FIG. 7. Potential multimodal mechanisms underlying the therapeutic effect of BM cells in myocardial damage.

After transplantation, the engrafted bone marrow (BM)-derived stem or progenitor cells may undergo differentiation into or fuse with endothelial cells or cardiomyocytes, leading to vasculogenesis or exogenous myogenesis. Moreover, the BM cells can exert humoral effects by secreting various biologic factors, which induce angiogenesis (growth of preexisting vessels), endogenous myogenesis (proliferation of host cardiomyocytes), and prevention of apoptosis of endangered myocardial cells. Furthermore, the engrafted BM cells may serve as cellular scaffolds. These multimodal effects (i.e., neovascularization, myogenesis, prevention of apoptosis, and cellular scaffolding) work together and induce favorable cardiac remodeling and improvement of cardiac function. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).