Basic study on the effect of mastication for growth and development of dentition

目前尚不清楚TRAP对机械应力条件下具有成骨细胞特征的牙周膜细胞的影响。本研究使用的重组蛋白为TRAP（NOVUS Co. Ltd.）。成骨细胞在STREX公司的拉伸室中培养，通过细胞拉伸系统（sibb -140）进行循环机械拉伸。细胞在培养基中加入或不加入TRAP培养72小时至预融合期，然后以20%伸长率水平拉伸，每分钟40次，16小时。Real-time PCR结果显示，TRAP的加入降低了MC3T3细胞Osterix和CBFA1的mRNA水平，而机械拉伸负荷增强了这种作用。研究机械应力对RANKL和OPG mRNA表达水平的影响。TRAP或机械拉伸均不影响OPG mRNA的表达水平。TRAP增加RANKL mRNA水平，机械拉伸降低RANKL mRNA水平。TRAP和机械拉伸抑制成骨细胞分化的机制。但机械拉伸的影响尚不清楚，表明牙槽骨中的成骨细胞在牙齿运动过程中抑制破骨细胞的分化。

It is not clear the effect of TRAP on the cells derived from periodontal ligament that have osteoblast like characters under the condition with mechanical stress. We used the recombinant protein of TRAP(NOVUS Co. Ltd.) in this study. Osteoblasts were cultured in the stretch chambers(STREX Co. Ltd.) and loaded with cyclic mechanical stretching by cell stretch system(SIB-140). The cells were cultured for 72 hours to preconfluent phase with or without TRAP in the culture medium then stretched with 20% elongation horizontally at 40 cycles per minutes for 16 hours. The results from Real-time PCR revealed that TRAP addition decreased the mRNA level of Osterix and CBFA1 on the MC3T3 cells furthermore loading with mechanical stretch enhanced the effects. We investigated the effect of mechanical stress on mRNA expression level of RANKL and OPG. TRAP or mechanical stretching did not affect the expression level of OPG mRNA. On the other hand RANKL mRNA level increased by TRAP addition while mechanical stretching decreased the mRNA level. Mechanism of the suppression on osteoblast differentiation by TRAP and mechanical stretching. Was not clear however the effect of mechanical stretching suggested the osteoblasts in alveolar bone suppress osteoclast differentiation during tooth movement.