Abstract 1045: The Potential Therapeutic Efficacy of Cyclic GMP-specific Phosphodiesterase-5 Inhibition for Angiogenesis in a Mouse Hindlimb Ischemia Model
Background: Recently, targeting cyclic-GMP specific phosphodiesterase-5 (PDE5) has attracted much interest not only in erectile dysfunction but also in several cardiovascular diseases. The aim of this study was to examine whether PDE5 inhibition can augment collateral blood flow to ischemic muscles after acute hindlimb ischemia in mice.
Methods and Results: To evaluate the angiogenic effect by PDE5 inhibition, we generated hindlimb ischemia in C3H/He mice, which were treated continuously with either vehicle or a PDE5 inhibitor, vardenafil (2.5 or 10 mg/kg/day) using subcutaneous osmotic pumps. The blood flow of the ischemic and non-ischemic legs was monitored weekly up to 5 weeks after surgery by laser Doppler imaging. In vehicle-group, the blood flow of the ischemic leg recovered gradually, however, it reached only less than half of the blood flow of the uninjured leg at 5 weeks. In contrast, vardenafil significantly enhanced the blood flow recovery in the ischemic leg, as it reached more than 75% of the blood flow of the uninjured leg at 3 weeks (p<0.05). Collateral formation was evaluated by the capillary density of the ischemic hindlimb muscle harvested 5 weeks after surgery. Consistent with the measurement by laser Doppler imaging, a significant increase in the capillary density of vardenafil-group was detected in a dose-dependent manner [353±43/mm2 (2.5 mg/kg/day) and 421±53/mm2 (10 mg/kg/day); p<0.05 and p<0.01 vs. 226±64/mm2 in vehicle-group]. Next, we investigated an in-vitro angiogenesis assay containing the co-culture of human umbilical vein endothelial cells and normal human dermal fibroblasts administered with vardenafil (10 to 200 nM). In this assay, vardenafil also significantly enhanced the lumen formation in a dose-dependent manner (65,725±3,882 μm2 at vardenafil 50 nM; p<0.0001 vs. 33,364±1,576 μm2 in control). In contrast, a soluble guanylate cyclase inhibitor, ODQ, or anti-VEGF neutralizing antibody diminished the angiogenic effect of vardenafil, respectively.
Conclusions: These results suggest that PDE5 inhibition may have a therapeutic potential to treat ischemic diseases, particularly peripheral arterial diseases, via NO-cGMP and VEGF pathway.