Transgenic mouse models with tau pathology to test therapeutic agents for Alzheimer's disease

The deposit of two proteins in the brain characterizes Alzheimer's disease: deposits of beta-amyloid protein to form senile plaques and tau protein in neurofibrillary tangles. This review discusses transgenic animals overexpressing normal or mutated tau protein as well as kinases involved in tau hyperphosphorylation. These animals hold a great potential as tools to test the effects of forthcoming therapeutical agents for Alzheimer's disease.     

Alzheimer's disease: transgenic mouse models and drug assessment.

Alzheimer's disease (AD), characterized by neuritic plaques and neurofibrillary tangles of the brain, is experienced by more and more elderly people in a form of senile dementia. Four genes are closely linked with AD and are located on chromosomes 21, 19, 14 and 1. Transgenic technology enables the development of animal models for research into this human disease. Recently reported transgenic AD mouse models, which express AD-related mutant human genes, develop some significant aspects of AD-like pathology. The specific role of these mice in representing different targets, the consequent pathology of AD and the availability of this increasingly popular tool for investigating new therapeutic strategies for AD are reviewed.     

Behavioral assays with mouse models of Alzheimer's disease: Practical considerations and guidelines

In Alzheimer's disease (AD) basic research and drug discovery, mouse models are essential resources for uncovering biological mechanisms, validating molecular targets and screening potential compounds. Both transgenic and non-genetically modified mouse models enable access to different types of AD-like pathology in vivo. Although there is a wealth of genetic and biochemical studies on proposed AD pathogenic pathways, as a disease that centrally features cognitive failure, the ultimate readout for any interventions should be measures of learning and memory. This is particularly important given the lack of knowledge on disease etiology – assessment by cognitive assays offers the advantage of targeting relevant memory systems without requiring assumptions about pathogenesis. A multitude of behavioral assays are available for assessing cognitive functioning in mouse models, including ones specific for hippocampal-dependent learning and memory. Here we review the basics of available transgenic and non-transgenic AD mouse models and detail three well-established behavioral tasks commonly used for testing hippocampal-dependent cognition in mice – contextual fear conditioning, radial arm water maze and Morris water maze. In particular, we discuss the practical considerations, requirements and caveats of these behavioral testing paradigms.     

Transgenic animals relevant to Alzheimer's disease

This article reviews the functional studies that have been carried out on transgenic and knockout animals that are relevant to Alzheimer's disease (AD). The discussion focuses upon the functional characterisation of these strains, particularly upon factors that affect synaptic processes that are thought to contribute to memory formation, including hippocampal long-term potentiation. We examine the use of transgenes associated with amyloid precursor protein and presenilin-1, their mutations linked to early onset familial AD, and the recent attempts to establish double transgenic strains that have an AD-like pathology which occurs with a more rapid onset. The development of new transgenic strains relevant to Alzheimer's disease has rapidly outpaced their characterisation for functional deficits in synaptic plasticity. To date most studies have focused on those transgenes linked to the minority of familial early onset rather than late-onset sporadic AD cases, and have focused on those changes linked to the induction of the early-phase of hippocampal long-term potentiation. Future studies will need to address the question of whether the development of AD pathology can be reversed or at least halted and this will be aided by the use of conditional transgenics in which genes linked to AD can either be switched on or off later in development. Furthermore, it remains to be resolved whether the deficits in synaptic function are specific to the hippocampus and whether deficits affect late-phase long-term potentiation. Nonetheless, the recent advances in genome sciences and the development of transgenic technology have provided a unique opportunity to study how genes associated with human cognitive dysfunction alter synaptic transmission between neurones in the mammalian brain.     

Transgenic mice as disease models

The methods used for making transgenic mice such as DNA microinjection in pronuclei, transformation of embryonic stem cells and production of chimeras, infection by retroviral vectors and sperm cells as carriers for foreign DNA are reported. Furthermore some characteristics of transgenic mice are mentioned, in particular factors influencing integration and expression of gene constructs. Different kinds of disease models using transgenic mice are available. This has been achieved by insertional mutagenesis, dominant negative mutations, changes caused by overexpression of transgenes, gene ablation, targeted mutation, and transfer of oncogenes. The importance of ongoing research in transgenic animals is emphasized.     

在肿瘤研究中转基因小鼠模型的研究进展

随着基因工程技术的飞速发展,转基因小鼠模型对研究肿瘤基因特征、肿瘤抑制基因的表达和功能有着重要的作用。近年来,肿瘤血管生成理论成为肿瘤研究的新热点。与肿瘤血管生成相关的调控基因的研究也越来越受到重视。该文对转基因小鼠模型在肿瘤研究中的进展作了综述,并着重介绍了关于肿瘤血管生成调控基因转基因小鼠模型的研究情况。     

Transgenic mouse models of Alzheimer disease: developing a better model as a tool for therapeutic interventions

Alzheimer disease (AD) is the leading cause of dementia among elderly. Currently, no effective treatment is available for AD. Analysis of transgenic mouse models of AD has facilitated our understanding of disease mechanisms and provided valuable tools for evaluating potential therapeutic strategies. In this review, we will discuss the strengths and weaknesses of current mouse models of AD and the contribution towards understanding the pathological mechanisms and developing effective therapies.     

The value and limitations of transgenic mouse models used in drug discovery for Alzheimer's disease: an update

INTRODUCTION: The exponential growth in the world's aged population has increased pressure on drug discovery efforts to identify innovative therapies for Alzheimer's disease (AD). The long and uncertain clinical trial path utilized to test the potential efficacy of these novel agents is challenging. For these and other reasons, there has been an explosion in the generation and availability of transgenic mouse models that mimic some, but not all aspects of AD. The largely overwhelmingly positive results obtained when testing potential clinical agents in these same animal models have failed to translate into similar positive clinical outcomes. AREAS COVERED: This review discusses the value and limitations associated with currently available transgenic mouse models of AD. Furthermore, the article proposes ways in which researchers can better characterize pharmacodynamic and pharmacokinetic endpoints to increase the success rate for novel therapies advancing into clinical development. Lastly, the author discusses ways in which researchers can supplement, expand and improve transgenic mouse models used in AD drug discovery. EXPERT OPINION: The use of transgenic mouse models that recapitulate various aspects of AD has expanded our knowledge and understanding of disease pathogenesis immensely. Further success in testing and translating novel therapies from animal models into bona fide medicines would be enhanced by i) the availability of better models that more fully recapitulate the disease spectrum, ii) defining and measuring standardized endpoints that display a pharmacodynamic range, iii) building and including translatable biomarkers and iv) including novel endpoints that would be expected to translate into clinically beneficial outcomes.     

The value and limitations of transgenic mouse models used in drug discovery for Alzheimer's disease: an update

Introduction: The exponential growth in the world's aged population has increased pressure on drug discovery efforts to identify innovative therapies for Alzheimer's disease (AD). The long and uncertain clinical trial path utilized to test the potential efficacy of these novel agents is challenging. For these and other reasons, there has been an explosion in the generation and availability of transgenic mouse models that mimic some, but not all aspects of AD. The largely overwhelmingly positive results obtained when testing potential clinical agents in these same animal models have failed to translate into similar positive clinical outcomes.

Areas covered: This review discusses the value and limitations associated with currently available transgenic mouse models of AD. Furthermore, the article proposes ways in which researchers can better characterize pharmacodynamic and pharmacokinetic endpoints to increase the success rate for novel therapies advancing into clinical development. Lastly, the author discusses ways in which researchers can supplement, expand and improve transgenic mouse models used in AD drug discovery.

Expert opinion: The use of transgenic mouse models that recapitulate various aspects of AD has expanded our knowledge and understanding of disease pathogenesis immensely. Further success in testing and translating novel therapies from animal models into bona fide medicines would be enhanced by i) the availability of better models that more fully recapitulate the disease spectrum, ii) defining and measuring standardized endpoints that display a pharmacodynamic range, iii) building and including translatable biomarkers and iv) including novel endpoints that would be expected to translate into clinically beneficial outcomes.     

散发性阿尔茨海默病动物模型研究进展

阿尔茨海默病(Alzheimer's disease,AD)是一种中枢神经退行性疾病,是最常见的痴呆类型。阿尔茨海默病多为散发性,目前暂无延缓疾病进程的药物上市。散发性阿尔茨海默病(sporadic Alzheimer's disease,s AD)动物模型的缺乏可能是主要原因之一。因此,研发散发性阿尔茨海默病动物模型非常有意义。本文现就散发性阿尔茨海默病动物模型的制作、病理特征及其可能机制加以归纳总结。此外,我们还对今后散发性阿尔茨海默病动物模型的发展做了探讨,以期对相关研究工作者的研究有所裨益。     

Genetically modified mice models for Alzheimer's disease

Transgenic mice models for Alzheimer's disease (AD) are essential to the understanding of disease pathophysiology, develop robust behavioral models and predict outcomes from pharmacological interventions. In the last 10 years, numerous mice models have been developed particularly focusing on the amyloid precursor protein-processing pathway and Tau pathology since brain amyloid deposits and Tau tangles are some of the primary neuropathological consequences of AD. Current views on the amyloid hypothesis and mice models relating to the role of soluble Abeta oligomers and intracellular Abeta in AD pathophysiology will be reviewed. Several novel transgenic mice models that have recently been developed and their potential impact on understanding disease pathogenesis will also be summarized.     

秀丽隐杆线虫模型在阿尔茨海默病研究中的应用

阿尔茨海默病(Alzheimer s disease,AD)是一种与衰老相关的神经退行性疾病,以Aβ沉积和Tau蛋白过度磷酸化为主要病理特征。秀丽隐杆线虫以其神经系统结构简单、遗传信息清晰等优势而作为一种AD研究的模式生物,尤其是人源Aβ1-42和Tau转基因线虫(CL2006/P301L)已被广泛应用。本文简述秀丽隐杆线虫及其AD模型,总结近几年应用模型线虫研究AD病理机制的文献,为进一步筛选治疗AD的药物提供可靠的线索和思路。     

类叶升麻苷对阿尔采末病小鼠皮层caspase-3基因表达的影响

目的探讨类叶升麻苷(acteoside,AS)对阿尔采末病(Alzheimer’s disease,AD)小鼠皮层组织中Caspase-3基因表达的影响。方法将昆明(kunming,KM)小鼠随机分为正常组,模型组,vitamin E(Vit E)组,类叶升麻苷低、中、高剂量组。除正常组外,其余各组小鼠均腹腔注射60 mg·kg-1·d-1的D-半乳糖和灌胃5 mg·kg-1·d-1的三氯化铝,连续造模60 d以制备AD模型。然后给以30、60、120 mg·kg-1·d-1的AS治疗30 d,期间造模继续。给药完成后,利用跳台法测定小鼠的学习和记忆能力,化学比色法测定小鼠血清及脑组织中的ACh E活性;HE染色观察各组小鼠皮层组织结构变化;免疫组化分析小鼠皮层组织中caspase-3基因表达的变化。结果与模型组相比,AS给药组小鼠的学习记忆能力有所改善,其下台潜伏期和错误次数均明显延长和减少(P<0.05或P<0.01),血清和脑组织中ACh E活性明显降低(P<0.05或P<0.01),皮层组织中神经细胞的形态和数量明显改善(P<0.01),且皮层组织中caspase-3基因表达明显下调(P<0.05或P<0.01)。结论 AS对D-半乳糖联合三氯化铝诱导的小鼠脑损伤具有明显保护作用,其保护机制可能是通过抑制小鼠皮层组织caspase-3基因表达,进而维持皮层组织神经细胞的正常形态及数量。     

Transgenic animal models of neurodegenerative diseases and their application to treatment development

Neurodegenerative disorders of the aging population affect over 5 million people in the US and Europe alone. The common feature is the progressive accumulation of misfolded proteins with the formation of toxic oligomers. Previous studies show that while in Alzheimer's disease (AD) misfolded amyloid-beta protein accumulates both in the intracellular and extracellular space, in Lewy body disease (LBD), Parkinson's disease (PD), Multiple System Atrophy (MSA), Fronto-Temporal dementia (FTD), prion diseases, amyotrophic lateral sclerosis (ALS) and trinucleotide repeat disorders (TNRD), the aggregated proteins accumulate in the plasma membrane and intracellularly. Protein misfolding and accumulation is the result of an altered balance between protein synthesis, aggregation rate and clearance. Based on these studies, considerable advances have been made in the past years in developing novel experimental models of neurodegenerative disorders. This has been in part driven by the identification of genetic mutations associated with familial forms of these conditions and gene polymorphisms associated with the more common sporadic variants of these diseases. Transgenic and knock out rodents and Drosophila as well as viral vector driven models of Alzheimer's disease (AD), PD, Huntington's disease (HD) and others have been developed, however the focus for this review will be on rodent models of AD, FTD, PD/LBD, and MSA. Promising therapeutic results have been obtained utilizing amyloid precursor protein (APP) transgenic (tg) models of AD to develop therapies including use of inhibitors of the APP-processing enzymes beta- and gamma-secretase as well as vaccine therapies.     

Calcium alterations in Alzheimer's disease: pathophysiology, models and therapeutic opportunities.

Calcium plays a pivotal role in mediating many important biological functions. The intracellular calcium concentration is tightly regulated by a variety of systems and mechanisms. Calcium is sequestered by various organelles such as mitochondria and/or endoplasmic reticulum and extruded across the plasma membrane by energy-dependent transport systems. Different Ca2+-binding proteins are also involved in these processes. Alterations in calcium homeostasis might be critically implicated in brain aging and in the neuropathology of Alzheimer's disease (AD). In fact, one of the postulated mechanisms of beta-amyloid toxicity seems to involve a Ca2+ dysregulation accompanied with enhanced vulnerability to excitotoxic stimuli. Although brain characteristic lesions-plaques and tangles-constitute the hallmarks of AD, accumulated evidence suggests the systemic feature of this disease. Therefore peripheral cell lines may represent a useful approach to explore the cellular pathophysiology of AD, including calcium alterations and associated phenomena.