Fig. 1
The rhythmic disturbance and its consequences in chondrocytes in osteoarthritis condition. During osteoarthritis process, the cartilage core rhythmic genes, including Bmal1, Clock and Per2 are disturbed. The disturbance of core rhythmic genes in cartilage increases the catabolism and decreases the anabolism through Tgfb pathway. Other rhythm-related genes, including Col2a1, Mmp13, Adamts5 are also associated to metabolic disorder in osteoarthritis cartilage. OA, osteoarthritis; Bmal1: brain and muscle arnt-like protein 1; Clock: circadian locomotor output cycles kaput; Per1: period 1; Per2: period 2; Cry1:cryptochrome 1; Mmp13: matrix metallopeptidase 13; Mmp14: matrix metallopeptidase 14; Adamts5: ADAM metallopeptidase with thrombospondin type 1 motif 5; Il6, interleukin 6; Nr1d1, nuclear receptor subfamily 1 group D member 1; Nr1d2, nuclear receptor subfamily 1 group D member 2; Dbp, D-box binding protein; Nampt, nicotinamide phosphoribosyltransferase; Sirt1, sirtuin 1; Sox9, SRY-box transcription factor 9; IL1B, interleukin 1 beta; NFKB: nuclear factor kappa B; Col2a1, type II collagen alpha 1 chain; Acan, aggrecan; Eln, elastin; Tnc, tenascin; Tgfb, transforming growth factor beta; Smad3, SMAD family member 3; Nfatc2, nuclear factor of activated T cells 2; Alk5/Smad2, transforming growth factor beta receptor 1/SMAD family member factor 2; Alk1/Smad1/5, ALK receptor tyrosine kinase/SMAD family member factor 1/5; Mcp1, monocyte chemoattractant protein 1