Altered microglial communication in brains with Alzheimer’s Disease pathology

Plasticity of human microglia and brain perivascular macrophages in aging and Alzheimer’s disease

Myeloid cells, including microglia and perivascular macrophages, are central to Alzheimer’s disease (AD) neurobiology, yet their role remains incompletely understood. We profiled 832,505 human myeloid cells from the prefrontal cortex of 1,607 donors spanning the lifespan and showing varying degrees of AD neuropathology. We delineated six subclasses comprising 13 transcriptionally distinct subtypes and identified adaptive changes associated with aging and AD progression. Here we show that a disease-associated microglial subtype, characterized by elevated GPNMB expression and enriched for polygenic AD risk, expands with AD pathology and shows increased phagocytic activity. We identify MITF as an upstream regulator required to maintain this microglial state. Cell–cell interaction analyses prioritize APOE–SORL1 and APOE–TREM2 signaling pairs associated with disease progression. Using human and mouse models, we demonstrate that the neuroprotective effects of this microglial subtype depend on TREM2. These findings provide mechanistic insights into myeloid cell function in aging and AD, aiding therapeutic discovery. Molecular profiling of myeloid cells from the prefrontal cortex of 1,607 donors with varying degrees of Alzheimer’s disease neuropathology delineates distinct myeloid subtypes and identifies changes associated with aging and disease progression.

Microglia-centered cellular crosstalk in neurodegeneration.

Microglia-derived extracellular vesicles uncover early alterations of inflammatory signaling in Alzheimer's disease.

Alzheimer's disease (AD) is increasingly recognized as a neurodegenerative disorder associated with chronic low-grade inflammation and age-related immune dysregulation. Microglial-derived extracellular vesicles (MDEVs) are emerging as important mediators of neuroimmune communication and potential biomarkers reflecting pathological processes occurring within the central nervous system (CNS). However, how EV-associated inflammatory signalling changes across different stages of AD remains poorly understood. In this study, we characterized the inflammatory molecular profile of serum-derived MDEVs in 22 AD patients, 19 prodromal AD subjects, and 23 healthy controls (HC). Cytokine concentrations were also evaluated in paired serum and cerebrospinal fluid (CSF) samples to compare vesicle-associated and soluble inflammatory signals across biological compartments. MDEVs were isolated by size exclusion chromatography followed by TMEM119-based immunoenrichment. Cytokine quantification was performed using the Ella Simple Plex automated immunoassay platform. MDEVs from AD patients showed a generalized reduction in both pro- and anti-inflammatory cytokines compared to HC, including IL-1β, TNF-α, IL-2, IFN-γ, IL-6, IL-12p70, IL-10, and IL-4. Notably, several alterations were already detectable at the prodromal stage. In contrast, soluble cytokines in serum and CSF displayed a predominantly pro-inflammatory profile in AD patients, with increased levels of IL-1β, TNF-α, and IL-12p70. No significant correlations were observed between cytokine levels measured in MDEVs and those detected in serum or CSF. Overall, these findings support the presence of a compartment-specific reorganization of inflammatory signalling during AD progression. Early alterations in MDEV inflammatory cargo may reflect disrupted EV-mediated neuroimmune communication and highlight the potential of MDEVs as accessible peripheral biomarkers of neuroinflammatory processes in AD.

Predicting Relevant Microglia‐Associated Cell–Cell Communication Pathways in Alzheimer's Disease: A Role for SPP1

Microglia play a key role in the pathophysiology of Alzheimer's Disease (AD) and their increased heterogeneity likely affects disease progression. We previously identified distinct microglial signatures that were enriched in AD donors and associated with amyloid and tau, respectively. Here we generated a snRNAseq dataset from postmortem control and AD cases and analyzed alterations in cell–cell communication pathways that might be relevant to AD pathophysiology. One signaling pathway perturbed in AD cases involved SPP1, and while this pathway was also present in control samples, microglia–microglia SPP1 signaling was restricted to AD donors. Further analyses within microglia–microglia signaling predict AD‐specific induction of GAS6‐AXL signaling (from inflammatory and ribosomal microglia), and SPP1‐ITGAV/ITGB5 signaling (from disease‐associated and inflammatory microglia, among others). Together, these findings might in part explain the increased microglia phagocytic profile described in AD. RNAscope confirmed enrichment of SPP1 expressing microglia near amyloid plaques in AD brain tissue samples. These data indicate altered cellular communications between microglia in the AD brain.

Core activation program and selective regional responsiveness of microglia during aging and parabiosis.

Aging is associated with immune dysregulation in the brain and is the greatest risk factor for many neurodegenerative diseases. Rejuvenation interventions can mediate beneficial effects. Microglia are major contributors to neurodegenerative disease progression; however, the molecular changes underlying brain aging and rejuvenation remain poorly understood at the single-cell level. We identified and benchmarked several reproducible microglial states and a core set of genes that drive microglial activation in the mouse brain. We investigated microglial heterogeneity and examined the impact of aging and parabiosis-mediated exposure to young and old blood on microglial subpopulations across four brain regions: the cerebellum, cortex, hippocampus, and striatum. We revealed region-specific differences in microglial composition and age-related changes. The cerebellum consistently emerged as the most responsive region, whereas the striatum showed minimal responsiveness to parabiosis interventions. These findings highlight regional vulnerability and inform microglia-targeted strategies to modulate brain aging.

Microglia-mediated neuroinflammation in Alzheimer’s disease: mechanisms and emerging therapeutic targets

A “cellular state–pathological network–therapeutic window” framework is proposed and the roles of microglia in amyloid-β plaque seeding and compaction, NLRP3 inflammasome activation, mitochondrial DNA–cGAS–STING signaling, complement-mediated synaptic engulfment, and bidirectional microglia–tau feedback are systematically discussed.