Person:

Choi, Se Hoon

Alzheimer’s disease (AD) is the most common form of dementia, characterized by two pathological hallmarks: β-amyloid plaques and neurofibrillary tangles1. The amyloid hypothesis of AD posits that excessive accumulation of β-amyloid peptide (Aβ) leads to neurofibrillary tangles composed of aggregated hyperphosphorylated tau2,3. However, to date, no single disease model has serially linked these two pathological events using human neuronal cells. AD mouse models with familial AD (FAD) mutations exhibited Aβ-induced synaptic and memory deficits but they were not able to fully recapitulate other key pathological events of AD including clear neurofibrillary tangle pathology4,5. AD patient-derived human neurons showed elevated levels of toxic Aβ species and phosphor-tau (p-tau) but they also could not replicate β-amyloid plaques or neurofibrillary tangles6-11. Here we show that FAD mutations in the amyloid-β precursor protein (APP) and presenilin (PS) 1 genes are able to induce robust extracellular deposition of Aβ, including β-amyloid plaques, in a human neural stem cell-derived three-dimensional (3D) culture system. More importantly, the 3D-differentiated neuronal cells expressing FAD mutations exhibited high levels of detergent-resistant, silver-positive aggregates of p-tau in the soma and neurites. Immunoelectron microscopy also demonstrated the presence of filamentous tau, only in detergent-resistant fractions from 3D-cultured cells expressing FAD mutations. Inhibition of Aβ generation with β- or γ-secretase inhibitors not only decreased Aβ pathology, but also attenuated tauopathy. We also found that glycogen synthase kinase 3 (GSK3) regulated Aβ-mediated tau phosphorylation. In summary, we have successfully recapitulated Aβ and tau pathology in a single 3D human neural cell culture system for the first time. Our unique strategy for recapitulating AD pathology in a 3D neural cell culture model should also serve to facilitate the development of more precise human neural cell models for other neurodegenerative disorders.

The amyloid-β peptide (Aβ) is a key protein in Alzheimer's disease (AD) pathology. We previously reported in vitro evidence suggesting Aβ is an antimicrobial peptide. Here we provide the first in vivo evidence showing high Aβ production protects against fungal and bacterial infections in mouse and nematode AD models. In Aβ-null mouse models low Aβ production is associated with attenuated resistance to infection. Regarding mechanism, we show Aβ oligomerization, a behavior traditionally viewed as intrinsically pathological, is necessary for the antimicrobial activities of the peptide. Soluble Aβ oligomers bind microbial cell walls, developing protofibrils inhibit pathogen host cell adhesion, and, finally, proteaseresistant β-amyloid fibrils agglutinate and entrap the invading microbes. We also show that infection of 5XFAD mouse brain with S. Typhimurium bacteria rapidly seeds and dramatically accelerates β-amyloid deposition, which closely co-localizes with invading bacteria. Collectively, our findings raise the intriguing possibility that β-amyloid plays a protective role in innate immunity and infectious or sterile inflammatory stimuli may drive amyloidosis. These data suggest a dual protective/damaging role for Aβ, as has been described for other antimicrobial peptides.

Stem cell technologies have facilitated the development of human cellular disease models that can be used to study pathogenesis and test therapeutic candidates. These models hold promise for complex neurological diseases such as Alzheimer’s disease (AD) because existing animal models have been unable to fully recapitulate all aspects of pathology. We recently reported the characterization of a novel three-dimensional (3D) culture system that exhibits key events in AD pathogenesis, including extracellular aggregation of β-amyloid and accumulation of hyperphosphorylated tau. Here we provide instructions for the generation and analysis of 3D human neural cell cultures, including the production of genetically modified human neural progenitor cells (hNPCs) with familial AD mutations, the differentiation of the hNPCs in a 3D matrix, and the analysis of AD pathogenesis. The 3D culture generation takes 1–2 days. The aggregation of β-amyloid is observed after 6-weeks of differentiation followed by robust tau pathology after 10–14 weeks.

Communication within the glial cell ecosystem is essential to neuronal and brain health1–3. The influence of glial cells on β-amyloid (Aβ) and neurofibrillary tau accumulation and clearance in Alzheimer’s disease (AD) is poorly understood, despite growing awareness that these are therapeutically important interactions4,5. Here we show, in humans and mice, that astrocyte-sourced interleukin-3 (IL-3) reprograms microglia to ameliorate AD pathology. Upon recognition of Aβ deposits, microglia augment IL-3Rɑ, IL-3’s specific receptor, rendering them responsive to IL-3. Astrocytes constitutively produce IL-3, which elicits transcriptional, morphological, and functional reprograming of microglia endowing them with an acute immune response program, enhanced motility, and the capacity to cluster and clear Aβ and tau aggregates. These changes restrict AD pathology and cognitive decline. This study identifies IL-3 as a critical mediator of astrocyte-microglia crosstalk and a node for therapeutic intervention in AD.