Involvement of Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Periodontal Tissue Destruction

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The immunohistochemical study on the expression of matrix metalloproeinase (MMP)-1, MMP-8, and tissue inhibitor of matrix proteinase (TIMP)-1 in the cyst wall was designed to understand the mechanism of the cyst growth. Total 68 cases of radicular cyst and 13 cases of odontogenic keratocyst were examined.Fibroblasts, capillary endothelial cells, macrophages, and cells of the lining epithelium in both radicular cysts and odontogenic keratocysts commonly expressed MMP-1 and TIMP-1 but not MMP-8. In radicular cysts, the positive cell rate for MMP-1 to total cells comprising the connective tissue wall, except for lymphocytes and plasma cells, was significantly higher than that for TIMP-1, the difference being more pronounced in the resting type of radicular cyst (71,2% for MMP-1 and 15.9% for TIMP-1) than inflamed type (64.8% for MMP-1 and 43.2% for TIMP-1). There was no difference in the lining epithelium of radicular cyst, in which most of the cells appeared to be immunoreactive for both MMP-1 and TIMP-1. In odontogenic keratocyst, in contrast, higher positive cell rate for MMP-1 compared to that for TIMP-1 was found in the lining epithelium and there was no significant difference in the connective tissue wall.From the present results, it is suggested that the disruption of the balance between MMP-1 and TIMP-1 activities may be responsible for tissue destruction associated with the cyst growth. The change takes place in the connective tissue wall in radicular cyst and in the lining epithelium in odontogenic keratocyst, respectively, suggesting that there is a different growth mechanism between the both.