Transplantation of induced pluripotent stem cells improves functional recovery in Huntington's disease rat model

Recent approaches in regenerative medicine in the fight against neurodegenerative disease

Neurodegenerative diseases arise due to slow and gradual loss of structure and/or function of neurons and glial cells and cause different degrees of loss of cognition abilities and sensation. The little success in developing effective treatments imposes a high and regressive economic impact on society, patients and their families. In recent years, regenerative medicine has provided a great opportunity to research new innovative strategies with strong potential to treatleva these diseases. These effects are due to the ability of suitable cells and biomaterials to regenerate damaged nerves with differentiated cells, creating an appropriate environment for recovering or preserving existing healthy neurons and glial cells from destruction and damage. Ultimately, a better understanding and thus a further investigation of stem cell technology, tissue engineering, gene therapy, and exosomes allows progress towards practical and effective treatments for neurodegenerative diseases. Therefore, in this review, advances currently being developed in regenerative medicine using animal models and human clinical trials in neurological disorders are summarized.

Anti-inflammatory effect of dental pulp stem cells

Dental pulp stem cells (DPSCs) have received a lot of attention as a regenerative medicine tool with strong immunomodulatory capabilities. The excessive inflammatory response involves a variety of immune cells, cytokines, and has a considerable impact on tissue regeneration. The use of DPSCs for controlling inflammation for the purpose of treating inflammation-related diseases and autoimmune disorders such as supraspinal nerve inflammation, inflammation of the pulmonary airways, systemic lupus erythematosus, and diabetes mellitus is likely to be safer and more regenerative than traditional medicines. The mechanism of the anti-inflammatory and immunomodulatory effects of DPSCs is relatively complex, and it may be that they themselves or some of the substances they secrete regulate a variety of immune cells through inflammatory immune-related signaling pathways. Most of the current studies are still at the laboratory cellular level and animal model level, and it is believed that through the efforts of more researchers, DPSCs/SHED are expected to be transformed into excellent drugs for the clinical treatment of related diseases.

The Use of Stem Cells as a Potential Treatment Method for Selected Neurodegenerative Diseases: Review

Stem cells have been the subject of research for years due to their enormous therapeutic potential. Most neurological diseases such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are incurable or very difficult to treat. Therefore new therapies are sought in which autologous stem cells are used. They are often the patient's only hope for recovery or slowing down the progress of the disease symptoms. The most important conclusions arise after analyzing the literature on the use of stem cells in neurodegenerative diseases. The effectiveness of MSC cell therapy has been confirmed in ALS and HD therapy. MSC cells slow down ALS progression and show early promising signs of efficacy. In HD, they reduced huntingtin (Htt) aggregation and stimulation of endogenous neurogenesis. MS therapy with hematopoietic stem cells (HSCs) inducted significant recalibration of pro-inflammatory and immunoregulatory components of the immune system. iPSC cells allow for accurate PD modeling. They are patient-specific and therefore minimize the risk of immune rejection and, in long-term observation, did not form any tumors in the brain. Extracellular vesicles derived from bone marrow mesenchymal stromal cells (BM-MSC-EVs) and Human adipose-derived stromal/stem cells (hASCs) cells are widely used to treat AD. Due to the reduction of Aβ42 deposits and increasing the survival of neurons, they improve memory and learning abilities. Despite many animal models and clinical trial studies, cell therapy still needs to be refined to increase its effectiveness in the human body.

Exploring the neuroprotective effects of montelukast on brain inflammation and metabolism in a rat model of quinolinic acid-induced striatal neurotoxicity

BACKGROUND

One intrastriatal administration of quinolinic acid (QA) in rats induces a lesion with features resembling those observed in Huntington's disease. Our aim is to evaluate the effects of the cysteinyl leukotriene receptor antagonist montelukast (MLK), which exhibited neuroprotection in different preclinical models of neurodegeneration, on QA-induced neuroinflammation and regional metabolic functions.

METHODS

The right and left striatum of Sprague Dawley and athymic nude rats were injected with QA and vehicle (VEH), respectively. Starting from the day before QA injection, animals were treated with 1 or 10 mg/kg of MLK or VEH for 14 days. At 14 and 30 days post-lesion, animals were monitored with magnetic resonance imaging (MRI) and positron emission tomography (PET) using [18F]-VC701, a translocator protein (TSPO)-specific radiotracer. Striatal neuroinflammatory response was measured post-mortem in rats treated with 1 mg/kg of MLK by immunofluorescence. Rats treated with 10 mg/kg of MLK also underwent a [18F]-FDG PET study at baseline and 4 months after lesion. [18F]-FDG PET data were then used to assess metabolic connectivity between brain regions by applying a covariance analysis method.

RESULTS

MLK treatment was not able to reduce the QA-induced increase in striatal TSPO PET signal and MRI lesion volume, where we only detected a trend towards reduction in animals treated with 10 mg/kg of MLK. Post-mortem immunofluorescence analysis revealed that MLK attenuated the increase in striatal markers of astrogliosis and activated microglia in the lesioned hemisphere. We also found a significant increase in a marker of anti-inflammatory activity (MannR) and a trend towards reduction in a marker of pro-inflammatory activity (iNOS) in the lesioned striatum of MLK-compared to VEH-treated rats. [18F]-FDG uptake was significantly reduced in the striatum and ipsilesional cortical regions of VEH-treated rats at 4 months after lesion. MLK administration preserved glucose metabolism in these cortical regions, but not in the striatum. Finally, MLK was able to counteract changes in metabolic connectivity and measures of network topology induced by QA, in both lesioned and non-lesioned hemispheres.

CONCLUSIONS

Overall, MLK treatment produced a significant neuroprotective effect by reducing neuroinflammation assessed by immunofluorescence and preserving regional brain metabolism and metabolic connectivity from QA-induced neurotoxicity in cortical and subcortical regions.

Stem cell therapy for central nervous system disorders: Metabolic interactions between transplanted cells and local microenvironments

Stem cell therapy is a promising and rapidly advancing treatment strategy for a multitude of neurologic disorders. Yet, while early phase clinical trials are being pursued in many disorders, the mechanism of action often remains unclear. One important potential mechanism by which stem cells provide neuroprotection is through metabolic signaling with diseased neurons, glia, and other cell types in the nervous system microenvironment. Early studies exploring such interactions report normalization of glucose metabolism, induction of protective mitochondrial genes, and even interactions with supportive neurovasculature. Local metabolic conditions also impact stem cell biology, which can have a large impact on transplant viability and efficacy. Epigenetic changes that occur in the donor prior to collection of stem cells, and even during in vitro culture conditions, may have effects on stem cell biology that are carried into the host upon stem cell transplantation. Transplanted stem cells also face potentially toxic metabolic microenvironments at the targeted transplant site. Novel approaches for metabolically "preconditioning" stem cells prior to transplant harness metabolic machinery to optimize stem cell survival upon transplant. Ultimately, an improved understanding of the metabolic cross-talk between implanted stem cells and the local nervous system environment, in both disease and injury states, will increase the likelihood of success in translating stem cell therapy to early trials in neurological disease.

Therapeutic Strategies in Huntington’s Disease: From Genetic Defect to Gene Therapy

Despite the identification of an expanded CAG repeat on exon 1 of the huntingtin gene located on chromosome 1 as the genetic defect causing Huntington’s disease almost 30 years ago, currently approved therapies provide only limited symptomatic relief and do not influence the age of onset or disease progression rate. Research has identified various intricate pathogenic cascades which lead to neuronal degeneration, but therapies interfering with these mechanisms have been marked by many failures and remain to be validated. Exciting new opportunities are opened by the emerging techniques which target the mutant protein DNA and RNA, allowing for “gene editing”. Although some issues relating to “off-target” effects or immune-mediated side effects need to be solved, these strategies, combined with stem cell therapies and more traditional approaches targeting specific pathogenic cascades, such as excitotoxicity and bioavailability of neurotrophic factors, could lead to significant improvement of the outcomes of treated Huntington’s disease patients.

Spermatozoan Metabolism as a Non-Traditional Model for the Study of Huntington’s Disease

Huntington’s Disease (HD) is a fatal autosomal dominant neurodegenerative disease manifested through motor dysfunction and cognitive deficits. Decreased fertility is also observed in HD animal models and HD male patients, due to altered spermatogenesis and sperm function, thus resulting in reduced fertilization potential. Although some pharmaceuticals are currently utilized to mitigate HD symptoms, an effective treatment that remedies the pathogenesis of the disease is yet to be approved by the FDA. Identification of genes and relevant diagnostic biomarkers and therapeutic target pathways including glycolysis and mitochondrial complex-I-dependent respiration may be advantageous for early diagnosis, management, and treatment of the disease. This review addresses the HD pathway in neuronal and sperm metabolism, including relevant gene and protein expression in both neurons and spermatozoa, indicated in the pathogenesis of HD. Furthermore, zinc-containing and zinc-interacting proteins regulate and/or are regulated by zinc ion homeostasis in both neurons and spermatozoa. Therefore, this review also aims to explore the comparative role of zinc in both neuronal and sperm function. Ongoing studies aim to characterize the products of genes implicated in HD pathogenesis that are expressed in both neurons and spermatozoa to facilitate studies of future treatment avenues in HD and HD-related male infertility. The emerging link between zinc homeostasis and the HD pathway could lead to new treatments and diagnostic methods linking genetic sperm defects with somatic comorbidities.

Current and Possible Future Therapeutic Options for Huntington’s Disease

Huntington’s disease (HD) is an autosomal neurodegenerative disease that is characterized by an excessive number of CAG trinucleotide repeats within the huntingtin gene ( HTT). HD patients can present with a variety of symptoms including chorea, behavioural and psychiatric abnormalities and cognitive decline. Each patient has a unique combination of symptoms, and although these can be managed using a range of medications and non-drug treatments there is currently no cure for the disease. Current therapies prescribed for HD can be categorized by the symptom they treat. These categories include chorea medication, antipsychotic medication, antidepressants, mood stabilizing medication as well as non-drug therapies. Fortunately, there are also many new HD therapeutics currently undergoing clinical trials that target the disease at its origin; lowering the levels of mutant huntingtin protein (mHTT). Currently, much attention is being directed to antisense oligonucleotide (ASO) therapies, which bind to pre-RNA or mRNA and can alter protein expression via RNA degradation, blocking translation or splice modulation. Other potential therapies in clinical development include RNA interference (RNAi) therapies, RNA targeting small molecule therapies, stem cell therapies, antibody therapies, non-RNA targeting small molecule therapies and neuroinflammation targeted therapies. Potential therapies in pre-clinical development include Zinc-Finger Protein (ZFP) therapies, transcription activator-like effector nuclease (TALEN) therapies and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system (Cas) therapies. This comprehensive review aims to discuss the efficacy of current HD treatments and explore the clinical trial progress of emerging potential HD therapeutics.

Morris water maze: a versatile and pertinent tool for assessing spatial learning and memory

Since its development about 40 years ago (1981–2021), Morris water maze has turned into a very popular tool for assessing spatial learning and memory. Its many advantages have ensured its pertinence to date. These include its effectiveness in evaluating hippocampal-dependent learning and memory, exemption from motivational differences across diverse experimental manipulations, reliability in various cross-species studies, and adaptability to many experimental conditions with various test protocols. Nonetheless, throughout its establishment, several experimental and analysis loopholes have galvanized researchers to assess ways in which it could be improved and adapted to fill this gap. Therefore, in this review, we briefly summarize these developments since the early years of its establishment through to the most recent advancements in computerized analysis, offering more comprehensive analysis paradigms. In addition, we discuss the adaptability of the Morris water maze across different test versions and analysis paradigms, providing suggestions with regard to the best paradigms for particular experimental conditions. Hence, the proper selection of the experimental protocols, analysis paradigms, and consideration of the assay’s limitations should be carefully considered. Given that appropriate measures are taken, with various adaptations made, the Morris water maze will likely remain a relevant tool to assess the mechanisms of spatial learning and memory.

Stem cells as a potential therapeutic option for treating neurodegenerative diseases

In future, neurodegenerative diseases will take over cancer's place and become the major cause of death in the world, especially in developed countries. Advancements in the medical field and its facilities have led to an increase in the old age population, and thus contributing to the increase in number of people suffering from neurodegenerative diseases. Economically it is of a great burden to society and the affected family. No current treatment aims to replace, protect, and regenerate lost neurons; instead, it alleviates the symptoms, extends the life span by a few months and creates severe side effects. Moreover, people who are affected are physically dependent for performing their basic activities, which makes their life miserable. There is an urgent need for therapy that could be able to overcome the deficits of conventional therapy for neurodegenerative diseases. Stem cells, the unspecialized cells with the properties of self-renewing and potency to differentiate into various cells types can become a potent therapeutic option for neurodegenerative diseases. Stem cells have been widely used in clinical trials to evaluate their potential in curing different types of ailments. In this review, we discuss the various types of stem cells and their potential use in the treatment of neurodegenerative disease based on published preclinical and clinical studies.

New Avenues for the Treatment of Huntington's Disease

Huntington’s disease (HD) is a neurodegenerative disorder caused by a CAG expansion in the HD gene. The disease is characterized by neurodegeneration, particularly in the striatum and cortex. The first symptoms usually appear in mid-life and include cognitive deficits and motor disturbances that progress over time. Despite being a genetic disorder with a known cause, several mechanisms are thought to contribute to neurodegeneration in HD, and numerous pre-clinical and clinical studies have been conducted and are currently underway to test the efficacy of therapeutic approaches targeting some of these mechanisms with varying degrees of success. Although current clinical trials may lead to the identification or refinement of treatments that are likely to improve the quality of life of those living with HD, major efforts continue to be invested at the pre-clinical level, with numerous studies testing novel approaches that show promise as disease-modifying strategies. This review offers a detailed overview of the currently approved treatment options for HD and the clinical trials for this neurodegenerative disorder that are underway and concludes by discussing potential disease-modifying treatments that have shown promise in pre-clinical studies, including increasing neurotropic support, modulating autophagy, epigenetic and genetic manipulations, and the use of nanocarriers and stem cells.

Utilising Induced Pluripotent Stem Cells in Neurodegenerative Disease Research: Focus on Glia

Induced pluripotent stem cells (iPSCs) are a self-renewable pool of cells derived from an organism's somatic cells. These can then be programmed to other cell types, including neurons. Use of iPSCs in research has been two-fold as they have been used for human disease modelling as well as for the possibility to generate new therapies. Particularly in complex human diseases, such as neurodegenerative diseases, iPSCs can give advantages over traditional animal models in that they more accurately represent the human genome. Additionally, patient-derived cells can be modified using gene editing technology and further transplanted to the brain. Glial cells have recently become important avenues of research in the field of neurodegenerative diseases, for example, in Alzheimer's disease and Parkinson's disease. This review focuses on using glial cells (astrocytes, microglia, and oligodendrocytes) derived from human iPSCs in order to give a better understanding of how these cells contribute to neurodegenerative disease pathology. Using glia iPSCs in in vitro cell culture, cerebral organoids, and intracranial transplantation may give us future insight into both more accurate models and disease-modifying therapies.

Stem cell in neurodegenerative disorders; an emerging strategy

Neurodegenerative disorders are a diversity of disorders, surrounding Alzheimer's (AD), Parkinson's (PD), Huntington's diseases (HD), and amyotrophic lateral sclerosis (ALS) accompanied by some other less common diseases generally characterized by either developed deterioration of central or peripheral nervous system structurally or functionally. Today, with the viewpoint of an increasingly aging society, the number of patients with neurodegenerative diseases and sociomedical burdens will spread intensely. During the last decade, stem cell technology has attracted great attention for treating neurodegenerative diseases worldwide because of its unique attributes. As acknowledged, there are several categories of stem cells being able to proliferate and differentiate into various cellular lineages, highlighting their significance in the context of regenerative medicine. In preclinical models, stem cell therapy using mesenchymal stem/stromal cells (MSCs), hematopoietic stem cells (HSCs), and neural progenitor or stem cells (NPCs or NSCs) along with pluripotent stem cells (PSCs)-derived neuronal cells could elicit desired therapeutic effects, enabling functional deficit rescue partially. Regardless of the noteworthy progress in our scientific awareness and understanding of stem cell biology, there still exist various challenges to defeat. In the present review, we provide a summary of the therapeutic potential of stem cells and discuss the current status and prospect of stem cell strategy in neurodegenerative diseases, in particular, AD, PD, ALS, and HD.

Transplantation of human dental pulp stem cells compensates for striatal atrophy and modulates neuro-inflammation in 3-nitropropionic acid rat model of Huntington's disease

Stem cell-based therapy has recently offered a promising alternative for the remedy of neurodegenerative disorders like Huntington's disease (HD). Herein, we investigated the potential ameliorative effects of implantation of dental pulp stem cells (DPSCs) in 3-nitropropionic acid (3-NP) rat models of HD. In this regard, human DPSCs were isolated, culture-expanded and implanted in rats lesioned with 3-NP. Post-transplantation examinations revealed that DPSCs were able to survive and augment motor skills and muscle activity. Histological analysis showed DPSCs treatment hampered the shrinkage of the striatum along with the inhibition of gliosis and microgliosis in the striatum of 3-NP rat models. We also detected the downregulation of Caspase-3 and pro-inflammatory cytokines such as TNF and IL-1β upon DPSCs grafting. Overall, these findings imply that the grafting of DPSCs could repair motor-skill impairment and induce neurogenesis, probably through the secretion of neurotrophic factors and the modulation of neuroinflammatory response in HD animal models.

Human stem cell models of polyglutamine diseases: Sources for disease models and cell therapy

Polyglutamine (polyQ) diseases are a group of neurodegenerative disorders involving expanded CAG repeats in pathogenic genes that are translated into extended polyQ tracts and lead to progressive neuronal degeneration in the affected brain. To date, there is no effective therapy for these diseases. Due to the complex pathologic mechanisms of these diseases, intensive research on the pathogenesis of their progression and potential treatment strategies is being conducted. However, animal models cannot recapitulate all aspects of neuronal degeneration. Pluripotent stem cells (PSCs), such as induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), can be used to study the pathological mechanisms of polyQ diseases, and the ability of autologous stem cell transplantation to treat these diseases. Differentiated PSCs, neuronal precursor cells/neural progenitor cells (NPCs) and mesenchymal stem cells (MSCs) are valuable resources for preclinical and clinical cell transplantation therapies. Here, we discuss diverse stem cell models and their ability to generate neurons involved in polyQ diseases, such as medium spiny neurons (MSNs), cortical neurons, cerebellar Purkinje cells (PCs) and motor neurons. In addition, we discuss potential therapeutic approaches, including stem cell replacement therapy and gene therapy.

Induced pluripotent stem cells (iPSCs) as game-changing tools in the treatment of neurodegenerative disease: Mirage or reality?

Based on investigations, there exist tight correlations between neurodegenerative diseases' incidence and progression and aberrant protein aggregreferates in nervous tissue. However, the pathology of these diseases is not well known, leading to an inability to find an appropriate therapeutic approach to delay occurrence or slow many neurodegenerative diseases' development. The accessibility of induced pluripotent stem cells (iPSCs) in mimicking the phenotypes of various late-onset neurodegenerative diseases presents a novel strategy for in vitro disease modeling. The iPSCs provide a valuable and well-identified resource to clarify neurodegenerative disease mechanisms, as well as prepare a promising human stem cell platform for drug screening. Undoubtedly, neurodegenerative disease modeling using iPSCs has established innovative opportunities for both mechanistic types of research and recognition of novel disease treatments. Most important, the iPSCs have been considered as a novel autologous cell origin for cell-based therapy of neurodegenerative diseases following differentiation to varied types of neural lineage cells (e.g. GABAergic neurons, dopamine neurons, cortical neurons, and motor neurons). In this review, we summarize iPSC-based disease modeling in neurodegenerative diseases including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease. Moreover, we discuss the efficacy of cell-replacement therapies for neurodegenerative disease.

Stem Cell-Derived Human Striatal Progenitors Innervate Striatal Targets and Alleviate Sensorimotor Deficit in a Rat Model of Huntington Disease

Huntington disease (HD) is an inherited late-onset neurological disorder characterized by progressive neuronal loss and disruption of cortical and basal ganglia circuits. Cell replacement using human embryonic stem cells may offer the opportunity to repair the damaged circuits and significantly ameliorate disease conditions. Here, we showed that in-vitro-differentiated human striatal progenitors undergo maturation and integrate into host circuits upon intra-striatal transplantation in a rat model of HD. By combining graft-specific immunohistochemistry, rabies virus-mediated synaptic tracing, and ex vivo electrophysiology, we showed that grafts can extend projections to the appropriate target structures, including the globus pallidus, the subthalamic nucleus, and the substantia nigra, and receive synaptic contact from both host and graft cells with 6.6 ± 1.6 inputs cell per transplanted neuron. We have also shown that transplants elicited a significant improvement in sensory-motor tasks up to 2 months post-transplant further supporting the therapeutic potential of this approach.

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hESC-derived striatal progenitors give rise to MSNs in a neurotoxin model of HD

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Donor transplants extend projections to appropriate striatal target regions

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Grafted cells establish synaptic contact with both donor and resident cells

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Transplanted animals show improvements in HD-related sensorimotor responses

Deconstructing Neurogenesis, Transplantation and Genome-Editing as Neural Repair Strategies in Brain Disease

Neural repair in injury and disease presents a pressing unmet need in regenerative medicine. Due to the intrinsically reduced ability of the brain to replace lost and damaged neurons, reversing long-term cognitive and functional impairments poses a unique problem. Over the years, advancements in cellular and molecular understanding of neurogenesis mechanisms coupled with sophistication of biotechnology tools have transformed neural repair into a cross-disciplinary field that integrates discoveries from developmental neurobiology, transplantation and tissue engineering to design disease- and patient-specific remedies aimed at boosting either native rehabilitation or delivering exogenous hypoimmunogenic interventions. Advances in deciphering the blueprint of neural ontogenesis and annotation of the human genome has led to the development of targeted therapeutic opportunities that have the potential of treating the most vulnerable patient populations and whose findings from benchside suggest looming clinical translation. This review discusses how findings from studies of adult neurogenesis have informed development of interventions that target endogenous neural regenerative machineries and how advances in biotechnology, including the use of new gene-editing tools, have made possible the development of promising, complex neural transplant-based strategies. Adopting a multi-pronged strategy that is tailored to underlying neural pathology and that encompasses facilitation of endogenous regeneration, correction of patient’s genomic mutations and delivery of transformed neural precursors and mature disease-relevant neuronal populations to replace injured or lost neural tissue remains no longer a fantasy.

Prion-like mechanisms in neurodegenerative disease: Implications for Huntington's disease therapy

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a CAG repeat expansions in the huntingtin gene resulting in the synthesis of a misfolded form of the huntingtin protein (mHTT) which is toxic. The current treatments for HD are only palliative. Some of the potential therapies for HD include gene therapy (using antisense oligonucleotides and clustered regularly interspaced short palindromic repeats-Cas9 system) and stem-cell-based therapies. Various types of stem cell transplants, such as mesenchymal stem cells, neural stem cells, and reprogrammed stem cells, have the potential to either replace the lost neurons or support the existing neurons by releasing trophic factors. Most of the transplants are xenografts and allografts; however, recent reports on HD patients who received grafts suggest that the mHTT aggregates are transferred from the host neurons to the grafted cells as well as to the surrounding areas of the graft by a "prion-like" mechanism. This observation seems to be true for autotransplantation paradigms, as well. This article reviews the different types of stem cells that have been transplanted into HD patients and their therapeutic efficacy, focusing on the transfer of mHTT from the host cells to the graft. Autotransplants of reprogramed stem cells in HD patients are a promising therapeutic option. However, this needs further attention to ensure a better understanding of the transfer of mHTT aggregates following transplantation of the gene-corrected cells back into the patient.

Behavioural phenotypes in the cuprizone model of central nervous system demyelination

The feeding of cuprizone (CPZ) to animals has been extensively used to model the processes of demyelination and remyelination, with many papers adopting a narrative linked to demyelinating conditions like multiple sclerosis (MS), the aetiology of which is unknown. However, no current animal model faithfully replicates the myriad of symptoms seen in the clinical condition of MS. CPZ ingestion causes mitochondrial and endoplasmic reticulum stress and subsequent apoptosis of oligodendrocytes leads to central nervous system demyelination and glial cell activation. Although there are a wide variety of behavioural tests available for characterizing the functional deficits in animal models of disease, including that of CPZ-induced deficits, they have focused on a narrow subset of outcomes such as motor performance, cognition, and anxiety. The literature has not been systematically reviewed in relation to these or other symptoms associated with clinical MS. This paper reviews these tests and makes recommendations as to which are the most important in order to better understand the role of this model in examining aspects of demyelinating diseases like MS.

Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias

Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections. All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits. The most common spinocerebellar ataxias (SCAs) are 6 polyglutamine (polyQ) SCAs. These diseases are all caused by a CAG repeat expansion in the coding region of a gene. Currently, no curative treatment is available for any of the polyQ SCAs, but increasing knowledge on the genetics and the pathological mechanisms of these polyQ SCAs has provided promising therapeutic targets to potentially slow disease progression. Potential treatments can be divided into pharmacological and gene therapies that target the toxic downstream effects, gene therapies that target the polyQ SCA genes, and stem cell replacement therapies. Here, we will provide a review on the genetics, mechanisms, and therapeutic progress in polyglutamine spinocerebellar ataxias.

Stem cell therapy for neurological disorders: A focus on aging

Age-related neurological disorders continue to pose a significant societal and economic burden. Aging is a complex phenomenon that affects many aspects of the human body. Specifically, aging can have detrimental effects on the progression of brain diseases and endogenous stem cells. Stem cell therapies possess promising potential to mitigate the neurological symptoms of such diseases. However, aging presents a major obstacle for maximum efficacy of these treatments. In this review, we discuss current preclinical and clinical literature to highlight the interactions between aging, stem cell therapy, and the progression of major neurological disease states such as Parkinson's disease, Huntington's disease, stroke, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, and multiple system atrophy. We raise important questions to guide future research and advance novel treatment options.

An update on intracerebral stem cell grafts

INTRODUCTION

Primary neurological disorders are notoriously debilitating and deadly, and over the past four decades stem cell therapy has emerged as a promising treatment. Translation of stem cell therapies from the bench to the clinic requires a better understanding of delivery protocols, safety profile, and efficacy in each disease. Areas covered: In this review, benefits and risks of intracerebral stem cell transplantation are presented for consideration. Milestone discoveries in stem cell applications are reviewed to examine the efficacy and safety of intracerebral stem cell transplant therapy for disorders of the central nervous system and inform design of translatable protocols for clinically feasible stem cell-based treatments. Expert commentary: Intracerebral administration, compared to peripheral delivery, is more invasive and carries the risk of open brain surgery. However, direct cell implantation bypasses the blood-brain barrier and reduces the first-pass effect, effectively increasing the therapeutic cell deposition at its intended site of action. These benefits must be weighed with the risk of graft-versus-host immune response. Rigorous clinical trials are underway to assess the safety and efficacy of intracerebral transplants, and if successful will lead to widely available stem cell therapies for neurologic diseases in the coming years.

Human Neural Stem Cell Transplantation Rescues Functional Deficits in R6/2 and Q140 Huntington's Disease Mice

Huntington's disease (HD) is an inherited neurodegenerative disorder with no disease-modifying treatment. Expansion of the glutamine-encoding repeat in the Huntingtin (HTT) gene causes broad effects that are a challenge for single treatment strategies. Strategies based on human stem cells offer a promising option. We evaluated efficacy of transplanting a good manufacturing practice (GMP)-grade human embryonic stem cell-derived neural stem cell (hNSC) line into striatum of HD modeled mice. In HD fragment model R6/2 mice, transplants improve motor deficits, rescue synaptic alterations, and are contacted by nerve terminals from mouse cells. Furthermore, implanted hNSCs are electrophysiologically active. hNSCs also improved motor and late-stage cognitive impairment in a second HD model, Q140 knockin mice. Disease-modifying activity is suggested by the reduction of aberrant accumulation of mutant HTT protein and expression of brain-derived neurotrophic factor (BDNF) in both models. These findings hold promise for future development of stem cell-based therapies.

Regenerative medicine in Huntington's disease: Strengths and weaknesses of preclinical studies

Huntington's disease (HD) is an inherited neurodegenerative disorder, characterized by impairment in motor, cognitive and psychiatric domains. Currently, there is no specific therapy to act on the onset or progression of HD. The marked neuronal death observed in HD is a main argument in favour of stem cells (SCs) transplantation as a promising therapeutic perspective to replace the population of lost neurons and restore the functionality of the damaged circuitry. The availability of rodent models of HD encourages the investigation of the restorative potential of SCs transplantation longitudinally. However, the results of preclinical studies on SCs therapy in HD are so far largely inconsistent; this hampers the individuation of the more appropriate model and precludes the comparative analysis of transplant efficacy on behavioural end points. Thus, this review will describe the state of the art of in vivo research on SCs therapy in HD, analysing in a translational perspective the strengths and weaknesses of animal studies investigating the therapeutic potential of cell transplantation on HD progression.

Protein aggregation, misfolding and consequential human neurodegenerative diseases

Proteins are major components of the biological functions in a cell. Biology demands that a protein must fold into its stable three-dimensional structure to become functional. In an unfavorable cellular environment, protein may get misfolded resulting in its aggregation. These conformational disorders are directly related to the tissue damage resulting in cellular dysfunction giving rise to different diseases. This way, several neurodegenerative diseases such as Alzheimer, Parkinson Huntington diseases and amyotrophic lateral sclerosis are caused. Misfolding of the protein is prevented by innate molecular chaperones of different classes. It is envisaged that work on this line is likely to translate the knowledge into the development of possible strategies for early diagnosis and efficient management of such related human diseases. The present review deals with the human neurodegenerative diseases caused due to the protein misfolding highlighting pathomechanisms and therapeutic intervention.

The translational potential of human induced pluripotent stem cells for clinical neurology : The translational potential of hiPSCs in neurology

The induced pluripotent state represents a decade-old Nobel prize-winning discovery. Human-induced pluripotent stem cells (hiPSCs) are generated by the nuclear reprogramming of any somatic cell using a variety of established but evolving methods. This approach offers medical science unparalleled experimental opportunity to model an individual patient’s disease “in a dish.” HiPSCs permit developmentally rationalized directed differentiation into any cell type, which express donor cell mutation(s) at pathophysiological levels and thus hold considerable potential for disease modeling, drug discovery, and potentially cell-based therapies. This review will focus on the translational potential of hiPSCs in clinical neurology and the importance of integrating this approach with complementary model systems to increase the translational yield of preclinical testing for the benefit of patients. This strategy is particularly important given the expected increase in prevalence of neurodegenerative disease, which poses a major burden to global health over the coming decades.

Cell-based technologies for Huntington's disease

Huntington's disease (HD) is a fatal genetic disorder, which causes the progressive breakdown of neurons in the human brain. HD deteriorates human physical and mental abilities over time and has no cure. Stem cell-based technologies are promising novel treatments, and in HD, they aim to replace lost neurons and/or to prevent neural cell death. Herein we discuss the use of human fetal tissue (hFT), neural stem cells (NSCs) of hFT origin or embryonic stem cells (ESCs) and induced pluripotent stem cells (IPSCs), in clinical and pre-clinical studies. The in vivo use of mesenchymal stem cells (MSCs), which are derived from non-neural tissues, will also be discussed. All these studies prove the potential of stem cells for transplantation therapy in HD, demonstrating cell grafting and the ability to differentiate into mature neurons, resulting in behavioral improvements. We claim that there are still many problems to overcome before these technologies become available for HD patient treatment, such as:

a) safety regarding the use of NSCs and pluripotent stem cells, which are potentially teratogenic;

b) safety regarding the transplantation procedure itself, which represents a risk and needs to be better studied; and finally

c) technical and ethical issues regarding cells of fetal and embryonic origin.

Neurodegeneration Alters Metabolic Profile and Sirt 1 Signaling in High-Fat-Induced Obese Mice

Different factors may contribute to the development of neurodegenerative diseases. Among them, metabolic syndrome (MS), which has reached epidemic proportions, has emerged as a potential element that may be involved in neurodegeneration. Furthermore, studies have shown the importance of the sirtuin family in neuronal survival and MS, which opens the possibility of new pharmacological targets. This study investigates the influence of sirtuin metabolic pathways by examining the functional capacities of glucose-induced obesity in an excitotoxic state induced by a quinolinic acid (QA) animal model. Mice were divided into two groups that received different diets for 8 weeks: one group received a regular diet, and the other group received a high-fat diet (HF) to induce MS. The animals were submitted to a stereotaxic surgery and subdivided into four groups: Standard (ST), Standard-QA (ST-QA), HF and HF-QA. The QA groups were given a 250 nL quinolinic acid injection in the right striatum and PBS was injected in the other groups. Obese mice presented with a weight gain of 40 % more than the ST group beyond acquiring an insulin resistance. QA induced motor impairment and neurodegeneration in both ST-QA and HF-QA, although no difference was observed between these groups. The HF-QA group showed a reduction in adiposity when compared with the groups that received PBS. Therefore, the HF-QA group demonstrated a commitment-dependent metabolic pathway. The results suggest that an obesogenic diet does not aggravate the neurodegeneration induced by QA. However, the excitotoxicity induced by QA promotes a sirtuin pathway impairment that contributes to metabolic changes.

Intracranial Transplantation of Hypoxia-Preconditioned iPSC-Derived Neural Progenitor Cells Alleviates Neuropsychiatric Defects After Traumatic Brain Injury in Juvenile Rats

Traumatic brain injury (TBI) is a common cause of mortality and long-term morbidity in children and adolescents. Posttraumatic stress disorder (PTSD) frequently develops in these patients, leading to a variety of neuropsychiatric syndromes. Currently, few therapeutic strategies are available to treat juveniles with PTSD and other developmental neuropsychiatric disorders. In the present investigation, postnatal day 14 (P14) Wistar rats were subjected to TBI induced by a controlled cortical impact (CCI) (velocity = 3 m/s, depth = 2.0 mm, contact time = 150 ms). This TBI injury resulted in not only cortical damages, but also posttrauma social behavior deficits. Three days after TBI, rats were treated with intracranial transplantation of either mouse iPSC-derived neural progenitor cells under normal culture conditions (N-iPSC-NPCs) or mouse iPSC-derived neural progenitor cells pretreated with hypoxic preconditioning (HP-iPSC-NPCs). Compared to TBI animals that received N-iPSC-NPCs or vehicle treatment, HP-iPSC-NPC-transplanted animals showed a unique benefit of improved performance in social interaction, social novelty, and social transmission of food preference tests. Western blotting showed that HP-iPSC-NPCs expressed significantly higher levels of the social behavior-related genes oxytocin and the oxytocin receptor. Overall, HP-iPSC-NPC transplantation exhibits a great potential as a regenerative therapy to improve neuropsychiatric outcomes after juvenile TBI.

Induced Pluripotent Stem Cells in Huntington's Disease: Disease Modeling and the Potential for Cell-Based Therapy

Huntington's disease (HD) is an incurable neurodegenerative disorder that is characterized by motor dysfunction, cognitive impairment, and behavioral abnormalities. It is an autosomal dominant disorder caused by a CAG repeat expansion in the huntingtin gene, resulting in progressive neuronal loss predominately in the striatum and cortex. Despite the discovery of the causative gene in 1993, the exact mechanisms underlying HD pathogenesis have yet to be elucidated. Treatments that slow or halt the disease process are currently unavailable. Recent advances in induced pluripotent stem cell (iPSC) technologies have transformed our ability to study disease in human neural cells. Here, we firstly review the progress made to model HD in vitro using patient-derived iPSCs, which reveal unique insights into illuminating molecular mechanisms and provide a novel human cell-based platform for drug discovery. We then highlight the promises and challenges for pluripotent stem cells that might be used as a therapeutic source for cell replacement therapy of the lost neurons in HD brains.

Cellular models to study bipolar disorder: A systematic review

BACKGROUND

There is an emerging interest in the use of cellular models to study psychiatric disorders. We have systematically reviewed the application of cellular models to understand the biological basis of bipolar disorder (BD).

METHOD

Published scientific literature in MEDLINE, PsychINFO and SCOPUS databases were identified with the following search strategy: [(Lymphoblastoid OR Lymphoblast OR Fibroblast OR Pluripotent OR Olfactory epithelium OR Olfactory mucosa) AND (Bipolar disorder OR Lithium OR Valproate OR Mania)]. Studies were included if they had used cell cultures derived from BD patients.

RESULTS

There were 65 articles on lymphoblastoid cell lines, 14 articles on fibroblasts, 4 articles on olfactory neuronal epithelium (ONE) and 2 articles on neurons reprogrammed from induced pluripotent stem cell lines (IPSC). Several parameters have been studied, and the most replicated findings are abnormalities in calcium signaling, endoplasmic reticulum (ER) stress response, mitochondrial oxidative pathway, membrane ion channels, circadian system and apoptosis related genes. These, although present in basal state, seem to be accentuated in the presence of cellular stressors (e.g. oxidative stress--rotenone; ER stress--thapsigargin), and are often reversed with in-vitro lithium.

CONCLUSION

Cellular modeling has proven useful in BD, and potential pathways, especially in cellular resilience related mechanisms have been identified. These findings show consistency with other study designs (genome-wide association, brain-imaging, and post-mortem brain expression). ONE cells and IPSC reprogrammed neurons represent the next generation of cell models in BD. Future studies should focus on family-based study designs and combine cell models with deep sequencing and genetic manipulations.

Advances in reprogramming-based study of neurologic disorders

The technology to convert adult human non-neural cells into neural lineages, through induced pluripotent stem cells (iPSCs), somatic cell nuclear transfer, and direct lineage reprogramming or transdifferentiation has progressed tremendously in recent years. Reprogramming-based approaches aimed at manipulating cellular identity have enormous potential for disease modeling, high-throughput drug screening, cell therapy, and personalized medicine. Human iPSC (hiPSC)-based cellular disease models have provided proof of principle evidence of the validity of this system. However, several challenges remain before patient-specific neurons produced by reprogramming can provide reliable insights into disease mechanisms or be efficiently applied to drug discovery and transplantation therapy. This review will first discuss limitations of currently available reprogramming-based methods in faithfully and reproducibly recapitulating disease pathology. Specifically, we will address issues such as culture heterogeneity, interline and inter-individual variability, and limitations of two-dimensional differentiation paradigms. Second, we will assess recent progress and the future prospects of reprogramming-based neurologic disease modeling. This includes three-dimensional disease modeling, advances in reprogramming technology, prescreening of hiPSCs and creating isogenic disease models using gene editing.

Developments in intracerebral stem cell grafts

The field of stem cell therapy has emerged as a promising research area for brain repair. Optimizing the safety and efficacy of the therapy for clinical trials will require revisiting transplantation protocols. The cell delivery route stands as a key translational item that warrants careful consideration in facilitating the success of stem cell therapy in the clinic. Intracerebral administration, compared to peripheral route, requires an invasive procedure to directly implant stem cells into injured brain. Although invasive, intracerebral transplantation circumvents the prohibitive blood brain barrier in allowing grafted cells when delivered peripherally to penetrate the brain and reach the discreet damaged brain tissues. This review will highlight milestone discoveries in cell therapy for neurological disorders, with emphasis on intracerebral transplantation in relevant animal models and provide insights necessary to optimize the safety and efficacy of cell therapy for the treatment of Parkinson's disease, Huntington's disease, stroke and traumatic brain injury.