IMMUNOHISTOLOGICAL LOCALIZATION OF CELL-ADHESION PROTEINS AND INTEGRINS IN THE PERIODONTIUM

THE DISTRIBUTION OF THE CELL ADHESION PROTEINS vitronectin, fibronectin, tenascin, and laminin as well as several integrin subunits, alpha-2, alpha-5, and alpha(v), was studied in primate periodontal tissues. Full baboon mandibular sections were analyzed by immunohistochemical methods in order to localize the molecules studied in both soft and hard tissues. Vitronectin was associated with the connective tissue of the marginal gingiva, the periodontal ligament, as well as the endosteum and periosteum. A notable finding was the particularly high staining intensity of vitronectin in the periodontal ligament. Fibronectin was widely distributed in the periodontal connective tissue and was also localized to the pericellular matrix of osteocytes and blood vascular elements. Epithelial basement membranes stained positively for both fibronectin and tenascin. These proteins were also expressed in the periosteal and endosteal connective tissues and the periodontal ligament. The staining intensity for tenascin was higher in zones along the cementum and bone surfaces. Laminin was, characteristically, limited to basement membranes of epithelium and endothelium. The distribution of fibronectin, tenascin, and laminin is related to previous findings in other species. The localization of the several integrin alpha-subunits is also described in full baboon mandibular sections. The vitronectin receptor (alpha(v)) had a uniquely strong expression in osteoclasts of the alveolar bone and was found, at lesser intensity, on periodontal ligament fibroblasts. The fibronectin receptor alpha-subunit, alpha-5, was also observed on osteoclasts, and, in addition, was widely distributed on fibroblasts, cementoblasts, and osteoblasts. The collagen receptor subunit, alpha-2, was detected on fibroblasts, osteoblasts, cells lining the alveolar bone, and root cementum, as well as basal cells of the epithelium. These findings demonstrate a characteristic distribution of several adhesion proteins and integrins in the primate periodontium. The results should provide a better understanding of cell-extracellular matrix interactions in the periodontal tissues and create the basis for future functional studies of extracellular matrix molecules in the periodontium.