Plasmin/ogen system is essential for the development of periodontal disease

Infectious conditions of the periodontal area, gingivitis and periodontitis, are one of the most common disease entities in adults. In this study, the role of the plasminogen activator system for the spontaneous development of periodontal disease was investigated by the analysis of plasminogen-deficient mice. Whereas essentially all of the wild-type control mice kept a healthy status of the periodontal area at different age of life examined, all the plasminogen-deficient mice gradually developed chronic periodontal disease with various degrees of inflammatory changes during an 20-week observation period. Morphological studies revealed the formation of an amorphous necrotic tissue, changes of inflammatory conditions, detachment of gingival tissue from the nearby tooth bone and severe bone degradation in the periodontal area of plasminogen-deficient mice. Immunohistochemical studies further indicate a mass infiltration of neutrophils in the gum tissue of these mice. Systemic supplementation of human plasminogen restored the normal periodontal conditions indicate that the spontaneous development of periodontal disease in plasminogen- deficient mice is due to the lack of plasminogen protein in these mice. These results suggest that plasminogen plays an essential role in protecting against the spontaneous development of chronic periodontal disease. Our findings also suggest the possibility of using plasminogen for clinical therapy of periodontal disease.