Effects of cyclic tensile stresses of different magnitudes on expressions of apoptosis cytokines in chondrocytes

Abstract

Objective To explore the effects of cyclic tensile stresses of different magnitudes on expressions of apoptosis cytokines and transforming growth factors (TGF) in chondrocytes. Methods Classical methods were used to culture primary chondrocytes in New Zealand rabbits. Mechanical stresses were exerted onto the mono-layer cells cultured by the FLEXERCELL-5000T system. The experiment was conducted in 3 groups: low magnitude stress group (5% ), high magnitude stress group (15% ) and control group. The stresses were applied for 5 days and 8 hours per day. The cultured cells were harvested on days 3 and S to measure gene copies of MMP3 (matrix metalloproteinases), MMP13, ADMATS-5 (a disintegrin and metalloproteinase with thrombospondin motifs), and TGF-β1 by quantitative RT-PCR. Results Expressions of ADMATS-5 and MMP3 were significantly enhanced in each stress group on day 3 but weakened on day 5 ( P = 0. 002). Expressions of MMP13 were significantly higher in the stress groups than in the control group on day 3, and significantly higher in the high magnitude stress group than in the low one on day 5 ( P = 0. 002) .Levels of TGF-β1 on day 5 were significantly higher in the stress groups than in the control group, and higher in the low magnitude stress group than in the high one (P = 0. 002). Conclusions Gene expressions of apoptosis cytokines and TGF in chondrocytes are differently influenced by cyclic tensile stresses of different magnitudes. TGF -β1 may play an important role in pathological repair of the deformed chondrocytes following tensile stress. Key words: Chondrocytes; Transforming growth factors; Mechanical stress; Apoptotic gene expression; Rabbits