The circadian clock is a specialised cell signalling pathway present in all cells. Loss of clock function leads to tissue degeneration and premature aging in animal models demonstrating the fundamental importance of clocks for cell, tissue and organism health There is now considerable evidence that the chondrocyte circadian clock is altered in osteoarthritis (OA). The purpose of this review is to summarise current knowledge regarding the nature of the change in the chondrocyte clock in OA and the implications of this change for disease development. Expression of the core clock component, BMAL1, has consistently been shown to be lower in OA chondrocytes. This may contribute to changes in chondrocyte differentiation and extracellular matrix turnover in disease. Circadian clocks are highly responsive to environmental factors. Mechanical loading, diet, inflammation and oxidative insult can all influence clock function. These factors may contribute to causing the change in the chondrocyte clock in OA.
Raewyn C Poulsen, James I Hearn, Nicola Dalbeth