Effects of cyclic tensile strain on the secretion of glycosaminoglycans in rabbit chondrocytes cultured in vitro at different times

Abstract

Objective To observe the effects of cyclic tensile strain (CTS) at different times on the secretion of Glycosaminoglycans (GAG) in rabbit chondrocytes cultured in vitro. Methods Nine male New Zealand white rabbits aged two monthes were randomly divided into 4 h/d group, 6 h/d group and 8 h/d group according to the daily loading time. Three rabbits in each group were scraped with bilateral knee cartilage under aseptic condition. The original chondrocytes were inoculated on BioFlex 6-well culture plates after digestion and separation. The Flexercell-4000 substrate loading system (sine wave, 6% elongation, 0.5 Hz) was used for 1, 2, 3, 4, 5 d and supernatant was left for pecimens at these times. GAG in the supernatant was measured by Alcian blue staining method, and compare the changes of GAG secretion at different times. Results The expression of GAG in the supernatant was different with the days loaded, and the difference was statistically significant (P=0.017). At the same time, the expression of GAG was significantly increased at 1, 2, 3 d (P=0.012). At 4 d and 5 d, the expression of GAG was the highest at the 6 h/d team, which is statistically significant (P=0.023). In addition, there was interaction between the time factor and the treatment factors of the supernatant (P=0.000). Compared with the 8 h/d group 1 d loaded [(10.81±0.97) g/ml], the expression of GAG was significantly higher than that in the 4 h/d group 2 d loaded [(12.36±1.15) g/ml], and the difference was statistically significant (P=0.014); There was no significant difference in GAG expression between the 6 h/d group 2 d loaded [(16.35±1.64) g/ml] and 4 h/d group 3 d loaded [(16.37±1.58) g/ml, P=0.074]; Compared with the 8 h/d group 2 d loaded [(18.83±1.76) g/ml], the expression of GAG was significantly higher than that in the 4 h/d group 4 d loaded [(22.92±2.10) g/ml], and the difference was statistically significant (P=0.029); Compared with the 8 h/d group 3 d loaded [(26.63±2.19) g/ml], the expression of GAG was significantly higher than that in the 6 h/d group 4 d loaded [(33.37±3.68) g/ml], and the difference was statistically significant (P=0.004). Conclusion The effect of CTS on the metabolism and apoptosis of chondrocytes in vitro was time-dependent. The expression of GAG in the extracellular matrix increased gradually with the prolongation of the stretching time, and the total loading time reached the peak at 24 h, and then the expression began to decline. Key words: Chondrocyte; Tensile; Strain; Time; Rabbit