Cell Lineage Tracing of Osteoblasts Within the Periodontal Ligament During Orthodontic Tooth Movement

Abstract

Background: The periodontal ligament is known to play a role in the bone remodeling response to orthodontic tooth movement and to contribute specifically to osteogenic cell populations involved in this process. Cell lineage tracing is a technique which enables the tracking of specific cell populations throughout differentiation in vivo. 3.2kbCol1α1 is present in early osteoblastogenesis and can therefore be used to trace osteoblasts and similar related osteogenic cells. Purpose: The purpose of this study was to a) create a valid murine model of orthodontic tooth movement and, b) orthodontically treat temporally inducible cell lineage tracing mice to study osteoblasts response within the periodontal ligament. Materials and methods: 3.2Col1α1 mice were used in this study. Orthodontic appliances were bonded between the maxillary first molar and the maxillary incisors to induce mesial movement of the maxillary first molar. The mesial root of the maxillary first molar was used for evaluation in this study. 5 groups of mice were studied with 4 mice in each group; group 1: no induction, no orthodontic treatment; group 2: induction, no orthodontic treatment; group 3: induction, 1-day orthodontic treatment; group 4: induction, 2-day orthodontic treatment; group 5: induction, 4-day orthodontic treatment. Radiological analysis was performed. Angle of first molar was quantified to determine presence of tooth movement. Mean widths of periodontal ligament were compared. 3.2Col1α1 signal was characterized. H&E staining and anti-Ki67 and anti-CathepsinK immunofluorescent staining was performed. Results: Orthodontic treatment induced orthodontic tooth movement. 3.2kbCol1α1-positive cells were identified within the periodontium. The number of 3.2kbCol1α1- positive cells increased in response to orthodontic treatment. Ki67 expression was inversely related to length of orthodontic treatment. CathepsinK activity was inconclusive regarding the determination of a relationship between 3.2kbCol1α1-positive osteoblast patterning and osteoclast activity. Conclusions: 3.2kbCol1α1-positive cells are present in the periodontal ligament and increase in response to orthodontic tooth movement.