Vascular Endothelial Growth Factor ₁₆₅ Gene Transfer Augments Circulating Endothelial Progenitor Cells in Human Subjects

TLDR

Preclinical studies and early clinical trials indicate that intramuscular plasmid VEGF promotes neovascularization of ischemic tissues, traditionally attributed to sprouting of endothelial cells from existing vessels. The study examined whether VEGF gene transfer could augment circulating endothelial progenitor cells. VEGF gene transfer transiently raised plasma VEGF and markedly increased circulating EPCs (219% by culture assay, up to 30‑fold rise in endothelial markers by FACS), demonstrating that angiogenic therapy mobilizes endothelial precursors that contribute to vasculogenesis in ischemic tissues.

Abstract

Preclinical studies in animal models and early results of clinical trials in patients suggest that intramuscular injection of naked plasmid DNA encoding vascular endothelial growth factor (VEGF) can promote neovascularization of ischemic tissues. Such neovascularization has been attributed exclusively to sprout formation of endothelial cells derived from preexisting vessels. We investigated the hypothesis that VEGF gene transfer may also augment the population of circulating endothelial progenitor cells (EPCs). In patients with critical limb ischemia receiving VEGF gene transfer, gene expression was documented by a transient increase in plasma levels of VEGF. A culture assay documented a significant increase in EPCs (219%, P<0.001), whereas patients who received an empty vector had no change in circulating EPCs, as was the case for volunteers who received saline injections (VEGF versus empty vector, P<0.001; VEGF versus saline, P<0.005). Fluorescence-activated cell sorter analysis disclosed an overall increase of up to 30-fold in endothelial lineage markers KDR (VEGF receptor-2), VE-cadherin, CD34, alpha(v)beta(3), and E-selectin after VEGF gene transfer. Constitutive overexpression of VEGF in patients with limb ischemia augments the population of circulating EPCs. These findings support the notion that neovascularization of human ischemic tissues after angiogenic growth factor therapy is not limited to angiogenesis but involves circulating endothelial precursors that may home to ischemic foci and differentiate in situ through a process of vasculogenesis.