Fig. 2

Metabolic disorder in osteoarthritis cartilage associated with rhythmic disturbance. Age, abnormal mechanical stress, and inflammation in osteoarthritis progression up regulate the catabolism by enhancing the core rhythmic gene Per2, and down regulate the anabolism by depressing the core rhythmic genes Bmal1 and Clock. Bmal1: brain and muscle arnt-like protein 1; Clock: circadian locomotor output cycles kaput; Per2: period 2; Nfatc2, nuclear factor of activated T cells 2; Sox9, SRY-box transcription factor 9; Col2a1, type II collagen alpha 1 chain; Mmp13: matrix metallopeptidase 13; Adamts5: ADAM metallopeptidase with thrombospondin type 1 motif 5; Nfkb: nuclear factor kappa B; Tgfb, transforming growth factor beta; Col10a1, collagen type X alpha 1 chain