Background Acute lung injury (ALI) and end-stage acute respiratory distress syndrome (ARDS) were among the most common causes of death in intensive care units.The activation of an inflammatory response and the damage of pulmonary epithelium and endotheliumwerethe hallmark of ALI/ARDS.Recent studies had demonstrated the importance of mesenchymal stem cells (MSCs) in maintaining the normal pulmonary endothelial and epithelial function as well as participating in modulating the inflammatory response and they are involved in epithelial and endothelial repair after injury.Here,our study demonstrates MSCs therapeutic potential in a rat model of ALI/ARDS.Methods Bone marrow derived MSCs were obtained from Sprague-Dawley (SD) rats and their differential potential was verified.ALl was induced in rats byoleic acid (OA),and MSCs were transplanted intravenously.The lung injury and the concentration of cytokines in plasma and lung tissue extracts were assessed at 8 hours,24 hours and 48 hours after OA-injection.Results The histological appearance and water content in rat lung tissue were significantly improved at different time points in rats treated with MSCs.The concentration of tumor necrosis factor-α and intercellular adhesion molecular-1 in rats plasma and lung tissue extracts were significantly inhibited after intravenous transplantation of MSCs,whereas interleukin-10 was significantly higher after MSCs transplantation at 8 hours,24 hours and 48 hours after OA-challenge.Conclusions Intravenous transplantation of MSCs could maintain the integrity of the pulmonary alveolar-capillary barrier and modulate the inflammatory response to attenuate the experimental ALI/ARDS.Transplantation of MSCs could be a novel cell-based therapeutic strategy for prevention and treatment of ALI/ARDS.