Marrow-derived mesenchymal stem cells regulate the inflammatory response and repair alveolar type II epithelial cells in acute lung injury of rats

OBJECTIVE: We investigated the effect of untransplantable bone marrow-derived mesenchymal stem cells (BMSCs) in acute lung injury (ALI) and whether BMSCs attenuate damage of lipopolysaccharide (LPS) to alveolar type II epithelial cells (AECIIs). METHODS: ALI models were prepared by nebulizing LPS and then BMSCs were infused 1 hour later. We observed histopathological changes of lung tissue and evaluated inflammatory exudation by the wet/dry weight ratio, bronchiolar lavage fluid cell count, and protein concentration determination. Inflammatory and vascular factors were detected by immunohistochemistry and western blotting. For in vitro experiments, AECIIs were stimulated with 10 μg/mL LPS for 4 hours and then BMSCs were seeded in transit inserts to co-culture for 24 hours. The activity of AECIIs was detected. RESULTS: In the LPS + BMSCs group, histopathological examination showed that the degree of lung injury was significantly reduced compared with the LPS group. Protein expression of inflammatory and vascular factors was significantly lower with treatment. Optical density values and cell viability of the LPS + BMSCs group were significantly higher than those of the LPS group. CONCLUSIONS: Untransplanted-BMSCs can inhibit the inflammatory response in ALI and promote repair of AECIIs. This might be due to substances secreted by BMSCs and interaction between these substances.