A novel mechanism of Smads/miR-675/TGFβR1 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 (TGF beta 1), investigating the mechanisms of TGF beta 1 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-beta 1 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 TGF beta 1 by bioinformatics analyses and experimental verification. Upon TGF beta 1 stimulation, the protein levels of Alpha-SMA Alpha-SMA, collagen I, and POSTN, and the secreted collagen in the cell culture supernatant significantly increased, whereas the miR-675 expression decreased. Smads mediate TGF beta 1-induced suppression on miR-675 via binding miR-675 promoter region. miR-675 overexpression could inhibit, whereas miR-675 inhibition could enhance TGF beta 1-induced mouse CFs (MCF) remodeling and proliferation. TGF beta receptor 1 (TGF beta R1), a critical receptor in TGF beta 1/Smad signaling, is a direct downstream target of miR-675. TGF beta R1 overexpression significantly reverses the effect of miR-675 overexpression on MCF remodeling and proliferation. In summary, miR-675 targets TGF beta R1 to attenuate TGF beta 1-induced MCF remodeling and proliferation. We demonstrate a novel mechanism of the Smads/miR-675/TGF beta R1 axis modulating TGF beta 1-induced MCF remodeling and proliferation.