Phagocytic osteoclasts in alveolar bone of diabetic rats with periodontitis

Abstract

Periodontitis is a bacteria-induced inflammatory disease associated with alveolar bone loss. Osteoclast is amacrophage-lineage cell that exhibits phagocytic activity; however, osteoclast phagocytic activity has not beendemonstrated under pathological conditions. Diabetes is a pathological condition that exacerbates alveolar bone lossvia periodontitis; therefore, we examined phagocytic osteoclasts in diabetic rats that had periodontitis. The rats weredivided into the control (C), periodontitis (P), and diabetes with periodontitis (DP) groups. Diabetes and periodontitiswere induced by streptozotocin injection and ligature of the mandibular first molars, respectively. On days 3 and 20after the ligature, the rats were sacrificed, and osteoclasts containing inclusions were quantified by tartrate-resistantacid phosphatase staining. On day 3, there were more osteoclasts containing inclusions in the DP group than in the Cgroup. Among inclusions, osteocyte-like cells and dense bodies were more frequently observed in the DP group thanin the C group. Cytoplasm-like structures were elevated more in the DP group than in the C and P groups. However,no differences were observed on day 20. Interestingly, some osteoclasts were in contact with the osteocytes withinthe exposed lacunae and contained several inclusions within a large vacuole. Thus, the elevation of phagocyticosteoclasts in rats with diabetes and periodontitis provides insight into the role of osteoclast phagocytic activity underpathological conditions.