Date of Award
Summer 2016
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Dentistry
First Advisor
Liu, Dawei
Second Advisor
Makky, Khadijah
Third Advisor
Bradley, Thomas G.
Abstract
Introduction: Inflammation is the biological basis of temporomandibular joint disorders (TMD), when severe it can lead to osteoarthritis. One of the physical therapies used to manage this condition is mechanical vibration, as has been used in medicine for many years as a non-pharmacological therapy. Recently an FDA approved dental device called AcceleDent has been introduced to increase the rate of tooth movement and decrease pain. As the device-generated vibration transmits to the TMJ, it is important for us to investigate whether mechanical vibration influences TMJ on its biologic basis – chondrocytes under normal and inflammatory conditions. Materials and Methods: Human chondrocyte cell line C-28/I2 cells were maintained in DMEM supplemented with 10% FBS. The cells were plated at a density of 5x105/well to 24-well plates for differentiation or 6-well plates for gene expression studies. For differentiation study, the cells were assigned to 4 subgroups i.e. osteogenic, normal, osteogenic + IL-1β (1ng/mL), and normal + IL-1β (1ng/mL) and subjected to vibration of 0 Hz (control) or 0.3g/30Hz. The vibration was applied for 1 hour per day for 21 consecutive days with medium refreshed every 3 days, followed by Alizarin Red staining. For gene expression study, the cells were subjected to vibration of 0 Hz (control) or 0.3g/30Hz with or without IL-1β (10ng/mL) for 1 hour, followed by quantitative Polymerized Chain Reaction (qPCR) to evaluate gene expression levels of SOX9 and MMP13 genes. One-way ANOVA was used to statistically test the difference between experimental groups (P ≤ 0.05 considered significant). Results: 0.3g/30Hz vibration exhibited a strong positive influence on the chondrocyte differentiation, while IL-1β showed a minimal effect. Vibration increased SOX9 mRNA expression by 1.28 fold when compared to controls. IL-1β decreased SOX9 mRNA expression by 0.65 fold which was partially recovered by the vibration to 0.83 fold. Vibration decreased MMP13 mRNA expression by 0.89 fold when compared to controls. IL-1β increased MMP13 mRNA expression by 1.44 fold, which was slightly recovered by the vibration to 1.30 fold. Conclusions: Mechanical vibration (0.3g/30Hz) is able to increase differentiation of human chondrocytes under normal and inflammatory conditions. Mechanical vibration anabolically regulates gene expressions of SOX9 (upregulated) and MMP13 (downregulated), and can partially recover the catabolic changes of SOX9 and MMP13 induced by inflammation. Mechanical vibration (0.3g/30Hz) does not appear to harm human chondrocytes in vitro and may help control or reduce inflammation.