Alterations of FOXO1 protein expression during orthodontic tooth movement in rats

Objective: To study alternations in forkhead box, class O1 (FOXO1) protein expression in the periodontal tissue of rats during orthodontic tooth movement (OTM). Methods: A total of 60 Sprague-Dawley (SD) rats were randomly and evenly divided into six groups: an untreated control group and 5 groups treated with applied orthodontic force for 1, 3, 7, 10, and 14 days. The left maxillary first molar was used for experimental treatment, whereas the right side remained untreated as an internal control. OTM was established and tissue samples were collected. Hematoxylin-eosin (HE) staining was used to observe cell morphology; tartrate resistant acid phosphatase (TRAP) staining, to determine the number of osteoclasts on the alveolar pressure side; and immunohistochemical analysis, to analyze the expression of FOXO1. Results: The movement of the maxillary first molar initially increased with 1-3 days of orthodontic force, followed by a flattening between 3 and 7 days and then a continuous, rapid increase between 7 and 14 days. The number of osteoclasts initially increased, peaking at the 7th day after the start of orthodontic force, and then slowly decreased. The average optical density of FOXO1-positive immunostaining was significantly different in the pressure zone at 1, 3 and 7 days, and in the tension zone at 1, 3, 7, 10 and 14 days from that of the internal control (all P < 0.05). Conclusion: The alternations of FOXO1expression might participant in the periodontal tissue remodeling during the OTM.