TLR2 agonist prevents the progression of periapical lesions in mice by reducing osteoclast activity and regulating the frequency of Tregs

Aim To evaluate the role of regulatory T lymphocytes (Tregs) in the presence or absence of the synthetic ligand Pam3Cys during the progression of periapical lesion in wild‐type (WT) and toll‐like receptor 2 knockout (TLR2KO) mice. Methodology. A total of 130 C57BL/6 male WT and TLR2KO mice were allocated into control (n = 5) and experimental (periapical lesion induction) (n = 10) groups. In specific groups (WT+Pam3cys and TLR2KO+Pam3cys), the synthetic ligand Pam3cys was administered intraperitoneally every 7 days, according to the experimental period (14, 21 and 42 days). At the end of those periods, the animals were euthanized, and the mandible and the spleen were submitted to histotechnical processing. Mandible histological sections were analysed by haematoxylin and eosin, TRAP histoenzymology and immunohistochemistry (FOXP3, RANK, RANKL and OPG). Spleen sections were analysed by immunohistochemistry (FOXP3). Results The inflammatory infiltrate and bone resorption were more intense in the TLR2KO group compared to the WT group. The animals that received the Pam3cys had smaller periapical lesions when compared to the animals that did not receive the ligand (p