CXCR4 and atherosclerosis: Considering that both cell types not only release CXCL12 and express CXCR4 but also implement sender and receiver functions for the CXCL12–CXCR4 signaling cascade with its double-edged role in injury-induced restenosis and atherosclerosis, we now sought to analyze the role of the CXCL12–CXCR4 axis in various modes of EPC–SMC interaction including migration, proliferation and phenotype control.