Granulocyte colony-stimulating factor facilitates the angiogenesis induced by ultrasonic microbubble destruction

Ultrasonic destruction of microbubbles (US/MB) in the microcirculation causes local inflammatory cell infiltration, which has been shown to induce angiogenesis. Granulocyte colony-stimulating factor (G-CSF), which mobilizes myelomonocytic cells from the bone marrow and enhances vascular endothelial growth factor (VEGF) release from these cells, has also been applied to therapeutic angiogenesis induction. In the present study, we sought to examine the potential of G-CSF pretreatment to enhance the angiogenic effect of US/MB. Ischemic hindlimbs in mice were treated with either a predetermined minimal effective dose (300 mug/kg) of G-CSF, US/MB alone or G-CSF pretreatment followed by US/MB at seven days after removal of the femoral artery. Ultrasonic destruction of microbubbles was performed as intermittent pulsed local insonation using a diagnostic ultrasound scanner at a peak negative pressure of 1.4 MPa after intravenous injection of perfluorocarbon microbubbles. At 21 days after the treatment, we quantified the surface vascularity using a grid method and the capillary density using an alkaline phosphatase stain. Relative to the capillary density in normal muscle, the capillary density in the treated limbs was restored to 74 +/- 13% by G-CSF alone and 90 +/- 20% by US/MB alone (p < 0.05 vs. both untreated and G-CSF alone), and further increased to 101 +/- 21% by G-CSF pretreatment. The collateral growth induced by the combination of G-CSF pretreatment and US/MB was 2.8- and 1.4-fold greater than the growth induced by G-CSF alone and US/MB alone, respectively (p < 0.05 for both). Thus, pretreatment with a single minimal effective dose of G-CSF can augment the angiogenic effect of US/MB.