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Introduction The purpose of this study was to evaluate a protocol for systemic administration of rosiglitazone in mice in order to stimulate apoptosis of osteocytes in the jaws and to evaluate the effect of osteocyte apoptosis induced by rosiglitazone in the progression of periapical lesions in mice at 7, 21, and 42 days. Methods C57BL/6 mice at 4–5 weeks of age were used. In phase 1, mice ( n = 24) were treated with rosiglitazone (gavage, 10 mg/kg dose) or without (phosphate-buffered saline + 10% dimethyl sulfoxide) for 1, 2, or 3 weeks. We used the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and 4′-6-diamidino-2-phenylindole methods for quantification of apoptotic cells. In phase 2, mice ( n = 30) received rosiglitazone for 2 weeks or just vehicle for 1 week ( n = 30), and periapical lesions were induced for 7, 21, or 42 days. We performed the measurement of periapical lesions, tartrate-resistant acid phosphatase staining, dual-energy x-ray absorptiometry for the evaluation of bone mineral density (BMD) in long bone, and gene evaluation using real time quantitative polymerase chain reaction of osteocyte markers ( Sost , Hyou1 , and Dmp1 ) and receptor activator of nuclear factor kappa-B ligand (RANKL) ( Tnfsf11 ). Results It was observed that systemic administration of rosiglitazone for 2 weeks showed apoptosis of osteocytes in a more expressive manner. In phase 2, in the groups that received rosiglitazone, a trend toward larger periapical lesions was observed ( P > .05). Rosiglitazone also induced a greater number of osteoclasts and a greater expression of Sost and Hyou1 at 21 days of lesions. Moreover, there were no statistically significant differences in RANKL and Dmp1 expression or in the BMD of femurs. Conclusions Rosiglitazone stimulated apoptosis of osteocytes, interfering in the progression of periapical lesions in mice. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The aim of this study was to characterize the formation and progression of experimentally induced periapical lesions in TLR2 knockout (TLR2 KO) mice. Methods: Periapical lesions were induced in molars of 28 wild type (WT) and 27 TLR2 KO mice. After 7, 21, and 42 days, the animals were euthanized, and the mandibles were subjected to histotechnical processing. Hematoxylin-eosin–stained sections were examined under conventional light microscopy for the description of pulpal, apical, and periapical features and under fluorescence microscopy for the determination of the periapical lesion size. The subsequent sections were evaluated by tartrate resistant acid phosphatase histoenzymology (osteoclasts), Brown and Brenn staining (bacteria), and immunohistochemistry (RANK, RANKL, and OPG). Data were analyzed by the Mann-Whitney U and Kruskal-Wallis tests (α = 0.05). Results: The WT group showed significant differences (P < .05) in the periapical lesion size and the osteoclast number between 7 and 42 days and between 21 and 42 days. In the TLR2 KO group, significant differences (P < .05) in the periapical lesion size and the osteoclast number were found between 7 days and the other periods. There was a significant difference (P < .05) between the 2 types of animal regarding the periapical lesion size, which was larger in the TLR2 KO animals. No significant differences (P > .05) were found between WT and TLR2 KO mice related to the pulpal, apical, and periapical features; bacteria localization; and immunohistochemical results (except for RANK expression). Conclusions: TLR2 KO animals developed larger periapical lesions with a greater number of osteoclasts, indicating the important role of this receptor in the host''s immune and inflammatory response to root canal and periradicular infection. [Copyright &y& Elsevier]