Osteocyte death during orthodontic tooth movement in mice.
OBJECTIVE
To investigate the time course of osteocyte death in a mouse model of orthodontic tooth movement (OTM) and its association to the caspase-3 activation pathway and osteoclast formation.


METHODS
Twenty-five male wild type CD-1 mice (8-12 weeks old) were loaded with an orthodontic appliance. A spring delivering 10-12 g of force was placed between the right first molar and the incisor to displace the first molar mesially. The contralateral unloaded sides served as the control. The animals were equally divided into five different time points: 6, 12, 24, and 72 hours and 7 days of orthodontic loading. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, caspase-3 immunostaining, and tartrate-resistant acid phosphatase (TRAP) staining was performed on histologic sections of the first molars. The labeling was quantified in osteocytes on the compression side of the alveolar bone at each time point.


RESULTS
TUNEL labeling significantly increased at 12, 24, and 72 hours after orthodontic loading; the peak was observed at 24 hours. Elevated caspase-3 labeling was noted at 12, 24, and 72 hours and 7 days after loading, although the increase was not significant. Significant osteoclast formation was initially evident after 72 hours and progressively increased up to 7 days.


CONCLUSIONS
Osteocyte death during OTM peaks at 24 hours, earlier than initial osteoclast activation. However, only a slight trend for increased caspase-3 activity suggests that other mechanisms might be involved in osteocyte death during OTM.
a  Private Practice, Clinician, Manchester, NH.
Sogole
S
Moin
Zana
Z
Kalajzic
Achint
A
Utreja
Jun
J
Nihara
Sunil
S
Wadhwa
Flavio
F
Uribe
Ravindra
R
Nanda
D000135:Acid Phosphatase / Q000032:analysis; D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001696:Biomechanical Phenomena; D053148:Caspase 3 / Q000032:analysis; D002452:Cell Count; D016923:Cell Death / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D020287:In Situ Nick-End Labeling; D007527:Isoenzymes / Q000032:analysis; D008297:Male; D051379:Mice; D009969:Orthodontic Wires; D010010:Osteoclasts / Q000473:pathology; D010011:Osteocytes / Q000473:pathology*; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*
D007527:Isoenzymes; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase; C505409:Casp3 protein, mouse; D053148:Caspase 3
Apoptosis; Osteocyte; Tooth movement