Molecular markers of early orthodontic tooth movement.
OBJECTIVE
To understand the molecular basis of early orthodontic tooth movement by looking at the expression of KI-67, runt-related transcription factor 2 (Runx2), and tumor necrosis factor ligand superfamily member 11 (RANKL) proteins.


METHODS
We employed a rat model of early orthodontic tooth movement using a split-mouth design (where contralateral side serves as a control) and performed immunohistochemical staining to map the spatial expression patterns of three proteins at 3 and 24 hours after appliance insertion.


RESULTS
We observed increased expression of KI-67, a proliferation marker, and RANKL, a molecule associated with osteoclastic differentiation, in the compression sites of the periodontal ligament subjected to 3 hours of force. In contrast, there was increased expression of KI-67 and Runx2, a marker of osteoblast precursors, in tension areas after 24 hours of force. Decreased KI-67 expression in the mesial and distal regions of the periodontal ligament was observed at the midpoint of the tooth root.


CONCLUSIONS
The early RANKL expression indicates that at this early stage cells are involved in osteoclast precursor signaling. Also, decreased KI-67 expression found near the midpoint of the tooth root is believed to represent the center of rotation, providing a molecular means of visualizing mechanical loading patterns.
Orthodontic Department, Faculty of Dentistry, University of Toronto, Toronto, Canada.
Patricia Joyce
PJ
Brooks
Dorrin
D
Nilforoushan
Morris Frank
MF
Manolson
Craig A
CA
Simmons
Siew-Ging
SG
Gong
D000135:Acid Phosphatase / Q000032:analysis; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002454:Cell Differentiation; D049109:Cell Proliferation; D050659:Core Binding Factor Alpha 1 Subunit / Q000032:analysis*; D007527:Isoenzymes / Q000032:analysis; D019394:Ki-67 Antigen / Q000032:analysis*; D008297:Male; D023421:Models, Animal; D008963:Molar / Q000473:pathology; D010006:Osteoblasts / Q000473:pathology; D010010:Osteoclasts / Q000473:pathology; D010513:Periodontal Ligament / Q000473:pathology; D053245:RANK Ligand / Q000032:analysis*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012399:Rotation; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors; D014087:Tooth Movement Techniques; D014092:Tooth Root / Q000473:pathology
D015415:Biomarkers; D050659:Core Binding Factor Alpha 1 Subunit; D007527:Isoenzymes; D019394:Ki-67 Antigen; D053245:RANK Ligand; C493717:Runx2 protein, rat; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase