The effect of sword bean extract on the relationship between rheumatoid arthritis and periodontitis in mice

ObjectivesSeveral studies in humans and experimental animals have reported an interaction between rheumatoid arthritis (RA) and periodontitis (PD). We previously showed that extracts of Canavalia gladiata (sword bean extract, SBE) can treat PD in rats. Here, we investigated the relationship between RA and PD and the effects of SBE in an experimental mouse model. MethodsFemale SKG mice were assigned to eight groups (n=6/group): (1) Untreated controls, (2) RA (induced at 6 weeks of age), (3) PD (induced at 10 weeks of age), (4) RA + PD, (5) SBE (2 mg/ml in drinking water starting at 5 weeks of age), (6) PD + SBE, (7) RA + SBE, and (8) RA + PD + SBE. Mice were sacrificed at 13 weeks of age, and alveolar bone resorption, periodontal tissue inflammation, and paw joint inflammation were assessed by histology and immunohistochemistry. ResultsMice in the RA + PD group exhibited significantly higher inflammation scores in the joint tissues as well as more abundant IL-17-positive cells and cathepsin K-positive osteoclasts in the radial bone compared with the RA mice. Alveolar bone resorption was also significantly more severe in the RA + PD mice than in the PD mice. SBE treatment significantly improved all bone resorption and tissue inflammation scores in mice with RA + PD. ConclusionConcomitant RA and PD exacerbates the tissue destruction symptomatic of each condition. SBE suppresses all parameters evaluated, suggesting that it is has anti-inflammatory activities in both RA and PD.