The Significance Of Epithelial-Mesenchymal Transition Of Alveolar Apithelial Cells Induced By TGF-β1 To Pulmonary Fibrosis

Objective:By inducing epithelial-mesenchymal transition (EMT) of A549 cells in vitro with transforming growth factorβ1 (TGF-β1), to investigate the significance of signalling pathway of EMT to the mechanisms underlying pulmonary fibrosis.Methods:A549 cells cultured in vitro were treated by TGF-β1 in a final concentration of 5ng/ml,then harvested at different time points to assay the mRNA expression of the markers of epithelial cell and mesenchymal cell by Real-time PCR at Oh,1h,3h,6h,12h and 24 h; protein expression of the markers of epithelial cell and mesenchymal cell by Western blot Oh,3h,6h,12h,24h,48h and 72 h,to assay the protein expression of signal transducer P-Smad 2/3,Snail1 and Snail2 by Western blot at 0h,24h,48h. Cellular morphology changes were observed by phase-contrast microscope before and after A549 cells being treated by TGF-β1, and were recorded by photograph at 0h,24h,48h.Results:After A549 cells being treated by TGF-β1 in a final concentration of 5ng/ml,mRNA and protein expression of epithelial markers were down-regulated (P＜0.05)along with time prolongation, and that of mesenchymocyte markers up-regulated (P＜0.05). Signal transducers P-Smad 2/3,Snail1 were also up-regulated (P＜0.05),with a weak expression of snail2 (P＞0.05). A549 cells were observed by inverted phase contrast microscope to turn from pebble shape to Fusiform shape,a myofibroblast-like morphology.Conclusions:TGF-β1 could induce EMT of alveolar epithelial cells in vitro,associated with signal transduction pathway Smad 2/3 and Snail1. All that suggested EMT of alveolar epithelial cells might be fundamental mechanism of pulmonary fibrosis and pathway Smad 2/3 and Snail1 might be the key points. Pulmonary fibrosis could be urged to onset by induceing or promoting EMT of alveolar epithelial cells,and be expected to be cured by blocking the process of EMT and its signalling pathways.