Platelet-derived endothelial cell growth factor gene therapy for limb ischemia

ObjectivesPlatelet-derived endothelial cell growth factor (PD-ECGF) is identical to thymidine phosphorylase (TP), and it can induce angiogenesis, including arteriogenesis, in chronically ischemic canine myocardium. Because its effect on peripheral arterial disease has not been elucidated, we investigated whether overexpression of PD-ECGF/TP could ameliorate chronic limb ischemia in rabbits.MethodsLeft femoral arteries were resected from 24 male rabbits. After 10 days, a plasmid vector containing human PD-ECGF/TP complimentary DNA was injected into 10 sites in the adductor muscles. Control groups received either the LacZ plasmid vector or saline vehicle only (n = 8 per group). Blood pressure was measured in the calf before surgery, at the onset of ischemia, 10 days later, and 20 and 30 days after gene transfer. Collateral vessel development and limb perfusion were assessed by angiography, and resected tissues underwent molecular and histologic examination.ResultsIn the PD-ECGF/TP group, human PD-ECGF/TP messenger RNA and protein were still detected at 30 days after treatment. Calf blood pressure decreased significantly after femoral artery resection in all three groups. It subsequently showed a greater increase in the PD-ECGF/TP group than in either control group, and the difference was significant at 20 days after treatment (PD-ECGF/TP, 97.4 ± 7.4; LacZ, 58.6 ± 6.9; saline, 41.3 ± 3.6). Immunohistochemical staining demonstrated an increased ratio of capillaries and arterioles to muscle fibers in the PD-ECGF/TP group (2.14 ± 0.13 and 1.51 ± 0.06), but not in the LacZ group (1.39 ± 0.04 and 0.71 ± 0.05) or the saline group (1.34 ± 0.05 and 0.71 ± 0.04, P < .01). The angiographic score was higher in the PD-ECGF/TP group (0.96 ± 0.08) than in the LacZ group (0.50 ± 0.02) or saline group (0.51 ± 0.03) at 30 days after gene transfer (P < .01).ConclusionsThis study demonstrated that PD-ECGF/TP gene transfer induced angiogenesis and decreased ischemia in a rabbit hindlimb model by promoting arteriogenesis, suggesting that targeting this gene may be a promising therapeutic strategy for peripheral vascular disease.

Clinical RelevanceLower extremity peripheral arterial disease (PAD) due to atherosclerotic vascular disease is a major health problem in the world. Surgical or percutaneous revascularization strategies may improve blood flow in selected patients with PAD; however, a large number of patients with PAD are not suitable for revascularization. A variety of strategies have been attempted for the effective development of collateral vessels, and the most widely studied procedures are local delivery of angiogenic growth factors, such as vascular endothelial growth factor, basic fibroblast growth factor, or bone marrow cells. In our previous studies, we have demonstrated the therapeutic effects of platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) in ischemic myocardium; however, the effect of PD-ECGF/TP on PAD has not been elucidated. The purpose of this study was to evaluate the effect of PD-ECGF/TP on a rabbit hindlimb ischemic model. We found that PD-ECGF/TP gene transfer into the ischemic area significantly induced angiogenesis and arteriogenesis after a functional improvement in collateral blood flow in a rabbit extremity ischemic limb model. This could lead to a new therapeutic strategy for treating PAD in the clinic.