The Effects of Compressive Stress on the Proliferation and TGF-¦Â1mRNA Expression of Condylar Chondrocytes in vitro

Objective: to investigate the consequential changes of proliferation and transforming growth factorb1 mRNA(TGF-b1mRNA) expression of mandibular condylar chondrocytes(MCC) stimulated by compressive stress. Methods: The primary MCC separated from the mandibular condylar cartilage of six neonatal SD rats were cultured and a finite cell line was established in vitro. A static compressive stress with a magnitude of 120g/cm2 was exerted on the third passage of MCC for 1 hour. On the time points of 0, 6, 12, 18 and 24hr after the stimulation of stress, the DNA content and cell cycle were evaluated using flow cytometry, and the expression of TGF-b1 m RNA was detected in the way of in situ hybridization. Results: the compressive stress had significantly improved the activity of cell proliferation and the percentage of cells in S phase. But such a change was eradicated in 12 hours after the stress was removed, and then no significant differences of the activity of cell proliferation and the percentage of cells in S phase were observed between the experiment groups and control groups. The expression of TGF-b1mRNA was also promoted by compressive stress, but it was regulated down to the level similar to that of control group in 6 hours. Then, there was no significant difference observed between experiment group and control group in the remaining testing time points. Conclusion: The compressive stress with a magnitude of 120g/cm2 and a duration of 1 hour can improve the activity of proliferation and the expression of TGF-b1mRNA of cultured MCC in vitro, but alteration of the activity of proliferation and the expression of TGF-b1mRNA induced by short-term compressive stress can be corrected in a certain period after the stimulation was removed.