Fig. (1) Cellular senescence is a common characteristic of preneoplasic tissue and cartilage in early osteoarthritis (OA). (A) Neoplasia genesis. Upon environmental stress (carcinogens, oncogenes, genotoxics), in highly proliferative tissues such as epithelium, some cells will respond by abortive proliferation and emergence of senescent cells. If one cell overcomes the senescent process by inactivation of the DNA damage response (DDR), cell proliferation will lead to neoplasia and eventually tumour. (B) OA genesis. Upon environmental stress (mechanical stress, aging factors), OA chondrocytes become senescent and display an imbalance between anabolic and catabolic activity in favour of catabolism, leading to cartilage degradation. In both tissues, common senescence-associated markers are expressed: activated DDR and secretion of reactive oxygen species (ROS), interleukin (IL)-1β, IL-8, insulin growth factor binding protein (IGFBP)-3, vascular endothelial growth factor (VEGF) and metalloproteinases (MMPs).