A three-dimensional human neural cell culture model of Alzheimer's disease

Alzheimer's disease is the most common form of dementia, characterized by two pathological hallmarks: amyloid-beta plaques and neurofibrillary tangles(1). The amyloid hypothesis of Alzheimer's disease posits that the excessive accumulation of amyloid-beta peptide leads to neurofibrillary tangles composed of aggregated hyperphosphorylated tau(2,3). However, to date, no single disease model has serially linked these two pathological events using human neuronal cells. Mouse models with familial Alzheimer's disease (FAD) mutations exhibit amyloid-beta-induced synaptic and memory deficits but they do not fully recapitulate other key pathological events of Alzheimer's disease, including distinct neurofibrillary tangle pathology(4,5). Human neurons derived from Alzheimer's disease patients have shown elevated levels of toxic amyloid-beta species and phosphorylated tau but did not demonstrate amyloid-beta plaquesor neurofibrillary tangles(6-11). Here we report that FAD mutations in beta-amyloid precursor protein and presenilin 1 are able to induce robust extracellular deposition of amyloid-beta, including amyloid-beta 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 phosphorylated tau in the soma and neurites, as well as filamentous tau, as detected by immunoelectron microscopy. Inhibition of amyloidb beta generation with beta- or gamma-secretase inhibitors not only decreased amyloid-beta pathology, but also attenuated tauopathy. We also found that glycogen synthase kinase 3 (GSK3) regulated amyloid-beta-mediated tau phosphorylation. We have successfully recapitulated amyloid-beta and tau pathology in a single 3D human neural cell culture system. Our unique strategy for recapitulating Alzheimer's disease pathology in a 3D neural cell culture model should also serve to facilitate the development of more precise human neural cell models of other neurodegenerative disorders.