Abstract 5117: Sustained Release of Granulocyte Colony-Stimulating Factor Using Biodegradable Gelatin Hydrogel Microspheres Persistently Improves Blood Flow of Ischemic Limbs in Mice

Abstract

Granulocyte colony-stimulating factor (G-CSF) is a potent angiogenetic factor, but its use is limited because of the unfavorable systemic effects. We hypothesized that G-CSF immersed gelatin hydrogel microspheres (GHM) injected into the ischemic limb might continuously release a small amount of G-CSF to locally stimulate angiogenesis without adverse effects. We ligated the right femoral artery of BALB/c mice and randomly assigned mice into 5 groups: the saline group with a single intramuscular injection of saline into the ischemic limb; the G-CSF sc group with a subcutaneus injection of G-CSF (100 μ g/kg) for 5 days; the G-CSF im group with an intramuscular injection of G-CSF (20 μ g/kg) into the ischemic limb for 5 days: the GHM group with a single intramuscular injection of GHM alone into the ischemic limb; and the G-CSF-GHM group with a single intramuscular injection of G-CSF (100 μ g/kg) immersed GHM into the ischemic limb. The blood flow ratio of the ischemic/non-ischemic limb assessed by a laser Doppler perfusion imager became significantly improved 6 weeks later in the G-CSF-GHM group compared with the other groups and lasted until 8 weeks (saline; 0.63±0.10, G-CSF sc; 0.70±0.14, G-CSF im; 0.61±0.15, GHM; 0.59±0.12, G-CSF-GHM; 0.88±0.20). Both in the G-CSF sc and im groups, the blood flow ratio was significantly improved at the early time (1 and 2 weeks later in the G-CSF sc group, 3days later in the G-CSF im group), but was only transient. Not only capillaries but also arterioles were significantly increased in the G-CSF-GHM group where granulocyte and endothelial progenitor cell counts were not elevated but the Akt/endothelial nitric oxide synthase pathway in the ischemic limb was significantly activated. The present drug delivery system is suggested to have potential as a novel noninvasive therapy in patients with peripheral artery disease because of not only its efficacy but also less invasiveness and less unfavorable systemic effect.