Abstract
Aging profoundly impacts bone homeostasis and regeneration, yet the cellular and molecular mechanisms underlying periosteal aging remain poorly understood. Using single-cell RNA sequencing, we profiled the periosteum of 3-, 9-, and 18-month-old mice, which revealed age-related shifts in progenitor, neutrophil, and macrophage subpopulations. Aging reduced mesenchymal cell populations and impaired osteogenic potential, may contribute to periosteal homeostasis. Periosteal progenitor subsets exhibited distinct aging trajectories: Dpt⁺ fibrous-layer cells undergoing early senescence, while Postn⁺ progenitors showed osteogenic decline. Aging also shifted immune profiles, increasing inflammatory Cd38(hi) macrophages and dysfunctional Nlrp3(hi) neutrophils, further disrupting bone homeostasis. Notably, aged progenitor cells upregulated CSF1 and CXCL signaling, driving macrophage and neutrophil infiltration, exacerbating bone loss. Our findings provide a comprehensive periosteal aging atlas, revealing aging-associated alterations in progenitor-immune crosstalk that may influence bone tissue dynamics, and offering insights into potential targets for age-related skeletal conditions.