SOX9 Knockdown Improves Atrial Fibrosis and Inflammation in Atrial Fibrillation Rats

Abstract

Background: SRY-Box Transcription Factor 9 (SOX9) is involved in transforming growth factor (TGF)-β-induced atrial fibrosis, an important pathological feature of atrial fibrillation (AF). This study aims to investigate the role of SOX9 in AF. Methods: Sprague-Dawley rats were used to develop an AF model. The incidence and duration of AF were recorded using electrocardiography. Atrial fibrosis and tissue damage were analyzed through Masson staining and hematoxylin-eosin staining. The level of hydroxyproline was measured using spectrophotometric kits. Immunohistochemistry was performed to quantify SOX9 and α-smooth muscle actin (α-SMA). The expressions of inflammatory factors were calculated using quantitative real-time polymerase chain reaction (qRT-PCR), and the expressions of proteins related to the protein kinase B (AKT) signaling pathway and epithelial-to-mesenchymal transition were measured by Western blot. Results: AF was successfully induced in rats, characterized by the absence of P-wave and the presence of typical F-wave. Overexpression of SOX9 increased the incidence and duration of AF, as well as exacerbated atrial fibrosis and inflammatory damage. In contrast, the silencing of SOX9 had the opposite effects in the AF model rats. The levels of hydroxyproline and the expression levels of SOX9, α-SMA, and inflammatory factors were elevated in AF rats. Additionally, the elevation was further enhanced by SOX9 overexpression but suppressed by SOX9 silencing. SOX9 overexpression promoted the up-regulation of β-catenin, Collagen I, Vimentin, and phosphorylated proteins of Focal adhesion kinase (FAK)/AKT/S6 kinase (S6K), and the downregulation of E-cadherin. However, SOX9 silencing exerted opposite effects in AF rats. Conclusions: SOX9 deficiency improves atrial fibrosis and inflammation in AF rats and inhibits the AKT-S6K and β-catenin proteins.