Level of VEGF, SDF-1a and their receptors in ischemic muscle. Expression of (A) VEGF, (B) VEGF-R1, (C) VEGF-R2, (D) SDF-1α, (E) CXCR4, and (F) CXCR7 mRNAs in gastrocnemius muscle of db/db mice subjected to hind limb ischemia and injected with conditioned media from C2C12-Luc-GFP, C2C12-Luc-GFP-HO1 cells or nonconditioned control media. Quantitative RT-PCR performed at day 28 after injection of media (n = 5 to 6). EF2 served as an internal control; *P < 0.05, **P < 0.01, versus control. SDF-1α, stromal cell-derived factor-1α; VEGF, vascular endothelial growth factor.