Objective The purpose of this study was to investigate the mechanism of extracellular matrix（ECM） metabolism regulation and the molecular biological basis of periodontal tissue remodeling, by which MMP-8/13 expression in the condition of cyclic mechanical strain with the same frequency and different strength and time to human periodontal ligament cells（HPDLC）. Methods HPDLC were cultured on flexible substrates and subjected to 6%, 12%, 18% elongation by strain unit at 0.1 Hz for 2, 6, 12 h, expression and secretion of MMP-8/13 mRNA were determined after loading cyclic tension strain. Results After loading cyclic tension strain, the cell growth direction was changed to force direction, HPDLC expression of MMP-8 and MMP-13. After loading of 6% and 12% cyclic tensile strain, the expression of MMP-8 mRNA was increased significantly and it was raised with time increased, in 18% group with different time, the levels of mRNA were increased, but the expression level of 12 h was lower than that of 6 h. After loading 6% cyclic tensile strain, the expression of MMP-13 mRNA was elevated with time increased. In 12%, 18% group with different time, the levels of mRNA increased, the expression level of 12 h was lower than that of 6 h, but they were not significantly different. Conclusion The cyclic tension strain up-regulated the expression of MMP-8/13, suggesting probable important role of MMP-8/13 in the remodeling of periodontal tissue during the orthodontic tooth movement.
