Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/11242
Epithelial-to-mesenchymal transition in human lung epithelial cells
Bandvefsumbreyting í mennskum lungnaþekjufrumum
Idiopathic pulmonary fibrosis (IPF) is a severe lung disease with high morbidity and mortality. The cellular source of IPF is currently unknown but one suggested source is epithelial-to-mesenchymal transition (EMT). EMT is a well defined process in embryonic development and is absolutely essential for the formation of branching organs where epithelial cells must migrate into the surrounding stroma. EMT has also been related to various pathological situations such as invasive and metastatic cancer growth. The connection of EMT to IPF has only recently been suggested and further studies are needed to confirm the different cellular processes in this disease.
The aim of this study was to evaluate the phenotype of normal lung tissue, tissue from patients suffering from IPF and the plasticity of lung epithelial cells in culture, emphasizing their ability to undergo EMT.
In this study, lung samples from patients with IPF were compared to normal reference samples. Marked increase in both Vimentin and CK14 expression was observed in epithelium adjacent to fibrotic areas (fibroblastic foci). This could indicate that cells within the epithelium have undergone partial EMT and might somehow be contributing to the fibrotic conditions in IPF.
To support these in situ studies experiments were also conducted on an immortalized human bronchial epithelial cell line, referred to as VA10. VA10 cells were treated with the serum substitute Ultroser G. After treatment, morphological changes were observed in a subset of cells. These cells lose their epithelial phenotype and become elongated and mesenchymal-like. The cells also lose expression of known epithelial surface markers and gain a more mesenchymal expression profile. After sorting, these mesenchymal-like cells can no longer undergo branching morphogenesis, one of the characteristics of the original VA10 cell line. Additionally, these cells show increased potential for migration and anchorage independent growth further confirming their mesenchymal traits. To further confirm that this change in morphology and marker expression was, in fact, caused by EMT the expression of microRNA 200c was assessed. The expression of miR200c has been shown to be down regulated in cells that have undergone EMT and it is also downregulated in mesenchymal-like VA10 cells.
In order to be able to analyze whether primary bronchial cells could undergo EMT when treated with Ultroser G protocols for the isolation and culture of primary bronchial cells from fresh lung tissue were established. Initial studies indicate that primary cells are not as prone to EMT as our cell line model. This indicates that normal primary cells do not exhibit the same level of plasticity as an immortalized cell line.
This study indicates that IPF is partly caused by EMT in pulmonary epithelial cells. It is, however, necessary to properly evaluate the involvement of EMT in IPF by analyzing more IPF patient samples. Additionally, it is very important to determine what factors within Ultroser G are responsible for EMT induction in VA10 cells.