Mitochondrial dysfunction and impaired osteogenic capacity define stress-induced osteoblast senescence
Cellular senescence has emerged as a key contributor to age-related skeletal deterioration; however, the defining characteristics of senescent osteoblasts remain incompletely understood, hindering efforts to identify the cellular mechanisms that drive age-associated bone loss and potential therapeutic targets. Here, we compared doxorubicin- and hydrogen peroxide-induced senescence and established a robust in vitro osteoblast model that enables the stable maintenance of stress-induced premature senescence. Doxorubicin-treated MC3T3-E1 cells exhibited persistent growth arrest, a pronounced senescence-associated secretory phenotype (SASP), and impaired osteogenic function accompanied by marked mitochondrial dysfunction, including reduced respiratory capacity and altered mitochondrial morphology. Transcriptomic comparison with aged murine bone revealed a partial overlap with in vivo aging-associated gene expression signatures, particularly among genes involved in extracellular matrix organization and skeletal development, supporting the physiological relevance of the model. Importantly, key features of senescence, including the senescence-associated mitochondrial phenotype and impaired osteogenic capacity, were recapitulated in primary human osteoblasts. Collectively, these findings establish a robust model of stress-induced osteoblast senescence and demonstrate that senescent osteoblasts exhibit mitochondrial dysfunction, impaired osteogenic capacity, and molecular features that resemble aspects of skeletal aging.