Osteopontin localization in the rat gingival tissues in an experimental model of periodontitis associated with obesity-related diabetes

Abstract

Although osteopontin (OPN) is a bone-matrix protein regulating bone metabolism, recent findings demonstrate that OPN also has various roles in inflammation and metabolic diseases, and that the plasma OPN levels are high in patients with diabetes. Diabetes patients are known to have a tendency to suffer from severe periodontitis. However, the definite factors influencing the severity of diabetic periodontitis have not yet been identified. The aim of this study was to investigate the association of OPN with the severity of diabetic periodontitis. Using a rat model of obesity-related type 2 diabetes, experimental periodontitis was induced by placing a ligature around an upper molar tooth. On days 3 and 20 after the ligature, the alveolar bone height and OPN localization in the periodontal tissues were investigated by micro-CT analysis and immunohistochemical staining, respectively. Micro-CT analysis revealed that the 20-day ligature treatment induced more severe bone resorption in the diabetic rats, with 1.3-fold more bone resorption, than in the control rats. Immunohistochemical staining of the gingival connective tissue on day 20 revealed marked OPN localization at the ligature site in the diabetic rats, whereas only mild staining at the site was observed in the control rats. These results indicate that this experimental system is useful for the study of diabetic periodontitis and the possible association of OPN with the severity of diabetic periodontitis.