【作者】 刘颖；

【导师】 陈扬熙； 赵志河；

【作者基本信息】 四川大学 ， 口腔临床医学， 2004， 博士

【摘要】 正畸医师移动牙齿的唯一良药是“力”,如何应用力关系到治疗的成败,而正畸治疗的本身也包含了极为丰富的生物学内涵,原先偏重于矫治技术方面的研究正趋向于正畸与基础科学的结合研究。机械性刺激是细胞在生物进化过程中受到的最基本的刺激之一,这些刺激可以是来自细胞本身在生长、分化、运动中所产生的张力,也可以是来自外部环境对细胞的影响。适当的力学刺激可以促进细胞的生长、分化和功能的维持,但过度或持续时间过长的机械力刺激又会对细胞造成损害,因此细胞是如何感受力学信号并将其转导为生物化学信号而最终产生基因转录响应便成为大家关注的焦点。即刻早期基因c-fos能对外界刺激引起的传入信息在数分钟内作出反应,进行表达。被看作是胞内“第三信使”的c-fos mRNA所编码的核磷蛋白c-Fos具有DNA结合活性,它是转录激活蛋白AP-1的重要组成部分。研究表明,机械力刺激可通过诱导成骨细胞c-fos的表达,引发一系列的生物学效应,尽管这一具体机制尚存争议,但c-fos仍被视为细胞力学信号转导过程中的一种重要的信号分子,起到了早期反应下游枢纽的作用。 本研究采用自行研发设计的四点弯曲细胞应力加载系统,以成骨样细胞MG-63为研究对象,以并行研究的方式观察不同性质、不同大更多还原

【Abstract】 It is well established that bone mass and architecture depend on the mechanical stimuli applied to the skeleton. Bone loss occurs in over-loading condition, while bone mass increases after appropriate skeletal loading. These changes in mechanical stimulus modulate bone turnover mainly through the osteoblast lineage. However, the signaling pathways involved in osteoblastic mechanotransduction are not fully understood. Among the early events linked to the response to mechanical strain, the expression of the immediate early gene, c-fos, has been specifically connected to bone biology. The c-Fos protein is an important component of the transcription factor activating protein-1 (AP-1), which can alter relative gene expression. In an effort to better understand what processes are involved in mechanotransduction, we have examined whether and how soon c-fos induction occurs in human MG-63 osteoblast shortly after the application of the mechanical stimuli lonely and coupled with the inhibitor of the relative signaling pathways.MG-63 were cultured in DMEM with 10% FBS for 48 hours and starved in DMEM with no FBS for 12 hours, then subjected to mechanicalstrain by self-made four-point bending system at a 0.5Hz frequency for 5min, 15min, 30min, lh, 3h, 6h, respectively. In each time-phase, the cells were loaded with tension and compression stress at lOOOustrain and 4000ustrain respectively, c-fos mRNA were analyzed by Real-time PCR and c-Fos protein by Western Blotting. Changes in the experiments were expressed as ratio (±standard error of the mean) to the controls. Statistical significance was determined for each comparison using the one-way ANOVA and multiple comparisons using the SNK, and p<0.05 was statistically considered significant. The ratios quoted were average changes from three independent experiments.Treatment of cultures with agonists: Before loading, the MG-63 cells were treated with Genistein, the inhibitor of Tyrosine kinase, and Cytochalasin D, which represses the formation of the stress fiber, for 30min and lhr respectively.According to this research, we found: application of mechanical strain to MG-63 cells produced a rapid increase in expression of c-fos mRNA and c-Fos protein within 15min and peaked at 30min-lh, then significantly reduced after lhr and returned to baseline by 3-6h.; the effect of 1000|j.strain mechanical stimulus on the expression of osteoblast c-fos mRNA was stronger than that of 4000^strain; difference mechanical stimuli could induce difference changes of c-fos mRNA and c-Fos protein; both Genistein and Cytochalasin D had obvious repression on the expression of c-fos gene, the repression of Genistein was more important in the expression of c-fos induced by the tension stimulus, while the induced expression of c-fos by the compression stimulus was mainly inhibited byCytochalasin D.So based on the results, we have these conclusions: acted as an immediate-early gene, c-fos could make a rapid and temporal response to mechanical strain; the mechanical stimulus at physiologic magnitude could induce the largest expression of c-fos; the mechanical tension and compression stress could induce c-fos expression through multiple signaling pathways, while the expression of c-fos by tension was mostly induced through the tyrosine kinase pathways and the compression stimulus induced c-fos expression mainly through the reorganization of the cytoskeleton.更多还原