Objective To investigate the effect of different kinds of mechanical stress on the mRNA expression of integrin β1 subunit in cultured human periodontal ligament fibroblasts（hPDLF）. Methods To scalp and remove the periodontal ligament attached to the mid- third part of the fresh root of young premolars extracted for the cause of orthodontics. Cultured hPDLF by the method of digesting by Ⅰ- type collagenase combining with tissue adhering. Then hPDLF was isolated and purified by cells passage. The sixth passage′s cells were selected to be loaded. A new cyclic strain loading apparatus. Forcel four point bending device was used for mechanically loading. Cells were loaded by three levels（1 000, 2 000, 4 000 μstrain） of tensional and compressive forces and collected at different times（0, 0.5, 1, 4, 8, 12 h）course after strain loading. The quantity of integrin β1 mRNA in every group was analyzed by means of quantitative real- time PCR with the special primers of up- and down- regulated genes. Results Dynamic mechanical forces down- regulated the expression of integrin β1 subunit mRNA in hPDLF and the difference in groups by different magnitude, different kinds, and different time of mechanical forces loading were statistically significant. The stronger stimulated forces, the more down- regulated expression. Compression down- regulated the expression of integrin β1 subunit mRNA more than tension did. Conclusion Dynamic mechanical forces could regulate the expression of integrin β1 subunit mRNA. The difference among all the groups by different magnitudes, different kinds, and different time of mechanical forces loading were statistically significant.
