Identifying specific functional roles for senescence across cell types

Cellular senescence plays critical roles in aging, regeneration, and disease, yet the ability to discern its contributions across various cell types to pathophysiological processes in vivo remains limited. In this study, we generated an in vivotoolbox, consisting of three p16INK4a-related intersectional genetic systems, enabling pulse- chase tracing (Sn-pTracer), Cre-based tracing and ablation (Sn-cTracer), and gene manipulation combined with tracing (Sn-gTracer) of defined senescent cell types. Using liver injury and repair as an example, we found that macrophages and endothelial cells (ECs) represent distinct senescent cell populations with different fates and functions during liver fibrosis and repair.Targeted reprogramming of p16INK4a+ ECs through Kdr overexpression markedly reduces liver fibrosis. This study illuminates the pathophysiological diversity of senescent cells and offers valuable insights for the development of future cell type-specific senolytic therapies. Furthermore, our model provides a versatile platform for investigating cellular senescence in any desired cell type.