The Physical Senotype in cellular senescence: Mechanical and physical strategies for senotherapy

Cellular senescence is traditionally described through durable cell-cycle arrest, DNA-damage signaling, metabolic remodeling, mitochondrial and lysosomal dysfunction, and acquisition of a senescence-associated secretory phenotype (SASP). However, senescent cells also undergo prominent structural and biomechanical changes, including enlarged and flattened cell shape, altered stiffness and force transmission, cytoskeletal reorganization, defective nucleo-cytoskeletal coupling, impaired organelle positioning, and extracellular matrix (ECM) remodeling. In this review, we use the term Physical Senotype as a working framework to describe this recurrent but heterogeneous mechanical state. Rather than proposing a separate hallmark of senescence, this framework emphasizes loss of mechanical plasticity: the reduced capacity of senescent cells and tissues to sense, buffer, dissipate, and adapt to mechanical stress. We discuss how cytoskeletal maladaptation may amplify nuclear damage, impair mitochondrial and lysosomal quality control, reinforce inflammatory signaling, and interact with a mechanically altered extracellular niche. We also critically evaluate emerging physical and mechanical approaches to senotherapy, including pressure-based senolysis, remotely activated nanomaterials, ultrasound, exercise-associated immune surveillance, mechanical stimulation, cytoskeletal re-dynamization, and mechanically tuned biomaterials. Current evidence suggests that these interventions may produce distinct outcomes, including direct senescent-cell killing, immune-assisted clearance, or functional reprogramming of mechanically recoverable cells. However, most approaches remain early-stage, and major questions remain regarding specificity, tissue dependence, dosing thresholds, durability, and safety. We argue that integrating mechanical phenotyping with canonical senescence markers will be essential for distinguishing mechanically recoverable senescent states from irreversible states requiring clearance, and for predicting how the aged tissue niche shapes senotherapeutic response.