White matter integrity is increasingly recognized as a critical determinant of cognitive aging, yet the specific cellular actors driving its deterioration have remained elusive. Identifying which cells go rogue — and whether they can be therapeutically reset — could reshape how researchers approach late-life cognitive decline and neurodegenerative disease prevention.
Using a suite of high-resolution spatial transcriptomic and imaging technologies — including GeoMx digital spatial profiling and CosMx single-molecule imaging — researchers mapped microglial states across the aged mouse brain with exceptional regional precision. They identified a previously uncharacterized microglial population concentrated in hippocampal-adjacent white matter, particularly the fimbria, that co-expresses genes associated with both disease-associated microglia (DAM) and cellular senescence — a signature they term 'SenBrain.' A key marker of this population is galectin-3 (GAL3/Lgals3), a lectin implicated in neuroinflammation and fibrosis. Single-cell spatial trajectory analyses suggest this proinflammatory state arises through multiple convergent cell fate transitions rather than a single linear pathway. Crucially, both pharmacogenetic and pharmacological senotherapeutic approaches reduced GAL3-positive DAM abundance and partially restored microglial organization toward a more youthful phenotype in aged fimbria.
This work is notable for several reasons. The convergence of DAM and senescence signatures in a spatially discrete white matter niche suggests these two phenomena — previously studied largely in isolation — may co-amplify neuroinflammation in aging. Galectin-3 has gained traction as a biomarker of inflammaging in peripheral tissues; its emergence as a core marker of aged white matter microglia strengthens its candidacy as a CNS aging indicator. However, this is an animal study with no human validation yet, and mouse white matter architecture differs meaningfully from the far more extensive white matter tracts in the human brain. Whether senolytic interventions translate to cognitive or structural benefit in humans remains an open, critical question. Still, the spatial resolution of the methodology and the partial reversibility finding represent a meaningful mechanistic advance — incremental but pointing toward tractable therapeutic targets.
