Immunohistochemical localization of extracellular matrix in human developing mandibles and tooth germs

Objectives: To investigate to extracellular matrix in human developing mandibles and tooth germs. Methods: Studies using specific antibodies to immunolocalize the extracellular matrix including collagen type I, collagen type III, bone sialoprotein (BSP), osteopotin (OPN), osteonectin (ON) and osteocalcin (OC) in the sections combined the tissues of human tooth germs with mandibles were undertaken to investigate the different distribution of these matrix components. Results: The sections incubated with type I collagen exhibited extensive immunohitochemical labeling, while staining with type III collagen appeared restricted in soft tissues such as oral epithelia and submucosal connective tissues. The first appearance of BSP, OPN, ON and OC during dentinogenesis was detected at the bell stage. Intensively positive immunostaining for BSP was seen in osteoblasts, the border of bone, odontoblasts, bone matrix, predentin, ameloblasts and enamel. Mineralized tissues including bone matrix, cartilage and dentin showed strong immunoreaction with OPN. Moderate positive immunostaining was seen in odontoblasts, dentin and cartilage. Positive staining for ON was observed both in the mineralized tissues and soft tissues. Only mineralized bone matrix, dentin and odontolasts were positively stained with OC. Conclusions: In view of the restricted distribution and temporal changes in the expression of the extracellular matrix, we believe that these collagens and proteins have specific and different roles in the initial stages of connective tissue mineralization