Enhanced Neuronal Activity and Asynchronous Calcium Transients Revealed in a 3D Organoid Model of Alzheimer's Disease

Advances in the development of three-dimensional (3D) brain organoids maintained in vitro have provided excellent opportunities to study brain development and neurodegenerative disorders, including Alzheimer's disease (AD). However, there remains a need to generate AD organoids bearing patient-specific a genomic backgrounds that can functionally recapitulate the key model features observed in the AD patient's brain. To address this need, we described a strategy to generate self-organizing 3D cerebral organoids which develop a functional neuronal network connectivity. This was achieved by neuroectoderm induction of human pluripotent stem cell (hPSCs) aggregates and subsequent differentiation into desired neuroepithelia and mature neurons in a 3D Matrigel matrix. Using this approach, we successfully generated AD cerebral organoids from human pluripotent stem cells (hPSCs) derived from a familial AD patient with a common mutation in presenilin 2 (PSEN2(N141I)). An isogenic control with an identical genetic background but wild-type PSEN2 was generated using CRISPR/Cas9 technology. Both control and AD organoids were characterized by analyzing their morphology, the A beta 42/A beta 40 ratio, functional neuronal network activity, drug sensitivity, and the extent of neural apoptosis. The spontaneous activity of the network and its synchronization was measured in the organoids via calcium imaging. We found that compared with the mutation-corrected control organoids, AD organoids had a higher A beta 42/A beta 40 ratio, asynchronous calcium transients, and enhanced neuronal hyperactivity, successfully recapitulating an AD-like pathology at the molecular, cellular, and network level in a human genetic context. Moreover, two drugs which increase neuronal activity, 4-aminopyridine (4-AP) and bicuculline methochloride, induced high-frequency synchronized network bursting to a similar extent in both organoids. Therefore, our study presents a promising organoid-based biosystem for the study of the pathophysiology of AD and a platform for AD drug development.

Automated summary

The study successfully generated Alzheimer's disease (AD) models in a human genetic context using self-organizing 3D brain organoids, characterizing them through morphology analysis, neuronal activity, drug sensitivity, and neural apoptosis to find that the AD organoids recapitulated AD-like pathology effectively.