Quantitative immunohistochemical evidence of a functional gradient of chondroitin 4-sulphate/dermatan sulphate, developmentally regulated in the predentine of rat incisor.

A quantitative examination was carried out on the early and mature stages of dentinogenesis in the rat incisor, using a post-embedding immunogold labelling with an anti-chondroitin 4 sulphate/dermatan sulphate antibody (2B6). At a very early stage of predentine formation, before polarizing odontoblasts have established junctional complexes, immunolabelling was weak. In contrast, when polarized odontoblasts established distal junctional complexes, immunolabelling in predentine was uniform and threefold denser than in initial predentine. The same gold particle density was found in the non-mineralized mantle dentine. During circumpulpal dentine formation, a gradient was seen in predentine, a larger number of gold particles being scored in the proximal zone compared with the distal region adjacent to the mineralization front. In circumpulpal dentine, some labelling was found within the lumen of the tubules and in the bordering dentine around the tubules. A few particles were also detected in intertubular matrix after demineralization. Together, these data provide evidence for a developmentally regulated gradient during the transition between mantle and circumpulpal dentine, and also in a more mature part of the tooth, a functional gradient that probably plays a role in the process of mineralization.