Senescent cells maintain viability through adhesion-dependent fragmentation that promotes debris deposition

Cellular senescence is a state of stable arrest and secretion linked to aging and disease. Here, we identify that senescent cells dispose of large fragments through cell-to-cell adhesion, which we term "senescent-cell adhesion fragments" (SCAFs). Found in many senescent states, including human and mouse cells, and mouse tissues, SCAFs lack nuclear material but contain organelles, including damaged mitochondria. Disrupting adherens junctions decreases SCAF formation but induces senescent-cell death, due to an inability to shed damaged mitochondria. Live imaging and proteomics show that SCAFs ultimately rupture, releasing a complex proteome, including damage-associated molecular patterns (DAMPs) and proteins linked to neurodegenerative disease. Functionally, SCAFs activate wound-healing and cancer-related programs, promoting migration and invasion. Immunostaining also reveals amyloid-like material in senescent cells that can be externalized through fragmentation. Altogether, these findings identify a feature that facilitates senescent cell survival but also externally deposits damaged intracellular contents, with implications for cancer and neurodegeneration.