Figure 1.

Signaling pathways of oxidative stress in chondrocyte senescence. Reactive oxygen species (ROS) are a main cause of senescence and they regulate signaling molecules, such as mitogen-activated protein kinases (MAPKs) (ERK/P38), P16, P21, and P53, which are eventually responsible for senescence. COL II = collagen type II, COL I = collagen type I, GADD45 β = DNA damage-inducible protein 45 β, C/EBP β = CCAAT/enhancer binding protein β, PCNA = proliferating cell nuclear antigen, MMPs = matrix metalloproteinases.