In situ detection of matrix metalloproteinase-9 (MMP-9) in gingival epithelium in human periodontal disease

Background and objective: As the periodontal lesion develops, the junctional epithelium migrates apically in conjunction with the dissolution of the most coronal Sharpey's fibers. Because matrix metalloprotemase-9 (MMP-9) has been identified in migrating epithelial cells and invading tumors, we propose that this enzyme is produced by gingival keratinocytes in advanced periodontal lesions. Methods: To test this idea, biopsies of inflamed gingival tissues were obtained from patients with advanced periodontitis. Healthy gingival tissue samples were utilized as controls. The presence and activity of MMP-9 was evaluated by combining indirect immunofluorescence of gingival tissue samples and gelatin zymography of gingival epithelium separated from connective tissue. Results and conclusions: The staining pattern showed the presence of MMP-9 in junctional and pocket gingival epithelial cells, polymorphonuclear neutrophils (PMNs) and as a scattered deposit along connective tissues of periodontitis-affected gingival tissues. Gelatin zymography permitted the identification of pro-MMP-9 in surcular/pocket epithelium derived from inflamed gingival tissues. Lower levels of MMP-9 were detected in epithelium not exposed to inflammation. These observations suggest a role for MMP-9 in gingival epithelial response to periodontal infection.