Immunohistochemical Analysis to Evaluate the Efficacy of Tetracycline‐Loaded Nano‐Chitosan in Treating Periodontitis Induced by <i>Porphyromonas gingivalis</i> in Albino Rats

<b>Aim:</b> In this study, we examined the efficacy of tetracycline (TC) loaded on nano-chitosan in alleviating <i>Porphyromonas gingivalis</i>-induced periodontitis in albino rats. The location of the proinflammatory cytokine interleukin-1beta (IL-1β) was examined via immunohistochemistry. <b>Methods:</b> Mature Wistar albino rats (<i>n</i> = 30; 150-180 g) were used in this study. The samples were split into five equal groups at random. The rats in all groups were subjected to antibiotics (for 3 days) in drinking water 1 week before the experiment started. Group I, which served as a control group, consisted of six albino rats. All groups except the control group were subjected to <i>P. gingivalis</i> injection by micro-pipetting 3 days weekly after ligation of the upper first molar (M1) for 4 weeks. Group II consisted of six rats that were injected with <i>P. gingivalis</i> twice weekly for 30 days. Six rats were assigned to Group III and subjected to the same treatments as those in Group II. However, in Group III, the infected regions were also injected with diluted TC powder daily for 2 weeks. Group IV was subjected to the same procedure as Group II before daily injections of nano-chitosan at the injection sites for 2 weeks. Group V consisted of six rats; once daily, they were administered localized injections of TC loaded on nano-chitosan for 2 weeks after the same procedure as Group II. After the rats were anesthetized, the maxilla, including the teeth and surrounding alveolar bone, was dissected. Light microscopy was performed for histological and immunohistochemical examinations of the biopsies. To check the normal distribution of samples Shapiro-Wilk test was performed, to determine the differences between the groups one-way analysis of variance (ANOVA) test was used, and to compare the groups pairwise, a Bonferroni post hoc correction was carried out. The results were statistically significant when <i>p</i> ≤ 0.05. <b>Results:</b> Histological examination revealed that the periodontal tissues in Group I were normal. An increase in inflammatory cells (plasma cells, lymphocytes, and macrophages) was found in Group II, with alveolar bone resorption. A decrease in the number of dilated blood vessels and resorption areas was found in Group III. Inflammation and resorption in alveolar bone persisted in Group IV. In Group V, few dilated blood vessels were observed, with a decrease in inflammatory cells and alveolar bone deposition. Immunohistochemical examination revealed a significant difference in the level of IL-1β in the periodontal ligaments and alveolar bone between the negative control group and all other groups; however, the level of IL-1β in the alveolar bone was not significantly different between Groups II, III, and IV, whereas a significant difference in the level of IL-1β was detected between the different groups of periodontal ligaments. <b>Conclusion:</b> Nano-chitosan may combat increasing TC resistance, with a noticeable enhancing effect on periodontal tissues infected with <i>P. gingivalis</i>.