Abstract
Chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer are deadly disease related to smoking. COPD and lung cancer were among the 10 leading causes of death in the world in 2012. Previous studies suggest that epithelial-mesenchymal transition (EMT) may play a role in COPD, IPF and lung cancer; however, the mechanism linking EMT to these dieases remains incompletely understood. EMT describes a biological process by which epithelial cells lose their epithelial characteristics and gradually acquire mesenchymal traits, and this process mainly occurs in embryogenesis, tissue regeneration, organ fibrosis, cancer progression and metastasis. The causes of lung diseases mentioned above are highly associated with fibrosis, cancer progression and metastasis. Therefore, study on cigarette smoke-induced EMT in lung epithelial cells contributes to understanding and better treatment for these diseases. We investigated the effect of cigarette smoke extract (CSE) on human lung epithelial A549 cell line in vitro. Our results demonstrated that CSE induced A549 cell death in a concentration- and time-dependent manner. In addition, the cells escaped from CSE-induced cell death exhibited some EMT properties: elongated shape, lack of apical microvilli, increased motility, decreased E-cadherin expression, and increased Vimentin and -smooth muscle actin expression. Recent studies suggest the therapeutic potential of mesenchymal stem cells for lung diseases, which is probably mediated by paracrine actions of mesenchymal stem cells. Accordingly, A549 cells were cultured with adipose-derived stem cell condition medium (ADSC-CM), and we found that ADSC-CM had a protective effect on CSE-induced cell death; moreover, ADSC-CM repressed CSE-indued EMT properties in A549 cells. These results imply that microenvironment plays an important role in EMT induction. A549 cells tended to undergo EMT in adverse condition, but CSE induced EMT properties in A549 cells became less evident in a less adverse condition such as with the inclusion of ADSC-CM. Finally, we investigated EMT related genes by microarray analysis. After CSE exposure, we found that genes as epithelial markers were downregulated in A549 cells, but only few genes as mesenchymal markers were upregualted. As a result, A549 cells underwent “partial EMT” by CSE induction, and we show that such EMT-like phenomena can be further confirmed by microarray analysis. In summary, we demonstrated the effect of CSE on A549 cells, including cell death and EMT. Furthermore, we discussed EMT-like features in A549 cells via different methods for image analysis. Finally, we used ADSC-CM to repress CSE-indued cell death and EMT in A549 cells, which suggest that ADSCs have therapeutic potential for smoking related lung diseases by paracrine actions.