The Effects Of Cyclic Tension Stress On Proliferation Of Fibroblasts

Objective The character and strength of the external force received by a tooth plays a key role in maintaining the health of the periodontal tissue and its reconstruction. Normal biting force can maintain the health of periodontal tissue. When biting force is beyond the physical limit, damage of the periodontal ligament and resorption of the alveolar bone will occur. When biting force abates, disusing atrophy of the alveolar bone and degeneration of the periodontal tissue will happen. There is close relationship between the force (such as the strength and status of the force) and the reconstruction of the periodontal tissue during the pathological development of periodontal disease (such as chronic periodontitis) and after its clinical treatment,. The periodontal ligament fibroblast (PDLF) not only is the largest number of cell in the periodontal membrane, but also has the most important function. PDLF plays an important role in the process of reconstruction. Under the mechanical stress, PDLF synthesizes directly and secrets the vast majority of collagen fibers in the extracellular matrix of the periodontal membrane. PDLF changes the metabolism of extracellular matrix of the periodontal ligament through the adjustment of the synthetic and catabolic metabolism. PDLF carries on the orderly reconstruction of periodontal tissue. To date, there is no conclusion of the biological changes of the PDLF after receiving the mechanical tensile stress. Therefore, it is very necessary to further study the changes of biological characteristics of PDLF under the mechanical stress. It will help exploring the etiology of the damage of periodontal tissue by occlusal traumatism in the cell level. It will also help seeking for new ways to restore the periodontal tissue. This project aims to study the influence of periodic tensile stress on the proliferation characteristics of the mouse embryos fibroblasts at the different time points. The tensile stress was applied by cell stress loading devices. Other methods in the research included:cell culture method, flow cytometry and MTT method.Methods Cell tensile stress application system were used to apply0.1Hz cyclic tensile stress, on the L929cells for1h,2h,4h, and8h separately, the tensile stress applied caused8%deformation of basement membrane. The percentage of cell cycle changes were observed with flow cytometry analysis, changes on proliferation were analysed by MTT.Results The S-phase fraction (SPF) of fibroblasts subjected to stress for1hand2h group decreased comparing to control group(P<0.01)., and the count of fibroblasts increased(P>0.05); The SPF picked up after the fibroblasts subjected to stress for4hours(P>0.05). It was lower than the control group(P>0.05). The count of fibroblasts increased (P>0.05). Both the SPF and the count increased excessively after the fibroblasts subjected to stress for8hours(P<0.05, P<0.01).Conclusion The proliferation of fibroblasts increased after continuiously stretched for1h and2h. But the proliferation was inhibited after continuiously stretched for8h under the same condition.