The Effect Of Cyclic Tensile Strain On The Prolifetation And Apoptosis Of Rat Growth Plate Chondrocytes

Objective1.To study the effect of cyclic tensile strain on the proliferation and apoptosis of rat growth plate chondrocytes and to explore whether YAP protein were involved in this process.2.To explore the effect of a motorized rodent treadmill on16weeks rat and to observe the effect of CSA on OA rats.3.To study the effect of a motorized rodent treadmill on4weeks rat and to observe the influence of exercise of different intensity on rat growth plate.Method1.Rat growth plate chondrocytes were isolated and cultured in vitro and were subjected to cyclic tensile strain. Apoptosis of chondrocytes was observed by Annexxin V-FITC/PI staining immunofluorescence and was analyzed by flow cytometry. The expression of Gene of proliferation and apoptosis were examined by Real-time PCR.Western blot was used to examine the change of proteins of proliferation and apoptosis.2.A motorized rodent treadmill was used to establish osteoarthritis model and at the same time the rats on the control group were given immunosuppressant CSA.The MR and microCT were used to evaluate the OA model and HE was used to study the change of OA.The expression of Gene of apoptosis were examined by Real-time PCR.Western blot was used to examine the change of proteins of apoptosis.3.A motorized rodent treadmill was used to establish proliferation model. MicroCT were used to evaluate the model and HE was used to study the change of proliferation of chondrocytes.The expression of Gene of proliferation were examined by Real-time PCR. Western blot was used to examine the change of proteins of proliferation. Result 1.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at2000μ strain,1Hz) for2hours, the activation of COL2gene and the expression of COL2and SOX9protein were significantly increased.and the expression of RUNX2gene and protein was not obviously changed.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at3000μ and4000μstrain,1Hz) for2hours, he expression of RUNX2gene and protein was significantly increased and the activation of COL2gene and the expression of COL2and SOX9protein were reduced.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at5000μ and6000μstrain,1Hz) for2hours, he expression of mmp13and activated caspase9gene and protein was significantly increased.The expression of BCL2protein was decreased obviously. With the increasing of strain stimulation intensity, apoptosis of growth plate chondrocytes increase.We observe that the high expression of YAP gene and protein in the process of proliferation and apoptosis.2.Early changes of OA were detected by MR and CT.We observe that thethickness of cartilage was decreased in Group C.the expression of CASPASE9,MMP13,COL2,SOX9genes were up-regulated and the expression of COL2, SOX9and BCL2protein were reduced.We observed that the reducing of severity of osteoarthritis and expression of apoptosis related protein in Group D(using CSA).3.We observed the increasing of the expression level of Ki67gene and the expression of PCNA gene and protein and the upregulation of SOX9and increasing the expression of SOX9and COL2protein after Exercise.Conclusion:1.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at2000μ strain),the proliferation of chondrocytes increased.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at3000-4000μ strain),chondrocytes mainly to become the trend of bone differentiation.When rat growth plate chondrocytes were subjected to cyclic tensile strain(at5000-6000μ strain) the apoptosis of chondrocytes increased.The proliferation and apoptosis of rat growth plate chondrocytes may be related to YAP.2.High intensity treadmill exercise (more than30km) can induce OA in rats by increasing the occurrence of articular cartilage mechanical stress, the occurrence of osteoarthritis and cartilage is closely related to cell apoptosis. The inhibitory effect of CSA on cell apoptosis, can reduce the expression of apoptosis related proteins, and reduce the severity of osteoarthritis.3.3.Exercise can promote rat growth plate chondrocyte proliferation,and in the appropriate exercise intensity, with the increase of exercise intensity, the proliferation of rat growth plate chondrocyte are also increased.