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Peripheral clocks are essential for driving cell differentiation. In osteoarthritis, loss of the normal differentiated chondrocyte (cartilage cell) phenotype is causative of disease. We investigated whether clock gene expression differed in osteoarthritic compared to "healthy" chondrocytes and used RNAi to determine whether the differences observed could affect chondrocyte phenotype. Following serum shock, PER2 expression was significantly higher, whereas BMAL1 expression was significantly lower, in osteoarthritic chondrocytes. Knockdown of BMAL1 in "healthy" chondrocytes was associated with higher cell proliferation and MMP13 expression, features characteristic of the osteoarthritic chondrocyte phenotype. Chondrocyte-intrinsic clock disruption may be a critical early step in osteoarthritis development.

Original publication




Journal article


Chronobiol Int

Publication Date





574 - 579


Cartilage, cell phenotype, cell proliferation, matrix metalloproteinases, peripheral circadian clocks, peripheral clocks in disease, Aged, Aged, 80 and over, Cell Differentiation, Cells, Cultured, Chondrocytes, Circadian Clocks, Circadian Rhythm, Female, Humans, Male, Middle Aged, Osteoarthritis, Period Circadian Proteins