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Gene expression profiling of overexpression of myocardin

ABSTRACT: ABSTRACT Aims Forced differentiation of non-muscle cells into heart muscle cells using cardiac transcription factors (cTFs) may constitute a novel strategy to accomplish myocardial regeneration. Methods We investigated the potential of the cTF myocardin to induce cardiomyocyte differentiation and compared the myocardin-induced gene expression program to that of fully differentiated cardiomyocytes using oligonucleotide microarray hybridizations, quantitative RT-PCR analyses and immunofluorescence microscopy. The experiments were performed in the recently described human cardiomyocytes progenitor cells (hCMPCs), which differentiate into fully functional cardiomyocytes upon stimulation with 5-azacytidine and transforming growth factor β1. Results and Conclusions Forced myocardin expression stimulated transcription of a surprisingly large repertoire of heart muscle-specific genes in hCMPCs but did not cause their differentiation into functional cardiomyocytes. Specifically, myocardin gene transfer did not stimulate the synthesis of several sarcomeric (regulatory) proteins and ion channel constituents. The heart and smooth muscle-enriched isoforms of myocardin stimulate equally well the transcription of many of their cardiomyocyte-specific and virtually all of their smooth muscle target genes. However, the heart muscle-enriched myocardin species is a much more potent transactivator of a subset of genes encoding mainly cardiomyocyte-specific myofibrillar components. This may explain the underestimation of myocardin's cardiomyogenic potential in previous studies utilizing the smooth muscle-enriched isoform of this cTF.

ORGANISM(S): Homo sapiens

PROVIDER: GSE12110 | GEO | 2008/07/15

SECONDARY ACCESSION(S): PRJNA113805

REPOSITORIES: GEO

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Project description:Ischemia, fibrosis, and remodeling lead to heart failure after severe myocardial infarction (MI). Myoblast sheet transplantation is a promising therapy to enhance cardiac function and induce therapeutic angiogenesis via a paracrine mechanism in this detrimental disease. We hypothesized that in a rat model of MI-induced chronic heart failure this therapy could further be improved by overexpression of the antiapoptotic, antifibrotic, and proangiogenic hepatocyte growth factor (HGF) in the myoblast sheets. We studied the ability of wild type (L6-WT) and human HGF-expressing (L6-HGF) L6 myoblast sheet-derived paracrine factors to stimulate cardiomyocyte, endothelial cell, or smooth muscle cell migration in culture. Further, we studied the autocrine effect of hHGF-expression on myoblast gene expression using microarray analysis. We induced MI in Wistar rats by left anterior descending coronary artery (LAD) ligation and allowed heart failure to develop for four weeks. Thereafter, we administered L6-WT (n=15) or L6-HGF (n=16) myoblast sheet therapy. Control rats (n=13) underwent LAD ligation and rethoracotomy without therapy and five rats underwent sham-operation in both surgeries. We evaluated cardiac function with echocardiography at 2 and 4 weeks after therapy administration. We analyzed cardiac angiogenesis and left ventricular architecture from histological sections 4 weeks after therapy. Paracrine mediators from L6-HGF myoblast sheets effectively induced migration of cardiac endothelial and smooth muscle cells but not cardiomyocytes. Microarray data revealed that hHGF-expression modulated myoblast gene expression. In vivo, L6-HGF sheet therapy effectively stimulated angiogenesis in the infarcted and non-infarcted areas. Both L6-WT and L6-HGF therapies enhanced cardiac function and inhibited remodeling in a similar fashion. In conclusion, L6-HGF therapy effectively induced angiogenesis in the chronically failing heart. Cardiac function, however, was not further enhanced by hHGF-expression. Analysis of the L6 rat skeletal myoblast cell line and myoblast cell sheets with constitutive human HGF expression.

Project description:Background: Cardiac transcription factors are master regulators during heart development. Recently, some were shown to transdifferentiate noncardiac mesoderm cells and cardiac fibroblasts into cardiomyocytes. However, the individual roles of each transcription factors in activating cardiac gene program have not been elucidated. We examined cardiac-specific and genome-wide gene expression in fibroblasts induced with cardiac transcription factors Nkx2.5 (N), Tbx5 (T), Gata4 (G), Myocardin (M) alone or different combinations. Methodology/Principal Findings: We applied different combinations of human Nkx2.5 (N), Tbx5 (T), Gata4 (G) and Myocardin (M) lentiviruses into 10T1/2 fibroblasts. Immunostaining and quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that N, T, G or M alone did not induce expression of cardiac marker genes M-NM-1-myosin heavy chain (M-NM-1MHC) and cardiac troponin T (cTnT). Only T+M and T+G+M combinations induced M-NM-1MHC and cTnT expression. Microarray-based gene ontology analysis revealed that T alone inhibited most genes involved in cardiac-related processes and activated genes involved in Wnt receptor signaling pathway and in aberrant processes. M alone inhibited genes involved in Wnt receptor signaling pathway and activated genes involved in cardiac-related processes and in aberrant processes. G alone inhibited genes involved in ectoderm development. T+G+M combination was the most effective activator of genes associated with cardiac-related processes including muscle cell differentiation, sarcomere, striated muscle contraction, regulation of heart contraction, and glucose metabolism and fatty acid oxidation (two significant forms of cardiomyocyte energy metabolism). And unlike T, M, G alone or T+M, T+G+M did not activate genes associated with aberrant processes. Conclusions: Tbx5, Gata4 and Myocardin play different roles in activating cardiac gene program and in avoiding aberrant gene program activation. The combination of T+G+M activated cardiac gene program and avoided aberrant gene program activation. Two weeks after doxycline induction, total RNA was isolated from 10T1/2-tTA cells infected with different combinations of Tbx5, Gata4, and Myocardin lentiviruses. Biological triplicated.

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Gene expression profiling of overexpression of myocardin

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