Tauopathy promotes spinal cord-dependent production of toxic amyloid-beta in transgenic monkeys

A mass-producible macaque model displays a durable Alzheimer-like cognitive deficit and hallmark amyloid-β/tau/neurofilament light chain pathologies

BackgroundAlzheimer's disease (AD) is the most prevalent neurodegenerative disorder characterized by cognitive deficit and pathological accumulation of amyloid-β (Aβ) and tau proteins. The rodent models have contributed greatly to unravel AD pathogenesis, but these AD models have been shown a modest clinical translational effectiveness.ObjectiveTherefore, developing mass-producible primate AD models is promising for more effective drug development.MethodsHere, we constructed the AD monkey models by simultaneously infusing AAV-Tau and Aβ into different brain regions.ResultsThe induced monkeys showed a durable cognitive impairment lasting for at least 10 months after the modeling. Simultaneously, the increased levels of total tau and hyperphosphorylated tau (pTau) at several AD-associated sites, and neurofilament light chains (NfL) with altered Aβ level were detected at different time points in cerebrospinal fluid and/or plasma by using MSD kits. The increased brain accumulation of Aβ and tau proteins was also detected by positron emission tomography/magnetic resonance imaging and immunohistochemical staining. The model monkeys also had significant glial activation; an indicator of inflammation commonly seen in the brains of AD patients.ConclusionsTogether, this study provides mass-producible monkey models showing durable AD-like hallmark pathologies (Aβ, tau, NfL, i.e., ATN) and cognitive deficits. As monkeys are genetically and metabolically the closest to humans, these models will offer more effective drug discovery and development for AD.

In Vivo Seeding of Amyloid-β Protein and Implications in Modeling Alzheimer's Disease Pathology

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by extracellular plaques containing amyloid β-protein (Aβ) and intracellular neurofibrillary tangles formed by tau. Cerebral Aβ accumulation initiates a noxious cascade that leads to irreversible neuronal degeneration and memory impairment in older adults. Recent advances in Aβ seeding studies offer a promising avenue for exploring the mechanisms underlying amyloid deposition and the complex pathological features of AD. However, the extent to which inoculated Aβ seeds can induce reproducible and reliable pathological manifestations remains unclear due to significant variability across studies. In this review, we will discuss several factors that contribute to the induction or acceleration of amyloid deposition and consequent pathologies. Specifically, we focus on the diversity of host animals, sources and recipe of Aβ seeds, and inoculating strategies. By integrating these key aspects, this review aims to offer a comprehensive perspective on Aβ seeding in AD and provide guidance for modeling AD pathogenesis through the exogenous introduction of Aβ seeds.

Human induced pluripotent stem cell models for Alzheimer's disease research: a bibliometric analysis

Introduction

Alzheimer's disease (AD), the leading cause of dementia, remains without adequate treatment. Current models do not fully replicate human physiology and pathology. The advent of human induced pluripotent stem cell (hiPSC) technology offers a novel approach to studying AD.

Methods

Our study conducted a bibliometric analysis to assess the application and development of hiPSC technology in AD research. We retrieved 531 articles on hiPSC models of AD from the Web of Science Core Collection, published between January 2010 and June 2024. CiteSpace and VOSviewer were used to analyze authorship, geographic contributions, journal influence, and citation patterns.

Results

Our findings reveal a steady increase in publications over 14 years, with the United States leading in contributions, followed by China. Li-Huei Tsai from the Massachusetts Institute of Technology is a prominent researcher. PLoS One emerges as the most influential journal. Research trends have focused on inflammation, astrocytes, microglia, apolipoprotein E (ApoE), and tau.

Discussion

Bibliometric analysis is crucial in identifying research gaps and trends and guiding future studies to address unmet needs in understanding and modeling human physiology and pathology. Leveraging hiPSC models to investigate the molecular mechanisms of familial and sporadic AD is expected to provide a crucial foundation for developing future treatment strategies.

Conclusion

In summary, the bibliometric findings from this study provide a comprehensive overview of the current research landscape in hiPSC models for AD. It also highlights emerging trends and research gaps, crucial for guiding future research efforts, particularly in exploring novel therapeutic targets and improving understanding of disease mechanisms.

Amyloid-β oligomers drive amyloid deposit and cascaded tau pathology of Alzheimer's disease in aged brains of non-human primates

Alzheimer's disease (AD), the most prevalent form of dementia, disproportionately affects the elderly population. While aging is widely recognized as a major risk factor for AD, the precise mechanisms by which aging contributes to the pathogenesis of AD remain poorly understood. In our previous work, the neuropathological changes in the brains of aged cynomolgus monkeys (≥18 years old) following parenchymal cerebral injection of amyloid-β oligomers (AβOs) have been characterized. Here, we extend our investigation to middle-aged cynomolgus monkeys (≤15 years old) to establish an AD model. Surprisingly, immunohistochemical analysis reveals no detectable AD-related pathology in the brains of middle-aged monkeys, even after AβOs injection. In a comprehensive pathological analysis of 38 monkeys, we observe that the amyloid-β (Aβ) burden increases significantly with advancing age. Notably, the density of Aβ plaques is markedly higher in the ventral regions compared to the dorsal regions of aged monkey brains. Furthermore, we demonstrate that tau phosphorylation coincides with the accumulation of extensive Aβ plaques and exhibits a positive correlation with Aβ burden in aged monkeys. Collectively, these findings underscore the critical role of the aged brain in providing the necessary conditions for AβO-induced AD pathologies in cynomolgus monkeys.

Unlocking potential of oxytocin: improving intracranial lymphatic drainage for Alzheimer's disease treatment

Background: The impediment to β-amyloid (Aβ) clearance caused by the invalid intracranial lymphatic drainage in Alzheimer's disease is pivotal to its pathogenesis, and finding reliable clinical available solutions to address this challenge remains elusive. Methods: The potential role and underlying mechanisms of intranasal oxytocin administration, an approved clinical intervention, in improving intracranial lymphatic drainage in middle-old-aged APP/PS1 mice were investigated by live mouse imaging, ASL/CEST-MRI scanning, in vivo two-photon imaging, immunofluorescence staining, ELISA, RT-qPCR, Western blotting, RNA-seq analysis, and cognitive behavioral tests. Results: Benefiting from multifaceted modulation of cerebral hemodynamics, aquaporin-4 polarization, meningeal lymphangiogenesis and transcriptional profiles, oxytocin administration normalized the structure and function of both the glymphatic and meningeal lymphatic systems severely impaired in middle-old-aged APP/PS1 mice. Consequently, this intervention facilitated the efficient drainage of Aβ from the brain parenchyma to the cerebrospinal fluid and then to the deep cervical lymph nodes for efficient clearance, as well as improvements in cognitive deficits. Conclusion: This work broadens the underlying neuroprotective mechanisms and clinical applications of oxytocin medication, showcasing its promising therapeutic prospects in central nervous system diseases with intracranial lymphatic dysfunction.

Photobiomodulation in experimental models of Alzheimer's disease: state-of-the-art and translational perspectives

Alzheimer's disease (AD) poses a significant public health problem, affecting millions of people across the world. Despite decades of research into therapeutic strategies for AD, effective prevention or treatment for this devastating disorder remains elusive. In this review, we discuss the potential of photobiomodulation (PBM) for preventing and alleviating AD-associated pathologies, with a focus on the biological mechanisms underlying this therapy. Future research directions and guidance for clinical practice for this non-invasive and non-pharmacological therapy are also highlighted. The available evidence indicates that different treatment paradigms, including transcranial and systemic PBM, along with the recently proposed remote PBM, all could be promising for AD. PBM exerts diverse biological effects, such as enhancing mitochondrial function, mitigating the neuroinflammation caused by activated glial cells, increasing cerebral perfusion, improving glymphatic drainage, regulating the gut microbiome, boosting myokine production, and modulating the immune system. We suggest that PBM may serve as a powerful therapeutic intervention for AD.

A nonhuman primate model with Alzheimer's disease-like pathology induced by hippocampal overexpression of human tau

BACKGROUND

Alzheimer's disease (AD) is one of the most burdening diseases of the century with no disease-modifying treatment at this time. Nonhuman primates (NHPs) share genetic, anatomical, and physiological similarities with humans, making them ideal model animals for investigating the pathogenesis of AD and potential therapies. However, the use of NHPs in AD research has been hindered by the paucity of AD monkey models due to their long generation time, ethical considerations, and technical challenges in genetically modifying monkeys.

METHODS

Here, we developed an AD-like NHP model by overexpressing human tau in the bilateral hippocampi of adult rhesus macaque monkeys. We evaluated the pathological features of these monkeys with immunostaining, Nissl staining, cerebrospinal fluid (CSF) analysis, magnetic resonance imaging (MRI), positron emission tomography (PET), and behavioural tests.

RESULTS

We demonstrated that after hippocampal overexpression of tau protein, these monkeys displayed multiple pathological features of AD, including 3-repeat (3R)/4-repeat (4R) tau accumulation, tau hyperphosphorylation, tau propagation, neuronal loss, hippocampal atrophy, neuroinflammation, Aβ clearance deficits, blood vessel damage, and cognitive decline. More interestingly, the accumulation of both 3R and 4R tau is specific to NHPs but not found in adult rodents.

CONCLUSIONS

This work establishes a tau-induced AD-like NHP model with many key pathological and behavioural features of AD. In addition, our model may potentially become one of the AD NHP models adopted by researchers worldwide since it can be generated within 2 ~ 3 months through a single injection of AAVs into the monkey brains. Hence, our model NHPs may facilitate mechanistic studies and therapeutic treatments for AD.