Ex vivo delivery of GDNF maintains motor function and prevents neuronal loss in a transgenic mouse model of Huntington's disease

Neurosurgical therapy possibilities in treatment of Huntington disease: An update

INTRODUCTION

Huntington's disease (HD) is a hereditary condition caused by the expansion of the CAG trinucleotide in the huntingtin gene on chromosome 4, resulting in motor, cognitive, and psychiatric disorders that significantly impact patients' quality of life. Despite the lack of effective treatments for the disease, various surgical strategies have been explored to alleviate symptoms and slow its progression.

METHODOLOGY

A comprehensive systematic literature review was conducted, including MeSH terms, yielding only 38 articles that were categorized based on the surgical procedure. The study aimed to describe the types of surgeries performed and their efficacy in HD patients.

RESULTS

Deep brain stimulation (DBS) involved 41 predominantly male patients with bilateral implantation in the globus pallidus, showing a preoperative Unified Huntington's Disease Rating Scale (UHDRS) score of 60.25 ± 16.13 and a marked postoperative value of 48.54 ± 13.93 with a p < 0.018 at one year and p < 0.040 at three years. Patients experienced improvement in hyperkinesia but worsening of bradykinesia. Additionally, cell transplantation in 119 patients resulted in a lower preoperative UHDRS score of 34.61 ± 14.61 and a significant postoperative difference of 32.93 ± 15.87 (p < 0.016), respectively, in the first to third years of following. Some now, less used procedures were crucial for understanding brain function, such as pallidotomies in 3 patients, showing only a 25 % difference from their baseline.

CONCLUSION

Despite advancements in technology, there is still no curative treatment, only palliative options. Promising treatments like trophic factor implantation offer new prospects for the future.

Neutralizing antibodies with neurotropic factor treatment maintain neurodevelopmental gene expression upon exposure to human cytomegalovirus

IMPORTANCE

Human cytomegalovirus (HCMV) infection is the leading cause of non-heritable birth defects worldwide. HCMV readily infects the early progenitor cell population of the developing brain, and we have found that infection leads to significantly downregulated expression of key neurodevelopmental transcripts. Currently, there are no approved therapies to prevent or mitigate the effects of congenital HCMV infection. Therefore, we used human-induced pluripotent stem cell-derived organoids and neural progenitor cells to elucidate the glycoproteins and receptors used in the viral entry process and whether antibody neutralization was sufficient to block viral entry and prevent disruption of neurodevelopmental gene expression. We found that blocking viral entry alone was insufficient to maintain the expression of key neurodevelopmental genes, but neutralization combined with neurotrophic factor treatment provided robust protection. Together, these studies offer novel insight into mechanisms of HCMV infection in neural tissues, which may aid future therapeutic development.

Pathogenesis and potential therapeutic application of stem cells transplantation in Huntington’s disease

Huntington's disease (HD) is a progressive neurodegenerative disorder which is caused due to repetitive CAG or glutamine expression along the coding region of the Huntington gene. This disease results in certain movement abnormalities, affective disturbances, dementia and cognitive impairments. To this date, there is no proper cure for this rare and fatal neurological condition but there have been certain advancements in the field of genetic animal model research studies to elucidate the understanding of the pathogenesis of this condition. Currently, HD follows a certain therapeutic approach which just relieves the symptoms but doesn't cure the underlying cause of the disease. Stem cell therapy can be a breakthrough in developing a potential cure for this condition. In this review, we have discussed the pathogenesis and the efficacy and clinical practicality of the therapeutic application of stem cell transplantation in Huntington's disease. The application of this groundbreaking therapy on genetically altered animal models has been listed and analyzed in brief.

Gene Therapy Approach with an Emphasis on Growth Factors: Theoretical and Clinical Outcomes in Neurodegenerative Diseases

The etiology of many neurological diseases affecting the central nervous system (CNS) is unknown and still needs more effective and specific therapeutic approaches. Gene therapy has a promising future in treating neurodegenerative disorders by correcting the genetic defects or by therapeutic protein delivery and is now an attraction for neurologists to treat brain disorders, like Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, spinal muscular atrophy, spinocerebellar ataxia, epilepsy, Huntington’s disease, stroke, and spinal cord injury. Gene therapy allows the transgene induction, with a unique expression in cells’ substrate. This article mainly focuses on the delivering modes of genetic materials in the CNS, which includes viral and non-viral vectors and their application in gene therapy. Despite the many clinical trials conducted so far, data have shown disappointing outcomes. The efforts done to improve outcomes, efficacy, and safety in the identification of targets in various neurological disorders are also discussed here. Adapting gene therapy as a new therapeutic approach for treating neurological disorders seems to be promising, with early detection and delivery of therapy before the neuron is lost, helping a lot the development of new therapeutic options to translate to the clinic.

Single-Cell Microwell Platform Reveals Circulating Neural Cells as a Clinical Indicator for Patients with Blood-Brain Barrier Breakdown

Central nervous system diseases commonly occur with the destruction of the blood-brain barrier. As a primary cause of morbidity and mortality, stroke remains unpredictable and lacks cellular biomarkers that accurately quantify its occurrence and development. Here, we identify NeuN⁺/CD45⁻/DAPI⁺ phenotype nonblood cells in the peripheral blood of mice subjected to middle cerebral artery occlusion (MCAO) and stroke patients. Since NeuN is a specific marker of neural cells, we term these newly identified cells as circulating neural cells (CNCs). We find that the enumeration of CNCs in the blood is significantly associated with the severity of brain damage in MCAO mice (p < 0.05). Meanwhile, the number of CNCs is significantly higher in stroke patients than in negative subjects (p < 0.0001). These findings suggest that the amount of CNCs in circulation may serve as a clinical indicator for the real-time prognosis and progression monitor of the occurrence and development of ischemic stroke and other nervous system disease.

Regenerative Stem Cell Therapy for Neurodegenerative Diseases: An Overview

Neurodegenerative diseases resulting from the progressive loss of structure and/or function of neurons contribute to different paralysis degrees and loss of cognition and sensation. The lack of successful curative therapies for neurodegenerative disorders leads to a considerable burden on society and a high economic impact. Over the past 20 years, regenerative cell therapy, also known as stem cell therapy, has provided an excellent opportunity to investigate potentially powerful innovative strategies for treating neurodegenerative diseases. This is due to stem cells' capability to repair injured neuronal tissue by replacing the damaged or lost cells with differentiated cells, providing a conducive environment that is in favor of regeneration, or protecting the existing healthy neurons and glial cells from further damage. Thus, in this review, the various types of stem cells, the current knowledge of stem-cell-based therapies in neurodegenerative diseases, and the recent advances in this field are summarized. Indeed, a better understanding and further studies of stem cell technologies cause progress into realistic and efficacious treatments of neurodegenerative disorders.

Differentiation of dental pulp stem cells into neuron-like cells

Background and objectives: With regard to their ease of harvest and common developmental origin, dental pulp stem cells (DPSCs) may act as a favorable source of stem cells in generation of nerves. Moreover; cellular migration and differentiation as well as survival, self-renewal, and proliferation of neuroprogenitor species require the presence of the central nervous system (CNS) mitogens including EGF and bFGF. Accordingly, the possibility of the induction of neuronal differentiation of DPSCs by EGF and bFGF was evaluated in the present study.Materials and methods: DPSCs were treated with 20 ng/ml EGF, 20 ng/ml bFGF, and 10 µg/ml heparin. In order to further induce the neuroprogenitor differentiation, DPSC-derived spheres were also incubated in serum-free media for three days. The resulting spheres were then cultured in high-glucose Dulbecco's Modified Eagle Medium (DMEM) with 10% FBS. The morphology of the cells and the expression of the differentiation markers were correspondingly analyzed by quantitative polymerase chain reaction (qPCR), western blotting, and immunofluorescence (IF).Results: The EGF/bFGF-treated DPSCs showed significant increase in the expression of the neuroprogenitor markers of Nestin and SRY (sex determining region Y)-box 2 (SOX2), 72 h after treatment. The up-regulation of Nestin and SOX2 induced by growth factors was confirmed using western blotting and IF. The cultures also yielded some neuron-like cells with a significant rise in Nestin, microtubule-associated protein 2 (MAP2), and Neurogenin 1 (Ngn1) transcript levels; compared with cells maintained in the control media (p < 0.05).Conclusion: DPSCs seemed to potentially differentiate into neuron-like cells under the herein-mentioned treatment conditions.

Effect of the micro-immunotherapy medicine 2LPARK® on rat primary dopaminergic neurons after 6-OHDA injury: oxidative stress and survival evaluation in an in vitro model of Parkinson's disease

Background

Parkinson’s disease (PD) is a neurodegenerative disease characterized by motor impairments and resulting from progressive degenerative loss of midbrain dopaminergic (DAergic) neurons in the substantia nigra. Although the main cause of the loss of DAergic neurons is still unknown, various etiopathogenic mechanisms are distinguished, including release and accumulation of endogenous excitotoxic mediators along with the production of oxidative free radicals. Several neurotrophic and growth factors are known to increase DAergic neuronal survival and enhance antioxidant mechanisms. In this context, the micro-immunotherapy (MI) approach consists to regulate the immune system in order to protect DAergic neurons and control oxidative stress.

Purpose

The aim of the present study was to investigate the effect of the MI medicine (MIM), 2LPARK^® (Labo’Life), on oxidative stress and on the number of neurons positive for tyrosine hydroxylase (TH), in an in vitro model of PD.

Methods

Rat primary mesencephalic DAergic neurons cultures were pre-treated for 1 hr with the MIM (10 μM and 10 mM), placebo (10 μM and 10 mM) or brain-derived neurotrophic factor (BDNF; 3.3 μM) and then intoxicated with 6-hydroxydopamine (6-OHDA; 20 μM) for 48 hrs. After incubation, cells were incubated 30 mins at 37°C with CellROX green reagent and number of labeled cells were quantified. Then, cells were fixed and incubated with anti-TH antibody and the number of TH⁺ neurons was evaluated.

Results

We showed that, contrary to placebo, MIM was able to reduce oxidative stress and protect DAergic neurons from 6-OHDA-induced cell death.

Conclusion

Our results demonstrate the in vitro efficacy of MIM on two essential mechanisms of PD and propose the MI approach as a new ally in the regulation of neuroinflammation and in the treatment of this degenerative disease.

Inducible Expression of GDNF in Transplanted iPSC-Derived Neural Progenitor Cells

Trophic factor delivery to the brain using stem cell-derived neural progenitors is a powerful way to bypass the blood-brain barrier. Protection of diseased neurons using this technology is a promising therapy for neurodegenerative diseases. Glial cell line-derived neurotrophic factor (GDNF) has provided benefits to Parkinsonian patients and is being used in a clinical trial for amyotrophic lateral sclerosis. However, chronic trophic factor delivery prohibits dose adjustment or cessation if side effects develop. To address this, we engineered a doxycycline-regulated vector, allowing inducible and reversible expression of a therapeutic molecule. Human induced pluripotent stem cell (iPSC)-derived neural progenitors were stably transfected with the vector and transplanted into the adult mouse brain. Doxycycline can penetrate the graft, with addition and withdrawal providing inducible and reversible GDNF expression in vivo, over multiple cycles. Our findings provide proof of concept for combining gene and stem cell therapy for effective modulation of ectopic protein expression in transplanted cells.

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Created plasmid with tetracycline transactivator along with dual reporters and GDNF

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Efficient, stable transduction of human iPSC-derived neural progenitor cells

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Inducible and reversible in vivo expression of GDNF, reporter protein, and luciferase

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Promising stem cell and gene therapy strategy for neurodegenerative diseases

Therapeutic effects of stem cells in rodent models of Huntington's disease: Review and electrophysiological findings

The principal symptoms of Huntington's disease (HD), chorea, cognitive deficits, and psychiatric symptoms are associated with the massive loss of striatal and cortical projection neurons. As current drug therapies only partially alleviate symptoms, finding alternative treatments has become peremptory. Cell replacement using stem cells is a rapidly expanding field that offers such an alternative. In this review, we examine recent studies that use mesenchymal cells, as well as pluripotent, cell-derived products in animal models of HD. Additionally, we provide further electrophysiological characterization of a human neural stem cell line, ESI-017, which has already demonstrated disease-modifying properties in two mouse models of HD. Overall, the field of regenerative medicine represents a viable and promising avenue for the treatment of neurodegenerative disorders including HD.

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.

Neural stem cell therapy for neurodegenerative disorders: The role of neurotrophic support

Neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease currently affect tens of millions of people worldwide. Unfortunately, as the world's population ages, the incidence of many of these diseases will continue to rise and is expected to more than double by 2050. Despite significant research and a growing understanding of disease pathogenesis, only a handful of therapies are currently available and all of them provide only transient benefits. Thus, there is an urgent need to develop novel disease-modifying therapies to prevent the development or slow the progression of these debilitating disorders. A growing number of pre-clinical studies have suggested that transplantation of neural stem cells (NSCs) could offer a promising new therapeutic approach for neurodegeneration. While much of the initial excitement about this strategy focused on the use of NSCs to replace degenerating neurons, more recent studies have implicated NSC-mediated changes in neurotrophins as a major mechanism of therapeutic efficacy. In this mini-review we will discuss recent work that examines the ability of NSCs to provide trophic support to disease-effected neuronal populations and synapses in models of neurodegeneration. We will then also discuss some of key challenges that remain before NSC-based therapies for neurodegenerative diseases can be translated toward potential clinical testing.

Ex vivo gene therapy for the treatment of neurological disorders

Ex vivo gene therapy involves the genetic modification of cells outside of the body to produce therapeutic factors and their subsequent transplantation back into patients. Various cell types can be genetically engineered. However, with the explosion in stem cell technologies, neural stem/progenitor cells and mesenchymal stem cells are most often used. The synergy between the effect of the new cell and the additional engineered properties can often provide significant benefits to neurodegenerative changes in the brain. In this review, we cover both preclinical animal studies and clinical human trials that have used ex vivo gene therapy to treat neurological disorders with a focus on Parkinson's disease, Huntington's disease, Alzheimer's disease, ALS, and stroke. We highlight some of the major advances in this field including new autologous sources of pluripotent stem cells, safer ways to introduce therapeutic transgenes, and various methods of gene regulation. We also address some of the remaining hurdles including tunable gene regulation, in vivo cell tracking, and rigorous experimental design. Overall, given the current outcomes from researchers and clinical trials, along with exciting new developments in ex vivo gene and cell therapy, we anticipate that successful treatments for neurological diseases will arise in the near future.

Discovery of Therapeutic Approaches for Polyglutamine Diseases: A Summary of Recent Efforts

Polyglutamine (PolyQ) diseases are a group of neurodegenerative disorders caused by the expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats in the coding region of specific genes. This leads to the production of pathogenic proteins containing critically expanded tracts of glutamines. Although polyQ diseases are individually rare, the fact that these nine diseases are irreversibly progressive over 10 to 30 years, severely impairing and ultimately fatal, usually implicating the full-time patient support by a caregiver for long time periods, makes their economic and social impact quite significant. This has led several researchers worldwide to investigate the pathogenic mechanism(s) and therapeutic strategies for polyQ diseases. Although research in the field has grown notably in the last decades, we are still far from having an effective treatment to offer patients, and the decision of which compounds should be translated to the clinics may be very challenging. In this review, we provide a comprehensive and critical overview of the most recent drug discovery efforts in the field of polyQ diseases, including the most relevant findings emerging from two different types of approaches-hypothesis-based candidate molecule testing and hypothesis-free unbiased drug screenings. We hereby summarize and reflect on the preclinical studies as well as all the clinical trials performed to date, aiming to provide a useful framework for increasingly successful future drug discovery and development efforts.

ESC-Derived BDNF-Overexpressing Neural Progenitors Differentially Promote Recovery in Huntington's Disease Models by Enhanced Striatal Differentiation

Huntington's disease (HD) is characterized by fatal motoric failures induced by loss of striatal medium spiny neurons. Neuronal cell death has been linked to impaired expression and axonal transport of the neurotrophin BDNF (brain-derived neurotrophic factor). By transplanting embryonic stem cell-derived neural progenitors overexpressing BDNF, we combined cell replacement and BDNF supply as a potential HD therapy approach. Transplantation of purified neural progenitors was analyzed in a quinolinic acid (QA) chemical and two genetic HD mouse models (R6/2 and N171-82Q) on the basis of distinct behavioral parameters, including CatWalk gait analysis. Explicit rescue of motor function by BDNF neural progenitors was found in QA-lesioned mice, whereas genetic mouse models displayed only minor improvements. Tumor formation was absent, and regeneration was attributed to enhanced neuronal and striatal differentiation. In addition, adult neurogenesis was preserved in a BDNF-dependent manner. Our findings provide significant insight for establishing therapeutic strategies for HD to ameliorate neurodegenerative symptoms.

Regenerative cellular therapies for neurologic diseases

The promise of stem cell regeneration has been the hope of many neurologic patients with permanent damage to the central nervous system. There are hundreds of stem cell trials worldwide intending to test the regenerative capacity of stem cells in various neurological conditions from Parkinson's disease to multiple sclerosis. Although no stem cell therapy is clinically approved for use in any human disease indication, patients are seeking out trials and asking clinicians for guidance. This review summarizes the current state of regenerative stem cell transplantation divided into seven conditions for which trials are currently active: demyelinating diseases/spinal cord injury, amyotrophic lateral sclerosis, stroke, Parkinson's disease, Huntington's disease, macular degeneration and peripheral nerve diseases. This article is part of a Special Issue entitled SI: PSC and the brain.

Mifepristone-inducible transgene expression in neural progenitor cells in vitro and in vivo

Numerous gene and cell therapy strategies are being developed for the treatment of neurodegenerative disorders. Many of these strategies use constitutive expression of therapeutic transgenic proteins, and although functional in animal models of disease, this method is less likely to provide adequate flexibility for delivering therapy to humans. Ligand-inducible gene expression systems may be more appropriate for these conditions, especially within the central nervous system (CNS). Mifepristone's ability to cross the blood-brain barrier makes it an especially attractive ligand for this purpose. We describe the production of a mifepristone-inducible vector system for regulated expression of transgenes within the CNS. Our inducible system used a lentivirus-based vector platform for the ex vivo production of mifepristone-inducible murine neural progenitor cells that express our transgenes of interest. These cells were processed through a series of selection steps to ensure that the cells exhibited appropriate transgene expression in a dose-dependent and temporally controlled manner with minimal background activity. Inducible cells were then transplanted into the brains of rodents, where they exhibited appropriate mifepristone-inducible expression. These studies detail a strategy for regulated expression in the CNS for use in the development of safe and efficient gene therapy for neurological disorders.

Modeling Huntington׳s disease with patient-derived neurons

Huntington׳s Disease (HD) is a fatal neurodegenerative disorder caused by expanded polyglutamine repeats in the Huntingtin (HTT) gene. While the gene was identified over two decades ago, it remains poorly understood why mutant HTT (mtHTT) is initially toxic to striatal medium spiny neurons (MSNs). Models of HD using non-neuronal human patient cells and rodents exhibit some characteristic HD phenotypes. While these current models have contributed to the field, they are limited in disease manifestation and may vary in their response to treatments. As such, human HD patient MSNs for disease modeling could greatly expand the current understanding of HD and facilitate the search for a successful treatment. It is now possible to use pluripotent stem cells, which can generate any tissue type in the body, to study and potentially treat HD. This review covers disease modeling in vitro and, via chimeric animal generation, in vivo using human HD patient MSNs differentiated from embryonic stem cells or induced pluripotent stem cells. This includes an overview of the differentiation of pluripotent cells into MSNs, the established phenotypes found in cell-based models and transplantation studies using these cells. This review not only outlines the advancements in the rapidly progressing field of HD modeling using neurons derived from human pluripotent cells, but also it highlights several remaining controversial issues such as the 'ideal' series of pluripotent lines, the optimal cell types to use and the study of a primarily adult-onset disease in a developmental model. This article is part of a Special Issue entitled SI: Exploiting human neurons.

Stem cells for cell replacement therapy: a therapeutic strategy for HD?

Much interest has been expressed over the last couple of decades in the potential application of stem cells to medicine, both for research and diagnostic tools and as a source of donor cells for therapeutic purposes. Potential therapeutic applications include replacement of cells in many body organs where the capacity for intrinsic repair is limited, including the pancreas, heart, and brain. A key challenge is to generate the relevant donor cell types, and this is particularly challenging in the brain where the number of different neuronal subtypes is so great. Although dopamine neuron replacement in Parkinson's disease has been the focus of most clinical studies, great interest has been shown in this approach for other disorders, including Huntington's disease. Replacing complete neural circuits in the adult brain is clearly challenging, and there are many other complexities with regard to both donor cells and host. This article presents the pros and cons of taking a cell therapy approach in Huntington's disease. It considers the implantation both of cells that are already of the same neural subtype as those lost in the disease process (ie, primary fetal cells derived from the developing striatum) and those derived from stem cells, which require "directing" toward that phenotype.

Stem cell therapy in neurodegenerative diseases: From principles to practice

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

Glial cell line-derived neurotrophic factor-secreting human neural progenitors show long-term survival, maturation into astrocytes, and no tumor formation following transplantation into the spinal cord of immunocompromised rats

Human neural progenitor cells (hNPCs) derived from the fetal cortex can be expanded in vitro and genetically modified through lentiviral transduction to secrete growth factors shown to have a neurotrophic effect in animal models of neurological disease. hNPCs survive and mature following transplantation into the central nervous system of large and small animals including the rat model of amyotrophic lateral sclerosis. Here we report that hNPCs engineered to express glial cell line-derived neurotrophic factor (GDNF) survive long-term (7.5 months) following transplantation into the spinal cord of athymic nude rats and continue to secrete GDNF. Cell proliferation declined while the number of astrocytes increased, suggesting final maturation of the cells over time in vivo. Together these data show that GDNF-producing hNPCs may be useful as a source of cells for long-term delivery of both astrocytes and GDNF to the damaged central nervous system.

Intraspinal transplantation of motoneuron-like cell combined with delivery of polymer-based glial cell line-derived neurotrophic factor for repair of spinal cord contusion injury

To evaluate the effects of glial cell line-derived neurotrophic factor transplantation combined with adipose-derived stem cells-transdifferentiated motoneuron delivery on spinal cord contusion injury, we developed rat models of spinal cord contusion injury, 7 days later, injected adipose-derived stem cells-transdifferentiated motoneurons into the epicenter, rostral and caudal regions of the impact site and simultaneously transplanted glial cell line-derived neurotrophic factor-gelfoam complex into the myelin sheath. Motoneuron-like cell transplantation combined with glial cell line-derived neurotrophic factor delivery reduced cavity formations and increased cell density in the transplantation site. The combined therapy exhibited superior promoting effects on recovery of motor function to transplantation of glial cell line-derived neurotrophic factor, adipose-derived stem cells or motoneurons alone. These findings suggest that motoneuron-like cell transplantation combined with glial cell line-derived neurotrophic factor delivery holds a great promise for repair of spinal cord injury.

Interaction between nonviral reprogrammed fibroblast stem cells and trophic factors for brain repair

There are currently no known treatment options that actually halt or permanently reverse the pathology evident in any neurodegenerative condition. Arguably, one of the most promising avenues for creating viable neuronal treatments could involve the combined use of cell replacement and gene therapy. Given the complexity of the neurodegenerative process, it stands to reason that adequate therapy should involve not only the replacement of loss neurons/synapses but also the interruption of multiple pro-death pathways. Thus, we propose the use of stem cells that are tailored to express specific trophic factors, thereby potentially encouraging synergistic effects between the stem cell properties and those of the trophic factors. The trophic factors, brain-derived neurotropic factor (BDNF), glial cell-derived neurotropic factor (GDNF), fibroblast growth factor (FGF) 2, and insulin-like growth factor (IGF) 1, in particular, have demonstrated neuroprotective actions in a number of animal models. Importantly, we use a nonviral approach, thereby minimizing the potential risk for DNA integration and tumor formation. The present study involved the development of a nonviral reprogramming system to transform adult mature mouse fibroblasts into progressive stages of cell development. We also tailored these stem cells to individually express each of the trophic factors, including BDNF, GDNF, FGF2, and IGF1. Significantly, central infusion of BDNF-expressing stem cells prevented the in vivo loss of neurons associated with infusion of the endotoxin, lipopolysaccharide (LPS). This is particularly important in light of the role of inflammatory processes that are posited to play in virtually all neurodegenerative states. Hence, the present results support the utility of using combined gene and cell-targeting approaches for neuronal pathology.

Co-culture with neurotrophic factor secreting cells induced from adipose-derived stem cells: promotes neurogenic differentiation

Adipose-derived stem cells (ADSCs) and bone marrow stem cells (BMSCs) can be equally proper in the treatment of neurodegenerative diseases. However, ADSCs have practical benefits. In this study, we attempted to induce the secretion of neurotrophic factors (NTF) in human ADSCs. We then evaluated the effects of co-culture with NTF secreting cells in neural differentiation of human ADSCs. Isolated human ADSCs were induced to neurotrophic factors secreting cells. To evaluate the in vitro effects of NTF-secreting ADSCs on neurogenic differentiation of ADSCs, we used neurogenic induction medium (control group), the combination of neurogenic medium and conditioned medium, or co-cultured NTF-secreting ADSCs which were encapsulated in alginate beads (co-culture) for 7 days. ELISA showed increased (by about 5 times) release of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in NTF-secreting ADSCs compared to human ADSCs. Real time RT-PCR analysis revealed that NTF-secreting ADSCs highly expressed NGF and BDNF. In addition, co-culture with NTF-secreting ADSCs could also promote neuronal differentiation relative to gliogenesis. Overall, NTF-secreting ADSCs secrete a range of growth factors whose levels in culture could promote neuronal differentiation and could support the survival and regeneration in a variety of neurodegenerative diseases.

Concise review: Can stem cells be used to treat or model Alzheimer's disease?

Alzheimer's disease (AD) is the leading cause of age-related dementia, affecting over 5 million people in the U.S. alone. AD patients suffer from progressive neurodegeneration that gradually impairs their memory, ability to learn, and carry out daily activities. Unfortunately, current therapies for AD are largely palliative and several promising drug candidates have failed in recent clinical trials. There is therefore an urgent need to improve our understanding of AD pathogenesis, create innovative and predictive models, and develop new and effective therapies. In this review, we will discuss the potential of stem cells to aid in these challenging endeavors. Because of the widespread nature of AD pathology, cell-replacement strategies have been viewed as an incredibly challenging and unlikely treatment approach. Yet recent work shows that transplantation of neural stem cells (NSCs) can improve cognition, reduce neuronal loss, and enhance synaptic plasticity in animal models of AD. Interestingly, the mechanisms that mediate these effects appear to involve neuroprotection and trophic support rather than neuronal replacement. Stem cells may also offer a powerful new approach to model and study AD. Patient-derived induced pluripotent stem cells, for example, may help to advance our understanding of disease mechanisms. Likewise, studies of human embryonic and NSCs are helping to decipher the normal functions of AD-related genes; revealing intriguing roles in neural development.

Oligodendroglia and neurotrophic factors in neurodegeneration

Myelination by oligodendroglial cells (OLs) enables the propagation of action potentials along neuronal axons, which is essential for rapid information flow in the central nervous system. Besides saltatory conduction, the myelin sheath also protects axons against inflammatory and oxidative insults. Loss of myelin results in axonal damage and ultimately neuronal loss in demyelinating disorders. However, accumulating evidence indicates that OLs also provide support to neurons via mechanisms beyond the insulating function of myelin. More importantly, an increasing volume of reports indicates defects of OLs in numerous neurodegenerative diseases, sometimes even preceding neuronal loss in pre-symptomatic episodes, suggesting that OL pathology may be an important mechanism contributing to the initiation and/or progression of neurodegeneration. This review focuses on the emerging picture of neuronal support by OLs in the pathogenesis of neurodegenerative disorders through diverse molecular and cellular mechanisms, including direct neuron-myelin interaction, metabolic support by OLs, and neurotrophic factors produced by and/or acting on OLs.

Modeling Huntington's disease with induced pluripotent stem cells

Huntington's disease (HD) causes severe motor dysfunction, behavioral abnormalities, cognitive impairment and death. Investigations into its molecular pathology have primarily relied on murine tissues; however, the recent discovery of induced pluripotent stem cells (iPSCs) has opened new possibilities to model neurodegenerative disease using cells derived directly from patients, and therefore may provide a human-cell-based platform for unique insights into the pathogenesis of HD. Here, we will examine the practical implementation of iPSCs to study HD, such as approaches to differentiate embryonic stem cells (ESCs) or iPSCs into medium spiny neurons, the cell type most susceptible in HD. We will explore the HD-related phenotypes identified in iPSCs and ESCs and review how brain development and neurogenesis may actually be altered early, before the onset of HD symptoms, which could inform the search for drugs that delay disease onset. Finally, we will speculate on the exciting possibility that ESCs or iPSCs might be used as therapeutics to restore or replace dying neurons in HD brains.

Mouse models of polyglutamine diseases in therapeutic approaches: review and data table. Part II

Mouse models of human diseases are created both to understand the pathogenesis of the disorders and to find successful therapies for them. This work is the second part in a series of reviews of mouse models of polyglutamine (polyQ) hereditary disorders and focuses on in vivo experimental therapeutic approaches. Like part I of the polyQ mouse model review, this work is supplemented with a table that contains data from experimental studies of therapeutic approaches in polyQ mouse models. The aim of this review was to characterize the benefits and outcomes of various therapeutic strategies in mouse models. We examine whether the therapeutic strategies are specific to a single disease or are applicable to more than one polyQ disorder in mouse models. In addition, we discuss the suitability of mouse models in therapeutic approaches. Although the majority of therapeutic studies were performed in mouse models of Huntington disease, similar strategies were also used in other disease models.

Implantation of undifferentiated and pre-differentiated human neural stem cells in the R6/2 transgenic mouse model of Huntington's disease

Background

Cell therapy is a potential therapeutic approach for several neurodegenetative disease, including Huntington Disease (HD). To evaluate the putative efficacy of cell therapy in HD, most studies have used excitotoxic animal models with only a few studies having been conducted in genetic animal models. Genetically modified animals should provide a more accurate representation of human HD, as they emulate the genetic basis of its etiology.

Results

In this study, we aimed to assess the therapeutic potential of a human striatal neural stem cell line (STROC05) implanted in the R6/2 transgenic mouse model of HD. As DARPP-32 GABAergic output neurons are predominately lost in HD, STROC05 cells were also pre-differentiated using purmorphamine, a hedgehog agonist, to yield a greater number of DARPP-32 cells. A bilateral injection of 4.5x10⁵ cells of either undifferentiated or pre-differentiated DARPP-32 cells, however, did not affect outcome compared to a vehicle control injection. Both survival and neuronal differentiation remained poor with a mean of only 161 and 81 cells surviving in the undifferentiated and differentiated conditions respectively. Only a few cells expressed the neuronal marker Fox3.

Conclusions

Although the rapid brain atrophy and short life-span of the R6/2 model constitute adverse conditions to detect potentially delayed treatment effects, significant technical hurdles, such as poor cell survival and differentiation, were also sub-optimal. Further consideration of these aspects is therefore needed in more enduring transgenic HD models to provide a definite assessment of this cell line’s therapeutic relevance. However, a combination of treatments is likely needed to affect outcome in transgenic models of HD.

Current challenges for the advancement of neural stem cell biology and transplantation research

Transplantation of neural stem cells (NSC) is hoped to become a promising primary or secondary therapy for the treatment of various neurodegenerative disorders of the central nervous system (CNS), as demonstrated by multiple pre-clinical animal studies in which functional recovery has already been demonstrated. However, for NSC therapy to be successful, the first challenge will be to define a transplantable cell population. In the first part of this review, we will briefly discuss the main features of ex vivo culture and characterisation of NSC. Next, NSC grafting itself may not only result in the regeneration of lost tissue, but more importantly has the potential to improve functional outcome through many bystander mechanisms. In the second part of this review, we will briefly discuss several pre-clinical studies that contributed to a better understanding of the therapeutic potential of NSC grafts in vivo. However, while many pre-clinical animal studies mainly report on the clinical benefit of NSC grafting, little is known about the actual in vivo fate of grafted NSC. Therefore, the third part of this review will focus on non-invasive imaging techniques for monitoring cellular grafts in the brain under in vivo conditions. Finally, as NSC transplantation research has evolved during the past decade, it has become clear that the host micro-environment itself, either in healthy or injured condition, is an important player in defining success of NSC grafting. The final part of this review will focus on the host environmental influence on survival, migration and differentiation of grafted NSC.

The sixth annual translational stem cell research conference of the New York Stem Cell Foundation

The New York Stem Cell Foundation's "Sixth Annual Translational Stem Cell Research Conference" convened on October 11-12, 2011 at the Rockefeller University in New York City. Over 450 scientists, patient advocates, and stem cell research supporters from 14 countries registered for the conference. In addition to poster and platform presentations, the conference featured panels entitled "Road to the Clinic" and "The Future of Regenerative Medicine."

Nucleic Acid-Based Therapy Approaches for Huntington's Disease

Huntington's disease (HD) is caused by a dominant mutation that results in an unstable expansion of a CAG repeat in the huntingtin gene leading to a toxic gain of function in huntingtin protein which causes massive neurodegeneration mainly in the striatum and clinical symptoms associated with the disease. Since the mutation has multiple effects in the cell and the precise mechanism of the disease remains to be elucidated, gene therapy approaches have been developed that intervene in different aspects of the condition. These approaches include increasing expression of growth factors, decreasing levels of mutant huntingtin, and restoring cell metabolism and transcriptional balance. The aim of this paper is to outline the nucleic acid-based therapeutic strategies that have been tested to date.

Neurotrophic factors and neurodegenerative diseases: a delivery issue

Neurotrophic factors (NTFs) represent one of the most stimulating challenge in neurodegenerative diseases, due to their potential in neurorestoring and neuroprotection. Despite the large number of proofs-of-concept and evidences of their activity, most of the clinical trials, mainly regarding Parkinson's disease and Alzheimer's disease, demonstrated several failures of the therapeutic intervention. A large number of researches were conducted on this hot topic of neuroscience, clearly evidencing the advantages of NTF approach, but evidencing the major limitations in its application. The inability in crossing the blood-brain barrier and the lack of selectivity actually represent some of the most highlighted limits of NTFs-based therapy. In this review, beside an overview of NTF activity versus the main neuropathological disorders, a summary of the most relevant approaches, from invasive to noninvasive strategies, applied for improving NTF delivery to the central nervous systems is critically considered and evaluated.

Stem cell technology for neurodegenerative diseases

Over the past 20 years, stem cell technologies have become an increasingly attractive option to investigate and treat neurodegenerative diseases. In the current review, we discuss the process of extending basic stem cell research into translational therapies for patients suffering from neurodegenerative diseases. We begin with a discussion of the burden of these diseases on society, emphasizing the need for increased attention toward advancing stem cell therapies. We then explain the various types of stem cells utilized in neurodegenerative disease research, and outline important issues to consider in the transition of stem cell therapy from bench to bedside. Finally, we detail the current progress regarding the applications of stem cell therapies to specific neurodegenerative diseases, focusing on Parkinson disease, Huntington disease, Alzheimer disease, amyotrophic lateral sclerosis, and spinal muscular atrophy. With a greater understanding of the capacity of stem cell technologies, there is growing public hope that stem cell therapies will continue to progress into realistic and efficacious treatments for neurodegenerative diseases.

Optimized quantities of GDNF overexpressed by engineered astrocytes are critical for protection of neuroblastoma cells against 6-OHDA toxicity

Optimized levels of glial cell line-derived neurotrophic factor (GDNF) are critical for protection of dopaminergic neurons against parkinsonian cell death. Recombinant lentiviruses harboring GDNF coding sequence were constructed and used to infect astrocytoma cell line 1321N1. The infected astrocytes overexpressed GDNF mRNA and secreted an average of 2.2 ng/mL recombinant protein as tested in both 2 and 16 weeks post-infection. Serial dilutions of GDNF-enriched conditioned medium from infected astrocytes added to growing neuroblastoma cell line SK-N-MC resulted in commensurate resistance against 6-OHDA toxicity. SK-N-MC cell survival rate rose from 51% in control group to 84% in the cells grown with astro-CM containing 453 pg secreted GDNF, an increase that was highly significant (P < 0.0001). However, larger volumes of the GDNF-enriched conditioned medium failed to improve cell survival and addition of volumes that contained 1,600 pg or more GDNF further reduced survival rate to below 70%. Changes in cell survival paralleled to changes in the percent of apoptotic cell morphologies. These data demonstrate the feasibility of using astrocytes as minipumps to stably oversecrete neurotrophic factors and further indicate that GDNF can be applied to neuroprotection studies in PD pending the optimization of its concentrations.

Interneuron progenitors attenuate the power of acute focal ictal discharges

Interneuron progenitors from the embryonic medial ganglionic eminence (MGE) can migrate, differentiate, and enhance local inhibition after transplantation into the postnatal cortex. Whether grafted MGE cells can reduce ictal activity in adult neocortex is unknown. We transplanted live MGE or killed cells (control) from pan green fluorescent protein expressing mice into adult mouse sensorimotor cortex. One week, 2 and 1/2 weeks, or 6 to 8 weeks after transplant, acute focal ictal epileptiform discharges were induced by injection of 4-aminopyridine (4-AP) 2 mm away from the site of transplantation. The local field potential of the events was recorded with 2 electrodes, 1 located in the 4-AP focus and the other 1 in the transplantation site. In all control groups and in the 1-week live cell transplant, 4-AP ictal discharges revealed no attenuation in power and duration from the onset site to the site of transplantation. However, 2.5 or 6 ~ 8 weeks after MGE transplants, there was a dramatic decrease in local field potential power at the MGE transplanted site with little decrease in ictal duration. Surprisingly, there was no relationship between grafted cell distribution or density and the degree of attenuation. As remarkably low graft densities still significantly reduced discharge power, these data provide further support for the therapeutic potential of interneuron precursor transplants in the treatment of neocortical epilepsy.

BDNF-, IGF-1- and GDNF-secreting human neural progenitor cells rescue amyloid β-induced toxicity in cultured rat septal neurons

Alzheimer's disease (AD) is characterized by the depositions of amyloid-β (Aβ) proteins, resulting in a reduction of choline acetyltransferase (ChAT) activity of AD brain in the early stages of the disease. Several growth factors, including brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF)-1 and glial cell-derived neurotrophic factor (GDNF) are known to protect neuronal cell death in several neurodegenerative both in vitro and in vivo models. In this study, septal neurons were prepared from septal nucleus of embryonic (day 16-17) rat brain and treated with monomeric, oligomeric or fibrillar Aβ(1-42) peptide. Oligomeric Aβ(1-42), (10 μM) was the most potent at sublethal dose. Septal neuron cultures treated with BDNF, IGF-1 or GDNF or co-cultured with genetically modified human neural progenitor cells (hNPCs) secreting these neurotrophic factors (but not allowing contact between the two cell types), were protected from oligomeric Aβ(1-42) peptide-induced cell death, and these trophic factors enhanced cholinergic functions by increasing ChAT expression level. These results indicate the potential of employing transplanted hNPCs for treatment of AD.

Gene therapy in mouse models of huntington disease

Huntingtin, the protein that when mutated causes Huntington disease (HD), has many known interactors and participates in diverse cellular functions. Mutant Htt (mHtt) engages in a variety of aberrant interactions that lead to pathological gain of toxic functions as well as loss of normal functions. The broad symptomatology of HD, including diminished voluntary motor control, cognitive decline, and psychiatric disturbances, reflects the multifaceted neuropathology. Although currently available therapies for HD focus on symptom management, the autosomal dominant cause and the adult onset make this disease an ideal candidate for genetic intervention. A variety of gene therapy approaches have been tested in mouse models of HD, ranging from those aimed at ameliorating downstream pathology or replacing lost neuronal populations to more upstream strategies to reduce mHtt levels. Here the authors review the results of these preclinical trials.

The development of flexible lentiviral vectors for gene transfer in the CNS

The use of recombinant lentiviral vectors (rLV) is emerging as a viable candidate for clinical gene therapy of the central nervous system. New generation vectors are being produced while addressing viral safety concerns as well as production capabilities. Furthermore, the ability to combine envelope proteins targeting specific cell types with specific promoters guiding the expression of the genetic payload will allow researchers and clinicians to precisely guide transgene expression to anatomically and phenotypically distinct populations of cells. In a recent issue of Experimental Neurology, Cannon and colleagues demonstrate the ability to transduce specific populations of cells in the rat midbrain by using differently pseudotyped lentiviral vectors which results in significant differences in transgene spread throughout the nigrostriatal tract. These results highlight the potential utility of rLV in clinical applications as well as in research involving neurodegenerative disease.

The importance of integrating basic and clinical research toward the development of new therapies for Huntington disease

Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that results from expansion of the polyglutamine repeat in the huntingtin (HTT) gene. There are currently no effective treatments for this devastating disease. Given its monogenic nature, disease modification therapies for HD should be theoretically feasible. Currently, pharmacological therapies aimed at disease modification by altering levels of HTT protein are in late-stage preclinical development. Here, we review current efforts to develop new treatments for HD based on our current understanding of HTT function and the main pathological mechanisms. We emphasize the need to enhance translational efforts and highlight the importance of aligning the clinical and basic research communities to validate existing hypotheses in clinical studies. Human and animal therapeutic trials are presented with an emphasis on cellular and molecular mechanisms relevant to disease progression.

Stem cell therapy for neurological disorders

Stem cells have long been in focus as potential therapy or even cure for a whole myriad of diseases. Many neurodegenerative disorders, both acute and chronic, are characterized by irreversible neuronal damage and loss, and only a few efficient treatment options exist. In contrast to many other tissues, the potential of self-regeneration of the central nervous system is highly limited. There is hope that stem cells could replace the damaged neuronal and glial cells, and provide biological and functional restoration based on their properties of self renewal and the ability to give rise to different cells. In recent years, the promising results of research on animal models has led to the establishment of the first clinical trials; although no clear evidence of therapeutic benefit for any of the conditions have been ascertained. Here we give a review of the current strategies of stem-cell based therapy for some of the more common neurological disorders, discussing the progress and current challenges, and giving an overview of future perspectives.

Experimental surgical therapies for Huntington's disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by abnormal movement, cognitive decline, and psychiatric disturbance. HD is caused by a trinucleotide repeat expansion in the HTT gene and a corresponding neurotoxic polyglutamine expansion in the huntingtin protein. There is currently no therapy to modify the progressive course of the disease, and symptomatic treatment options are limited. In this review we describe a diverse set of emerging experimental therapeutic strategies for HD: deep brain stimulation; delivery of neurotrophic factors; cell transplantation; HTT gene silencing using RNA interference or antisense oligonucleotides; and delivery of intrabodies. The common feature of these experimental therapies is that they all require a neurosurgical intervention, either for implantation of an electrode or for brain delivery of molecules, viruses or cells that do not cross the blood-brain barrier upon oral or intravenous administration. We summarize available data on the rationale, safety, efficacy, and intrinsic limitations of each of these approaches, focusing mainly on studies in HD patients and genetic animal models of HD. Although each of these strategies holds significant promise, their efficacy remains to be proven in HD patients.

Stem Cells for the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases are characterized by neurodegenerative changes or apoptosis of neurons involved in networks, leading to permanent paralysis and loss of sensation below the site of the injury. Cell replacement therapy has provided the basis for the development of potentially powerful new therapeutic strategies for a broad spectrum of human neurological diseases. In recent years, neurons and glial cells have successfully been generated from stem cells, and extensive efforts by investigators to develop stem cell-based brain transplantation therapies have been carried out. We review here notable previously published experimental and preclinical studies involving stem cell-based cell for neurodegenerative diseases and discuss the future prospects for stem cell therapy of neurological disorders in the clinical setting. Steady and solid progress in stem cell research in both basic and preclinical settings should support the hope for development of stem cell-based cell therapies for neurological diseases.