Immunohistochemical localization of proteoglycans in human periodontium

Proteoglycans (PGs) are extracellular and cell surface-associated macromolecules that regulate cell adhesion, cell growth, matrix formation, and bind growth factors. In this work we studied the distribution of core proteins of four PGs (decorin, biglycan, a large molecular weight PG, and CD44) in human gingiva and periodontal ligament by immunohistochemical staining of frozen tissue sections with specific antibodies. Decorin, a major PG of this tissue, was localized on collagen fiber bundles in the gingival and periodontal connective tissues. Staining for decorin was most intense at the subepithelial region. Biglycan was a minor PG component of the human periodontium, showing some accumulation in connective tissue under the oral epithelium. At the immunohistochemical level, biglycan appeared to form fine filament-like structures on extracellular matrix fibers. Localization of large molecular weight PG differed from that of decorin and biglycan. It was concentrated in deep connective tissue areas of the gingiva and in the periodontal ligament, and was only weakly present at the subepithelial region. CD44 was mainly concentrated in cell-cell contact areas of basal and spinous layers of oral epithelium. In the connective tissue of gingiva and periodontal ligament, CD44 was localized on fibroblast cell surfaces. Connective tissue area under the junctional epithelium contained relatively small amounts of PGs. The results indicate that different parts of human periodontium contain a typical variety of PGs, suggesting a specific function for each PG species in the location at which they accumulate.