Up-regulation of miR-21 promotes cell proliferation and collagen synthesis in pulmonary fibroblasts

Objective: To explore the expression of miR-21 in lung tissues of mice with pulmonary fibrosis, and its role in proliferation, trans-differentiation and collagen synthesis of pulmonary fibroblasts.

Methods: Thirty C57BL/6 mice were randomly divided into control group (n=5) and model group (n=25). Mice in the latter group were intratracheally administered with bleomycin to establish pulmonary fibrosis model. Five animals in the model group were sacrificed on days 3, 7, 14, 28 and 56, while all ones of the control group were killed on day 56 as total control. The expression of miR-21 in lung tissues was then measured through fluorescence real-time quantitative PCR. Pulmonary fibroblasts were treated with Lipofectamine™2000 (blank control group) as well as miR-21 negative control, mimics and inhibitor, respectively. Cell proliferative ability was analyzed by MTT assay. The mRNA and protein expressions of α-smooth muscle actin (α-SMA), a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS-1), collagen type I (Col1) and collagen type III (Col3) were detected using fluorescence real-time quantitative PCR and Western blotting, respectively.

Results: The expression levels of miR-21 in lung tissues of the model group on days 7-56 were higher than those in the control group, and reached the peak on day 28. After 24, 48, 72 and 96 hours of co-culture, cell viability significantly increased in miR-21 mimics group but decreased in miR-21 inhibitor group as compared with blank control group. In comparison with blank control group, miR-21 mimics group showed up-regulated mRNA and protein expression levels of α-SMA, Col1 and Col3 while down-regulated ADAMTS-1 mRNA and protein expression levels; however, miR-21 inhibitor group presented with reduced mRNA and protein expression levels of α-SMA, Col1 and Col3 but increased ADAMTS-1 mRNA and protein expression levels. There was no significant difference in the above indicators between negative control group and blank control group.

Conclusions: miR-21 expression is raised in lung tissues of mice with pulmonary fibrosis. Up-regulation of miR-21 facilitates the proliferation, trans-differentiation and collagen synthesis of pulmonary fibroblasts.