Modeling late-onset Alzheimer's disease neuropathology via direct neuronal reprogramming
Late-onset Alzheimer's disease (LOAD) is the most common form of AD. However, modeling sporadic LOAD, without clear genetic predispositions, to capture hallmark neuronal pathologies such as extracellular amyloid-ß (Aß) plaque deposition, intracellular tau tangles, and neuronal loss, remains an unmet need. Here, we demonstrate that neurons generated by microRNA-based direct reprogramming of fibroblasts from patients affected by autosomal dominant AD (ADAD) and LOAD in a three-dimensional (3D) environment, effectively recapitulate key neuropathological features of AD without additional cellular or genetic insults. These LOAD neurons exhibit Aß-dependent neurodegeneration, as treatment with ß- or ?-secretase inhibitors before (but not subsequent to) Aß deposit formation mitigated neuronal death. Moreover, inhibiting age-associated retrotransposable elements (RTEs) in LOAD neurons reduced both Ab deposition and neurodegeneration. Our study underscores the efficacy of modeling late-onset neuropathology of LOAD through high-efficiency microRNA-based neuronal reprogramming. Overall design: By optimizing the potency of microRNA-mediated direct neuronal conversion of patient fibroblasts, we developed a matrigel-based three-dimensional (3D) culture system for generating cortical neurons, a subtype known to be susceptible to develop AD pathologies. For characterizing amyloid ß(Aß) plaques, tau pathology, and neurodegeneration in the reprogrammed cortical neurons, we carried out immunofluorescence staining, RNA-sequencing and other biochemistry-based assays for AD-associated phenotypes.