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MiR‐125b regulates SFRP5 expression to promote growth and activation of cardiac fibroblasts

Myocardial fibrosis (MF), which typically occurs after a myocardial infarction (MI), is a major factor involved in the process of ventricular remodeling and subsequent progression to heart failure. Current studies have found that various microRNAs (miRNAs), such as miR‐125b, play an important role in this process. However, few studies have investigated the specific mechanism of miR‐125b. Transfection of miR‐125b mimics into cardiac fibroblasts (CFs) resulted in significantly increased expression of the myofibroblast marker alpha‐smooth muscle actin (α‐SMA) and vinculin by Western blot analysis, while transfection of miR‐125b inhibitors resulted in the opposite effect. Analysis of putative CF target genes for miR‐125b revealed that miR‐125b specifically inhibits expression of secreted frizzled‐related protein 5 (SFRP5). SFRP5 inhibited expression of α‐SMA and collagen I and III in CFs, while miR‐125b promoted the expression of these proteins. Cotransfection of the SFRP5 overexpression vector and miR‐125b mimics did not result in significant upregulation of SFRP5 expression or downregulation of α‐SMA and collagen I and III. Further analysis revealed that miR‐125b promotes the proliferation and migration of CFs and inhibits their apoptosis, while SFRP5 exhibits the opposite effects. These results indicate that miR‐125b can regulate SFRP5 expression and thus influence the growth and activation of CFs. Hence, this study provides important insight into possible approaches for the prevention and treatment of MF after an MI.