# Isotope Encoded Spatial Biology Identifies Amyloid Plaque-Age-Dependent Structural Maturation, Synaptic Loss, and Increased Toxicity

## TL;DR

This study uses isotope labeling to track how amyloid plaques age, showing that older plaques are more toxic and cause more synaptic loss in Alzheimer's disease.

## Contribution

A novel isotope-based method to timestamp and spatially track Aβ plaque maturation and its effects in Alzheimer’s disease.

## Key findings

- Plaque age negatively correlates with synaptic gene expression in individual mice.
- Older plaques are more structurally mature and associated with greater synapse loss and toxicity.
- Spatial transcriptomics reveals gene-expression changes specific to plaque age, independent of mouse age or disease severity.

## Abstract

Understanding how amyloid beta (Aβ) plaques form and progress to neurotoxicity in Alzheimer’s disease remains a significant challenge. This study aims to elucidate the processes involved in Aβ plaque formation and maturation using a knock-in Aβ mouse model (AppNL-F/NL-F). By employing mass spectrometry imaging and stable isotope labeling, we timestamped Aβ plaques from their initial deposition, enabling the spatial tracking of plaque aging. Correlating single-plaque spatial transcriptomics with time since seeding, allowed us to track gene-expression changes specifically associated with plaque age, independent of chronological age of the mouse or disease severity. We found that plaque age, within sections from individual mice aged from 10 to 18 months, negatively correlates with synaptic gene expression. Further, correlation with hyperspectral confocal microscopy using structure-specific dyes revealed a positive link between plaque age and structural maturity, with older plaques identified as more compact and associated with significantly greater synapse loss and toxicity.