Effective repair of the infarcted heart depends on mechanisms that suppress the inflammatory response after granulation tissue formation has occurred, and that limit expansion of fibrosis to the non-infarcted myocardium. Our project examines the mechanisms responsible for resolution of post-infarction inflammation and transition to fibrous tissue deposition. Our preliminary experiments suggest that Thrombospondin (TSP)-1, a potent angiostatic mediator and crucial TGF-2 activator, and the matrix crosslinking enzyme tissue transglutaminase (tTG), are selectively induced in the infarct border zone and that TSP-1 plays a key role in suppression of the chemokine response and resolution of the inflammatory infiltrate in healing infarcts. The selective localization of TSP-1 and tTG suggests that, through its unique composition, the infarct border zone may serve as a barrier preventing expansion of granulation tissue formation into the non- infarcted myocardium.
Specific aim 1 will examine the role of TSP-1 in suppression and containment of the post-infarction inflammatory response. In vivo experiments examining activation of TGF-2 signaling pathways and neovessel formation, in vitro studies using endothelial cells and infarct myofibroblasts isolated from TSP-1 -/- and WT mice and injections of peptides that restore specific actions of the TSP-1 molecule will be used to examine the mechanistic basis of the TSP-1-mediated effects.
Specific aim 2 will test the hypothesis that tTG may protect the non-infarcted myocardium by locally activating TGF- beta and by forming a """"""""barrier"""""""" composed of proteolysis-resistant matrix, preventing leukocyte migration. In vivo studies using tTG -/- mice and in vitro experiments using infarct myofibroblasts and endothelial cells from WT and tTG -/- mice will be performed.
Specific aim 3 will explore the signaling pathways responsible for the distinct effects of TGF-2 in suppressing inflammation by repressing chemokine and cytokine expression in endothelial cells, and in promoting fibrosis, by inducing extracellular matrix proteins and by altering the MMP:TIMP balance in cardiac fibroblasts. The importance of Smad- dependent and Smad-independent pathways in post-infarction inflammation and fibrous tissue deposition will be examined using myocardial infarction experiments and in vitro studies on isolated endothelial cells and fibroblasts. These studies may lead to therapeutic interventions aimed at optimizing cardiac repair by preventing prolongation and extension of the inflammatory injury.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Myocardial Ischemia and Metabolism Study Section (MIM)
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Schwartz, Lisa
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Baylor College of Medicine
Internal Medicine/Medicine
Schools of Medicine
United States
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Shinde, Arti V; Humeres, Claudio; Frangogiannis, Nikolaos G (2017) The role of ?-smooth muscle actin in fibroblast-mediated matrix contraction and remodeling. Biochim Biophys Acta 1863:298-309
Hanif, Waqas; Alex, Linda; Su, Ya et al. (2017) Left atrial remodeling, hypertrophy, and fibrosis in mouse models of heart failure. Cardiovasc Pathol 30:27-37
Shinde, Arti V; Frangogiannis, Nikolaos G (2017) Mechanisms of Fibroblast Activation in the Remodeling Myocardium. Curr Pathobiol Rep 5:145-152
Frangogiannis, Nikolaos G (2016) The Functional Pluralism of Fibroblasts in the Infarcted Myocardium. Circ Res 119:1049-1051
Chen, Bijun; Frangogiannis, Nikolaos G (2016) Macrophages in the Remodeling Failing Heart. Circ Res 119:776-8
Saxena, Amit; Russo, Ilaria; Frangogiannis, Nikolaos G (2016) Inflammation as a therapeutic target in myocardial infarction: learning from past failures to meet future challenges. Transl Res 167:152-66
Frangogiannis, Nikolaos G (2016) Fibroblast-Extracellular Matrix Interactions in Tissue Fibrosis. Curr Pathobiol Rep 4:11-18
Spinale, Francis G; Frangogiannis, Nikolaos G; Hinz, Boris et al. (2016) Crossing Into the Next Frontier of Cardiac Extracellular Matrix Research. Circ Res 119:1040-1045
Frunza, Olga; Russo, Ilaria; Shinde, Arti V et al. (2016) Authors' Reply. Am J Pathol 186:2234-2235
Prabhu, Sumanth D; Frangogiannis, Nikolaos G (2016) The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis. Circ Res 119:91-112

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