Differences in the ultrastructural localization of sulfated glycoconjugates between dentine and bone in the ganoid scales of Polypterus senegalus

ObjectivesSulfated glycoconjugates (S-GCs) are essential components of dentinogenesis and osteogenesis, and are involved in the regulation of the mineralization process. The scales of Polypterus senegalus, which are homologous to teeth and phylogenetically derived from ancestral dermal skeleton, comprise true enamel, dentine, and bone. As part of the phylogenic evolutional studies on mesenchyme-derived hard tissues, we investigated the ultrastructural distribution patterns and histochemical properties of S-GCs in the dentine and bone of scales.MethodsFor detection of S-GCs, a high iron diamine–thiocarbohydrazide–silver proteinate (HID–TCH–SP) staining technique was used.ResultsS-GCs were observed in unmineralized predentine and osteoid, mineralized dentine, osteocyte pericellular matrix, but not in mineralized bone and isopedine. Most S-GCs in the dentine and osteoid were susceptible to testicular hyaluronidase, indicating that they are chondroitin sulfates.ConclusionDistinct differences in the S-GC distribution pattern between the dentine and bone were observed. The S-GC distribution pattern associated with the dentinogenesis of scales is very similar to that of mammalian mantle dentine.