To investigate the effect of mesenchymal stem cell microvesicles (MSC-MVs) on pulmonary fibrosis in mice with acute respiratory distress syndrome (ARDS).

MSC-MVs with low expression of hepatocyte growth factor (siHGF-MSC-MVs) were obtained by lentivirus transfection. A mouse model of ARDS pulmonary fibrosis was established by injecting lipopolysaccharide (LPS) three times, and then MSC-MVs or siHGF-MSC-MVs were injected from the tail vein of ARDS mice with pulmonary fibrosis. Immunohistochemistry, Western blot, ELISA, and other methods were used to detect the expression of pulmonary fibrosis related proteins, and to compare the effects of MSC-MVs on pulmonary fibrosis and fibrosis related indicators in ARDS mice with pulmonary fibrosis.

The pulmonary fibrosis score in the pulmonary fibrosis group was significantly higher than that of the control group. After MSC-MVs were injected into the tail vein of pulmonary fibrosis mice, the pulmonary fibrosis score was significantly reduced. However, the siHGF-MSC-MVs group had a significantly higher pulmonary fibrosis score than the MSC-MVs group. Compared with the pulmonary fibrosis group, the expression levels of type Ⅰ and Ⅲ collagen antigens, TGF-β, α-SMA protein were significantly reduced in the MSC-MVs group, while these indicators significantly increased in the siHGF-MSC-MVs group compared to the MSC-MVs group. The amount of lung wet/dry and Evans blue leakage in the ARDS pulmonary fibrosis group was higher than that in the control group. After MSC-MVs injection, the wet/dry weight ratio and the amount of Evans blue leakage was significantly reduced. However, the effect of MSC-MVs was significantly inhibited after HGF knockdown.

MSC-MVs inhibit pulmonary fibrosis in ARDS mice partly by secreting HGF.