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Enhancing cardiomyocyte survival from myocardial infarction with cardiac stromal cell-secreted factors

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Title: Enhancing cardiomyocyte survival from myocardial infarction with cardiac stromal cell-secreted factors
Authors: Constantinou, Chrystalla
Item Type: Thesis or dissertation
Abstract: Myocardial infarction is the leading cause of death globally, and progression to heart failure is directly proportional to infarct size. Targeting cardiomyocyte loss is vital to stop cardiac damage. Previous data from our group show that intramyocardial injection of cardiac stromal cells (CSC) at time of infarct results in scar size reduction and improvement in ejection fraction. However, injected CSC are poorly retained, hence early paracrine signals might explain the observed improvement of cardiac function. Here we showed that injecting CSC-conditioned media into the mouse infarct border zone reduced apoptotic cardiomyocytes >70% locally. Subsequently, the paracrine effects of CSC were investigated, using human pluripotent stem cell-derived cardiomyocytes (hPSC-CM) as a target more relevant to translation. In co-culture and conditioned medium studies, the CSC secretome markedly inhibited human myocyte death, induced by three different cardiotoxic molecules; menadione, doxorubicin and imatinib. Follow-on studies were chiefly performed with menadione, showing preserved mitochondrial membrane depolarization and inhibited ROS generation in the presence of CSC-conditioned media. Functional assays revealed that calcium cycling and action potential generation were also preserved following CSC- conditioned medium treatment of menadione-stressed cells. Characterization studies on the protective secretome pointed to exosome-independent molecules, which were thermolabile and > 3 kDa in size. RNA-sequencing revealed that the CSC-secretome downregulated pro-apoptotic genes and preserved cardiac function and contractility markers in stressed hPSC-CM. A novel bioinformatic tool was used to predict the potential ligand-receptor interactions under conditions of cardiomyocyte stress. In terms of proteomics, cytokine arrays highlighted protein factors enriched in conditioned media from protective versus non-protective populations. Human CSC were also characterized and found to resemble mouse CSC in molecular signature, as well as in their paracrine protective ability. Thus, hPSC-CM provide an auspicious, relevant human platform to investigate extracellular signals for cardiac muscle survival, corroborating human cardioprotection by the CSC-secretome and supporting the further investigation of CSC-conditioned medium as a potential cell-free therapeutic product.
Content Version: Open Access
Issue Date: Mar-2020
Date Awarded: Jul-2020
URI: http://hdl.handle.net/10044/1/81573
DOI: https://doi.org/10.25560/81573
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Schneider, Michael
Noseda, Michela
Sponsor/Funder: National Institute for Health Research (Great Britain)
British Heart Foundation
Wellcome Trust (London, England)
Funder's Grant Number: PG/16/47/32156
Department: NHLI
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:National Heart and Lung Institute PhD theses

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