Immunolocalization of interstitial collagenase (MMP-1) and tissue inhibitor of metalloproteinases-1 (TIMP-1) in radicular cysts.

To investigate the mechanisms involved in expansion of radicular cysts, monoclonal antibodies against interstitial collagenase (MMP-1) and tissue inhibitor of metalloproteinases-1 (TIMP-1) were used to localize the sites of MMP-1 and TIMP-1 expression in 30 radicular cysts. Positive MMP-1 staining was detected in the lining epithelium and subepithelial fibroblasts, macrophages, endothelial cells and osteoblasts/osteocytes in all specimens. Positive TIMP-1 staining was identified in osteoblasts/osteocytes and endothelial cells of all specimens, and in the lining epithelium and subepithelial fibrous connective tissue wall of five radicular cysts with an intense inflammatory cell infiltrate. The number and distribution of positive cells for MMP-1 or TIMP-1 varied widely among individual specimens, but strong immunostaining was constantly detected at sites with prominent subepithelial inflammation. Results here support the hypothesis that MMP-1 may play an important role in the expansion of radicular cysts. The absence of TIMP-1 expression in lining epithelium and subepithelial fibroblasts and macrophages in most cases studied indicated that an imbalance between MMP-1 and TIMP-1 production may lead to radicular cyst expansion.