CXCR4 and its ligand CXCL12 are expressed in cardiac myocytes and fibroblasts, and myocardial ischemia significantly upregulates CXCL12 (Pillarisetti and Gupta, 2001; Yamani et al., 2005; Hu et al., 2007). Here, CXCR4 is linked to myocardial ischemia.