OBJECTIVEThe purpose of this study was to investigate the effects of static tension-stress on proliferation of mandibular condylar chondrocytes in rats.

METHODSThe fourth-passage chondrocytes were harvested from the mandibular condyles of 2-week-old SD rats. A continuous static tension-stress was applied on the cells in vitro using a cellular static tension-stress device, and the proliferation of mandibular condylar chondrocytes were examined using a flow cytometry. The other 30 specimens in the control group were divided into six groups to examine the effects of calf serum on cellular static tension-stress without any stress. The experimental group consisted of 70 specimens which were divided into seven groups under continuous static tension-stress (5 kPa, 10 kPa) for 0 to 12 hours. Multivariable analyses were conducted to test the associations between proliferation of condylar chondrocytes and different continuous static tension stresses.

RESULTSThe results showed that the lower calf serum inhibited the proliferation of rat mandibular condylar chondrocytes. There was little effect on the proliferation of chondrocytes under continuous static tension-stress (5 kPa, 10 kPa) for 2 hours. The proliferation of mandibular condylar chondrocytes was promoted as the application time of stress was prolonged (0-10 hours in 5 kPa groups and 0-8 hours in 10 kPa groups). The maximal proliferation appeared, when the condylar chondrocytes were cultured under 5 kPa continuous static tension-stress for 10 hours, and 8 hours under 10 kPa stress (P < 0.05). The proliferation of cells in the 5 kPa group was more obvious than in the 10 kPa group (P < 0.05).

CONCLUSIONThe data prove that mechanical stimulates in vitro can influence and regulate the growth of condylar chondrocytes. It provides experimental evidence for advanced study on cellular mechanical research in functional orthopedics.