Project description:Analysis of gene expression patterns in enlarged left atrial appendage (LAA) in mitral/aortic valve replacement or coronary artery bypass graft surgery can help to identify a comprehensive panel of gene biomarkers for predicting clinical outcomes and to discover potential new therapeutic targets. However, the transcriptional profiles triggered by extended mechanical stretch in cardiac myocytes are not fully understood. Here we performed the first genome-wide study of gene expression changes in human enlarged left atium, resulting in 335 differentially expressed (> 2-fold, P < 0,05) genes in response to mechanical stretch.
Project description:The goal of this study was to examine the effect of the major axis of biaxial mechanical stretch on cardiac myocyte gene expression and to identify the signaling pathways and transcription factors regulating these changes. Neonatal cardiac myocytes were cultured on a micropatterned substrate, and the primary stretch axis was applied either parallel or transverse to the myofibril direction. RNA sequencing was conducted to study whole genomic expression changes after acute cardiac myocyte stretch. The results showed a more robust gene response to longitudinal than to transverse stretch. After 30 minutes of stretch, 53 and 168 genes were considered differentially expressed (DE) from transverse and longitudinal stretch, respectively. After 4 hours, the number of DE genes increased to 795 in longitudinal stretch while it decreased to 35 in transverse stretch. Gene ontology term (GO) analysis indicated enrichment of TF activity and protein kinase activity by both stretch axes; whereas longitudinal but not transverse stretch caused expression of genes involved in sarcomere organization and cytoskeletal protein binding.
Project description:Myocardial damage caused for example by cardiac ischemia leads to ventricular volume overload resulting in increased stretch of the remaining myocardium. In adult mammals, these changes trigger an adaptive cardiomyocyte hypertrophic response which, if the damage is extensive, will ultimately lead to pathological hypertrophy and heart failure. Conversely, in response to extensive myocardial damage, cardiomyocytes in the adult zebrafish heart and neonatal mice proliferate and completely regenerate the damaged myocardium. We therefore hypothesized that in adult zebrafish, changes in mechanical loading due to myocardial damage may act as a trigger to induce cardiac regeneration. Based, on this notion we sought to identify mechanosensors which could be involved in detecting changes in mechanical loading and triggering regeneration. Here we show using a combination of knockout animals, RNAseq and in vitro assays that the mechanosensitive ion channel Trpc6a is required by cardiomyocytes for successful cardiac regeneration in adult zebrafish. Furthermore, using a cyclic cell stretch assay, we have determined that Trpc6a induces the expression of components of the AP1 transcription complex in response to mechanical stretch. Our data highlights how changes in mechanical forces due to myocardial damage can be detected by mechanosensors which in turn can trigger cardiac regeneration.
Project description:Engineered cardiac tissues (ECTs) are platforms to investigate cardiomyocyte maturation and functional integration, to evaluate the feasibility of generating implantable tissues for cardiac repair and regeneration, and may be useful models for pharmacology and toxicology bioassays. These ECTs rapidly mature in vitro to acquire the features of functional cardiac muscle and respond to mechanical load with increased proliferation and maturation. ECTs can be generated from various immature cardiac cell sources and little is known regarding the broad changes in regulatory transcript expression that occur in these in vitro tissues during normal maturation and in response to mechanical or pharmacologic interventions. We tested the hypothesis that global ECT gene expression patterns are sensitive to mechanical loading conditions and tyrosine kinase inhibitors, similar to the maturing myocardium. We generated 3D ECTs from day 14.5 rat embryo ventricular cells, as previously published, and then treated constructs after 5 days in culture for 48 hours with mechanical stretch (5%, 0.5 Hz) and/or the p38MAPK (p38 mitogen-activated protein kinase) selective inhibitor BIRB796. RNA was isolated from 3 sets of experiments and assayed using a standard Agilent rat 4x44k V3 microarray and Pathway Analysis software for transcript expression fold changes and changes in regulatory molecules and networks. At the threshold of a 1.5 fold change in expression, mechanical stretch altered 1,559 transcripts, versus 1,411 for BIRB796, and 1,846 for stretch plus BIRB796. As anticipated, top pathways altered in response to these stimuli include Cellular Development, Cellular Growth and Proliferation; Tissue Development; Cell Death, Cell Signaling, and Small Molecule Biochemistry as well as numerous other pathways. Changes in transcript expression were confirmed by quantitative-PCR for selected regulatory molecules. Thus, ECTs display a broad spectrum of altered gene expression in response to mechanical load and/or tyrosine kinase inhibition, reflecting the complex regulation of proliferation, differentiation, and architectural alignment that occurs during ECT maturation and adaptation. This approach can now be used to test the role of individual molecules and pathways on the regulation of ECT maturation and remodeling. 7 and 4 biological replicates with four groups (control, mechanical stretch, BIRB and mechanical stretch with BIRB)