| Objective:To investigate the biomechanical mechanism of the growth andreconstruction of mandibular condylar,the effect of tensile loadings with variousfrequencies on the proliferation and differentiation of mandibular condylarchondrocytes in the process of endochondral ossification was evaluated.Method:Mandibular condylar chondrocytes (MCC) from two-week-old NewZealand rabbits were cultured in vitro.The second generation of MCC were exposedto different frequency of tensile stress(0,0.1,0.5,1HZ) at2000u for a period of2h perday for3days using four-point bending system In the control group, cells werecultured on the similar plate and kept in the same incubator without mechanical stressloading.Morphology of MCC was observed by inverted phase contrast microscopeafter exposure to mechanical loading.The proliferation of articular chondrocyte wasdetermined by CCK-8assay.Flow cytometry（FCM) was used to examine the contentof DNA and the index of proliferation (PI).The gene expression level ofchondrogenesis (Sox9, col2a1）and hypertrophy (Runx2, col10a1) was analyzed usingreal-time RT-PCR respectively.Result: The proliferation of chondrocyte was significantly increased under thestatic (0HZ) tensile stress and was significantly reduced under periodic tensile stress(0.1,0.5,1HZ)(p<0.01), moreover, the static (0HZ) tensile stress increase the DNAsynthesis (P<0.05) and the proliferation index (PI)(P<0.01).The relative mRNAexpression level of Sox9and Runx2was significantly affected by the stimulatingfrequency which was upregulated at the higher tensile stress in the groups of0.5HZand1HZ, and was suppressed in the group of static (0HZ) tensile stress.(comparedwith the control group, p＜0.01), meanwhile, the expression of col2a1was higher inthe group of periodic tensile stress (0.1，0.5，1HZ) compared with the group of statictensile stress and control group, while the expression of col10a1was highest in thegroup of1HZ and lowest in the static (0HZ) group. Conclusion：There are different effect on the proliferation and differentiation ofMCC under different frequency of tensile stress. This suggest that load-inducedalterations in endochondral ossification could be regulated by loading patterns. |
