Cardiac-Specific Overexpression of Human Stem Cell Factor Promotes Epicardial Activation and Arteriogenesis After Myocardial Infarction

Background-The adult epicardium is a potential source of cardiac progenitors after myocardial infarction (MI). We tested the hypothesis that cardiomyocyte-specific overexpression of membrane-associated human stem cell factor (hSCF) enhances epicardial activation, epicardium-derived cells (EPDCs) production, and myocardial arteriogenesis post MI. Methods and Results-Wild-type and the inducible cardiac-specific hSCF transgenic (hSCF/tetracycline transactivator) mice were subjected to MI. Wilms tumor-1 (Wt1)-positive epicardial cells were higher in hSCF/tetracycline transactivator compared with wild-type mice 3 days post MI. Arteriole density was significantly higher in the peri-infarct area of hSCF/tetracycline transactivator mice compared with wild-type mice 5 days post MI. In cultured EPDCs, adenoviral hSCF treatment significantly increased cell proliferation and growth factor expression. Furthermore, adenoviral hSCF treatment in wild-type cardiomyocytes significantly increased EPDC migration. These effects of hSCF overexpression on EPDC proliferation and growth factor expression were all abrogated by ACK2, a neutralizing antibody against c-kit. Finally, lineage tracing using ROSA(mTmG); Wt1(CreER) mice showed that adenoviral hSCF treatment increased Wt1(+) lineage-derived EPDC migration into the infarcted myocardium 5 days post MI, which was inhibited by ACK2. Conclusions-Cardiomyocyte-specific overexpression of hSCF promotes epicardial activation and myocardial arteriogenesis post MI.