Failing heart-specific cardiac fibroblasts induce heart failure via c-Myc Expansion [snRNA-seq]

Heart failure (HF) is a major global problem with increasing numbers of patients and deaths in many countries. Existing studies on HF have focused primarily on cardiomyocytes, with few studies targeting non-cardiomyocytes. This study focused on cardiac fibroblasts (CFs) as a cause of HF. Single-cell RNA sequencing of mouse hearts revealed six distinct subclusters of CFs at various stages after pressure overload, with one subcluster being specific to the HF stage. The transcription factor c-Myc is specifically expressed in HF-specific CFs. CFs-specific deletion of c-Myc ameliorates pressure overload-induced cardiac dysfunction without affecting fibrosis. The chemokine Cxcl1 is highly expressed in HF-specific CFs and downregulated in CFs-specific c-Myc knockout mice. Chromatin immunoprecipitation analysis revealed that c-Myc binds to the promoter region of Cxcl1 in CFs. Cxcr2, the receptor for Cxcl1, is expressed in cardiomyocytes, and blockade of the Cxcl1-Cxcr2 signalling pathway prevents pressure overload-induced cardiac dysfunction. The addition of CXCL1 reduces the contractility of cardiomyocytes of neonatal rats and human iPS-derived cardiomyocyte organoids. Human CFs from failing hearts expressed c-MYC and CXCL1, while CFs from control hearts did not. These findings suggest that HF-specific CFs play an important role in inducing HF by upregulating c-Myc and Cxcl1 and that CFs could be a novel therapeutic target for HF. Overall design: Nuclei were extracted from hearts of dilated cardiomyopathy patients and control, and single-nucleus RNA-seq was performed on each sample. Human heart tissue samples were obtained from the left ventricular apex myocardium of four heart failure patients undergoing implantation of left ventricular assist devices due to reduced cardiac function and two patients with preserved cardiac function who underwent pathological autopsy.