Regulation of Mechanical Strain on Expression of MMP-13 in Osteoblasts

Objectives: Osteoblasts have been shown to respond to mechanical loading of bone tissue by changes in enzyme activity and protein production. But, the effect of different magnitudes of mechanical strain on the proteolytic mechanisms responsible for the turnover of the organic matrix of bone is not clear. Therefore, we determined the effect of different magnitudes of mechanical strain on the expression of matrix metalloproteinase (MMP)-13 in osteoblasts. Methods:MC3T3-E1 osteoblasts were cultured onto elastic membrane, then imposed different magnitudes of cyclic tensile strain (0%, 6%, 12%, and 18%) in vitro to the adherent cells and later examined the induction of the MMP-13 expression by reverse transcriptase-PCR and Western blotting, respectively. In addition, signal transduction pathways that mediate cellular responses to mechanical strain were investigated using specific inhibitors. Results:The results showed that the gene and protein expression of MMP-13 increased significantly and in a magnitude-dependent manner by mechanical strain with 6%, 12% or 18% elongation in comparison with the control (0% elongation) cultures. The induction of MMP-13 mRNA expression by stretching was inhibited by PD098059, Conclusion:The results indicate that the expression of MMP-13 in osteoblasts is regulated by different magnitudes of mechanical strain, which profoundly affects bone matrix metabolism.This study was supported by the National Natural Science Foundation of China (No.30300393,No.30570455).