A co-culture model of mesenchymal stem cells (MSCs) and fibroblasts is an efficient and rapid method to evaluate the anti-fibrotic effects of MSCs-based cell therapy. Transforming growth factor (TGF)-β1 plays a key role in promotion of fibroblast activation and differentiation which can induce collagen deposition, increase ECM production in lung tissue, eventually resulted in pulmonary fibrosis. Here, we use this co-culture system and examine the ECM production in activated fibroblasts by western blot and quantitative real-time analysis to understand the therapeutic effects of MSCs.