Effects Of Cyclic Tensile Strain Induces Chondrocyte Hypertrophy Through P38MAPK Pathway

Objective:To tset whether p38MAPK plays a role to regulate chondrocyte hypertrophy under cyclic tensile strain using SB203580, a specific inhibitor of the p38MAPK.Methods:Chicken chondrocytes isolated from day17embryos knee joint were divided into four groups:the control group,stretching,stretching+drug group,and drug group alone.Flexcell5000cell loading system was used in the study.We used sin10%,1Hz,6h loading every day for two days.SB203580was added into the culture wells before loading. Western blot was applied to test p38MAPK and p-p38MAPK;Real time PCR was used to detect the gene expression of Col-X,MMP-13and Col-Ⅱ;ELISA was used to detect the amount of Col-X in DMEM culture medium.Results:Western blot results showed that there was no significant different of p38among the four groups,but p-p38MAPK was increased after loading in stretching group, implying p38MAPK was activated due to loading. While the chondrocytes treated with SB203580before loading was significantly decrease of p-p38, suggesting that p38inhibitors have blocked p38MAPK pathway.Real time-PCR demonstrated that mRNA levels of MMP-13were similar to Col-X.Compared to the control group,the stretching group increased the mRNA levels of MMP-13and Col-X significantly(P<0.05).In the SB203580drug treated group, these gene expression significantly reduced(P<0.05).In the stretching+drug group, these gene expression significantly reduced(P<0.05).High tensile stress and stretching+drug groups decreased Col-Ⅱ gene expression(P<0.05),while SB203580alone didn’t significantly effect Col-Ⅱ expression.The ELISA analysis indicated that the level of Col-X released into the culture medium in which group was significantly increased compared with the control group(P<0.05).while the amount of Col-X significantly decreased(P<0.05) in the drug group alone and stretching+drug groups compared with the control group(P<0.05).Conclusion:p-p38MAPK activated by cyclic tension increases MMP-13and Col-X mRNA expression while SB203580inhibits p-p38MAPK,MMP-13and Col-X induced by cyclic tension.Our finding suggests that p38MAPK plays a key role under cyclic high tension to regulate chondrocytes hypertrophy.