Spatial proteomic analysis in human Alzheimer's disease brains enables identification of microenvironment-dependent microglial cell states.

Disease-associated microglial states are thought to contribute to Alzheimer's disease (AD) progression, but characterizing them and their relationships to pathology remains challenging. Here we introduce CODEX-CNS-a multiplexed protein imaging technology with a custom data analysis pipeline for use in human brain samples. We profiled 704,706 cells in samples from the frontal cortex of 8 people with AD and 8 healthy controls and mapped features including blood-brain barrier, meningeal components and cell-cell interactions within the same tissue sections. Amongst the myeloid cell populations we identified, we found a border-associated macrophage-like microglial subset associated with aging. Further classifying myeloid cell subsets based on their spatial neighborhood, we identified a border-associated macrophage-like microglial subpopulation that was associated significantly with dense amyloid-β plaques, which we termed human plaque-associated microglia. This work offers insights into myeloid cell heterogeneity in AD and provides a new spatial approach to characterizing brain cells at the single-cell protein level.