A novel mechanism of Smads/miR-675/TGFßR1 axis modulating the proliferation and remodeling of mouse cardiac fibroblasts.

Cardiac fibroblasts (CFs) can over-proliferate during the progression of cardiac fibrosis, accompanied by a net accumulation of extracellular matrix proteins. Based on the profibrotic actions of transforming growth factor beta 1 (TGFß1), investigating the mechanisms of TGFß1 function in CFs may provide new directions to treatment for cardiac fibrosis. microRNAs (miRNAs) could control CFs proliferation or remodeling via binding to 3'-untranslated region of messenger RNA (mRNA) to negatively regulate gene expression. In the present study, we downloaded several microarray analyses results from GEO attempting to identify miRNAs and possible downstream targets that may be involved in TGF-ß1 function in CFs and to detect the cellular and molecular functions of the identified miRNA-mRNA axis. Here, we identified miR-675 as a downregulated miRNA by TGFß1 by bioinformatics analyses and experimental verification. Upon TGFß1 stimulation, the protein levels of Α-SMAΑ-SMA, collagen I, and POSTN, and the secreted collagen in the cell culture supernatant significantly increased, whereas the miR-675 expression decreased. Smads mediate TGFß1-induced suppression on miR-675 via binding miR-675 promoter region. miR-675 overexpression could inhibit, whereas miR-675 inhibition could enhance TGFß1-induced mouse CFs (MCF) remodeling and proliferation. TGFß receptor 1 (TGFßR1), a critical receptor in TGFß1/Smad signaling, is a direct downstream target of miR-675. TGFßR1 overexpression significantly reverses the effect of miR-675 overexpression on MCF remodeling and proliferation. In summary, miR-675 targets TGFßR1 to attenuate TGFß1-induced MCF remodeling and proliferation. We demonstrate a novel mechanism of the Smads/miR-675/TGFßR1 axis modulating TGFß1-induced MCF remodeling and proliferation.