The Effects Of Compressive Stress On The Proliferation And TGF-β1mRNA Expression Of Condylar Chondrocytes In Vitro

[Objective] The purpose of this study is to investigate the consequential changes of proliferation and transforming growth factor β 1 mRNA(TGF-β 1mRNA) expression of mandibular condylar chondrocytes(MCC) stimulated by compressive stress, so that to make a primary understanding of the relationship between the expression of TGF-β 1mRNA and cell proliferation during the process of stress induced remodeling of mandibular cartilage. [Materials and Methods] The primary MCC separated from the mandibular condylar cartilage of six neonatal SD rats were cultured and a finite cell line wasestablished in vitro. A static compressive stress with a magnitude of 120g/cm 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-β1mRNA wasdetected in the way of in situ hybridization. To set control groups, stress-free cells were also cultured in the same conditions and tested on different time points according to the experiment groups.[Results] It was found that the compressive stress, when exerted on the in vitro cultured MCC for 1 hour, had significantly improved the activity of cell proliferation and the percentage of cells in S phase (P<0.05). 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- β 1RNA was also promoted at the end of compressive stress loading(P<0.05), 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- β 1mRNA of cultured MCC in vitro, but alteration of the activity of proliferation and the expression of TGF- β 1mRNA induced by short-term compressive stress can be corrected in a certain period after the stimulation was removed; it is predictable that the effects of compress on the proliferation of cultured MCC are partially mediated and regulated by TGF- β 1, of which the mechanism is possibly related to up regulating the proportion of cells in S phase of cell cycle.