Abstract: Objective To investigate whether heart tissue-derived extracellular matrix (ECM) promotes the differentiation of cardiosphere-derived cells (CDCs) implanted in rat infracted myocardium to improve the cardiac structure and function. Methods Rat CDCs were cultured by cardiac explant methods, and ECM was prepared by decelluariztion method. In a Wistar rat model of acute myocardial infarction established by ligating the left anterior descending branch, IMDM solution, ECM suspension, 106 CDCs in IMDM solution, or 106 CDCs in ECM suspension were injected into the infracted rat myocardium (6 rats in each group). The cardiac function of the rats was evaluated by cardiac ultrasonography, and the percentage of positive heart fibrosis area after infarction was determined with Masson staining. The differentiation of implanted CDCs in the infarcted myocardium was detected using immunofluorescence assay for the markers of cardiac muscle cells (α-SA), vascular endothelial cells (vWF) and smooth muscle cells (α-SMA). Results Three weeks after acute myocardial infarction, the rats with injection of CDCs in ECM showed the highest left ventricular ejection fraction (LVEF) and percentage of fraction shortening with the lowest percentage of positive heart fibrosis area; implantation of CDCs with ECM resulted in significantly higher rates of CDC differentiation into cardiac muscle cells, vascular endothelial cells and smooth muscle cell (P<0.05). Conclusion Heart-tissue derived ECM significantly promotes the differentiation of CDCs implanted in the infracted myocardium into cardiac muscle cells, vascular endothelial cells and smooth muscle cells to improve the cardiac structure and cardiac functions in rats.