CD34 and ischemia: Our results reveled that hindlimb ischemia surgery may have induced more intense CXCR4 expression on circulating CD34+/Flk-1+ EPCs; treatment with either atorvastatin or rosuvastatin may have significantly up-regulated the relative intensity of CXCR4 expression on CD34+/Flk-1+ EPCs (Fig 4C).