Abstract 3955: Chemokines Fused to a Fractalkine Backbone and a GPI-Anchor Attract Embryonic Endothelial Progenitor Cells to the Site of Ischemia
Recruitment of endothelial progenitor cells to the sites of ischemia is a prerequisite for efficient therapeutic neovascularization via vasculogenesis. Chemokines play a major role in the homing of EPCs at the ischemic vasculature, a mechanism fading in chronic ischemia. To overcome this limitation, we constructed an artificial adhesion molecule consisting of a GPI-anchor, a fractalkine-backbone and an SDF-1 head (SDF-1-fra-GPI), which was applied for enhanced recruitment of embryonic EPCs (eEPCs: CXCR4++, Tie2++, Thrombomodulin++, CD34-, MHCI-, vWF inducible, eNOS inducible) in vitro and in vivo.
Methods: In a flow chamber adhesion assay, Control plasmids (pcDNA or GPI-SDF-1 cDNA) were compared to the SDF-1-fra-GPI construct for eEPC recruitment 24h after liposomal transfection of rat endothelial cells. In vivo, in rabbits (n=5 per group) at day 7 (d7) after femoral artery excision, 1 mg of the SDF-1-fra-GPI or eGFP cDNA was transfected into the ischemic limb. At d9, ischemic hindlimbs were retroinfused with 5x106 eEPCs. Angiography was performed for collateral quantification and frame count score at d9 and d37 (% of d9), capillary density was assessed via PECAM-1-staining (capillaries/muscle fiber = c/mf).
Results: In vitro, eEPC adhesion (16±12 cells/field) was increased to a higher extent by SDF-1-fra-GPI (79±13) than SDF1-GPI (54±8) or control vector (37±8). In vivo, eEPC adhesion in the ischemic hindlimb after SDF-1-fra-GPI transfection compared to mock transfection (30±3 vs. 9±1 cells/field). Whereas capillary density was unaffected (1.66±0.30 SDF-1-Fra-GPI vs. 1.56±0.29 eEPCs), collateral growth (152±10% SDF-1-fra-GPI vs. 124±13%) as well as perfusion score (198±17% SDF-1-fra-GPI vs.160±6% eEPCs) further increased after SDF-1-fra-GPI transfection (controls: 1.24±0.12 c/mf, collaterals 105±8%, perfusion score 112±11%). We conclude that recruitment of EPCs expressing CXCR4 (the SDF-1 receptor) may benefit from pre-treatment of the recipient vasculature with SDF-1-Fra-GPI, an artificial adhesion molecule. This approach might be valuable for enhancing EPC recruitment in the scenario of therapeutic neovascular-ization of chronic ischemic syndromes.