Objective To investigate the therapeutic effects of bone marrow mesenchymal stem cells(BMSCs)for radi-ation-induced lung injury(RILI)and the underlying mechanism.Methods Forty-five healthy adult male C57BL/6 mice were randomly divided into control,model,and BMSCs groups.The model and BMSCs groups received a single irradiation dose of 20 Gy to the chest,while the control group did not receive X-ray irradiation.For the BMSCs group,an injection of 1 × i06 BMSCs cells was administered via the tail vein within 6 h after irradiation.In the 5th week,the lung tissue was taken to observe pathological changes with HE staining;examine the expression of the inflammatory factors interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α)with immunohistochemical staining;observe the polarization of macrophages with im-munofluorescence staining;and measure the expression of the epithelial-mesenchymal transition markers E-cadherin,N-cad-herin,and vimentin proteins by Western blot.Results After radiation,the model group developed pulmonary vasodilation and congestion with septal thickening and inflammatory cell infiltration,and these changes were markedly reduced in the BMSCs group.The model group showed significantly down-regulated expression of IL-6 and TNF-α compared with signi-ficantly increased levels in the model group(P＜0.01,P＜0.05).Treatment with BMSCs significantly increased the polariz-ation of lung macrophages towards the M2 type,while significantly decreasing the abnormally increased N-cadherin and vi-mentin levels in RILI mice(P＜0.05,P＜0.01).Conclusion BMSCs have therapeutic effects for RILI mice,which may be through promoting macrophage polarization from Ml to M2.
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