LIGHT AND ELECTRON-MICROSCOPIC IMMUNOHISTOCHEMICAL LOCALIZATION OF LARGE PROTEOGLYCANS IN HUMAN TOOTH GERMS AT THE BELL STAGE

The immunohistochemical localization of large hyaluronate-binding prot eoglycans has been studied in human tooth germs at the bell stage usin g a monoclonal antibody, 5D5, which is derived from bovine sclera and specifically recognizes the core protein of large proteoglycans, such as versican, neurocan and brevican, but not that of aggrecan. In the e arly bell stage before predentine secretion, when the enamel organs co nsisted of the inner and outer enamel epithelia, stratum intermedium a nd stellate reticulum, the enamel organs were not stained by 5D5, but the dental papillae and follicles stained strongly. Concomitant with t he secretion of predentine, dentine and subsequent enamel matrix, stro ng 5D5 immunostaining distributed over the entire cell surfaces of sec retory ameloblasts was observed. The forming enamel matrix showed stro ng staining. While most of the inner and outer enamel epithelia and st ratum intermedium lacked staining, the cervical loop region and stella te reticulum showed weak staining. Although the forming dentine and od ontoblasts appeared to lack 5D5 affinity, the predentine, dental papil la and dental follicle demonstrated moderate to strong reactivity. At the ultrastructural level, specific immunoreaction by immunogold parti cle deposition was clearly detected over the basal lamina of presecret ory ameloblasts, secretion granules of secretory ameloblasts and the f orming enamel matrix. These results indicate that a marked increase in the large proteoglycan associated with secretory ameloblasts may corr elate with cell differentiation and enamel matrix biosynthesis.