The distribution of fibronectin and laminin in the murine periodontal membrane, indicating possible functional roles in the apical migration of the junctional epithelium

Periodontal tissue shows various morphological changes with ageing. A typical example of these changes is the apical migration of the junctional epithelium. The distribution of fibronectin and laminin was investigated by immunofluorescent and immunoelectron-microscope methods in mice to clarify any possible functional roles of these proteins in the apical migration of junctional epithelium. Apical migration begins in 20-week-old mice, and then progresses with increasing age until the mice reach 80 weeks. In the apical tip of the junctional epithelium, fibronectin was demonstrated in the subepithelial fibrillar matrix, preceding the progression of apical migration. Fibronectin was also demonstrated in association with the stromal side of focal contacts between epithelial cells and basement membrane. Therefore, these focal contacts are assumed to be fibronectin receptors. There was no apparent relation between the localization of laminin and the migration of the junctional epithelium. These results suggest that the fibronectin provides a provisional matrix for the apical migration of junctional epithelium, but laminin does not appear to play a major part in that migration.