Adenoviral-mediated Delivery of Early Growth Response Factor-1 Gene Increases Tissue Perfusion in a Murine Model of Hindlimb Ischemia

To test the hypothesis that overexpression of early growth response factor-1 (Egr-1) contributes to the revascularization of ischemic limbs, a constitutively active form of Egr-1 (Egr-1*) was made and evaluated in vitro and in vivo. Analyses of the transduced myocytes revealed significant upregulation of bFGF, PDGF-A, PDGF-B, IGF-II, and TGF-beta1. A coculture assay of the paracrine effects indicated that Ad-Egr-1* promoted proliferation and migration of endothelial cells. When Ad-Egr-1* was injected into the tibialis anterior muscle of mice, followed by explant culture in growth factor-reduced Matrigel, many capillary-like structures were observed in the Egr-1* group compared with minimal sprouting from the LacZ group, suggesting an angiogenic potential of Egr-1*. Next we evaluated Ad-Egr-1* in a murine model of hindlimb ischemia. Compared with slow revascularization in the control PBS or LacZ group, a rapid increase in tissue perfusion was observed in the Egr-1* group and the difference in flux ratio was statistically significant at day 7. In the injected muscle, expression of Egr-1*, upregulation of its target genes, and increased number of vessels staining positive for smooth muscle alpha-actin were observed. These results suggest that Egr-1 plays an important role in vascular recovery after occlusion and could be a potential target for therapeutic angiogenesis.