The results show that muscle micro-vessel densities were comparable between PD-1-/- mice and WT mice 7 days after femoral artery ligation, while the vessel density was significantly lower in PD-1-/- mice as compared with WT mice 14 days (27.4 ± 1.74 in WT mice vs 15.89 ± 1.62 in PD-1-/- mice, P<0.05) after hindlimb ischemia (Figures 1D, E), indicating PD-1-/- impaired micro-vessel regeneration. The gene discussed is PDCD1; the disease is ischemia.