Chemotherapy-induced adipo-lineage cell senescence drives bone loss.

Chemotherapy-induced bone loss is a debilitating and common side effect of cancer treatment, though its underlying mechanisms remain poorly understood. Here, we show that, despite the systemic administration of chemotherapy, cellular senescence is restricted to bone marrow adipo-lineage cells specifically Cxcl12-abundant reticular (CAR) cells and bone marrow adipocytes (BMAds). Induction of senescence within these populations promotes RANK ligand (RANKL)-mediated osteoclastogenesis, leading to significant bone loss. Notably, we find that inhibition of the p38MAPK-MK2 pathway suppresses the senescence-associated secretory phenotype (SASP), including RANKL production abrogating bone loss. Furthermore, treatment with the senolytic combination dasatinib and quercetin (D + Q) selectively eliminates senescent CAR cells and BMAds, effectively preventing chemotherapy-induced bone loss. Given that nearly all chemotherapy treated patients experience bone loss and associated fracture risk, our findings offer a promising therapeutic avenue to preserve bone integrity and improve quality of life for cancer patients.