Immunohistochemical localisation of extracellular matrix proteins in the periodontium during cementogenesis in the rat molar

Objective: The development of the periodontium involves the coordinated expression of numerous extracellular matrix (ECM) macromolecules and their receptors (integrins). The aim of this study was to determine the expression of selected hard and soft tissue matrix molecules and the integrin α5β1 in the periodontal tissues, during cementogenesis in the rat molar. Methods: Using immunohistochemical methods, the distribution of the extracellular matrix proteins, fibronectin, tenascin, and bone sialoprotein (BSP), as well as the integrin subunits α5 and β1 were studied in rats aged 3, 5 and 8 weeks. Results: Fibronectin was widely distributed in the gingival epithelium, gingival connective tissue and in the periodontal ligament. Tenascin expression was less marked compared with fibronectin, but was more distinctly associated with cells and peri-cellular areas of the epithelial-connective tissue interface, the gingiva and within the periodontal ligament. The fibronectin-receptor α5β1 integrins were expressed by epithelial cells, periodontal ligament cells and gingival fibroblasts. A notable finding was the increased staining intensity of fibronectin, tenascin and α5β1 integrin in all 5-week old molar sections in the periodontal ligament matrix and cells, apical to the cemento-enamel junction (CEJ) along the alveolar crest (AC) ridge height. Bone sialoprotein was distinctly associated with the hard tissues of the periodontium as acellular cementum and alveolar bone matrix expressed bone sialoprotein throughout all sections, in all age groups. Conclusions: In conclusion, this study has demonstrated the selective distribution of several hard and soft tissue matrix molecules during periodontogenesis. The results highlight the complex nature of interactions of various proteins and molecules during development. The interactions between these molecules and their specific roles in development and regeneration await further investigation.