Periodontal disease development in the periodontitis and arthritis mouse models. (A) Alveolar bone evaluated at timeline day D73 by micro-computed tomography analysis for bone mineral content and tissue mineral content. Mice that received either Porphyromonas gingivalis (Pg), arthritis induction by complete Freund’s adjuvant (CFA)/collagen II (CII), arthritis induction by incomplete Freund’s adjuvant (IFA)/CII, or both P. gingivalis and arthritis induction had less alveolar bone compared with vehicle, representing increased bone loss. Data represented as mean ± standard error of the mean, n = 8/group, P <0.05, Dunn’s multiple comparison test. (B) Gingival tissues and submandibular lymph nodes evaluated for mRNA expression showed increased expression of RORγt, T-bet, GATA-3, and Foxp3 in mice that received all treatments (Student’s t test, *p≤0.05, **p≤0.01, ***p≤0.001). (C) Representative histological sagittal sections of the mesial region of M1 and the interproximal region between M1 and M2 stained with hematoxylin and eosin from mice in the vehicle group and mice that developed chronic periodontal disease. M1 and M2, molars 1 and 2; A, alveolar bone crest; yellow arrows, presence of a dense fibroblast population and disorganized tissue; red arrows, presence of blood vessels; blue arrows, irregular alveolar bone crest, indicating bone resorption.