O6 Analysis of angiogenic gene profiling after E-selectin + stem cell therapy in murine ischemic limb

Abstract

Introduction: There remains a paucity of novel therapeutics for limb salvage in patients with critical limb ischemia (CLI) for whom revascularization procedures have failed and amputation is imminent. We have shown that E-selectin+/Mesenchymal Stem Cell (MSC) injections into the ischemic limb tissue of a CLI mouse model improves revascularization and limb function. Thus, we sought to determine a mechanism of action for E-selectin+/MSC's pro-angiogenic and tissue salvage properties Methods: MSC were extracted from donor mice bone marrow and subsequently engineered via viral transduction with E-selectin-ires-GFP/ AAV and GFP/AAV (control) to create E-selectin-GFP+/MSC vs GFP+/ MSC. Intramuscular injections of E-selectin-GFP+/MSC, GFP+/MSC, or PBS were performed in a mouse model of hindlimb ischemia. Laser doppler imaging (LDI), confocal laser microscopy, and treadmill exhaustion test were utilized to determine neovascularization and limb function. RNA extraction from engineered MSC (E-selectin-GFP+/MSC vs GFP+/MSC) and ischemic hindlimb tissues treated with E-selectin- GFP+/MSC vs GFP+/MSC was performed, followed by RT2 Profiler PCR Array analysis of 84 genes involved in angiogenesis. GFP+/MSC treated hindlimb tissue served as control. Student's t-test or ANOVA was utilized to compare means and significance set at P0.05 Results: Compared with GFP+/MSC and PBS, treatment with E-selectin- GFP+/MSC increased ischemic leg LDI reperfusion (54% vs. 39% vs. 22% P0.001), treadmill distance traversed (162m vs. 111m vs. 110 m P0.01) and ischemic mouse footpad vessel density (23% vs. 14% vs 14%, P0.01). RT2 Profiler PCR Array demonstrated pro-angiogenic gene upregulation occurred in 7 genes (Csf3, Cxcl2, Cxcl5, Serpine1, F2 Lep, Tbx1, Table I.) in E-selectin-GFP+/MSC treated ischemic leg tissue while tumour necrosis factor (TNF) was found to be downregulated when compared with GFP+/MSC treated tissues. Of these 7 upregulated genes, CXCl2, F2, Leptin and T-box1 (Table I.) are likely produced by Eselectin- GFP+/MSC, as analysis of cellular gene expression profiles of Eselectin- GFP+/MSC also revealed upregulation by 2-fold or more in these factors when compared to GFP+/MSC. Validation of gene functions in-vivo are under investigation Conclusion: Stem cell therapy using E-selectin-GFP+/MSC, in a murine model of CLI, confers both augmented postnatal neovascularization and increased limb function. The pro-angiogenic and pro-repair effects are likely mediated by upregulation of a panel of chemokines/cytokines and down-regulation of TNF in ischemic tissues treated with E-selectin- GFP+/MSC .