Genetically engineered mesenchymal stem cells reduce behavioral deficits in the YAC 128 mouse model of Huntington's disease

Concise review: adult mesenchymal stem cells, adult neural crest stem cells, and therapy of neurological pathologies: a state of play

Adult stem cells are endowed with in vitro multilineage differentiation abilities and constitute an attractive autologous source of material for cell therapy in neurological disorders. With regard to lately published results, the ability of adult mesenchymal stem cells (MSCs) and neural crest stem cells (NCSCs) to integrate and differentiate into neurons once inside the central nervous system (CNS) is currently questioned. For this review, we collected exhaustive data on MSC/NCSC neural differentiation in vitro. We then analyzed preclinical cell therapy experiments in different models for neurological diseases and concluded that neural differentiation is probably not the leading property of adult MSCs and NCSCs concerning neurological pathology management. A fine analysis of the molecules that are secreted by MSCs and NCSCs would definitely be of significant interest regarding their important contribution to the clinical and pathological recovery after CNS lesions.

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.

Upregulation of TrkB by forskolin facilitated survival of MSC and functional recovery of memory deficient model rats

Mesenchymal stem cells (MSCs) are effective vectors in delivering a gene of interest into degenerating brain. In ex vivo gene therapy, viability of transplanted MSCs is correlated with the extent of functional recovery. It has been reported that BDNF facilitates survival of MSCs but dividing MSCs do not express the BDNF receptor, TrkB. In this study, we found that the expression of TrkB is upregulated in human MSCs by the addition of forskolin (Fsk), an activator of adenylyl cyclase. To increase survival rate of MSCs and their secretion of tropic factors that enhance regeneration of endogenous cells, we pre-exposed hMSCs with Fsk and transduced with BDNF-adenovirus before transplantation into the brain of memory deficient rats, a degenerating brain disease model induced by ibotenic acid injection. Viability of MSCs and expression of a GABA synthesizing enzyme were increased. The pre-treatment improved learning and memory, as detected by the behavioral tests including Y-maze task and passive avoidance test. These results suggest that TrkB expression of hMSCs elevates the neuronal regeneration and efficiency of BDNF delivery for treating degenerative neurological diseases accompanying memory loss.

Mesenchymal stem cells: a revolution in therapeutic strategies of age-related diseases

The great evolutionary biologist Theodosius Dobzhansky once said: "Nothing in biology makes sense except in the light of evolution". Aging is a complex biological phenomenon and the factors governing the process of aging and age-related diseases are only beginning to be understood, oxidative stress, telomere shortening in DNA components and genetic changes were shown to be the mainly regulating mechanisms during the recent decades. Although a considerable amount of both animal and clinical data that demonstrate the extensive and safe use of mesenchymal stromal cells (MSCs) is available, the precise summarization and identification of MSCs in age-related diseases remains a challenge. Along this line, this review discussed several typical age-related diseases for which MSCs have been proved to confer protection and put forward a hypothesis for the association among MSCs and age-related diseases from an evolutionary perspective. Above all, we hope further and more research efforts could be aroused to elucidate the role and mechanisms that MSCs involved in the age-related diseases.

Mesenchymal stem cells for trinucleotide repeat disorders

Mesenchymal stem cells/marrow stromal cells (MSCs) are ideally suited for cellular therapy due to their ease of isolation, manipulation, and strong safety profile in the clinic. They can be expanded from normal qualified human donors in large quantities and can be infused without tissue matching, since they shield themselves from the immune system. The ability to be transplanted without tissue matching has allowed large multicenter trials to be conducted with direct comparison of the same batches of MSCs, without adverse events or rejection reactions. MSCs are now approved as drugs in several countries outside of the USA. MSCs can be genetically modified to provide sustained and long-term delivery of growth factors at supraphysiological levels. Gene-modified MSCs are in clinical trials for the treatment of stroke and are under consideration for the treatment of neurodegenerative disorders such as Huntington's disease.

Assessing the potential clinical utility of transplantations of neural and mesenchymal stem cells for treating neurodegenerative diseases

Treatments for neurodegenerative diseases have little impact on the long-term patient health. However, cellular transplants of neuroblasts derived from the aborted embryonic brain tissue in animal models of neurodegenerative disorders and in patients have demonstrated survival and functionality in the brain. However, ethical and functional problems due to the use of this fetal tissue stopped most of the clinical trials. Therefore, new cell sources were needed, and scientists focused on neural (NSCs) and mesenchymal stem cells (MSCs). When transplanted in the brain of animals with Parkinson's or Huntington's disease, NSCs and MSCs were able to induce partial functional recovery by promoting neuroprotection and immunomodulation. MSCs are more readily accessible than NSCs due to sources such as the bone marrow. However, MSCs are not capable of differentiating into neurons in vivo where NSCs are. Thus, transplantation of NSCs and MSCs is interesting for brain regenerative medicine. In this chapter, we detail the methods for NSCs and MSCs isolation as well as the transplantation procedures used to treat rodent models of neurodegenerative damage.

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.

Current advances in using neurotrophic factors to treat neurodegenerative disorders

Neurotrophic factors are best known for their roles in both development and continued maintenance of the nervous system. Their strong potential to elicit pro-survival and pro-functional responses in neurons of the peripheral and central nervous system make them good drug candidates for treatment of a multitude of neurodegenerative disorders. However, significant obstacles remain and need to be overcome before translating the potential of neurotrophins into the therapeutic arena. This article addresses current efforts and advances in resolving these challenges and provides an overview of roadmaps for future translational research and neurotrophin-based drug developments.

Intrastriatal transplantation of neurotrophic factor-secreting human mesenchymal stem cells improves motor function and extends survival in R6/2 transgenic mouse model for Huntington's disease

Stem cell-based treatment for Huntington's disease (HD) is an expanding field of research. Although various stem cells have been shown to be beneficial in vivo, no long standing clinical effect has been demonstrated. To address this issue, we are developing a stem cell-based therapy designed to improve the microenvironment of the diseased tissue via delivery of neurotrophic factors (NTFs). Previously, we established that bone marrow derived human mesenchymal stem cells (MSCs) can be differentiated using medium based cues into NTF-secreting cells (NTF+ cells) that express astrocytic markers. NTF+ cells were shown to alleviate neurodegeneration symptoms in several disease models in vitro and in vivo, including the model for excitotoxicity. In the present study, we explored if the timing of intrastriatal transplantation of hNTF+ cells into the R6/2 transgenic mouse model for HD influences motor function and survival. One hundred thousand cells were transplanted bilaterally into the striatum of immune-suppressed mice at 4.5, 5.5 and 6.5 weeks of age. Contrary to our expectations, early transplantation of NTF+ cells did not improve motor function or overall survival. However, late (6.5 weeks) transplantation resulted in a temporary improvement in motor function and an extension of life span relative to that observed for PBS treated mice. We conclude that late transplantation of NTF+ cells induces a beneficial effect in this transgenic model for HD. Since no transplanted NTF+ cells could be detected in vivo, we suspect that the temporary nature of the beneficial effect is due to poor survival of transplanted cells. In general, we submit that NTF+ cells should be further evaluated for the therapy of HD.

Genetic correction of Huntington's disease phenotypes in induced pluripotent stem cells

Huntington's disease (HD) is caused by a CAG expansion in the huntingtin gene. Expansion of the polyglutamine tract in the huntingtin protein results in massive cell death in the striatum of HD patients. We report that human induced pluripotent stem cells (iPSCs) derived from HD patient fibroblasts can be corrected by the replacement of the expanded CAG repeat with a normal repeat using homologous recombination, and that the correction persists in iPSC differentiation into DARPP-32-positive neurons in vitro and in vivo. Further, correction of the HD-iPSCs normalized pathogenic HD signaling pathways (cadherin, TGF-β, BDNF, and caspase activation) and reversed disease phenotypes such as susceptibility to cell death and altered mitochondrial bioenergetics in neural stem cells. The ability to make patient-specific, genetically corrected iPSCs from HD patients will provide relevant disease models in identical genetic backgrounds and is a critical step for the eventual use of these cells in cell replacement therapy.

Bone marrow transplantation confers modest benefits in mouse models of Huntington's disease

Huntington's disease (HD) is caused by an expanded polyglutamine tract in the protein huntingtin (htt). Although HD has historically been viewed as a brain-specific disease, htt is expressed ubiquitously, and recent studies indicate that mutant htt might cause changes to the immune system that could contribute to pathogenesis. Monocytes from HD patients and mouse models are hyperactive in response to stimulation, and increased levels of inflammatory cytokines and chemokines are found in pre-manifest patients that correlate with pathogenesis. In this study, wild-type (WT) bone marrow cells were transplanted into two lethally irradiated transgenic mouse models of HD that ubiquitously express full-length htt (YAC128 and BACHD mice). Bone marrow transplantation partially attenuated hypokinetic and motor deficits in HD mice. Increased levels of synapses in the cortex were found in HD mice that received bone marrow transplants. Importantly, serum levels of interleukin-6, interleukin-10, CXC chemokine ligand 1, and interferon-γ were significantly higher in HD than WT mice but were normalized in mice that received a bone marrow transplant. These results suggest that immune cell dysfunction might be an important modifier of pathogenesis in HD.

Genetically engineered mesenchymal stem cells as a proposed therapeutic for Huntington's disease

There is much interest in the use of mesenchymal stem cells/marrow stromal cells (MSC) to treat neurodegenerative disorders, in particular those that are fatal and difficult to treat, such as Huntington's disease. MSC present a promising tool for cell therapy and are currently being tested in FDA-approved phase I-III clinical trials for many disorders. In preclinical studies of neurodegenerative disorders, MSC have demonstrated efficacy, when used as delivery vehicles for neural growth factors. A number of investigators have examined the potential benefits of innate MSC-secreted trophic support and augmented growth factors to support injured neurons. These include overexpression of brain-derived neurotrophic factor and glial-derived neurotrophic factor, using genetically engineered MSC as a vehicle to deliver the cytokines directly into the microenvironment. Proposed regenerative approaches to neurological diseases using MSC include cell therapies in which cells are delivered via intracerebral or intrathecal injection. Upon transplantation, MSC in the brain promote endogenous neuronal growth, encourage synaptic connection from damaged neurons, decrease apoptosis, reduce levels of free radicals, and regulate inflammation. These abilities are primarily modulated through paracrine actions. Clinical trials for MSC injection into the central nervous system to treat amyotrophic lateral sclerosis, traumatic brain injury, and stroke are currently ongoing. The current data in support of applying MSC-based cellular therapies to the treatment of Huntington's disease is discussed.

Adenoviral astrocyte-specific expression of BDNF in the striata of mice transgenic for Huntington's disease delays the onset of the motor phenotype

Huntington's disease (HD) is a neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. The most characteristic structural feature of this disease is neurodegeneration accompanied by gliosis in the striatum. BDNF has been proposed to protect striatal neurons from degeneration, because it is an important survival factor for these neurons from development to adulthood. Considering the extensive gliosis and the survival effects of BDNF, we constructed an adenovirus to express a BDNF cDNA in astrocyte cells using a promoter of the glial fibrillary acidic protein gene. Cells stably transfected in vitro with a BDNF cDNA driven by this promoter expressed BDNF and responded to external stimuli increasing BDNF production. When the vector was applied into the striata of mice transgenic for HD, long-term expression of the transgene was observed, associated with a delay of onset of the motor phenotype of the R6/2 HD transgenic mice. The present data indicate that the striatal expression of BDNF is a potential adjuvant for the treatment of HD.

Convergent pathogenic pathways in Alzheimer's and Huntington's diseases: shared targets for drug development

Neurodegenerative diseases, exemplified by Alzheimer's disease and Huntington's disease, are characterized by progressive neuropsychiatric dysfunction and loss of specific neuronal subtypes. Although there are differences in the exact sites of pathology, and the clinical profiles of these two conditions only partially overlap, considerable similarities in disease mechanisms and pathogenic pathways can be observed. These shared mechanisms raise the possibility of exploiting common therapeutic targets for drug development. As Huntington's disease has a monogenic cause, it is possible to accurately identify individuals who carry the Huntington's disease mutation but do not yet manifest symptoms. These individuals could act as a model for Alzheimer's disease to test therapeutic interventions that target shared pathogenic pathways.

Human mesenchymal stem cells prolong survival and ameliorate motor deficit through trophic support in Huntington's disease mouse models

We investigated the therapeutic potential of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) in Huntington's disease (HD) mouse models. Ten weeks after intrastriatal injection of quinolinic acid (QA), mice that received hBM-MSC transplantation showed a significant reduction in motor function impairment and increased survival rate. Transplanted hBM-MSCs were capable of survival, and inducing neural proliferation and differentiation in the QA-lesioned striatum. In addition, the transplanted hBM-MSCs induced microglia, neuroblasts and bone marrow-derived cells to migrate into the QA-lesioned region. Similar results were obtained in R6/2-J2, a genetically-modified animal model of HD, except for the improvement of motor function. After hBM-MSC transplantation, the transplanted hBM-MSCs may integrate with the host cells and increase the levels of laminin, Von Willebrand Factor (VWF), stromal cell-derived factor-1 (SDF-1), and the SDF-1 receptor Cxcr4. The p-Erk1/2 expression was increased while Bax and caspase-3 levels were decreased after hBM-MSC transplantation suggesting that the reduced level of apoptosis after hBM-MSC transplantation was of benefit to the QA-lesioned mice. Our data suggest that hBM-MSCs have neural differentiation improvement potential, neurotrophic support capability and an anti-apoptotic effect, and may be a feasible candidate for HD therapy.

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.

Recent progress in cell therapy for basal ganglia disorders with emphasis on menstrual blood transplantation in stroke

Cerebrovascular diseases are the third leading cause of death and the primary cause of long-term disability in the United States. The only approved therapy for stroke is tPA, strongly limited by the short therapeutic window and hemorrhagic complications, therefore excluding most patients from its benefits. Parkinson's and Huntington's disease are the other two most studied basal ganglia diseases and, as stroke, have very limited treatment options. Inflammation is a key feature in central nervous system disorders and it plays a dual role, either improving injury in early phases or impairing neural survival at later stages. Stem cells can be opportunely used to modulate inflammation, abrogate cell death and, therefore, preserve neural function. We here discuss the role of stem cells as restorative treatments for basal ganglia disorders, including Parkinson's disease, Huntington's disease and stroke, with special emphasis to the recently investigated menstrual blood stem cells. We highlight the availability, proliferative capacity, pluripotentiality and angiogenic features of these cells and explore their present and future experimental and clinical applications.

Mesenchymal stem cells for the treatment of neurodegenerative disease

Mesenchymal stem cells/marrow stromal cells (MSCs) present a promising tool for cell therapy, and are currently being tested in US FDA-approved clinical trials for myocardial infarction, stroke, meniscus injury, limb ischemia, graft-versus-host disease and autoimmune disorders. They have been extensively tested and proven effective in preclinical studies for these and many other disorders. There is currently a great deal of interest in the use of MSCs to treat neurodegenerative diseases, in particular for those that are fatal and difficult to treat, such as Huntington's disease and amyotrophic lateral sclerosis. Proposed regenerative approaches to neurological diseases using MSCs include cell therapies in which cells are delivered via intracerebral or intrathecal injection. Upon transplantation into the brain, MSCs promote endogenous neuronal growth, decrease apoptosis, reduce levels of free radicals, encourage synaptic connection from damaged neurons and regulate inflammation, primarily through paracrine actions. MSCs transplanted into the brain have been demonstrated to promote functional recovery by producing trophic factors that induce survival and regeneration of host neurons. Therapies will capitalize on the innate trophic support from MSCs or on augmented growth factor support, such as delivering brain-derived neurotrophic factor or glial-derived neurotrophic factor into the brain to support injured neurons, using genetically engineered MSCs as the delivery vehicles. Clinical trials for MSC injection into the CNS to treat traumatic brain injury and stroke are currently ongoing. The current data in support of applying MSC-based cellular therapies to the treatment of neurodegenerative disorders are discussed.

Small changes, big impact: posttranslational modifications and function of huntingtin in Huntington disease

Huntington disease (HD) is a neurodegenerative disorder caused by an elongated polyglutamine tract in huntingtin (htt). htt normally undergoes different posttranslational modifications (PTMs), including phosphorylation, SUMOylation, ubiquitination, acetylation, proteolytic cleavage, and palmitoylation. In the presence of the HD mutation, some PTMs are significantly altered and can result in changes in the clinical phenotype. A rate-limiting PTM is defined as one that can result in significant effects on the phenotype in animal models. For example, the prevention of proteolysis at D586 as well as constitutive phosphorylation at S13 and S16 can obviate the expression of phenotypic features of HD. The enzymes involved in these modifications such as caspase-6, the IκB kinase (IKK) complex, and still to be characterized phosphatases therefore represent promising therapeutic targets for HD. Identifying and testing specific modulators of PTMs now constitute the next big challenges in order to further validate these targets and proceed towards the goal of a mechanism-based treatment for HD.

Mesenchymal stem cell transplantation and DMEM administration in a 3NP rat model of Huntington's disease: morphological and behavioral outcomes

Transplantation of mesenchymal stem cells (MSCs) may offer a viable treatment for Huntington's disease (HD). We tested the efficacy of MSC transplants to reduce deficits in a 3-nitropropionic acid (3NP) rat model of HD. Five groups of rats (Sham, 3NP, 3NP+vehicle, 3NP+TP(low), 3NP+TP(high)), were given PBS or 3NP intraperitoneally, twice daily for 42 days. On day 28, rats in all groups except Sham and 3NP, received intrastriatal injections of either 200,000 MSCs (TP(low)), 400,000 (TP(high)) MSCs or DMEM (VH, the vehicle for transplantation). MSCs survived 72 days without inducing a strong inflammatory response from the striatum. Behavioral sparing was observed on tests of supported-hindlimb-retraction, unsupported-hindlimb-retraction, visual paw placement and stepping ability for 3NP+TP(low) rats and on the unsupported-hindlimb-retraction and rotarod tasks for 3NP+VH rats. Relative to 3NP controls, all treated groups were protected from 3NP-induced enlargement of the lateral ventricles. In vitro, MSCs expressed transcripts for numerous neurotrophic factors. In vivo, increased striatal labeling in BDNF, collagen type-I and fibronectin (but not GDNF or CNTF) was observed in the brains of MSC-transplanted rats but not in DMEM-treated rats. In addition, none of the transplanted MSCs expressed neural phenotypes. These findings suggest that factors other than neuronal replacement underlie the behavioral sparing observed in 3NP rats after MSC transplantation.