Utilizing advanced biomedical imaging to determine the role of cardiac stem cells in physiological remodeling of the heart

Strategic Research Priority: World Class Bioscience
Abstract
Stem-cells have the potential to repair the heart after physiological and pathological stress. Better understanding of stem-cell biology may enhance this process, providing effective treatments for heart-failure. We recently identified endogenous cardiac stem-cells (eCSCs) which are necessary and sufficient for cardiac regeneration in physiological remodeling. This project will use cutting-edge in-vivo biomedical imaging to simultaneously monitor cardiac function and follow the fate of eCSCs tagged with a lineage specific bioluminescent reporter-gene in response to physiological remodeling. This novel in-vivo eCSC lineage-tracing approach has never been undertaken previously and will inform on the critical link between eCSC activation and cardiac regeneration.

Project
Aim 1: 0-18 months

Derive an in vivo lineage tracing mouse through stem cell marker driven Cre recombination of luciferase
Bioluminescent luciferase can be used to track cells within living mice. Using Cre-Lox recombination technology we will cross existing mouse lines so that luciferase expression is restricted to c-kit and Sca-1 expressing CSCs and their progeny (Vandeputte et al.2014, Neurobiology of Disease). This will provide a powerful model for non-invasive serial monitoring of the fate/expansion of eCSCs in vivo.

Aim-2: 0-18 months

Advanced biomedical imaging of physiological remodeling following acute injection of isoproterenol
A single injection of isoproterenol induces diffuse myocardial damage with a drop out of 8-10% cardiomyocytes, resulting in acute cardiac failure (Takotsubo-like stress cardiomyopathy), which is both structurally and functionally spontaneously reversible within 28 days(1,2). We have shown that c-kit positive eCSCs are responsible for cardiomyocyte renewal in this physiological remodeling(1). Here, we will fully characterize the isoproterenol model using novel MRI, optical and nuclear imaging techniques that serially assess myocardial hypertrophy, edema, contractility, fibrosis, inflammation and cell death. These studies are independent of the outcome of Aim-1 and will be undertaken in tandem using existing transgenic mouse models that allow fate mapping of eCSCs through inducible CRE-lineage tracing by their expression of c-kit (Heger et al.2014.Eur J Immunol), Sca-1 (Uchida et al.2013.Stem Cell Rep) and Wt1 (Chong et al.2011.Cell Stem Cell). Tissue sections from these mice will be analysed at the cellular level for myocardial regeneration and remodeling by immunohistochemistry and confocal microscopy(1).

Aim-3: 18-36 months

Advanced biomedical imaging of the role of cardiac stem cells in physiological remodeling
Aims 1 and 2 will be combined allowing simultaneous in vivo lineage tracing of eCSCs using bioluminescence imaging and monitoring of cardiac function using MRI, nuclear and optical imaging after isoproterenol-induced physiological remodeling.