In naturally aged mice, a previously uncharacterized microglial population accumulates specifically in hippocampal-adjacent white matter — particularly the fimbria — co-expressing disease-associated microglia (DAM) genes alongside a 'SenBrain' senescence signature anchored by galectin-3 (GAL3/Lgals3). Using CosMx spatial molecular imaging and GeoMx digital spatial profiling, the researchers mapped this convergent senescent-DAM phenotype at single-cell resolution, then demonstrated that both pharmacogenetic and pharmacological senolytic interventions significantly reduced GAL3+ DAM abundance and restored more youthful microglial spatial organization in aged tissue.
This finding matters because white matter degeneration is increasingly recognized as a primary driver of late-life cognitive decline — not merely a bystander — yet its cellular mechanism has been poorly resolved. The identification of galectin-3 as a hub molecule is particularly significant: GAL3 has emerging roles in neuroinflammation, microglial activation, and even Alzheimer's pathology, making it a plausible therapeutic target independent of amyloid. The fact that senolytic intervention partially reverses this microglial state in aged animals elevates this beyond descriptive mapping — it suggests a causal, modifiable relationship. Limitations are real: findings are in mice only, and translating microglial senescence biology to humans remains technically and biologically challenging. Still, this is more than incremental — it spatially grounds the senescent microglia hypothesis in a functionally vulnerable brain region and pairs it with actionable intervention data, strengthening the case for senolytic strategies targeting white matter-specific neuroinflammation.
