Local and systemic characterization of inflammatory profile in long-term ligature-induced periodontitis and repair in rats

Aim: High heterogeneity in ligature and repair models might reflect different disease status and preclude comparisons. This study aimed to characterize time-dependent alveolar bone loss, histological changes, and immunoinflammatory profiles in rats during ligature-induced periodontitis progression and repair in the long term. Methods: Forty-eight male Wistar rats were included. The negative control group (n=8) received no ligature, while experimental groups (Ligature and Repair; n=40) received a cotton ligature around the lower first molars, bilaterally. After 7d (baseline), ligatures were either maintained or removed for another 28 or 56 days (n=8/group). Hemi-mandibles were collected for radiographic, histological and stereometric analyses. Serum and gingival tissues were collected for the analysis of inflammatory markers using multiplex. Results: Mean bone loss progressively increased in ligated rats (p<0.05). Ligature placement increased the percentage of inflammatory cells at all timepoints and blood vessels at 7 and 35 days, while reducing fibroblasts and extracellular matrix (p<0.05). After 56 days of ligature removal, radiographic bone loss increased compared to 28 days (p<0.05). Ligature removal significantly decreased the percentage of inflammatory cells and blood vessels, while increasing fibroblasts and extracellular matrix only at 56 days. Immunological assay revealed significant time-dependent alterations in serum and gingival markers during disease progression and repair. Conclusion: Ligatures led to cumulative alveolar bone loss and heightened pro-inflammatory cytokines, with distinct inflammatory profiles over time. During repair, despite reducing inflammatory cells and cytokines, bone loss increased in the long term. Our data can assist in designing future experiments and clarify previously published findings.