Single‐Nucleus <scp>RNA</scp> ‐Seq Reveals Aerobic Exercise‐Induced Remodeling of Spinal Cord Aging in Mice

Spinal cord aging is a critical physiological process that compromises central nervous system (CNS) homeostasis and plasticity. Exercise, as a systemic intervention with broad health benefits, has been shown to delay neurodegeneration and preserve tissue function; however, its impact on dynamic cellular lineage evolution and intercellular communication within the aging spinal cord remains poorly characterized. In this study, we employed single-nucleus RNA sequencing (snRNA-seq) to construct a high-resolution cellular atlas of the mouse spinal cord under young, aged, and aerobic exercise-intervened conditions. By integrating unsupervised clustering, cell proportion analysis, pseudotime trajectory reconstruction, gene regulatory network (GRN) inference, and intercellular communication mapping, we systematically characterized transcriptional and cellular alterations associated with aging and their modulation through exercise. Aging induced pronounced shifts in cell-type composition and subpopulation structures, which were partially reversed by exercise intervention. Pseudotime analyses of oligodendrocytes, astrocytes, and microglia revealed that exercise remodeled their differentiation trajectories and restored functional states associated with myelin formation, metabolic homeostasis, and inflammation control. GRN analysis identified several key regulators whose centrality and expression were disrupted during aging but reestablished after exercise, suggesting a recovery of transcriptional network organization. Furthermore, intercellular communication analysis revealed reduced signaling strength and connectivity during aging, particularly within gap junction pathways, which were partially restored by exercise, indicating improved cellular coordination. Together, these findings provide a comprehensive single-cell landscape of the aging spinal cord and demonstrate that exercise reprograms cellular lineages and regulatory networks, offering mechanistic insights into how it mitigates CNS aging and preserves neural function.