[Effect of microRNA-133b on Myocardial Fibrosis]

Objective To investigate the effect of microRNA-133b(miR-133b)on cardiac fibrosis and its mechanism.Methods Human cardiac fibroblasts(CFs)were harvested.The proliferation of CFs was detected by CCK8 during the overexpression and knock-down of miR-133b.The expressions of connective tissue growth factor(CTGF),α-smooth muscle actin(α-SMA),collagen Ⅰ,and collagen Ⅲ were detected with qRT-PCR and Western blot analysis after miR-133b overexpression or downexpression.Target genes of miR-133b were predicted by bioinformatics software.Dual-luciferase activity assay were used to verify a target gene of miR-133b.Results qRT-PCR showed that the expression level of miR-133b in the miR-133b mimic group was significantly higher than that in the negative control group(t=26.219,P=0.000).The expression level of miR-133b in the miR-133b inhibitor group was significantly lower than that in the negative control group(t=6.738,P=0.003).After 21,45,69,93,and 117 hours of transfection,the proliferation ability of CFs significantly decreased in the miR-133b mimic group but significantly increased in the miR-133b group(all P<0.05,compared with the negative control group).After overexpression of miR-133b,the mRNA and protein levels of CTGF(t=9.213,P=0.001;t=8.195,P=0.001),α-SMA(t=6.511,P =0.003;t=4.434,P=0.011),collagenⅠ(t=3.172,P=0.034;t=4.053,P=0.015)and collagen Ⅲ(t=6.404,P=0.003;t=5.319,P=0.006)were significantly down-regulated.After the expression of miR-133b was knocked down,the mRNA and protein levels of CTGF(t=9.439,P=0.001;t=14.100,P=0.000),α-SMA(t=4.519,P=0.011;t=4.377,P=0.012),collagen Ⅰ(t=5.966,P=0.004;t=5.514,P=0.005)and collagen Ⅲ(t=4.622,P=0.010;t=4.996,P=0.008)were significantly increased.The relative luciferase activity of the cells co-transfected with miR-133b mimic and WT 3'UTR expression vector was significantly lower than that of the cells co-transfected with mimic control and WT 3'UTR expression vectors(t=5.654,P=0.005);however,there was no significant difference in relative luciferase activity between cells co-transfected with miR-133b mimic and MUT 3'UTR expression vectors and cells co-transfected with mimic control and MUT 3'UTR expression vectors(t=0.380,P=0.724).Conclusion miR-133b may affect the activation and proliferation of CFs by targeting CTGF and thus improve cardiac fibrosis.