Mechanism of bone marrow mesenchymal stem cells in alleviating pulmonary alveolitis in mice exposed to silica dust / 中国职业医学

ABSTRACT

OBJECTIVE: To explore the mechanism of bone marrow mesenchymal stem cells( BMSCs) in alleviating pulmonary alveolitis in mice exposed to silica dust. METHODS: Five specific pathogen free healthy male C57 BL /6 mice were used to isolate BMSCs using bone marrow adherent method. The poly-potent differentiation ability of BMSCs were identified by 3 differentiation-inducing experiments. Forty-five mice of similar background were randomly divided into 3groups control group,silica group and BMSCs transplantation group. The mice of the control group were given 20. 0 μL of0. 90% sodium chloride solution by one time intratracheal injection. The mice of silica group and BMSCs transplantation group were first received 20. 0 μL( 250 g / L mass concentration) of silica dust suspension by one time intratracheal injection; followed by 500. 0 μL of 0. 90% sodium chloride solution or 500. 0 μL of BMSCs suspension( cell density 1 ×109/ L) by tail vein infusion 6 hours later. Mice were euthanized on the 3rd day of the experiment. Lung functional coefficient and pathologic changes in the lung were examined. The level of cytokines in bronchoalveolar lavage fluid( BALF) was detected by enzyme linked immunosorbent assay. Wright-Giemsa staining was used for staining cells in BALF for counting. Flow cytometry( FCM) was used to measure the percentage of macrophages of BALF in the mice. RESULTS: BMSCs were successfully induced to differentiate into osteogenic,adipogenic and chondrogenic cells and developed into osteoblast,adipogenic cells and chondroblast. On the 3rd day of the experiment,the mice in silica group showed histopathological changes similar to pulmonary alveolitis; while there was no obvious inflammatory change observed in the BMSCs transplantation group,and the structure of lung tissue appeared normal. The lung coefficient of the silica group was higher than that of the control group( P < 0. 05); the lung coefficient of BMSCs transplantation group was lower than that of the silica group( P < 0. 05),but it showed no significant difference when compared to the control group( P > 0. 05). The interleukin( IL)-1β,IL-6 and chemokine ligand 3 levels in BALF in the silica group were higher than those of the control group( P < 0. 05),and the above 3 indices in the BMSCs transplantation group regaining the level of the control group( P > 0. 05) were lower than those of the silica group( P < 0. 05). The level of tumor necrosis factor-α in BALF in silica group and BMSCs transplantation group were higher than that of the control group( P < 0. 05),but there was no significant difference between silica group and BMSCs transplantation group( P > 0. 05). The level of IL-10 in BALF showed no significant difference in these 3 groups( P > 0. 05). Wright-Giemsa staining results showed that the number of total cells and macrophages in BALF in the silica group was higher than that of the control group( P < 0. 05),and the above cell number of BMSCs transplantation was lower than that of silica group( P < 0. 05),but it showed no significant difference when compared to the control group( P > 0. 05). The FCM result showed that the percentage of macrophages was in accordance with that of the Wright-Giemsa staining. CONCLUSION: The BMSCs can alleviate pulmonary alveolitis in the mice exposed to silica dust by inhibiting the amounts and activity of alveolar macrophages and down-regulating the expression of IL-1β and IL-6 in BALF.