Mechanical stress has been shown to play a role in bone remodelling during orthodontic tooth movement. Receptor activator of nuclear factor kβ - ligand (RANKL), osteoprotegerin (OPG), monocyte colony stimulating factor (M-CSF) and interleukin 1-β (IL-1β) play key roles in the regulation of bone remodelling, but the role of these cytokines in orthodontic tooth movement is poorly understood.
Aim: The aim of this experiment was to examine the response of periodontal ligament (PDL) fibroblasts in monolayer culture to intermittent tensile stress as regards RANKL, OPG, M-CSF and IL-1β production.
Methods: Human PDL fibroblasts were dissected from premolars extracted for orthodontic purposes. Explants were seeded out in 1cm wells and grown to confluence in Dulbecco�s modification of Eagle�s medium, containing 10% foetal calf serum and antibiotics, at 37�C in a humidified atmosphere of 5% CO₂/95% air. Upon reaching confluence, the cells were passaged into sequentially larger flasks. Fibroblasts were passaged 6 times. After reaching confluence in T175 flasks, the cells were detached and plated at a cell density of 10⁵/dish in 35mm Bioflex� Plates coated with type 1 collagen. The cells were placed under a continuous uni-axial strain of 12% for 6s of every 90s by a Flexercell FX 4000C[TM] for 0, 12, 24 and 48 hours. Cells were then detached and stored in RNAlater. Quantitative RT-PCR was used to determine the mRNA of the cytokines of interest.
Results: Tensile force led to the down regulation of mRNA expression for OPG and IL-1β at 12 and 24 hours respectively, while M-CSF was up-regulated at 6 hours. RANKL was not detected at a significant level for quantification.
Conclusion: This osteoclastic-type response indicates the complexity of mechanotransduction in an in vitro setting.
Acknowledgments: This research was supported by the New Zealand Dental Research Foundation, the New Zealand Lottery Grants Board and the New Zealand Association of Orthodontists.
| Identifer | oai:union.ndltd.org:ADTP/217775 |
| Date | January 2007 |
| Creators | Gaffey, Benjamin James, 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 Benjamin James Gaffey |
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