Background and objectives: The most widely accepted tooth movement model is defined by the pressure-tension hypothesis. An orthodontic force applied to a tooth generates areas of compression and tension in the periodontal ligament (PDL), which are transmitted to the alveolar bone. Areas of tissue exposed to tensile strain undergo bone deposition, whereas areas of tissue exposed to compressive strain undergo bone resorption. We propose that human PDL cells in monolayer culture exposed to tensile mechanical strain would express multiple genes involved in osteogenesis.
Materials and Methods: Human PDL cells were isolated and cultured from premolar teeth that were extracted for orthodontic reasons. These cells were plated on control and experimental Uniflex[TM] plates. Using a Flexercell FX4000 strain unit, PDL cells on experimental plates were exposed to a 12% uni-axial cyclic strain for 6 seconds out of every 90 seconds over a 24 hour period. RNA was extracted from the PDL cells at 6 hours, 12 hours and 24 hours. The differential expression of 78 genes implicated in osteoblast differentiation and bone metabolism was analysed using real-time reverse transcriptase polymerase chain reaction (RT-PCR) array technology.
Results: Of the 78 genes tested, sixteen genes showed statistically significant (p<0.05) changes in expression in response to the mechanical strain regime. Eight genes were up-regulated (ALPL, BMP2, BMP6, COL2A1, ICAM1, PHEX, SOX9, and VEGFA) and eight genes were down-regulated (ANXA5, BMP4, COL11A1, COL3A1, EGF, ITGB1, MSX and SMAD1).
Conclusions: This study has demonstrated that cultured human PDL cells express multiple osteogenic genes under tensile strain, which suggests that PDL cells may have a potential role in osseous remodeling during tooth movement.
Key Words: Tooth movement, human PDL cells, tensile mechanical strain, osteogenic genes, real-time RT-PCR array, and Flexercell FX4000.
| Identifer | oai:union.ndltd.org:ADTP/208003 |
| Date | January 2008 |
| Creators | Wescott, David Clark, n/a |
| Publisher | University of Otago. School of Dentistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright David Clark Wescott |
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