Altered expression of

A small number of cardiac stem cells that express the c-Kit and Nanog biomarkers can be differentiated into myocardial cells, which suggests that these stem cells may be able to repair damage and provide an internal reserve for tissue regeneration. It is unknown, however, whether the levels of myocardial stem cells are altered after heart failure (HF), and whether HF affects the myocardial regenerative ability. In this study, to address this question, we developed a rat model of chronic HF induced by Adriamycin, and examined the morphological changes in c-Kit and Nanog-expressing stem cells in heart tissue of normal and HF rats. We further measured levels of c-Kit and Nanog expression in the hearts of HF vs. healthy control rats using immunohistochemistry, immunofluorescence, and semi-quantitative reverse transcription (RT)-PCR methods. c-Kit and Nanog were expressed in both normal and HF rats; c-Kit was mainly found in and around the epicardial region, whereas Nanog was primarily expressed in vascular endothelium of some myocardial cells and in stem cells. However, expression of both c-Kit and Nanog was significantly decreased in myocardial cells from HF rats, which may be reflective of reduced myocardial regeneration capacity. These findings indicate that HF not only seriously damages the heart muscle cells, but also the cardiac stem cells. This reduced pool of cardiac stem cells and their related factors is likely to be deleterious for tissue repair after myocardial injury.