Treatment effect of Low Intensity Pulsed Ultrasound either alone, with functional appliance and with gene therapy on the mandibular condylar growth

  • Author / Creator
    Kaur, Harmanpreet
  • The aim of this thesis was to investigate the effect of Low intensity pulsed ultrasound (LIPUS) with or without the use of forward bite jumping appliance, also known as functional appliance (FA) on the mandibular condylar growth in the rat model and also to investigate the biological effect on MC 3T3E1 pre-osteoblast and C28/I2 chondrocyte cell lines. In addition, we need to explore the effect of LIPUS and local injection of gene therapy on the mandibular condylar growth. In the animal study, fifty four Sprague-Dawley (SD) rats were divided into six groups (n=9) namely: control, LIPUS 20 minutes, LIPUS 40 minutes, Functional Appliance (FA), FA + LIPUS 20 minutes and FA + LIPUS 40 minutes. Right mandibular condyle was used as the experimental side and the left mandibular condyle was the internal control. After 4 weeks, the mandibles were evaluated for morphometric analysis while the condylar heads were evaluated using Micro-CT, histomorphometric and immunohistochemistry analyses. 20 minutes LIPUS application either alone or in combination with FA showed a significant increase in mandibular condylar length, increased cell number and layer width of proliferative and hypertrophic layers along with increased protein expression of SOX9, Collagen II, Collagen X and Aggrecan in the mandible condyle. Also, Micro-CT analysis demonstrated a significant increase in bone micro-architecture and bone mineral density. We hypothesized that LIPUS application leads to reactive oxygen species (ROS) generation which is involved in mitogen-activated protein kinases (MAPKs) activation. C28/I2 chondrocyte and MC 3T3E1 pre-osteoblast cell lines were stimulated with one time LIPUS application for either 10 minutes or 20 minutes; control groups were treated with sham transducers. For ROS inhibition, diphenylene iodonium was added to the culture medium before LIPUS application. In C28/I2 chondrocytes, LIPUS showed a significant increase in ROS generation, ERK1/2 activation as well as increased gene expressions of SOX9, COL2A1, and ACAN while the effect was reversed in ROS inhibition. On the contrary, in MC 3T3E1 pre-osteoblasts, LIPUS increased ERK1/2 activation and increased gene expressions of RUNX2, OCN, and OPN in ROS inhibition. In both the cell lines, the amount of ROS generated was non-toxic. Gene therapy is rapidly growing treatment modality in the field of tissue engineering and bone regeneration. We conducted a pilot study to investigate the effect of LIPUS with non-viral gene delivery of basic fibroblast growth factor (bFGF). Fifteen SD rats were divided into 5 groups (n=3): control, gWiz, bFGF plasmid- polyethyleneimine- linoleic acid (bFGF-PEI-LA), LIPUS 20 minutes and bFGF-PEI-LA + LIPUS 20 minutes. The plasmid-polymer complex was injected on the left side of the mandible condyle on the first day of the experiment and LIPUS was applied for 20 minutes for next 4 weeks. After 4 weeks, the mandibles were analyzed for morphometric, histomorphometric and Micro-CT analyses. There was a significant increase in mandibular condyle length in either bFGF-PEI-LA or LIPUS alone groups while the combination group showed an increase in bone volume fraction. Collectively, these results are indicative of the distinct anabolic effect of LIPUS application that enhances the mandibular condylar growth.

  • Subjects / Keywords
  • Graduation date
    Fall 2016
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.