Aim: To determine whether or not matrix metalloproteinase 13 (MMP-13) is present in periapical granulomas with and without epithelium.
Methodology: Seventeen open periapical granulomas of pulpal origin (seven lesions without epithelium and 10 with proliferating epithelium) were fixed in formalin and then embedded in paraffin prior to being processed for immunohistochemical analysis. A monoclonal antibody against human MMP-13 was used to evaluate MMP-13 expression. Immunocomplexes were subsequently treated with the secondary antibody and then detected by means of streptavidin peroxidase. Immunoreactivity was visualized by development with 3,3'-diaminobenzidine.
Results: An immunopositive cytoplasmatic reaction for MMP-13 was observed in all the specimens, although the immunostaining by anti-MMP-13 antibody was heterogeneous and its levels varied according to histopathological findings. In periapical lesions without epithelium MMP-13 immunolabelling was detected in a few fibroblast-like cells, and in some plasma cells within the granulomatous tissue. A clear upregulation of MMP-13 expression was detected in periapical lesions with epithelium, especially in small island and thin strands of epithelium.
Conclusions: The expression pattern of MMP-13 demonstrates that it is involved in the conversion of a periapical granuloma with epithelium into a radicular cyst. This property is related to the ability of MMP-13 to influence not only the migration of epithelial cell but also the invasion of granulomatous tissue.