Expression of autophagy and apoptosis during orthodontic tooth movement alveolar bone remodeling in rats with varied periodontal conditions

Objective

Orthodontic treatment in periodontitis patients is challenging due to unpredictable bone remodeling and tissue damage. Therefore, this study aimed to investigate the effects of orthodontic force on periodontal ligament cell autophagy, apoptosis, and bone remodeling under various inflammatory states using a rat orthodontic tooth movement (OTM) model.

Material and methods

Seventy-five male Sprague – Dawley rats were used to establish OTM models for the periodontal health, active periodontitis, and stable periodontitis groups. Orthodontic force was applied at twelve weeks of age, with rats euthanized on days 0, 1, 3, 7, and 14 after force application. Microcomputed tomography quantified the OTM distance, alveolar bone crest resorption, and trabecular bone microarchitecture parameters. Immunohistochemistry and tartrate-resistant acid phosphatase staining evaluated the expression levels of inflammation, autophagy, apoptosis, osteogenesis, and osteoclast numbers in the periodontal ligament.

Results

The active periodontitis group exhibited the greatest OTM distance, alveolar bone resorption, and osteoclast activity, along with consistently high inflammatory factor expression. In this group, autophagy-related proteins increased on the tension side but decreased on the compression side, while apoptotic protein expression significantly rose. Osteokine levels were low, with an earlier peak decline observed in the active periodontitis group. The periodontal health group maintained high osteogenic activity, and the stable periodontitis group fell in between the two.

Conclusions

The inflammatory microenvironment in active periodontitis interacts with orthodontic force to disrupt the protective autophagy-apoptosis balance, coinciding with increased tissue destruction. Healthy, stable periodontium shows adaptive remodeling, emphasizing the importance of controlling inflammation before orthodontic treatment. This animal experimental procedure complies with the ARRIVE guidelines, and this research was approved by the Animal Ethics and Welfare Committee of the School of Stomatology, Capital Medical University (N^o̊ KQYY-202207-005).