Isotope-encoded spatial biology identifies plaque-age-dependent maturation and synaptic loss in an Alzheimer's disease mouse model.

Understanding how amyloid beta (Aβ) plaques develop and lead to neurotoxicity in Alzheimer's disease remains a major challenge, particularly given the temporal delay and weak correlation between plaque deposition and cognitive decline. This study investigates how the evolving pathology of plaques affects the surrounding tissue, using a knock-in Aβ mouse model (App). We combined mass spectrometry imaging with stable isotope labeling to timestamp Aβ plaques from the moment of their initial deposition, enabling us to track their aging spatially. By integrating spatial transcriptomics, we linked changes in gene expression to the age of the plaques, independent of the mice's chronological age or disease stage. Here we show that older plaques were associated with reduced expression of synaptic genes. Additionally, when correlated with structure-specific dyes, we show that plaque age positively correlated with structural maturation. These more compact and older plaques were linked to greater synapse loss and increased toxicity.