Project description:In diseased organs, stress-activated signaling cascades alter chromatin, triggering maladaptive cell state transitions. Fibroblast activation is a common tissue stress response that worsens lung, liver, kidney and heart disease, yet its mechanistic basis remains obscure. Pharmacologic BET inhibition alleviates cardiac dysfunction, providing a tool to interrogate and modulate cardiac cell states as a potential therapeutic approach. Here, we leverage single-cell epigenomic interrogation of hearts dynamically exposed to BET inhibitors to reveal a reversible transcriptional switch underlying fibroblast activation. Resident cardiac fibroblasts demonstrated robust toggling between the quiescent and activated state in a manner directly correlating with BET inhibitor exposure and cardiac function. Single-cell chromatin accessibility revealed novel DNA elements whose accessibility dynamically correlated with cardiac performance. Among the most dynamic elements was an enhancer regulating the transcription factor MEOX1, which was specifically expressed in activated fibroblasts, occupied putative regulatory elements of a broad fibrotic gene program, and was required for TGFβ-induced fibroblast activation. Selective CRISPR inhibition of the single most dynamic cis-element within the enhancer blocked TGFβ-induced Meox1 activation. We identify MEOX1 as a central regulator of fibroblast activation associated with cardiac dysfunction, and also demonstrate its upregulation upon activation of human lung, liver and kidney fibroblasts. The plasticity and specificity of BET-dependent regulation of MEOX1 in tissue fibroblasts provide new trans- and cis- targets for treating fibrotic disease.
Project description:Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. However, the in vivo role of fibroblasts in structuring the basal ECM network is poorly understood. To examine the effects of fibroblast loss on the microenvironment in the adult murine heart, we generated mice with reduced fibroblast numbers and evaluated the tissue microenvironment during homeostasis and after injury. We determined that a 60-80% reduction in fibroblasts numbers did not overtly change the fibrillar collagen network but did alter the distribution and abundance of type VI collagen, a microfibrillar collagen that forms an open network with the basement membrane. In fibroblast ablated mice, myocardial infarction did not result in ventricular wall rupture, and heart function was more effectively preserved during angiotensin II/phenylephrine (AngII/PE) induced fibrosis. Analysis of cardiomyocyte contractility demonstrated weaker contractions and slower calcium release and reuptake in uninjured and AngII/PE infused fibroblast ablated animals. Moreover, fibroblast ablated hearts have a similar gene expression prolife to hearts with exercise-induced and physiological hypertrophy after AngII/PE infusion. These results suggest that hearts are resilient to a significant degree of fibroblast loss and that fibroblasts can directly impact cardiomyocyte function. Furthermore, a reduction in fibroblasts may have cardioprotective effects heart after injury suggesting that manipulation of the number of fibroblasts may have therapeutic value.
Project description:Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. However, the in vivo role of fibroblasts in structuring the basal ECM network is poorly understood. To examine the effects of fibroblast loss on the microenvironment in the adult murine heart, we generated mice with reduced fibroblast numbers and evaluated the tissue microenvironment during homeostasis and after injury. We determined that a 60-80% reduction in fibroblasts numbers did not overtly change the fibrillar collagen network but did alter the distribution and abundance of type VI collagen, a microfibrillar collagen that forms an open network with the basement membrane. In fibroblast ablated mice, myocardial infarction did not result in ventricular wall rupture, and heart function was more effectively preserved during angiotensin II/phenylephrine (AngII/PE) induced fibrosis. Analysis of cardiomyocyte contractility demonstrated weaker contractions and slower calcium release and reuptake in uninjured and AngII/PE infused fibroblast ablated animals. Moreover, fibroblast ablated hearts have a similar gene expression prolife to hearts with exercise-induced and physiological hypertrophy after AngII/PE infusion. These results suggest that hearts are resilient to a significant degree of fibroblast loss and that fibroblasts can directly impact cardiomyocyte function. Furthermore, a reduction in fibroblasts may have cardioprotective effects heart after injury suggesting that manipulation of the number of fibroblasts may have therapeutic value.
Project description:Cardiac fibroblasts (CFs) are the primary cells tasked with extracellar matrix reorganization and significantly associated with heart failure (HF). Previous studies have shown that TEAD1 deficiency deteriorated heart development and homeostasis. However, the role of TEAD1 in fibroblasts during cardiac remodeling was still undiscovered. Our study demonstrated that TEAD1 was upregulated predominently in cardiac fibroblasts in mice 4 weeks after transverse aortic constriction (TAC) and Ang-II infusion. Echocardiographic and histological analyses demonstrated that CFs- and myofibroblasts-specific TEAD1 deficiency ameliorated TAC-induced cardiac remodeling and treatment with TEAD1 inhibitor, VT103, mimiced this phenotypic effect. Mechanistically, RNA-seq analysis , ChIP-Seq analysis identified TEAD1 promotes the fibroblast-to-myofibroblast transition through the Wnt signalling pathway. In conclusion, TEAD1 is an essential regulator of the pro-fibrotic CFs phenotype associated with pathological cardiac remodeling via the BRD4/Wnt4 signalling pathway.
Project description:We studied the cell compositon of two types of human heart disease (coronary atherosclerotic heart disease and dilated cardiomyopathy) by single-cell sequencing. Distinct subgroups of cardiac muscle, fibroblast cell and endothelial cell were detected. We generated a cell-cell interaction network using specific expressed ligands and receptors of cells. And we also observed the change of interaction and cell transformation with age.