex, show good host-graft interaction when transplanted to rodent models of spinal cord injury.

Scalable Expansion of Human Pluripotent Stem Cell-Derived Neural Progenitors in Stirred Suspension Bioreactor Under Xeno-free Condition

Recent advances in neural differentiation technology have paved the way to generate clinical grade neural progenitor populations from human pluripotent stem cells. These cells are an excellent source for the production of neural cell-based therapeutic products to treat incurable central nervous system disorders such as Parkinson's disease and spinal cord injuries. This progress can be complemented by the development of robust bioprocessing technologies for large scale expansion of clinical grade neural progenitors under GMP conditions for promising clinical use and drug discovery applications. Here, we describe a protocol for a robust, scalable expansion of human neural progenitor cells from pluripotent stem cells as 3D aggregates in a stirred suspension bioreactor. The use of this platform has resulted in easily expansion of neural progenitor cells for several passages with a fold increase of up to 4.2 over a period of 5 days compared to a maximum 1.5-2-fold increase in the adherent static culture over a 1 week period. In the bioreactor culture, these cells maintained self-renewal, karyotype stability, and cloning efficiency capabilities. This approach can be also used for human neural progenitor cells derived from other sources such as the human fetal brain.

Bringing Neural Cell Therapies to the Clinic: Past and Future Strategies

Cell replacement therapy in the nervous system has a rich history, with ∼40 years of research and ∼30 years of clinical experience. There is compelling evidence that appropriate cells can integrate and function in the dysfunctioning human nervous system, but the clinical results are mixed in practice. A number of factors conspire to vary patient outcome: the indication, cell source, patient selection, and team performing transplantation are all variables that can affect efficacy. Most early clinical trials have used fetal cells, a limited cell source that resists scale and standardization. Direct fetal cell transplantation creates significant challenges to commercialization that is the ultimate goal of an effective cell therapy. One approach to help scale and standardize fetal cell preparations is the expansion of neural cells in vitro. Expansion is achieved by transformation or through the application of mitogens before cryopreservation. Recently, neural cells derived from pluripotent stem cells have provided a scalable alternative. Pluripotent stem cells are desirable for manufacturing but present alternative concerns and manufacturing obstacles. All cell sources require robust and reproducible manufacturing to make nervous system cell replacement therapy an option for patients. Here, we discuss the challenges and opportunities for cell replacement in the nervous system. In this review, we give an overview of completed and ongoing neural cell transplantation clinical trials, and we discuss the challenges and opportunities for future cell replacement trials with a particular focus on pluripotent stem cell-derived therapies.

Highly Expandable Human iPS Cell-Derived Neural Progenitor Cells (NPC) and Neurons for Central Nervous System Disease Modeling and High-Throughput Screening

Reprogramming of human somatic cells into induced pluripotent stem (iPS) cells has greatly expanded the set of research tools available to investigate the molecular and cellular mechanisms underlying central nervous system (CNS) disorders. Realizing the promise of iPS cell technology for the identification of novel therapeutic targets and for high-throughput drug screening requires implementation of methods for the large-scale production of defined CNS cell types. Here we describe a protocol for generating stable, highly expandable, iPS cell-derived CNS neural progenitor cells (NPC) using multi-dimensional fluorescence activated cell sorting (FACS) to purify NPC defined by cell surface markers. In addition, we describe a rapid, efficient, and reproducible method for generating excitatory cortical-like neurons from these NPC through inducible expression of the pro-neural transcription factor Neurogenin 2 (iNgn2-NPC). Finally, we describe methodology for the use of iNgn2-NPC for probing human neuroplasticity and mechanisms underlying CNS disorders using high-content, single-cell-level automated microscopy assays. © 2017 by John Wiley & Sons, Inc.

Pluripotent stem cell-derived radial glia-like cells as stable intermediate for efficient generation of human oligodendrocytes

Neural precursor cells (NPCs) derived from human pluripotent stem cells (hPSCs) represent an attractive tool for the in vitro generation of various neural cell types. However, the developmentally early NPCs emerging during hPSC differentiation typically show a strong propensity for neuronal differentiation, with more limited potential for generating astrocytes and, in particular, for generating oligodendrocytes. This phenomenon corresponds well to the consecutive and protracted generation of neurons and GLIA during normal human development. To obtain a more gliogenic NPC type, we combined growth factor-mediated expansion with pre-exposure to the differentiation-inducing agent retinoic acid and subsequent immunoisolation of CD133-positive cells. This protocol yields an adherent and self-renewing population of hindbrain/spinal cord radial glia (RG)-like neural precursor cells (RGL-NPCs) expressing typical neural stem cell markers such as nestin, ASCL1, SOX2, and PAX6 as well as RG markers BLBP, GLAST, vimentin, and GFAP. While RGL-NPCs maintain the ability for tripotential differentiation into neurons, astrocytes, and oligodendrocytes, they exhibit greatly enhanced propensity for oligodendrocyte generation. Under defined differentiation conditions promoting the expression of the major oligodendrocyte fate-determinants OLIG1/2, NKX6.2, NKX2.2, and SOX10, RGL-NPCs efficiently convert into NG2-positive oligodendroglial progenitor cells (OPCs) and are subsequently capable of in vivo myelination. Representing a stable intermediate between PSCs and OPCs, RGL-NPCs expedite the generation of PSC-derived oligodendrocytes with O4-, 4860-, and myelin basic protein (MBP)-positive cells that already appear within 7 weeks following growth factor withdrawal-induced differentiation. Thus, RGL-NPCs may serve as robust tool for time-efficient generation of human oligodendrocytes from embryonic and induced pluripotent stem cells.

Translation: screening for novel therapeutics with disease-relevant cell types derived from human stem cell models

The advent of somatic cell reprogramming technologies-which enables the generation of patient-specific, induced pluripotent stem cell and other trans-differentiated human neuronal cell models-provides new means of gaining insight into the molecular mechanisms and neural substrates of psychiatric disorders. By allowing a more precise understanding of genotype-phenotype relationship in disease-relevant human cell types, the use of reprogramming technologies in tandem with emerging genome engineering approaches provides a previously "missing link" between basic research and translational efforts. In this review, we summarize advances in applying human pluripotent stem cell and reprogramming technologies to generate specific neural subtypes with a focus on the use of these in vitro systems for the discovery of small molecule-probes and novel therapeutics. Examples are given where human cell models of psychiatric disorders have begun to reveal new mechanistic insight into pathophysiology and simultaneously have provided the foundation for developing disease-relevant, phenotypic assays suitable for both functional genomic and chemical screens. A number of areas for future research are discussed, including the need to develop robust methodology for the reproducible, large-scale production of disease-relevant neural cell types in formats compatible with high-throughput screening modalities, including high-content imaging, multidimensional, signature-based screening, and in vitro network with multielectrode arrays. Limitations, including the challenges in recapitulating neurocircuits and non-cell autonomous phenotypes are discussed. Although these technologies are still in active development, we conclude that, as our understanding of how to efficiently generate and probe the plasticity of patient-specific stem models improves, their utility is likely to advance rapidly.

Human neural stem cells induce functional myelination in mice with severe dysmyelination

Shiverer-immunodeficient (Shi-id) mice demonstrate defective myelination in the central nervous system (CNS) and significant ataxia by 2 to 3 weeks of life. Expanded, banked human neural stem cells (HuCNS-SCs) were transplanted into three sites in the brains of neonatal or juvenile Shi-id mice, which were asymptomatic or showed advanced hypomyelination, respectively. In both groups of mice, HuCNS-SCs engrafted and underwent preferential differentiation into oligodendrocytes. These oligodendrocytes generated compact myelin with normalized nodal organization, ultrastructure, and axon conduction velocities. Myelination was equivalent in neonatal and juvenile mice by quantitative histopathology and high-field ex vivo magnetic resonance imaging, which, through fractional anisotropy, revealed CNS myelination 5 to 7 weeks after HuCNS-SC transplantation. Transplanted HuCNS-SCs generated functional myelin in the CNS, even in animals with severe symptomatic hypomyelination, suggesting that this strategy may be useful for treating dysmyelinating diseases.

Automated large-scale culture and medium-throughput chemical screen for modulators of proliferation and viability of human induced pluripotent stem cell-derived neuroepithelial-like stem cells

The aim of this study was to demonstrate proof-of-concept feasibility for the use of human neural stem cells (NSCs) for high-throughput screening (HTS) applications. For this study, an adherent human induced pluripotent stem (iPS) cell-derived long-term, self-renewing, neuroepithelial-like stem (lt-NES) cell line was selected as a representative NSC. Here, we describe the automated large-scale serum-free culture ("scale-up") of human lt-NES cells on the CompacT SelecT cell culture robotic platform, followed by their subsequent automated "scale-out" into a microwell plate format. We also report a medium-throughput screen of 1000 compounds to identify modulators of neural stem cell proliferation and/or survival. The screen was performed on two independent occasions using a cell viability assay with end-point reading resulting in the identification of 24 potential hit compounds, 5 of which were found to increase the proliferation and/or survival of human lt-NES on both occasions. Follow-up studies confirmed a dose-dependent effect of one of the hit compounds, which was a Cdk-2 modulator. This approach could be further developed as part of a strategy to screen compounds to either improve the procedures for the in vitro expansion of neural stem cells or to potentially modulate endogenous neural stem cell behavior in the diseased nervous system.

A high-throughput screen for Wnt/β-catenin signaling pathway modulators in human iPSC-derived neural progenitors

Wnt/β-catenin signaling has emerged as a central player in pathways implicated in the pathophysiology and treatment of neuropsychiatric disorders. To identify potential novel therapeutics for these disorders, high-throughput screening (HTS) assays reporting on Wnt/β-catenin signaling in disease-relevant contexts are needed. The use of human patient-derived induced pluripotent stem cell (iPSC) models provides ideal disease-relevant context if these stem cell cultures can be adapted for HTS-compatible formats. Here, we describe a sensitive, HTS-compatible Wnt/β-catenin signaling reporter system generated in homogeneous, expandable neural progenitor cells (NPCs) derived from human iPSCs. We validated this system by demonstrating dose-responsive stimulation by several known Wnt/β-catenin signaling pathway modulators, including Wnt3a, a glycogen synthase kinase-3 (GSK3) inhibitor, and the bipolar disorder therapeutic lithium. These responses were robust and reproducible over time across many repeated assays. We then conducted a screen of ~1500 compounds from a library of Food and Drug Administration-approved drugs and known bioactives and confirmed the HTS hits, revealing multiple chemical and biological classes of novel small-molecule probes of Wnt/β-catenin signaling. Generating these type of pathway-selective, cell-based phenotypic assays in human iPSC-derived neural cells will advance the field of human experimental neurobiology toward the goal of identifying and validating targets for neuropsychiatric disorders.