Immunohistochemical detection of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in ameloblastomas.

BACKGROUND To evaluate the roles of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in tumor progression, expression of MMP-1, -2 and -9 and TIMP-1 and -2 was analyzed in ameloblastomas as well as tooth germs. METHODS Frozen tissue sections of seven tooth germs and 22 ameloblastomas were immunohistochemically examined using anti-MMP-1, -2 and -9 and anti-TIMP-1 and -2 antibodies. RESULTS MMP-1, -2 and -9 and TIMP-1 and -2 were expressed strongly in mesenchymal components of tooth germs, and stromal cells of ameloblastomas. Immunoreactivity for MMP-9 in stromal cells of ameloblastomas was significantly stronger than in mesenchymal cells of dental follicles and dental papillae. Dental laminae showed weak MMP-2 expression in six tooth germs, MMP-9 expression in two tooth germs and TIMP-1 expression in six tooth germs. Some tumor cells showed weak MMP-2 expression in 19 ameloblastomas, MMP-9 expression in four ameloblastomas and TIMP-1 expression in all cases. TIMP-2 reactivity was prominently found in basement membrane zones of dental laminae in tooth germs, and tumor cell islands or nests in ameloblastomas. CONCLUSION Expression of MMPs and TIMPs was considered to be associated with interactions between epithelial cells and mesenchymal components in normal and neoplastic odontogenic tissues; these molecules might play a role in regulation of tumor progression in ameloblastomas as well as regulation of developmental processes in tooth germs.