Effects of static tension-stress and TGF-beta 1 on proliferation of mandibular condylar chondrocytes

OBJECTIVE: The purpose of this study was to investigate effects of static tension-stress and TGF-beta 1 on proliferation of mandibular condylar chondrocytes in vitro. METHODS: The fourth-passage chondrocytes were harvested from the mandibular condyles of 2-week-old SD rats for this study, and a cellular static tension-stress device was used to apply stress on cells. The effects of continuous static tension-stress and/or transforming growth factor-beta 1 (TGF-beta 1) on the proliferation of mandibular condylar chondrocytes were examined using flow cytometry. The experiment was divided into two parts. The first part consisted of 100 specimens which were divided into 20 groups with different TGF-beta 1 dosage (0 ng/ml, 0.1 ng/ml, 1 ng/ml and 10 ng/ml) for 0, 6, 12, 18 and 24 hours respectively. The second part consisted of 30 specimens which were divided into six groups under continuous static tension-stress (5 kPa) and different TGF-beta 1 dosage (0.1 ng/ml, 1 ng/ml, 10 ng/ml) for 0, 6 and 12 hours. Multivariable analyses were conducted to test for associations between proliferation of mandibular condylar chondrocytes and TGF-beta 1 and/or different stresses. RESULTS: The results showed that TGF-beta 1 had a mitogenic effect on rat mandibular condyle at the concentrations of 0.1, 1 and 10 ng/ml, and the mitogenic effects of TGF-beta 1 on condylar chondrocytes were demonstrated in 12 to 18 hours after application of stresses, and the peak of mitogenic effects appeared at 18 hour (P < 0.05). The most active mitogenesis happened in the group with continuous static tension-stress (5 kPa) combined with TGF-beta 1. CONCLUSION: These results prove mechanical stimulates and TGF-beta 1 in vitro could influence and regulate the growth of condylar chondrocytes.