Neuronal and vascular genome-maintenance states organize opposing multicellular architectures in the aging brain.

Genome maintenance is usually treated as cell-intrinsic, yet brain cells age within multicellular neighborhoods. Whether a cell's DNA damage response (DDR) state is systematically embedded in native tissue architecture is unknown. We used MERFISH to map curated repair programs across 604,252 cells in matched sections from 2-3 and 22-month-old mice. Regional DDR expression and coordination formed an age-dependent mosaic, accompanied by immune and oligodendroglial shifts. Independent metacell and distance-resolved analyses identified a consistent anchor-dependent organization. Low-DDR neurons occupied immune- and OPC-oligodendroglial-rich niches. In contrast, DDR-high vascular anchors were associated with vascular-cell enrichment and, in cortex and cerebral nuclei, OPC-oligodendroglial enrichment, whereas immune cells were enriched around DDR-low vascular anchors. Thus, genome-maintenance state was associated with distinct anchor-cell-specific spatial context depending on anchor-cell identity and its DDR transcriptional state. These opposing neuronal and vascular patterns define anchor-dependent genome-maintenance niches as a spatial feature of brain aging, with implications for regional vulnerability.