Bones, teeth, and genes: a genomic homage to Harry Sicher's "Axial Movement of Teeth".
OBJECTIVE
The model of the unopposed rodent molar was used to study the morphologic and genetic mechanisms of tooth eruption.


METHODS
Left maxillary molar teeth of 12-day-old Swiss-Webster mice were extracted under anesthesia, and mandibular molars were allowed to supererupt. To trace areas of tissue remodeling and to determine areas of new tissue formation, mice were injected with fluorescent dyes, tetracycline, alizarin red, and calcein blue. Subsequent to sacrifice, mandibular tissue blocks were prepared for ultrathin ground sections, fluorescent microscopy, and von Kossa's mineral detection procedure. A second set of specimens was prepared for RNA extraction and microarray analysis.


RESULTS
The data established significant eruption of first and second mandibular mouse molars 12 days after complete extraction of antagonists, exceeding the control side by 0.13 mm. Labeled tissue sections revealed significant amounts of new bone and cementum apposition on the unopposed side compared to the control side, as revealed by fluorescent markers and ultrathin ground sections. Microarray transcript level comparisons between the experimental and the control groups demonstrated significant (more than twofold) increase in gene expression of elastin and tenascin C extracellular matrix proteins; brevican, lumican, and biglycan proteoglycans; as well as fibroblast growth factor 9.


CONCLUSIONS
In this study, the authors have established the unopposed mouse molar as a model to study tissue dynamics during the axial movement of teeth. The data indicated significant new formation of bone and cementum in tandem with increased expression of extracellular matrix-related genes.
Holliday
Sean
S
Department of Orthodontics , University of Illinois at Chicago, College of Dentistry, Chicago, Illinois 60612, USA.
Schneider
Bernard
B
Galang
Maria Therese
MT
Fukui
Tadayoshi
T
Yamane
Akira
A
Luan
Xianghong
X
Diekwisch
Thomas G H
TG
D000818:Animals; D058578:Biglycan; D016723:Bone Remodeling / Q000235:genetics; D058581:Brevican; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis; D003739:Dental Cementum / Q000502:physiology; D004549:Elastin / Q000032:analysis; D016326:Extracellular Matrix Proteins; D051525:Fibroblast Growth Factor 9; D005346:Fibroblast Growth Factors / Q000032:analysis; D005456:Fluorescent Dyes; D005786:Gene Expression Regulation; D007632:Keratan Sulfate / Q000032:analysis; D037181:Lectins, C-Type; D000071234:Lumican; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology; D051379:Mice; D008963:Molar / Q000033:anatomy & histology / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000032:analysis; D010012:Osteogenesis / Q000235:genetics; D011509:Proteoglycans / Q000032:analysis; D012313:RNA / Q000032:analysis; D019063:Tenascin / Q000032:analysis; D014078:Tooth Eruption / Q000235:genetics*
C553057:Bcan protein, mouse; C546885:Bgn protein, mouse; D058578:Biglycan; D058581:Brevican; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; C496460:Fgf9 protein, mouse; D051525:Fibroblast Growth Factor 9; D005456:Fluorescent Dyes; D037181:Lectins, C-Type; C000604307:Lum protein, mouse; D000071234:Lumican; D009419:Nerve Tissue Proteins; D011509:Proteoglycans; D019063:Tenascin; D005346:Fibroblast Growth Factors; D012313:RNA; D004549:Elastin; D007632:Keratan Sulfate