Age-related Change of the Immunohistochemical Localization of Fibronectin and Laminin in association with the Apical Migration of the Junctional Epithelium

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Periodontal tissue shows various morphological changes with aging. A typical example of these changes is the apical migration of the junctional epithelium. The distribution of fibronectin (FN) and laminin (LN) was investigated by means of immunofluorescent and immunoelectron microscopic methods in mice to clarify any possible functional roles of these proteins in the progression of apical migration of the junctional epithelium. Apical migration starts in 20-week-old mice, and then progresses with increasing age until the mice reached 80 weeks. In the apical tip of the junctional epithelium, FN was demonstrated in the subepithelial fibrillar matrix, and this phenomenon preceded the progression of apical migration in the junctional epithelium. FN was also demonstrated in association with the stromal side of the focal contact observed between epithelial cells and the basement membrane. Therefore, this focal contact is presumed to be a FN receptor. No apparent relationship between the localization of LN and the migration of the junctional epithelium was observed. These results suggest that the FN provides a provisional matrix for the apical migration of the junctional epithelium. Meanwhile, LN does not appear to play a major role in apical migration.