Human cardiac stem cells with reduced notch signaling show enhanced therapeutic potential in a rat acute infarction model.

Background: Because human cardiac stem cells (CSC) have regeneration potential in damaged cardiac tissue, there is increasing interest in using them in cell-based therapies for cardiac failure. However, culture conditions, by which CSCs are expanded while maintaining their therapeutic potential, have not been optimized. We hypothesized that the plating cell-density would affect proliferation activity, differentiation and therapeutic potential of CSCs through the Notch signaling pathway. Methods and Results: Human CSCs were plated at 4 different densities. The population doubling time, C-KIT positivity, and dexamethasone-induced multidifferentiation potential were examined in vitro. The therapeutic potential of CSCs was assessed by transplanting them into a rat acute myocardial infarction (AMI) model. The low plating density (340 cells/cm(2)) maintained the multidifferentiation potential with greater proliferation activity and C-KIT positivity in vitro. On the other hand, the high plating density (5,500 cells/cm(2)) induced autonomous differentiation into endothelial cells by activating Notch signaling in vitro. CSCs cultured at low or high density with Notch signal inhibitor showed significantly greater therapeutic potential in vivo compared with those cultured at high density. Conclusions: CSCs cultured with reduced Notch signaling showed better cardiomyogenic differentiation and therapeutic potentials in a rat AMI model. Thus, reducing Notch signaling is important when culturing CSCs for clinical applications.