Investigation of mechanism of periodontal destruction in rat experimental periodontitis caused by topical application of lipopolysaccharide

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To elucidate histopathological mechanism of periodontal ligament destruction in the marginal periodontitis caused by lipopolysaccharide, (1) we have firstly tried to investigate the collagen-phagocytotic and/or collagenolytic activities of periodontal ligament fibroblasts using tissue culture cells with histochical and immunohistochemical methods. We could establish the fibroblastic cell lines from rat molar periodontat ligaments. These cells were polyhedral, round or spindle in shape on the bottom surface of tissue culture plate. Histochemically and immunohistochemically, they showed characteristics of periodontal ligament fibroblasts, such as positive reaction of alkaline phosphatase and alizarin red staining for calcification, immunostaining for vimentin and type I collagen. They also revealed slight immunohistochemical positivities for keratin, osteocalcine and OX-43 (marker for endothelial cell and macrophage). We cultured these fibroblasts three-dimensionally in the collagen gel … More and tried to demonstrate phagocytosis of collagen by the culture cells under the electron microscopic observation. But, it was difficult to find the ingested collagen fibrils in the cultured cells even under the ultrastructural level. Trial to demonstrate the phagicytosed collagen immunohisto-chemically in the cultured fibroblastic cells was also unsuccessful, as it was difficult to differentiate the ingested collagen fibrils from the synthesized collagen in the cells. On the other hand, (2) we studied dynamics of macrophages in the rat experimental periodontitis caused by topical application of lipopolysaccharide, because synthesis of collagenase and/or IL-1beta by macrophage is suspected to cause destruction of periodontal ligament. As a result, it was revealed that ED1 positive exudative tissue macrophages from blood monocytes increased in the inflammatory periodontal lesion after LPS-administration. These macrophages produced IL-1beta and was suggested to participate destruction of periodontal tissue. Ia antigen positive dendritic cells also increased in the lesion after LPS-administration, which suggested that much of these macrophages changed to antigen presenting cells and might have important role for reactivity of local immune response. Less