Background: Therapeutic angiogenesis has been shown to promote blood vessel growth and improve tissue perfusion. Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis. However, it has side effects that limit its therapeutic utility in vivo, especially at high concentrations. This study aimed to investigate whether an intramuscular injection of a genetically engineered zinc finger VEGF-activating transcription factor modulates the endothelial progenitor cells (EPC) and promotes therapeutic angiogenesis in a hindlimb ischemia model with type 1 diabetes.
Methods: Alloxan (intravenous injection) was used to induce type I diabetes in C57BL/6 mice (n = 58). The ischemic limb received ZFP-VEGF (125 µg ZFP-VEGF plasmid in 1% poloxamer) or placebo (1% poloxamer) intramuscularly. Mice were sacrificed 3, 5, 10, or 20 days post-injection. Limb blood flow was monitored using laser Doppler perfusion imaging. VEGF mRNA and protein expression were examined using real-time PCR and ELISA, respectively. Capillary density, proliferation, and apoptosis were examined using immunohistochemistry techniques. Flow cytometry was used to detect the EPC population in bone marrow. Two-tailed Student's paired t test and repeated-measures analysis of variance were used for statistical analysis.
Results: ZFP-VEGF increased VEGF mRNA and protein expression at 3 and 10 days post-injection, and increased EPC in bone marrow at day 5 and 20 post-injection compared with controls (P < 0.05). ZFP-VEGF treatment resulted in better perfusion recovery, a higher capillary density and proliferation, and less apoptosis compared with controls (P < 0.05).
Conclusions: Intramuscular ZFP-VEGF injection promotes therapeutic angiogenesis in an ischemic hindlimb model with type 1 diabetes. This might be due to the effects of VEGF on cell survival and EPC recruitment.