# Autophagy Activators Normalize Aberrant Tau Proteostasis and Rescue Synapses in Human Familial Alzheimer's Disease iPSC‐Derived Cortical Organoids

## TL;DR

A new lab-grown brain model with Alzheimer's mutations shows disease features and responds to drugs that clear harmful proteins and restore brain connections.

## Contribution

A novel cerebrocortical organoid model using isogenic hiPSCs with familial AD mutations is developed and tested with autophagy activators.

## Key findings

- AD organoids show amyloid-beta and phospho-Tau accumulation, neuronal hyperexcitability, and synapse loss.
- Autophagy activators reduce pathological proteins and rescue synapses in AD organoids.
- Single-cell RNA-seq reveals divergent molecular changes in excitatory and inhibitory neurons in AD.

## Abstract

Alzheimer's disease (AD) is the leading cause of dementia worldwide. Nevertheless, its cellular and molecular mechanisms remain incompletely understood, partially due to inadequate disease models. To illuminate early changes in AD, we developed a cerebrocortical organoid (CO) model with improved methodology. Our COs produce excitatory and inhibitory neurons alongside glia, utilizing established isogenic wild‐type and diseased human induced pluripotent stem cells (hiPSCs) carrying heterozygous familial AD mutations in PSEN1ΔE9/WT, PSEN1M146V/WT, or APPSwe/WT. In addition to amyloid‐beta (Aβ) accumulation, the AD COs display time‐progressive loss of monomeric Tau, and accumulation of aggregated high‐molecular‐weight (HMW) phospho(p)‐Tau species (pT181 and pT217). They also exhibit neuronal hyperexcitability reminiscent of early electroencephalography (EEG) clinical findings and synapse loss in AD patient brains. Single‐cell RNA‐sequencing analyses of AD and WT control COs reveal significant divergent molecular abnormalities in excitatory vs. inhibitory neurons, with several pathways being upregulated in one while downregulated in the other, providing insight into AD phenotypes. Finally, we show that chronic dosing with autophagy activators, including a novel mTOR inhibitor‐independent drug candidate, prevents pathologic Aβ and HMW p‐Tau accumulation, normalizes hyperexcitability, and rescues synaptic loss in AD COs. Collectively, our results demonstrate this CO model as a useful platform for assessing early features of familial AD pathogenesis and for testing small‐molecule candidate therapeutics.

A new cerebrocortical organoid model using isogenic hiPSCs with familial Alzheimer's mutations recapitulates key AD features, including amyloid‐beta and phospho‐Tau aggregation, neuronal hyperexcitability, and synapse loss. Single‐cell RNA‐seq reveals aberrant pathways in excitatory and inhibitory neurons. Known and novel autophagy activators prevent pathological and synaptic deficits, supporting the model's utility for AD research and drug screening in the setting of early disease.