Objective--In vivo administration of granulocyte colony-stimulating factor (G-CSF) has been shown to facilitate regeneration of cardiovascular tissues. However, G-CSF causes marked leukocytosis that potentially induces adverse cardiovascular events. Earlier studies showed that G-CSF had direct stimulatory actions on mature endothelial cells, resulting in promotion of angiogenesis. We thus examined whether low doses of recombinant human G-CSF (rhG-CSF) locally injected into ischemic tissues would stimulate angiogenesis without inducing severe leukocytosis.

Methods and Results--Reverse-transcription polymerase chain reaction (PCR) revealed expression of G-CSF receptor in human umbilical vein endothelial cells (HUVECs). rhG-CSF (100 ng/mL) enhanced migration and tube formation but not proliferation of HUVECs in vitro. We then examined the effects of rhG-CSF on angiogenesis in a rat model of hindlimb ischemia. Nude rats received in their ischemic skeletal muscles either rhG-CSF (2, 10, 20 µg/kg per day) or saline (control) for 6 days. Laser Doppler blood flowmetry (LDBF) revealed an augmented ischemic/normal limb LDBF ratio and an increased capillary density in the rhG-CSF-treated groups compared with the control at days 14, 21, and 28 (P<0.05). These doses of rhG-CSF induced only mild leukocytosis (1.4-fold increases versus baseline).

Conclusions--rhG-CSF promoted endothelial migration and tube formation in vitro. Local injection of low doses rhG-CSF effectively augmented ischemia-induced angiogenesis in vivo. This treatment regimen of low-dose rhG-CSF may become a new and safe modality for therapeutic angiogenesis.