Three-Dimensional Micro-Computed Tomography Analyses of Induced Periapical Lesions in Transgenic Mice

The aim of this study was to evaluate the three-dimensional (3D) parameters given by the micro-computed tomography (µCT) analysis of experimentally induced periapical lesions in wild type (WT) and knockout mice for the interleukin 22 (IL-22 KO). Periapical lesions were induced in the mandibular first molars of wild type and IL-22 KO mice (n = 12 teeth/group). The animals were euthanized after the experimental periods of 7, 21 and 42 days. The mandibles were removed and exposed to µCT scanning. The analyses were performed by the CTAn software for the tree-dimensional parameters: Tissue Volume (TV), Lesion Volume (LV), Tissue Surface (TS), Lesion Surface (LS), Intersection Surface (IS), and Trabecular Pattern factor (Tb.Pf). After that, the tissue was subjected to routine histologic procedures and to immunohistochemistry analysis. Statistical analysis was performed in the GraphPad software. A t-test was used to compare the differences between the groups with significance level of 5%. The evaluation of the 3D parameters showed statistical significant difference between the groups only at the latest period of periapical lesion development (42 days), for the TV, LV, TS, LS and IS parameters. The immunohistochemistry evaluation confirmed the immunostaining for IL-22 only in the WT mice, surrounding the periapical lesion. There were no differences regarding the trabecular alveolar bone (Tb.Pf) that could influence the lesion development. In conclusion, the 3D parameters showed that the absence of IL-22 leads to detectable differences at 42 days of lesion progression, resulting in smaller periapical lesions.