TGF-β1 Induces Human Bronchial Epithelial Cell-to-Mesenchymal Transition in Vitro

Abstract

The subepithelial fibrosis component of airway remodeling in asthma is mediated through induction of transforming growth factor-beta1 (TGF-beta1) expression with consequent activation of myofibroblasts to produce extracellular matrix proteins. The number of myofibroblasts is increased in the asthmatic airway and is significantly correlated with the thickness of lamina reticularis. However, much is still unknown regarding the origin of bronchial myofibroblasts. Emerging evidence suggests that myofibroblasts can derive from epithelial cells by an epithelial-to-mesenchymal transition (EMT). In this study we investigated whether TGF-beta1 could induce bronchial epithelial EMT in the human bronchial epithelial cell. Cultured human bronchial epithelial cells, 16HBE-14o, were stimulated with 10 ng/ml TGF-beta1. Morphologic changes were observed and stress fiber by actin reorganization was detected by indirect immunostaining. The expression of alpha-SMA (alpha-smooth muscle actin) and the epithelial cell marker E-cadherin were detected in those 16HBE-14o cells after TGF-beta1 stimulation for 72 h, using immunostaining and RT-PCR. The contents of collagen I were determined by radioimmunoassay, and the levels of endogenous TGF-beta1 were measured with ELISA. Human bronchial epithelial cells stimulated with TGF-beta1 were converted from a "cobblestone" epithelial structure into an elongated fibroblast-like shape. Incubation of human bronchial epithelial cells with TGF-beta1 induced de novo expression of alpha-SMA, increased formation of stress fiber by F-actin reorganization, and loss of epithelial marker E-cadherin. Moreover, a significant increase in the levels of collagen I and endogenous TGF-beta1 released from bronchial epithelial cells stimulated with TGF-beta1 were observed. These results suggested that human bronchial epithelial cells, under stimulation of TGF-beta1, underwent transdifferentiation into myofibroblasts.

Tissue remodelling in chronic bronchial diseases: from the epithelial to mesenchymal phenotype

“…In the first stages of the pathology TGF-b acts as a tumour suppressor, but in the late stages of cancer TGF-b favours type III EMT contributing to the dissemination of metastases. In vitro studies in different pulmonary epithelial cells obtained from healthy donors have shown that exposure to TGF-b induces a mesenchymal phenotype in these cells [29,[63][64][65][66][67][68].…”

Pseudomonas aeruginosa accentuates epithelial-to-mesenchymal transition in the airway

“…Transforming growth factor (TGF)-b1 is regarded as the ''master switch'' for fibrosis in several organs, including the lung [6,[10][11][12][13][14], and has been shown to be elevated in the bronchoalveolar lavage (BAL) of patients with BOS [15][16][17]. TGFb1 is a pleiotropic molecule, and its ability to drive EMT is dependent on both the amount of activated growth factor and the microenvironment in which it acts.…”

Overexpression of farnesoid X receptor in small airways contributes to epithelial to mesenchymal transition and COX-2 expression in chronic obstructive pulmonary disease

“…Moreover, EMT features of the bronchial epithelium are associated with the severity of airway limitation (3,4), suggesting the involvement of EMT in progression of COPD. The induction of EMT in human bronchial epithelial (HBE) cells was also observed upon the stimulation with cigarette smoke or TGF-β1 in vitro (3,5). Taken together, these findings indicate the involvement of EMT in airway remodelling of COPD.…”