The role of extracellular vesicles in synovial fibroblast senescence

In arthritis, synovial fibroblast (SF) senescence is linked to the activation of a pro-inflammatory phenotype contributing to chronic arthritis pathogenesis. Additionally, senescent cells accumulate in ageing tissues further promoting ageing and inflammation. These cells have dysregulated mitochondrial function and metabolism, limited tissue regeneration, produce reactive oxygen species (ROS) and secrete bioactive molecules, including pro-inflammatory cytokines, chemokines and matrix-remodelling enzymes known as SASP (senescence-associated secretory phenotype). In vitro, senescent cells can induce a senescent phenotype in surrounding bystander cells. Interestingly, extracellular vesicles (EVs) have critical roles in cellular senescence and ageing and are mediators in intercellular communication. We hypothesize that senescent cells in osteoarthritic SFs induce senescence and/or a proinflammatory phenotype in non-senescent osteoarthritic SFs, mediated through EV cargo.