Investigating the effect of the Toll-like receptor-4 inhibitor TAK-242 on alveolar bone resorption in severe periodontitis in rats

Abstract

Objective The goal of this study was to investigate the effect of the Toll-like receptor-4 (TLR-4) inhibitor TAK-242 on bone resorption in severe periodontitis in rats in order to provide an experimental basis for finding new adjuvant treatments for severe periodontitis.Methods Eighteen three-week-old male Wistar rats were randomly divided into three groups (n=6). One group was the control group, and the other two groups were modelled with severe periodontitis in bilateral maxillary molars ligated with 5-0 silk thread containing P. gingivalis ATCC33277 (periodontitis and TAK-242 groups, respectively). The TAK-242 group was injected with TAK-242 (2 mg/kg) in DMSO every other day through the tail vein from the first day of silk ligation, and the other two groups were injected with DMSO solvent at the same proportion of body weight for 8 consecutive weeks. At the end of the 8th week, rats in the 3 groups were sacrificed, and maxillary specimens were taken. Three-dimensional reconstruction was achieved after micro-CT scanning to measure the distance between the enamel cementum boundary and alveolar crest at specific sites to assess the amount of bone loss. The parameters related to alveolar bone and bone microstructure were analyzed, and the pathological changes of periodontal tissue were observed by hematoxylin-eosin (HE) staining. Alveolar bone resorption was observed by Methyl Green staining, and the distribution of osteoclasts was observed by anti-tartrate acid phosphatase double staining (TRAP).Results Micro-CT quantitative analysis showed that alveolar bone resorption in the periodontitis group and TAK-242 group was significantly higher than that in the control group. Compared with the periodontitis group, bone loss of the mesial and distal root resorption sites of maxillary first molars was significantly reduced in the TAK-242 group (P < 0.001), the bone mineral density (P < 0.05) and bone volume/total volume fraction (P < 0.01) were significantly increased, and the number of trabeculae and the trabeculae thickness (P < 0.01) were relatively increased. The trabecular separation (P < 0.01) and trabecular structure model index were significantly decreased. In the periodontitis group, the bone exhibited a sparse and porous honeycomb structure, with deterioration of the trabecular structure and a shift towards a rod-strength structure. In the TAK-242 group, the bone microstructure was improved, the bone volume was enriched, the distribution of trabeculae was relatively denser and the trabecular structure shared more similarities with the control group. HE staining displayed that the attachment loss and bone absorption were significantly higher in the periodontitis group and TAK-242 group than in the control group. Compared with the periodontitis group, MG staining displayed significantly alleviated bone absorption in the TAK-242 group. TRAP staining showed that osteoclast infiltration decreased in the TAK-242 group compared with the periodontitis group (P < 0.001).Conclusions The TLR-4 inhibitor TAK-242 can alleviate bone resorption in severe periodontitis and improve the porous, sparse and disorganized inflammatory bone trabecular structure in rats.

Keywords

• severe periodontitis，
• toll like receptor-4，
• alveolar bone，
• inflammatory bone resorption，
• micro-ct，
• bone microstructure，
• tak-242，
• bone volume/total volume fraction，
• the number of trabeculae，
• trabeculae thickness，
• trabecular separation，
• rod structure，