ABSTRACT
Transplantation of neural stem cells (NSCs) can improve cognition in animal models of Alzheimer's disease (AD). However, AD is a protracted disorder, and prior studies have examined only short-term effects. We therefore used an immune-deficient model of AD (Rag-5xfAD mice) to examine long-term transplantation of human NSCs (StemCells Inc.; HuCNS-SCs). Five months after transplantation, HuCNS-SCs had engrafted and migrated throughout the hippocampus and exhibited no differences in survival or migration in response to ß-amyloid pathology. Despite robust engraftment, HuCNS-SCs failed to terminally differentiate and over a quarter of the animals exhibited ectopic human cell clusters within the lateral ventricle. Unlike prior short-term experiments with research-grade HuCNS-SCs, we also found no evidence of improved cognition, no changes in brain-derived neurotrophic factor, and no increase in synaptic density. These data, while disappointing, reinforce the notion that individual human NSC lines need to be carefully assessed for efficacy and safety in appropriate long-term models.
Subject(s)
Alzheimer Disease/pathology , Alzheimer Disease/psychology , Cell Differentiation , Cognition , Neural Stem Cells/pathology , Alzheimer Disease/etiology , Alzheimer Disease/therapy , Amyloid beta-Peptides/metabolism , Animals , Biomarkers , Brain-Derived Neurotrophic Factor/metabolism , Cell Aggregation , Cell Movement , Cell Survival , Disease Models, Animal , Hippocampus/metabolism , Humans , Immunophenotyping , Lateral Ventricles/metabolism , Lateral Ventricles/pathology , Maze Learning , Memory , Mice , Neural Stem Cells/cytology , Neural Stem Cells/metabolism , Phenotype , Stem Cell Transplantation , Time FactorsABSTRACT
Alzheimer's disease (AD) is the most prevalent age-related neurodegenerative disorder, affecting over 35 million people worldwide. Pathologically, AD is characterized by the progressive accumulation of ß-amyloid (Aß) plaques and neurofibrillary tangles within the brain. Together, these pathologies lead to marked neuronal and synaptic loss and corresponding impairments in cognition. Current treatments, and recent clinical trials, have failed to modify the clinical course of AD; thus, the development of novel and innovative therapies is urgently needed. Over the last decade, the potential use of stem cells to treat cognitive impairment has received growing attention. Specifically, neural stem cell transplantation as a treatment for AD offers a novel approach with tremendous therapeutic potential. We previously reported that intrahippocampal transplantation of murine neural stem cells (mNSCs) can enhance synaptogenesis and improve cognition in 3xTg-AD mice and the CaM/Tet-DT(A) model of hippocampal neuronal loss. These promising findings prompted us to examine a human neural stem cell population, HuCNS-SC, which has already been clinically tested for other neurodegenerative disorders. In this study, we provide the first evidence that transplantation of research grade HuCNS-SCs can improve cognition in two complementary models of neurodegeneration. We also demonstrate that HuCNS-SC cells can migrate and differentiate into immature neurons and glia and significantly increase synaptic and growth-associated markers in both 3xTg-AD and CaM/Tet-DTA mice. Interestingly, improvements in aged 3xTg-AD mice were not associated with altered Aß or tau pathology. Rather, our findings suggest that human NSC transplantation improves cognition by enhancing endogenous synaptogenesis. Taken together, our data provide the first preclinical evidence that human NSC transplantation could be a safe and effective therapeutic approach for treating AD.
Subject(s)
Alzheimer Disease , Cognition Disorders/etiology , Cognition Disorders/surgery , Neural Stem Cells/transplantation , Neurons/pathology , Synapses/physiology , Alzheimer Disease/complications , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Amyloid beta-Protein Precursor/genetics , Animals , Cell Death/physiology , Cell Differentiation/genetics , Cell Movement/genetics , Disease Models, Animal , Gene Expression Regulation/genetics , Glial Fibrillary Acidic Protein/metabolism , Hippocampus/pathology , Humans , Maze Learning , Mice , Mice, Transgenic , Mutation/genetics , Neural Stem Cells/physiology , Neurogenesis/genetics , tau Proteins/geneticsABSTRACT
INTRODUCTION: Short-term neural stem cell (NSC) transplantation improves cognition in Alzheimer's disease (AD) transgenic mice by enhancing endogenous synaptic connectivity. However, this approach has no effect on the underlying beta-amyloid (Aß) and neurofibrillary tangle pathology. Long term efficacy of cell based approaches may therefore require combinatorial approaches. METHODS: To begin to examine this question we genetically-modified NSCs to stably express and secrete the Aß-degrading enzyme, neprilysin (sNEP). Next, we studied the effects of sNEP expression in vitro by quantifying Aß-degrading activity, NSC multipotency markers, and Aß-induced toxicity. To determine whether sNEP-expressing NSCs can also modulate AD-pathogenesis in vivo, control-modified and sNEP-NSCs were transplanted unilaterally into the hippocampus of two independent and well characterized transgenic models of AD: 3xTg-AD and Thy1-APP mice. After three months, stem cell engraftment, neprilysin expression, and AD pathology were examined. RESULTS: Our findings reveal that stem cell-mediated delivery of NEP provides marked and significant reductions in Aß pathology and increases synaptic density in both 3xTg-AD and Thy1-APP transgenic mice. Remarkably, Aß plaque loads are reduced not only in the hippocampus and subiculum adjacent to engrafted NSCs, but also within the amygdala and medial septum, areas that receive afferent projections from the engrafted region. CONCLUSIONS: Taken together, our data suggest that genetically-modified NSCs could provide a powerful combinatorial approach to not only enhance synaptic plasticity but to also target and modify underlying Alzheimer's disease pathology.
Subject(s)
Alzheimer Disease/therapy , Neprilysin/biosynthesis , Neural Stem Cells/physiology , Stem Cell Transplantation/methods , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Animals , Disease Models, Animal , Female , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neprilysin/genetics , Neural Stem Cells/cytology , Neural Stem Cells/metabolism , TransfectionABSTRACT
Human embryonic stem cells (hESCs) offer tremendous potential for not only treating neurological disorders but also for their ability to serve as vital reagents to model and investigate human disease. To further our understanding of a key protein involved in Alzheimer disease pathogenesis, we stably overexpressed amyloid precursor protein (APP) in hESCs. Remarkably, we found that APP overexpression in hESCs caused a rapid and robust differentiation of pluripotent stem cells toward a neural fate. Despite maintenance in standard hESC media, up to 80% of cells expressed the neural stem cell marker nestin, and 65% exhibited the more mature neural marker ß-3 tubulin within just 5 days of passaging. To elucidate the mechanism underlying the effects of APP on neural differentiation, we examined the proteolysis of APP and performed both gain of function and loss of function experiments. Taken together, our results demonstrate that the N-terminal secreted soluble forms of APP (in particular sAPPß) robustly drive neural differentiation of hESCs. Our findings not only reveal a novel and intriguing role for APP in neural lineage commitment but also identify a straightforward and rapid approach to generate large numbers of neurons from human embryonic stem cells. These novel APP-hESC lines represent a valuable tool to investigate the potential role of APP in development and neurodegeneration and allow for insights into physiological functions of this protein.
