Matrix stiffness induces endothelial network senescence

Identifying the drivers of cellular senescence that contribute to the decline in tissue function related to aging- and disease is critical for developing restorative interventions. Here, we investigated how increased mechanical stress from extracellular matrix (ECM) stiffening shapes endothelial cell (EC) senescence. We developed a 3D human in vitro model that decouples mechanical stress from inflammatory or biochemical inputs, enabling the study of senescence responses to tissue stiffening alone. We found that matrix stiffening induces an EC senescence phenotype with elevated p16/p21 and an immunomodulatory senescence-associated secretory phenotype (SASP), in the absence of inflammatory signals. This mechano-induced senescence state engaged a Notch-JNK-FOS signaling axis, and pharmacologic inhibition of Notch attenuated stiffness-induced senescence. Supporting the translational relevance of this mechanism, analysis of fibrotic capsule tissue from patients with synthetic breast implants, a model of localized, mechanically driven fibrosis, revealed increased p16⁺Notch1⁺ endothelial populations. Complementary single-cell RNA sequencing data confirmed their enrichment in Notch/JNK- and SASP-related gene programs. Together, these findings define vascular senescence as a mechanosensitive process and identify tissue stiffening as an upstream aging signal. Our work offers a human-relevant platform for studying targetable stages of endothelial mechanoaging.