Septin4 Promotes Fibrosis In The Heart After Pressure Overload

Background: In response to cardiac injury, the heart undergoes a remodeling process, which may be defined by a complex set of genomic, expression, molecular, cellular and interstitial changes, which can become maladaptive and contribute to the development of heart failure (HF). One of the most important components in cardiac remodeling is the development of fibrosis, which is characterized by excessive deposition of extracellular matrix (ECM) proteins by cardiac fibroblasts, which disrupts the myocardial architecture and function, thus predisposing the progression of cardiac diseases to HF. The small GTPase Septin4 (Sept4) has been described to regulate regeneration and apoptosis in several organs. However, the role of Sept4 in regulating the cardiac stress response is unknown. The present study was designed to investigate if Sept4 would be mediating the alterations associated with cardiac remodeling induced by cardiac pressure overload. Hypothesis: We hypothesized that Sept4 deletion prevents the fibrotic response associated with cardiac remodeling, and the development and progression of HF triggered by transverse aortic constriction (TAC). Methods: 10-week-old wild type (WT) and Sept4 knockout (KO) mice were subjected to TAC to induce cardiac pressure overload. Functional and molecular analyses on WT and KO hearts were performed either at baseline, 1- or 4-weeks post-injury timepoints. Results: After TAC injury, WT mice showed a significant reduction of cardiac function and the development of heart failure, while KO mice were able to maintain normal cardiac function. KO hearts exhibited decreased levels of cardiac ECM deposition and fibrosis compared with WT hearts. Furthermore, KO hearts were more compliant and demonstrated improved end diastolic pressure compared with their WT counterparts. The differentiation of fibroblasts into myofibroblasts was impaired in KO hearts compared with WT controls, which appeared to be associated with attenuated TGF-β-triggered signaling pathway in KO hearts after TAC injury. In line with these findings, we verified in cultured cardiac fibroblasts (CFBs) that Sept4 deletion resulted in reduced myofibroblasts differentiation and a blunted ability of CFBs to contract. Conclusion: Our results demonstrate that Sept4 is an important regulator of ECM remodeling in the heart. Sept4 deletion leads to reduced levels of cardiac fibrosis and attenuation of pressure overload-induced cardiac dysfunction. These findings highlight Sept4 as a potential target to prevent fibrosis in cardiac stress response. This study was supported by grants from the National Institutes of Health (HL155993 and HL160665). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.