FIG. 4.

The role of host cells for sustained paracrine or humoral effects in ischemic myocardium after EPC transplantation. When endothelial progenitor cells (EPCs) are transplanted into ischemic myocardium, the transplanted cells release beneficial biologic factors in the beginning. However, over the 2-week period, the transplanted cells gradually disappeared, and thus the expression level of the factors decreased. In the later phase, the host cells that have been stimulated by the transplanted cells, secrete beneficial cytokines, and maintain the humoral effects >2 weeks. Yellow arrows, the secretion of beneficial cytokines. (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).