IMMUNOHISTOCHEMICAL EXPRESSION OF EXTRACELLULAR-MATRIX COMPONENTS OF NORMAL AND HEALING PERIODONTAL TISSUES IN THE BEAGLE DOG

PERIODONTAL REGENERATION REQUIRES FORMATION Of periodontal tissues los t due to periodontal disease. To better understand the formation of ne w periodontal tissues during periodontal repair and regeneration, immu nohistochemical expression of extra-cellular matrix components of norm al as well as healing periodontal tissues was evaluated and compared u sing the avidin-biotin complex immunohistochemical technique. For this purpose, horizontal furcation defects were created around mandibular P2 and P4 of 6 dogs after extraction of P1 and P3. The root surfaces w ere conditioned with citric acid and expanded polytetrafluoroethylene (ePTFE) membranes were placed and retained 0.5 mm above the cemento-en amel junction. The mucoperiosteal flaps were sutured in a coronal posi tion. Two animals were sacrificed at 2, 4, and 8 weeks, and mesio-dist al tissue slices containing normal or healing periodontal tissues were demineralized, dehydrated, and embedded in paraffin. Immunohistochemi cal localization of type I collagen (CI), fibronectin (FN), secreted p rotein, acidic and rich in cysteine (SPARC), vitronectin (VN), and bon e sialoprotein (BSP) was performed on 6 mu m thick sections. Morpholog ical results demonstrated that at 2 weeks after defect creation, lesio ns were filled primarily with granulation tissue which was gradually r eplaced by newly-formed fibrous connective tissue, periodontal ligamen t (PDL), cementum, and bone between 4 and 8 weeks. The results of immu nohistochemical study revealed that at 2 weeks the granulation tissue, especially in the intercellular spaces of inflammatory cells, was int ensively stained for FN and VN. At 4 and 8 weeks, staining for CI, FN, and VN was found in fibrous connective tissue, the newly-formed PDL, cementum, and osteoid. Further the attachment zone of the PDL collagen fibers to cementum showed intense staining for FN. Immunostaining for SPARC was positive in the new PDL, cementum, and bone, while staining for BSP was restricted to the new cementum and bone. Interestingly, t he PDL, especially in areas adjacent to active bone formation, demonst rated intense staining for BSP. However, fibrous connective tissue and PDL proper were unstained for BSP. These results indicate that FN and VN are involved in the early stages of periodontal repair, and period ontal regeneration is achieved through formation of periodontal tissue s that are composed of different matrix components specific to differe nt types of periodontal tissues.