Single-cell mapping reveals age-related alterations in periosteal progenitor cells and immune microenvironment

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.