Human embryonic stem cell-derived neurons as a tool for studying neuroprotection and neurodegeneration

Human-Induced Pluripotent Stem Cell-Based Models for Studying Sex-Specific Differences in Neurodegenerative Diseases

The prevalence of neurodegenerative diseases is steadily increasing worldwide, and epidemiological studies strongly suggest that many of the diseases are sex-biased. It has long been suggested that biological sex differences are crucial for neurodegenerative diseases; however, how biological sex affects disease initiation, progression, and severity is not well-understood. Sex is a critical biological variable that should be taken into account in basic research, and this review aims to highlight the utility of human-induced pluripotent stem cells (iPSC)-derived models for studying sex-specific differences in neurodegenerative diseases, with advantages and limitations. In vitro systems utilizing species-specific, renewable, and physiologically relevant cell sources can provide powerful platforms for mechanistic studies, toxicity testings, and drug discovery. Matched healthy, patient-derived, and gene-corrected human iPSCs, from both sexes, can be utilized to generate neuronal and glial cell types affected by specific neurodegenerative diseases to study sex-specific differences in two-dimensional (2D) and three-dimensional (3D) human culture systems. Such relatively simple and well-controlled systems can significantly contribute to the elucidation of molecular mechanisms underlying sex-specific differences, which can yield effective, and potentially sex-based strategies, against neurodegenerative diseases.

Cell-based therapies for amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Amyotrophic lateral sclerosis (ALS), which is also known as motor neuron disease (MND), is a fatal disease associated with rapidly progressive disability, for which no definitive treatment exists. Current treatment approaches largely focus on relieving symptoms to improve the quality of life of those affected. The therapeutic potential of cell-based therapies in ALS/MND has not been fully evaluated, given the paucity of high-quality clinical trials. Based on data from preclinical studies, cell-based therapy is a promising treatment for ALS/MND. This review was first published in 2015 when the first clinical trials of cell-based therapies were still in progress. We undertook this update to incorporate evidence now available from randomised controlled trials (RCTs).

OBJECTIVES

To assess the effects of cell-based therapy for people with ALS/MND, compared with placebo or no treatment.

SEARCH METHODS

On 31 July 2019, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, and Embase. We also searched two clinical trials registries for ongoing or unpublished studies.

SELECTION CRITERIA

We included RCTs that assigned people with ALS/MND to receive cell-based therapy versus a placebo or no additional treatment. Co-interventions were allowed, provided that they were given to each group equally.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodology.

MAIN RESULTS

Two RCTs involving 112 participants were eligible for inclusion in this review. One study compared autologous bone marrow-mesenchymal stem cells (BM-MSC) plus riluzole versus control (riluzole only), while the other study compared combined intramuscular and intrathecal administration of autologous mesenchymal stem cells secreting neurotrophic factors (MSC-NTF) to placebo. The latter study was reported as an abstract and provided no numerical data. Both studies were funded by biotechnology companies. The only study that contributed to the outcome data in the review involved 64 participants, comparing BM-MSC plus riluzole versus control (riluzole only). It reported outcomes after four to six months. It had a low risk of selection bias, detection bias and reporting bias, but a high risk of performance bias and attrition bias. The certainty of evidence was low for all major efficacy outcomes, with imprecision as the main downgrading factor, because the range of plausible estimates, as shown by the 95% confidence intervals (CIs), encompassed a range that would likely result in different clinical decisions. Functional impairment, expressed as the mean change in the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) score from baseline to six months after cell injection was slightly reduced (better) in the BM-MSC group compared to the control group (mean difference (MD) 3.38, 95% CI 1.22 to 5.54; 1 RCT, 56 participants; low-certainty evidence). ALSFRS-R has a range from 48 (normal) to 0 (maximally impaired); a change of 4 or more points is considered clinically important. The trial did not report outcomes at 12 months. There was no clear difference between the BM-MSC and the no treatment group in change in respiratory function (per cent predicted forced vital capacity; FVC%; MD -0.53, 95% CI -5.37 to 4.31; 1 RCT, 56 participants; low-certainty evidence); overall survival at six months (risk ratio (RR) 1.07, 95% CI 0.94 to 1.22; 1 RCT, 64 participants; low-certainty evidence); risk of total adverse events (RR 0.86, 95% CI 0.62 to 1.19; 1 RCT, 64 participants; low-certainty evidence) or serious adverse events (RR 0.47, 95% CI 0.13 to 1.72; 1 RCT, 64 participants; low-certainty evidence). The study did not measure muscle strength.

AUTHORS' CONCLUSIONS

Currently, there is a lack of high-certainty evidence to guide practice on the use of cell-based therapy to treat ALS/MND. Uncertainties remain as to whether this mode of therapy is capable of restoring muscle function, slowing disease progression, and improving survival in people with ALS/MND. Although one RCT provided low-certainty evidence that BM-MSC may slightly reduce functional impairment measured on the ALSFRS-R after four to six months, this was a small phase II trial that cannot be used to establish efficacy. We need large, prospective RCTs with long-term follow-up to establish the efficacy and safety of cellular therapy and to determine patient-, disease- and cell treatment-related factors that may influence the outcome of cell-based therapy. The major goals of future research are to determine the appropriate cell source, phenotype, dose and method of delivery, as these will be key elements in designing an optimal cell-based therapy programme for people with ALS/MND. Future research should also explore novel treatment strategies, including combinations of cellular therapy and standard or novel neuroprotective agents, to find the best possible approach to prevent or reverse the neurological deficit in ALS/MND, and to prolong survival in this debilitating and fatal condition.

SOD3 overexpression alleviates cerebral ischemia-reperfusion injury in rats

Background

Ischemic stroke is a deadly disease that poses a serious threat to human life. Superoxide dismutase 3 (SOD3, ECSOD) is the main antioxidant enzyme that removes superoxide anions from cells. This study aimed to investigate the effect of SOD3 overexpression on cerebral ischemia‐reperfusion injury in rats.

Methods

GV230‐EGFP‐ECSOD, the recombinant SOD3‐overexpressed vector, was constructed by genetic engineering technology, and mesenchymal stem cells (MSCs) were infected with lentiviral packaging. In animal experiment, cerebral ischemia‐reperfusion injury model rats were successfully established. ECSOD‐MSCs are the MSCs that successfully transfected with SOD3 overexpression vector. The animals were injected with ECSOD‐MSCs (ECSOD‐MSC group), normal MSCs (MSCs group), PBS (PBS group), and not do any processing (Model group) via the tail vein. Then MRI was used to detect the infarct volume of rats, modified Neurological Severity Scores (mNSS), and immunohistochemistry were used to evaluate the expression of neurological function and apoptosis‐related genes in rats.

Results

Western blot analysis revealed that the SOD3 was highly expressed in MSCs. Animal experiments showed that the transplantation of ECSOD‐MSCs significantly reduced the infarct volume of ischemic stroke rats (p < 0.05), significantly improved neurological function in rats (p < 0.05), and found proapoptotic gene, Bax, expression was significantly decreased (p < 0.05), the expression of anti‐apoptotic gene, Bcl‐2, was significantly increased (p < 0.05). The highly expressed SOD3 has no correction with brain infarct volume, and the highly expressed SOD3 has a positive correlation with cell apoptosis. It is speculated that overexpression of SOD3 affects the expression of Bax and Bcl‐2, and improves apoptosis to alleviate ischemic stroke.

Conclusion

Our results indicated that MSCs transfected with SOD3 can effectively alleviate cerebral ischemia‐reperfusion injury in rats.

Cultured networks of excitatory projection neurons and inhibitory interneurons for studying human cortical neurotoxicity

Translating neuroprotective treatments from discovery in cell and animal models to the clinic has proven challenging. To reduce the gap between basic studies of neurotoxicity and neuroprotection and clinically relevant therapies, we developed a human cortical neuron culture system from human embryonic stem cells or human inducible pluripotent stem cells that generated both excitatory and inhibitory neuronal networks resembling the composition of the human cortex. This methodology used timed administration of retinoic acid to FOXG1(+) neural precursor cells leading to differentiation of neuronal populations representative of the six cortical layers with both excitatory and inhibitory neuronal networks that were functional and homeostatically stable. In human cortical neuronal cultures, excitotoxicity or ischemia due to oxygen and glucose deprivation led to cell death that was dependent on N-methyl-D-aspartate (NMDA) receptors, nitric oxide (NO), and poly(ADP-ribose) polymerase (PARP) (a cell death pathway called parthanatos that is distinct from apoptosis, necroptosis, and other forms of cell death). Neuronal cell death was attenuated by PARP inhibitors that are currently in clinical trials for cancer treatment. This culture system provides a new platform for the study of human cortical neurotoxicity and suggests that PARP inhibitors may be useful for ameliorating excitotoxic and ischemic cell death in human neurons.

Cell-based therapies for amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Amyotrophic lateral sclerosis (ALS), which is also known as motor neuron disease (MND) is a fatal disease associated with rapidly progressive disability, for which no definitive treatment as yet exists. Current treatment regimens largely focus on relieving symptoms to improve the quality of life of those affected. Based on data from preclinical studies, cell-based therapy is a promising treatment for ALS/MND.

OBJECTIVES

To assess the effects of cell-based therapy for people with ALS/MND, compared with placebo or no additional treatment.

SEARCH METHODS

On 21 June 2016, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, and Embase. We also searched two clinical trials' registries for ongoing or unpublished studies.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs), quasi-RCTs and cluster RCTs that assigned people with ALS/MND to receive cell-based therapy versus a placebo or no additional treatment. Co-interventions were allowable, provided that they were given to each group equally.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodology.

MAIN RESULTS

No studies were eligible for inclusion in the review. We identified four ongoing trials.

AUTHORS' CONCLUSIONS

Currently, there is a lack of high-quality evidence to guide practice on the use of cell-based therapy to treat ALS/MND.We need large, prospective RCTs to establish the efficacy of cellular therapy and to determine patient-, disease- and cell treatment-related factors that may influence the outcome of cell-based therapy. The major goals of future research should be to determine the appropriate cell source, phenotype, dose, and route of delivery, as these will be key elements in designing an optimal cell-based therapy programme for people with ALS/MND. Future research should also explore novel treatment strategies, including combinations of cellular therapy and standard or novel neuroprotective agents, to find the best possible approach to prevent or reverse the neurological deficit in ALS/MND, and to prolong survival in this debilitating and fatal condition.

Simulation of developing human neuronal cell networks

Background

Microelectrode array (MEA) is a widely used technique to study for example the functional properties of neuronal networks derived from human embryonic stem cells (hESC-NN). With hESC-NN, we can investigate the earliest developmental stages of neuronal network formation in the human brain.

Methods

In this paper, we propose an in silico model of maturating hESC-NNs based on a phenomenological model called INEX. We focus on simulations of the development of bursts in hESC-NNs, which are the main feature of neuronal activation patterns. The model was developed with data from developing hESC-NN recordings on MEAs which showed increase in the neuronal activity during the investigated six measurement time points in the experimental and simulated data.

Results

Our simulations suggest that the maturation process of hESC-NN, resulting in the formation of bursts, can be explained by the development of synapses. Moreover, spike and burst rate both decreased at the last measurement time point suggesting a pruning of synapses as the weak ones are removed.

Conclusions

To conclude, our model reflects the assumption that the interaction between excitatory and inhibitory neurons during the maturation of a neuronal network and the spontaneous emergence of bursts are due to increased connectivity caused by the forming of new synapses.

Pluripotent Human embryonic stem cell derived neural lineages for in vitro modelling of enterovirus 71 infection and therapy

BACKGROUND

The incidence of neurological complications and fatalities associated with Hand, Foot & Mouth disease has increased over recent years, due to emergence of newly-evolved strains of Enterovirus 71 (EV71). In the search for new antiviral therapeutics against EV71, accurate and sensitive in vitro cellular models for preliminary studies of EV71 pathogenesis is an essential prerequisite, before progressing to expensive and time-consuming live animal studies and clinical trials.

METHODS

This study thus investigated whether neural lineages derived from pluripotent human embryonic stem cells (hESC) can fulfil this purpose. EV71 infection of hESC-derived neural stem cells (NSC) and mature neurons (MN) was carried out in vitro, in comparison with RD and SH-SY5Y cell lines.

RESULTS

Upon assessment of post-infection survivability and EV71 production by the various types, it was observed that NSC were significantly more susceptible to EV71 infection compared to MN, RD (rhabdomyosarcoma) and SH-SY5Y cells, which was consistent with previous studies on mice. The SP81 peptide had significantly greater inhibitory effect on EV71 production by NSC and MN compared to the cancer-derived RD and SH-SY5Y cell lines.

CONCLUSIONS

Hence, this study demonstrates that hESC-derived neural lineages can be utilized as in vitro models for studying EV71 pathogenesis and for screening of antiviral therapeutics.

Human stem cell-derived astrocytes and their application to studying Nrf2-mediated neuroprotective pathways and therapeutics in neurodegeneration

Glia, including astrocytes, are increasingly at the forefront of neurodegenerative research for their role in the modulation of neuronal function and survival. Improved understanding of underlying disease mechanisms, including the role of the cellular environment in neurodegeneration, is central to therapeutic development for these currently untreatable diseases. In these endeavours, experimental models that more closely reproduce the human condition have the potential to facilitate the transition between experimental studies in model organisms and patient trials. In this review we discuss the growing role of astrocytes in neurodegenerative diseases, and how astrocytes generated from human pluripotent stem cells represent a useful tool for analyzing astrocytic signalling and influence on neuronal function.

NMDA receptor-dependent glutamate excitotoxicity in human embryonic stem cell-derived neurons

Thanks to the development of efficient differentiation strategies, human pluripotent stem cells (HPSC) offer the opportunity for modelling neuronal injury and dysfunction in human neurons in vitro. Critically, the effective use of HPSC-derived neural cells in disease-modelling and potentially cell replacement therapies hinges on an understanding of the biology of these cells, specifically their development, subtype specification and responses to neurotoxic signalling mediators. Here, we generated neurons from human embryonic stem cells and characterised the development of vulnerability to glutamate excitotoxicity, a key contributor to neuronal injury in several acute and chronic neurodegenerative disorders. Over two months of differentiation we observed a gradual increase in responsiveness of neurons to glutamate-induced Ca(2+) influx, attributable to NMDA receptor activity. This increase was concomitant with an increase in expression of mRNA encoding NMDA and AMPA receptor subunits. Differentiated neurons were vulnerable to glutamate excitotoxicity in a dose-dependent manner, which was reduced by NMDA receptor antagonists.

Experimental and therapeutic opportunities for stem cells in multiple sclerosis

Multiple Sclerosis (MS) is an inflammatory demyelinating neurodegenerative disorder of the brain and spinal cord that causes significant disability in young adults. Although the precise aetiopathogenesis of MS remains unresolved, its pathological hallmarks include inflammation, demyelination, axonal injury (acute and chronic), astrogliosis and variable remyelination. Despite major recent advances in therapeutics for the early stage of the disease there are currently no disease modifying treatments for the progressive stage of disease, whose pathological substrate is axonal degeneration. This represents the great and unmet clinical need in MS. Against this background, human stem cells offer promise both to improve understanding of disease mechanism(s) through in-vitro modeling as well as potentially direct use to supplement and promote remyelination, an endogenous reparative process where entire myelin sheaths are restored to demyelinated axons. Conceptually, stem cells can act directly to myelinate axons or indirectly through different mechanisms to promote endogenous repair; importantly these two mechanisms of action are not mutually exclusive. We propose that discovery of novel methods to invoke or enhance remyelination in MS may be the most effective therapeutic strategy to limit axonal damage and instigate restoration of structure and function in this debilitating condition. Human stem cell derived neurons and glia, including patient specific cells derived through reprogramming, provide an unprecedented experimental system to model MS “in a dish” as well as enable high-throughput drug discovery. Finally, we speculate upon the potential role for stem cell based therapies in MS.

Therapeutic implications of disorders of cell death signalling: membranes, micro-environment, and eicosanoid and docosanoid metabolism

Disruptions of cell death signalling occur in pathological processes, such as cancer and degenerative disease. Increased knowledge of cell death signalling has opened new areas of therapeutic research, and identifying key mediators of cell death has become increasingly important. Early triggering events in cell death may provide potential therapeutic targets, whereas agents affecting later signals may be more palliative in nature. A group of primary mediators are derivatives of the highly unsaturated fatty acids (HUFAs), particularly oxygenated metabolites such as prostaglandins. HUFAs, esterified in cell membranes, act as critical signalling molecules in many pathological processes. Currently, agents affecting HUFA metabolism are widely prescribed in diseases involving disordered cell death signalling. However, partly due to rapid metabolism, their role in cell death signalling pathways is poorly characterized. Recently, HUFA-derived mediators, the resolvins/protectins and endocannabinoids, have added opportunities to target selective signals and pathways. This review will focus on the control of cell death by HUFA, eicosanoid (C20 fatty acid metabolites) and docosanoid (C22 metabolites), HUFA-derived lipid mediators, signalling elements in the micro-environment and their potential therapeutic applications. Further therapeutic approaches will involve cell and molecular biology, the multiple hit theory of disease progression and analysis of system plasticity. Advances in the cell biology of eicosanoid and docosanoid metabolism, together with structure/function analysis of HUFA-derived mediators, will be useful in developing therapeutic agents in pathologies characterized by alterations in cell death signalling.

In vivo tumorigenesis was observed after injection of in vitro expanded neural crest stem cells isolated from adult bone marrow

Bone marrow stromal cells are adult multipotent cells that represent an attractive tool in cellular therapy strategies. Several studies have reported that in vitro passaging of mesenchymal stem cells alters the functional and biological properties of those cells, leading to the accumulation of genetic aberrations. Recent studies described bone marrow stromal cells (BMSC) as mixed populations of cells including mesenchymal (MSC) and neural crest stem cells (NCSC). Here, we report the transformation of NCSC into tumorigenic cells, after in vitro long-term passaging. Indeed, the characterization of 6 neural crest-derived clones revealed the presence of one tumorigenic clone. Transcriptomic analyses of this clone highlighted, among others, numerous cell cycle checkpoint modifications and chromosome 11q down-regulation (suggesting a deletion of chromosome 11q) compared with the other clones. Moreover, unsupervised analysis such as a dendrogram generated after agglomerative hierarchical clustering comparing several transcriptomic data showed important similarities between the tumorigenic neural crest-derived clone and mammary tumor cell lines. Altogether, it appeared that NCSC isolated from adult bone marrow represents a potential danger for cellular therapy, and consequently, we recommend that phenotypic, functional and genetic assays should be performed on bone marrow mesenchymal and neural crest stem cells before in vivo use, to demonstrate whether their biological properties, after ex vivo expansion, remain suitable for clinical application.

Using human pluripotent stem cells to study post-transcriptional mechanisms of neurodegenerative diseases

Post-transcriptional regulation plays a major role in the generation of cell type diversity. In particular, alternative splicing increases diversification of transcriptome between tissues, in different cell types within a tissue, and even in different compartments of the same cell. The complexity of alternative splicing has increased during evolution. With increasing sophistication, however, comes greater potential for malfunction of these intricate processes. Indeed, recent years have uncovered a wealth of disease-causing mutations affecting RNA-binding proteins and non-coding regions on RNAs, highlighting the importance of studying disease mechanisms that act at the level of RNA processing. For instance, mutations in TARDBP and FUS, or a repeat expansion in the intronic region of the C9ORF72 gene, can all cause amyotrophic lateral sclerosis. We discuss how interspecies differences highlight the necessity for human model systems to complement existing non-human approaches to study neurodegenerative disorders. We conclude by discussing the improvements that could further increase the promise of human pluripotent stem for cell-based disease modeling. This article is part of a Special Issue entitled "RNA-Binding Proteins".

Gene expression in the Parkinson's disease brain

The study of gene expression has undergone a transformation in the past decade as the benefits of the sequencing of the human genome have made themselves felt. Increasingly, genome wide approaches are being applied to the analysis of gene expression in human disease as a route to understanding the underlying pathogenic mechanisms. In this review, we will summarise current state of gene expression studies of the brain in Parkinson's disease, and examine how these techniques can be used to gain an insight into aetiology of this devastating disorder.

Anti-apoptosis and cell survival: a review

Type I programmed cell death (PCD) or apoptosis is critical for cellular self-destruction for a variety of processes such as development or the prevention of oncogenic transformation. Alternative forms, including type II (autophagy) and type III (necrotic) represent the other major types of PCD that also serve to trigger cell death. PCD must be tightly controlled since disregulated cell death is involved in the development of a large number of different pathologies. To counter the multitude of processes that are capable of triggering death, cells have devised a large number of cellular processes that serve to prevent inappropriate or premature PCD. These cell survival strategies involve a myriad of coordinated and systematic physiological and genetic changes that serve to ward off death. Here we will discuss the different strategies that are used to prevent cell death and focus on illustrating that although anti-apoptosis and cellular survival serve to counteract PCD, they are nevertheless mechanistically distinct from the processes that regulate cell death.