TIMP1 regulation of cardiac fibroblast proliferation via the TGF-β/Smad pathway in an in vitro model of atrial fibrillation

Background: Atrial fibrillation (AF) is closely associated with atrial fibrosis and is primarily driven by cardiac fibroblast-mediated extracellular matrix (ECM) production. Tissue inhibitor of metalloproteinases-1 (TIMP1), a key ECM regulator, has been implicated in cardiovascular fibrosis, but its role in AF remains unclear. This study examined the function of TIMP1 in the angiotensin II (ang II)-induced activation of rat cardiac fibroblasts. Methods: Differentially expressed gene (DEG) and functional enrichment analyses were performed using the GSE115574 dataset. Key gene modules were identified via protein-protein interaction (PPI) network analysis, and critical module intersection gene expression was analyzed in AF samples from the GSE115574 and GSE14975 datasets. Different concentrations and times of ang II administration were used to treat rat cardiac fibroblasts to mimic AF pathology, and their effects on TIMP1 expression and ang II-induced proliferation and related fibrosis pathways were investigated via transfection, quantitative polymerase chain reaction, Western blotting (WB), and Cell Counting Kit-8 (CCK-8), and colony formation assays. Results: Functional enrichment analysis showed that DEGs were enriched in collagen fibrillar organization and ECM-receptor interactions. Seven essential intersecting genes (BGN, COL1A1, COL1A2, COL3A1, FMOD, THBS2, and TIMP1) identified from the PPI network analysis were highly expressed in AF samples from the GSE115574 and GSE14975 datasets. In vitro studies revealed ang II-induced upregulation of TIMP1 expression and activation of the TGF-β/Smad pathway. Knockdown of TIMP1 enhanced ang II-induced proliferation of rat cardiac fibroblasts and upregulated the expression of fibrotic markers and proteins related to the TGF-β/Smad signaling pathway. Conclusions: Our study demonstrated that TIMP1 regulates myocardial fibrosis through the TGF-β/ Smad pathway, particularly affecting cardiac fibroblast proliferation. Our findings provide new insights into the molecular process of AF and may offer new targets for therapeutic strategies.