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Title: Increased senescence and altered ECM remodelling in oral submucous fibrosis
Author: Pitiyage, Gayani
ISNI:       0000 0004 2684 8181
Awarding Body: Queen Mary, University of London
Current Institution: Queen Mary, University of London
Date of Award: 2010
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Background: Oral submucous fibrosis (OSMF) is a pre-neoplastic condition, causally linked to areca nut consumption, the pathogenesis of which is poorly understood. TGF-β and disturbances in the balance between MMPs and TIMPs have been implicated in increased collagen deposition and fibrosis but no previous study has addressed the role of mesenchymal senescence in OSMF. Materials & Methods: Senescence and its secretome, DNA damage, oxidative damage, ROS production and mitochondrial damage were studied in OSMF in vivo and in vitro using ELISA, immunofluorescence, western blot and FACS techniques. Results: Senescent cells increased in all OSMF samples (1.9±0.3; p=0.004) peaking when dysplasia was present in the OSMF epithelium. There was increased oxidative damage (6.7±1.8; p=0.004); elevated DSBs (10.4±1.1; p=0.004) and P16ink4a accumulation (4.2±1.7; p=0.004). The results were similar in vitro. The OSMF fibroblasts demonstrated a reduced replicative lifespan (MPD-22±7.2; p=0.0001), despite having normal telomere lengths and in vivo growth rates. However, the OSMF fibroblasts showed increased ROS production and increased mitochondrial density and hyperpolarization, suggesting mitochondrial damage. The antioxidant, N-tert-Butyl-α- phenylnitrone (PBN) reduced the frequency of senescent fibroblasts and their associated markers in both OSMF and the control cultures. The mild uncoupling of mitochondrial oxidative phosphorylation from ROS generation with dinitrophenol (DNP) gave similar results. Cytokine profiles from cells obtained from OSMF showed a significant elevation of TIMP-1 (2217.4±406.5; p=0.003) and TIMP-2 (1763.2+/-363.7 pg/ml; p=0.004) production as compared to normal. The levels of MMP-1 (7.0±2.2 ng/ml; p=0.30), MMP-2 (157.8±91.3 ng/ml; p=0.75) and TGF-β1 (389.5±250.6 ng/ml; p=0.22) were not different to the normal and non-diseased controls (ND) collagen production was not elevated in OSMF in vitro (20.6±4.4 μg/ml; p=0.22). 3 Conclusion: Senescence, DNA damage, oxidative damage and P16inka accumulation are associated with neoplastic progression of OSMF. Elevated TIMP levels did not result in increased collagen secretion but may be an early marker of fibroblast aging and senescence.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Dentistry