Abstract: Abstract： Objective To investigate the effect of microRNA(miR)- 21 on proliferation and differentiation of murine
pulmonary fibroblasts. Methods C57BL/6 mice of SPF grade (n=24) were randomly divided into Sham group and Pulmo⁃
nary fibrosis model group with 12 mice in each group. Pulmonary fibrosis model was established by trans-tracheal jet ventila⁃
tion of bleomycin into mice. The transcription levels of miR-21 were examined by quantitative real-time PCR in various pul⁃
monary fibrosis tissues. Primary fibroblast were isolated and digested by Trypsin then inoculated into 6 well plate to reach
confluence of 30%-50%. PBS (2.5 μL), negative control stock solution and miR-21 mimic stock solution (20 μmol/L) were
added into Opti-MEM (50 μL) as control group, blank group and miR-21 mimic group respectively.The cell viability was as⁃
sessed by CCK-8. Expressions of ADAMTS-1 and TGF-β1 in the pulmonary fibroblasts were tested using Western blot. Re⁃
sults The expression of miR-21 was significantly increased in lungs of mice in pulmonary fibrosis model group than that in
sham group. Expression of miR-21 was higher in miR-21 mimic group than that in control group and blank group. Expres⁃
sion of miR-21 was significantly higher with better cell viability in miR-21 mimic group than that in control group and blank
group. The expression of ADAMTS-1 was significantly decreased in miR-21mimic group, while the expression of TGF-β1, a
target gene of miR-21, was significantly increased in miR-21 mimic group compared with the other two groups. There is no
significant different in expressions of ADAMTS-1 and TGF-β1 between control group and blank group. Conclusion Over⁃
expression of miR-21 in pulmonary fibroblasts disrupts TGF-β1 signaling pathway by reducing expression of ADAMTS-1,
which promotes the proliferation and differentiation of pulmonary fibroblast.

Key words: pulmonary fibrosis, fibroblasts, transforming growth factor beta1, microRNAs, cell proliferation, cell differ?
entiation, ADAMTS-1, microRNA-21