Epithelial to mesenchymal transition in drug induced gingival overgrowth and CCN2CTGF regulation of collagen deposition in human gingival fibroblasts
Date
2010
DOI
Authors
Sume, Siddika Selva
Version
OA Version
Citation
Abstract
Epithelial to mesenchymal transition (EMT) is a process, which normally occurs during development. EMT has been associated with various pathological conditions such as cancer and fibrosis during later stages of life. This project has been primarily focused on investigating the hypothesis that EMT could contribute to the development of fibrotic changes in gingival overgrowth due to various types of medications such as phenytoin, nifedipine & cyclosporine A. The results demonstrate that phenytoin-induced human gingival overgrowth tissues, the most fibrotic drug-induced form of gingival enlargement showed diminished epithelial E-cadherin expression, and increased FSP-1 and αvβ6 integrin levels. In connective tissue stroma, fibronectin and fibronectin ED-A levels were increased. TGF-β1 treatment of primary human gingival epithelial cells cultured in transwell plates resulted in inhibited barrier function as determined by reduced electrical resistance, paracellular permeability assays and cell surface E-cadherin expression. TGF-β1 increased the expression of other markers of EMT at the mRNA and protein levels: SLUG, MTl-MMP, MMP2, MMP9 and MMP13. Similar to phenytoin-induced gingival overgrowth, nifedipine- and cyclosporine A-induced gingival overgrowth tissues expressed diminished E-cadherin- and higher FSP-1 and fibronectin ED-A compared to non-overgrowth gingival samples while αvβ6 levels were similar. Overall, in vitro data suggested that human gingival epithelial cells undergo functional and gene expression changes consistent with EMT in response to TGF- β1, while in vivo studies showed that important EMT markers were expressed in clinical gingival overgrowth tissues. These findings support the hypothesis that EMT occurs in drug induced gingival overgrowth. Meanwhile, previous work has shown that CCN2/CTGF was highly expressed in phenytoin-induced gingival overgrowth tissues. In our study, CCN2/CTGF treatment of human primary gingival epithelial cells showed increased paracellular permeability at lower concentrations of CCN2/CTGF, which suggested that CCN2/CTGF could induce EMT. CCN2/CTGF further induces collagen deposition in gingival fibroblasts. Increased phosphorylation of JNK MAP Kinase in response to CCN2/CTGF treatment also suggests a role for JNK MAP Kinase in CCN2/CTGF regulation of matrix deposition in gingival fibroblasts. Finally, we have developed a mouse model for gingival fibrosis. In this model, preliminary data suggested that CCN2/CTGF was increased and E-cadherin levels were decreased in response to phenytoin injection. These findings were consistent with human data. Macroscopic and histomorphometric analyses of mouse tissue sections indicated a trend towards EMT. In summary, mechanism mediated by CCN2/CTGF may be a two-step process during which CCN2/CTGF first stimulate collagen deposition and second, CCN2/CTGF may induce EMT.
Description
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.
Dissertation (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2010 (Department of Periodontology and Oral Biology).
Includes bibliography: leaves 157-177.
Dissertation (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2010 (Department of Periodontology and Oral Biology).
Includes bibliography: leaves 157-177.
License
This work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.