| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 102 === Matrix metalloproteinase-3 (MMP-3) degrades a number of extracellular matrix proteins and participates in multiple physiological functions and pathological processes. Mechanical force stimulation has been found to up-regulate MMP-3 expression in orthodontic tooth movement (OTM). To further understand the mechanism of regulation of MMP-3 by the mechanical force, we cloned the human MMP-3 gene promoter and identified its up-regulation in mouse osteoblasts, and then generated a MMP-3 promoter-green fluorescent protein (GFP) transgenic mouse model for in vivo test. After MMP-3-GFP transgenic mice lines were established, we applied mechanic force on teeth and addressed the following: 1) the location of GFP expression and its relationship with the direction of tooth movement; 2) the timeline of GFP expression after mechanical stimulation; and 3) the spatial correlation of MMP-3 and GFP by using the immunohistochemistry (IHC).
The results showed that GFP appeared mainly at the tension side and located at the junction of periodontal ligaments and alveolar bone, while it was not found at the pressure side. The intensity of GFP reached its peak after continuous mechanical stimulation for 1 to 2 days in the incisor expansion model. After we applied force for 1 day and then removed the appliance for 3 to 4 hours, the fluorescence was no longer detectable. IHC further improved the understanding of the spatial distribution of MMP-3 and GFP: MMP-3 protein was stained longer and more broadly than GFP since GFP could hardly be observed after 3 days of mechanical stimulation while MMP-3 still existed. Therefore, we conclude that the MMP-3-GFP transgenic mice can be used in OTM study since signals were triggered in a site- and time-specific manner. Further experiment should improve the accuracy and efficiency for detecting the expression of MMP-3 via reporter gene expression and possibly to find optimal mechanical parameter to stimulate the level of MMP-3.
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