Figure 1.

The cardiac progenitor cell resident microenvironment. (a) The simplified representation shows some of the key players of the healthy CPC niche: (1) cellular elements (CPCs and supporting cells: cardiomyocytes, endothelial cells, smooth muscle cells, stromal cells, and immune cells) and cell-cell interactions such as signaling via Notch; (2) extracellular matrix (ECM); (3) mechanical stimuli, such as the cyclic strain provided by the beating heart; and (4) soluble factors, such as cytokines, oxygen gradients, and growth factors. (b) Simplified representation of the infarcted heart, where the microenvironment is altered and the niche components modified: (1) cardiomyocyte death and infiltration of myofibroblasts and immune cells; (2) excessive and disordered formation of ECM; (3) increased ECM stiffness and thus altered mechanical behavior; and (4) increased secretion of growth factors and cytokines.