Osteocytic sclerostin expression in alveolar bone in rats with diabetes mellitus and ligature-induced periodontitis

Background: Osteocytic sclerostin inhibits bone formation, and its expression is stimulated by tumor necrosis factor (TNF)-α. This study investigates sclerostin and TNF-α expression in rats with diabetes mellitus (DM) and periodontitis. Methods: Rats were divided into control (C), periodontitis (P), and DM + periodontitis (DP) groups. After induction of DM by streptozotocin, periodontitis was induced by ligature. At day 0 (control) and at days 3 and 20 after induction of periodontitis, alveolar bone, osteoclasts, osteoid area, and TNF-α and sclerostin expression were evaluated. Results: The distance between the cemento-enamel junction and the alveolar bone crest of the DP group was longer than that of the P group at day 20 after induction of periodontitis, but the number of osteoclasts was not different. Osteoid area decreased in both the P and DP groups by day 3, but whereas sustained osteoid suppression was observed in the DP group at day 20, osteoid formation was increased in the P group. The number of sclerostin-positive osteocytes increased in both groups at day 3, but the increased number of sclerostin-positive osteocytes was maintained only in the DP group through day 20. The number of TNF-α-positive cells increased more in the DP group than in the P group. Conclusions: Enhanced alveolar bone loss, suppressed bone formation, and prevalent TNF-a expression were characteristic of the DP group compared with the P group. Suppressed bone formation in the DP group was observed simultaneously with increased sclerostin and TNF-α expression. These results suggest that upregulated osteocytic sclerostin expression in periodontitis accompanied by DM may play a role in suppressed bone formation.