Cyclic Tensile Stress On The Pterygoid Muscle Apoptosis

Objective:External pterygoid muscle plays an important role in generating, developing,treating and retention of dentofacial deformity.The structure and function of external pterygoid muscle can be adapted to the stimuli.Cellular proliferation,differentiation and apoptosis is indispensable in the reconstruction.of external pterygoid muscle.The purpose of the study is to investigate the effect of peiodical stretching on the apoptosis after an external pterygoid muscle myoblast model is builted in vitro.Methods:Based on an external pterygoid muscle myoblasts.cultured in vitro---stretching stimuli model,a multichannel cell tensile stress loader was used to stretch the cells contiuously for 6,12 and 24 hours respectively.The value of stretched cells group is 15%,10cycle/min,each cycle including 3-s stretch/3-s relaxation with non-stretch team as control.The effect of different stretching duration on cell apoptosis was detected and analyzed by optical microscope,Hocest fluorescent dye,lactic dehydrogenase releasing test and TUNEL method.Results:1.By optical microscope and fluorescence dye,it is observed morphologically skeletal muscle myoblast cells were apoptosed to different degrees under continuous stretch.Cell apoptosis ratio of controlled group is3.1%±0.25,which rised to 14.0%±1.6 with the stretch duration increased from 6 to 24 hours.The discrepancy is significant(P＜0.05).2,By TUNEL,it is detected each stretched group has cell apoptosis to different extents.3,Lactic dehydrogenase releasing test displays the releasing rate of lactic dehydrogenase increased obviously with the enhanced stretching duration.There is significant change of LDH between controlled and all stretched groups(P＜0.05);The comparison between every two groups shows LDH activities increased significantly(P＜0.05)between other groups except those between group 6h and group 12h(P＞0.05).Conclusion:There is certain proportionate apoptosis during culturation of myoblast cells.Cell apoptosis can be induced by periodical stretching.