Project description:Adult cardiomyocytes are embedded within a highly organized myocardial microenvironment that imposes critical geometric cues essential for the alignment and distribution of organelles and the shaping of their unique, rectangular cellular morphology. Despite the association of cardiomyocyte disarray with human heart disease, the functional consequences of this cellular disorganization remain poorly understood. Here, we leveraged micropatterned substrates to promote structural alignment in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), contrasting the effects of mechanical alignment on mitochondrial form and function with hiPSC-CMs cultured under standard unconstrained conditions. Cardiomyocytes cultured under unconstrained conditions exhibited misaligned sarcomeres and a perinuclear mitochondrial distribution while micropatterned hiPSC-CMs developed linear myofibrils and reconfigured sarcomere and mitochondrial organization, which increased mitochondrial respiration without augmenting mitochondrial mass. Notably, micropatterned hiPSC-CMs exhibited an increased number of mitochondria-associated membranes, as determined by proximity ligation assays and transmission electron microscopy, suggesting enhanced interactions between the sarcoplasmic reticulum and mitochondria. Together, these findings demonstrate that mitochondrial-sarcoplasmic architecture and geometry are critical spatial features that ensure bioenergetic efficiency of cardiomyocytes. This work underscores the importance of cellular organization in cardiomyocyte metabolism and function, providing insights into the pathophysiology of cardiac diseases marked by cellular disarray.
Project description:Acute occlusion of a coronary artery results in swift tissue necrosis. Bordering areas of the infarcted myocardium may also experience impaired blood supply and reduced oxygen delivery leading to altered metabolic and mechanical processes. While transcriptional changes in hypoxic cardiomyocytes are well-studied, little is known about the proteins that are actively secreted from these cells. We established a novel secretome analysis of cardiomyocytes by combining stable isotope labeling and click chemistry with subsequent mass spectrometry analysis. Further functional validation experiments included ELISA measurement of human samples, murine LAD ligation and adeno-associated virus (AAV) 9-mediated in vivo overexpression in mice. The presented approach is feasible for the analysis of the secretome of primary cardiomyocytes without serum starvation. 1026 proteins were identified to be secreted within 24 hours, indicating a 5-fold increase in detection compared to former approaches. Among them, a variety of proteins have so far not been explored in the context of cardiovascular pathologies. One of the most strongly upregulated secreted factors upon hypoxia was proprotein convertase subtilisin/kexin type 6 (PCSK6). Validation experiments revealed an increase of PCSK6 on mRNA and protein level in hypoxic cardiomyocytes. PCSK6 expression was elevated in hearts of mice following 3 days of ligation of the left anterior descending artery, a finding confirmed by immunohistochemistry. ELISA measurements in human serum also indicate distinct kinetics for PCSK6 in patients suffering from acute myocardial infarction, with a peak on day 3 post-infarction. Transfer of PCSK6-depleted cardiomyocyte secretome resulted in decreased expression of collagen I and III in fibroblasts compared to control treated cells, and siRNA mediated knockdown of PCSK6 in cardiomyocytes impacted transforming growth factor-β activation and mothers against decapentaplegic homolog 3 (SMAD3) translocation in fibroblasts. An Adeno-associated virus (AAV) 9-mediated, cardiomyocyte-specific overexpression of PCSK6 in mice resulted in increased collagen expression and cardiac fibrosis as well as decreased left ventricular function after myocardial infarction. In conclusion, a novel mass spectrometry-based approach allows the investigation of the secretome of primary cardiomyocytes. Analysis of hypoxia-induced secretion led to the identification of PCSK6 to be crucially involved in cardiac remodeling after acute myocardial infarction. Secretome analysis was performed on neonatal rat ventricular cardiomyocytes (NRVCMs) which were incubated under hypoxic conditions (1.5% O2, 5% CO2, 93.5% N2) for 12 (Hypoxia 0-12h), 24 (Hypoxia 0-24h) and 30 (Hypoxia 24-30h) hours. Furthermore, knockdown (KD) of PCSK6 in vitro mediated by small interfering RNA (siRNA) was performed to investigate changes in the secretome of cardiomyocytes with PCSK6 KD vs. control (control siRNA) during 24 hours of hypoxia (PCSK6 KD 0-24h). Cells were pulse-labeled with AHA (L-azidohomoalanine) and SILAC (stable isotope labeling with amino acids in cell culture) for 12 (Hypoxia 0-12h), 24 (Hypoxia 0-24h/PCSK6 KD 0-24h) and 6 hours (Hypoxia 24-30h). For Hypoxia 0-12h 3 replicates, Hypoxia 0-24h 6 replicates, PCSK6 KD 0-24h 3 Replicates and Hypoxia 24-30h 2 replicates were performed with label-swap.
Project description:Klf9 deficiency leads to increased mortality and cardiac rupture rate after myocardial infarction(MI) in mice. We use single-cell RNA sequencing (scRNA-seq) to detect differences in non-cardiomyocytes between WT and Klf9-/- mice after MI.
Project description:Arrhythmogenic cardiomyopathy (ACM) is frequently attributed to desmosomal mutations, such as those in the desmoplakin (DSP) gene. Patients with DSP- cardiomyopathy are predisposed to myocardial degeneration and arrhythmias. Despite advancements, the underlying molecular mechanisms remain incompletely understood, thus limiting therapeutic options. Here, we employed spatial transcriptomics on an explanted heart from a patient with a pathogenic DSP variant. Our transcriptional analysis revealed endothelial PAS domain-containing protein 1 (EPAS1) as a potential regulator of mitochondrial homeostasis in stressed cardiomyocytes. Elevated EPAS1 levels were associated with mitochondrial dysfunction and hypoxic stress in both human-relevant in vitro ACM models and additional explanted hearts with genetic cardiomyopathy. Collectively, cardiomyocytes bearing pathogenic DSP variants exhibit mitochondrial dysfunction, increased apoptosis, and impaired contractility, which are linked to the increased EPAS1 levels. These findings implicate EPAS1 as a key regulator of myocardial degeneration in DSP-cardiomyopathy, which expand to other forms of ACM.
Project description:Arrhythmogenic cardiomyopathy (ACM) is frequently attributed to desmosomal mutations, such as those in the desmoplakin (DSP) gene. Patients with DSP- cardiomyopathy are predisposed to myocardial degeneration and arrhythmias. Despite advancements, the underlying molecular mechanisms remain incompletely understood, thus limiting therapeutic options. Here, we employed spatial transcriptomics on an explanted heart from a patient with a pathogenic DSP variant. Our transcriptional analysis revealed endothelial PAS domain-containing protein 1 (EPAS1) as a potential regulator of mitochondrial homeostasis in stressed cardiomyocytes. Elevated EPAS1 levels were associated with mitochondrial dysfunction and hypoxic stress in both human-relevant in vitro ACM models and additional explanted hearts with genetic cardiomyopathy. Collectively, cardiomyocytes bearing pathogenic DSP variants exhibit mitochondrial dysfunction, increased apoptosis, and impaired contractility, which are linked to the increased EPAS1 levels. These findings implicate EPAS1 as a key regulator of myocardial degeneration in DSP-cardiomyopathy, which expand to other forms of ACM.
Project description:Genome-wide gene expression analysis of new cardiomyocytes (CMs) derived from resident c-kitpos endogenous cardiac stem cells (eCSCs) after myocardial injury by Isoproterenol (ISO) in mice. These data show that of new CMs derived from resident c-kitpos eCSCs have a gene expression profile that closely resembles the specific gene expression of adult cardiomyocytes. This result supports a role of c-kitpos eCSCs in the regeneration and repair of myocardial damage. To test the identity and the degree of differentiation of new cardiomyocytes (CMs) derived from resident c-kitpos endogenous cardiac stem cells (eCSCs) after myocardial injury by Isoproterenol (ISO) in mice. Global gene expression profiles by microarray was obtained in c-kitpos eCSCs, c-kitpos eCSC-derived YFPpos CMs and normal adult CMs. c-kitposCD45neg eCSCs were isolated from B6.129X1-Gt(ROSA)26Sortm1(EYFP)Cos/J mice and harvested at 4th passage (n=3). YFPpos cardiomyocytes were FACS sorted from left ventricle apex of Lentirius-c-kit/cre recombined B6.129X1-Gt(ROSA)26Sortm1(EYFP)Cos/J mice 28 days after ISO (N=3). Normal adult CMs were isolated from B6.129X1-Gt(ROSA)26Sortm1(EYFP)Cos/J mice (n=3).
Project description:Cardiac hypertrophy consists in the enlargement of cardiomyocytes and alteration of the extracellular matrix organization in response to physiological or pathological stress. In pathological hypertrophy ocuurs myocardial damage, loss of cardiomyocytes, fibrosis, inflammation, sarcomere disorganization and metabolic impairment, leading to cardiac dysfunction.The rodent model treated with isoproterenol induces cardiac hypertrophy due the constant activation of β-adrenergic receptors. We conducted a quantitative label-free proteomic analysis of cardiomyocytes isolated from hearts of mice treated or not with isoproterenol to better understand the molecular bases of cellular response due to isoproterenol-induced injury.
Project description:The importance of regenerative potential of cardiac stem/progenitor cells (CSCs) after acute myocardial infarction (AMI) has been emphasized in the last decade. Several studies have demonstrated that this cell population has a relevant role in myocardial repair, supported by the establishment of a paracrine cross-talk between CSCs and the injured tissue. However, the majority of current in vitro strategies to study these cells fails to include important modulators of CSC activity, such as the paracrine effect of cardiomyocytes (CMs) and the physicochemical changes occurring in tissue during Ischemia/Reperfusion (I/R) injury. In this work, we established the first human in vitro heterotypic model of myocardial I/R injury with human CSCs (hCSCs) and human induced pluripotent cell-derived cardiomyocytes (hiPSC-CMs) using transwell inserts. hCSCs response to I/R was characterized using advanced whole proteomic mass spectrometry-based tools that allowed us to propose new pathways in hCSCs regenerative process, including: cell cycle regulation inhibition, proliferation through EGF signaling, gluthathione-mediated reactive oxygen species detoxification, and signaling through several paracrine growth factors. The model established in this work contributes with new insights regarding hCSC biology in response to AMI and provides an important tool to study and modulate molecular mechanisms involved in the regenerative potential of CSCs.