Morphological Change and Inactivation of MRC-5 Cell Line, a Lung Myofibroblast, by Conditioned Media of Lung Carcinoma Cell Line

摘要

The differentiation of fibroblast to myofibroblast is a crucial step in the pathogenesis of lung fibrosis, characterized by the expression of cytoskeletal protein a-smooth muscle actin (SMA). Several substances, such as cAMP, are known to cause the inactivation of myofibroblasts, but its mechanism has not been fully understood yet. Previously, we reported that the conditioned medium of a human lung carcinoma cell line, A549, causes the inactivation of myofibroblast cell line, MRC-5. In the present study, we further investigated the effect of the conditioned medium of A549 on the inactivation of MRC-5 cell. The conditioned medium was collected from A549 cell culture in 10% FBS-DMEM for 4 days. The shape of the MRC-5 cells was changed to stellate form by treatment with the conditioned medium, along with decreased a-SMA expression and decrease of cell growth. However, conditioned media of other carcinoma cell lines (PC-9, PC-14, A431, COS-7) failed to influence the shape of MRC-5 cells. Western blot analysis and reverse transcription-polymerase chain reaction analysis revealed that the a-SMA expression was tran-scriptionally decreased. Further study revealed that during the inactivation, cyclin-dependent kinase inhibitors, such as p21, were increased after 2 days by conditioned medium treatment. Cell cycle arrest was induced at early stage of morphological change.