Bone marrow mesenchymal stem cells protect lungs from smoke inhalation injury by differentiating into alveolar epithelial cells via Notch signaling.

To examine the protective effect of transplanting bone marrow mesenchymal stem cells (BMSCs) in treating lung injuryinduced by smoke exposure and to investigate the underlying mechanisms of this protection. SD rats were randomlydivided into four groups: normal group, normal +BMSCGFP group, smoke group, and smoke +BMSCGFP group. Todetect lung injury, we measured arterial blood gas, the wet-to-dry weight ratio, and levels of interleukin-1b, tumor necrosisfactor-a, interleukin-10, and interleukin-13 in bronchoalveolar lavage fluid and lung tissues. We also conductedhistopathology examinations. The protein markers of alveolar epithelial cells were measured to determine the BMSCdifferentiation. The protein levels of Notch1, Jagged-1, and Hes-1 also were detected. In the present study, BMSCtransplantation significantly decreased the wet-dry weight ratio of the lung, reduced the production of inflammatorymediators, and alleviated lung injury simply through differentiating into alveolar type II cells and alveolar type I cells. Western blot analysis confirmed that the protein expression of Notch-1, Jagged-1, and Hes-1 increased significantly aftersystemic BMSC transplantation. No significant difference was observed between the normal group and the nor-mal +BMSCGFP group. Our findings indicate that systemic transplantation of BMSCs alleviated lung injury induced bysmoke exposure, which may be associated with BMSCs' ability to differentiate into alveolar-type cells via the Notchsignaling pathway.