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

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 P < 0.05. Results Compared with GFP+/MSC and PBS, treatment with E-selectin-GFP+/MSC increased ischemic leg LDI reperfusion (54% vs. 39% vs. 22%, P < 0.001), treadmill distance traversed (162 m vs. 111 m vs. 110 m, P < 0.01) and ischemic mouse footpad vessel density (23% vs. 14% vs. 14%, P < 0.01). 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 E-selectin-GFP+/MSC, as analysis of cellular gene expression profiles of E-selectin-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.

Copper promotion of myocardial regeneration

Myocardial regeneration is the key to the functional recovery of ischemic heart. Angiogenesis plays a pivotal role in myocardial regeneration by resetting a rejuvenation microenvironment under ischemic conditions. Hypoxia-inducible factor 1 (HIF-1) is the predominant transcription factor in the regulation of angiogenesis. In prolonged myocardial infarction, HIF-1α, the critical subunit of HIF-1, is accumulated in the infarcted myocardium, but fails to activate angiogenesis, suggesting a missing of a critical factor in the HIF-1 regulation of angiogenesis. Copper is involved in multiple steps of HIF-1 regulation of target gene expression. However, copper is deprived during myocardial ischemic injury, leading to deactivation of HIF-1-regulated angiogenesis. Multiple approaches are applied to increasing copper availability in the ischemic heart, effectively reactivating transcription of HIF-1 target angiogenic genes. Copper-induced angiogenesis thus reconstructs the conduit for the transduction of tissue injury signaling, recruitment of tissue repair materials such as stem cells, and the homing of stem cells, leading to the promotion of myocardial regeneration. Thus, copper promotes myocardial regeneration through reactivation of HIF-1-regulated angiogenesis. This would constitute an alternative therapeutic approach to ischemic heart disease. Impact statement Copper promotes angiogenesis, but the mechanistic insights have not been fully elucidated until recently. In addition, the significance of copper promotion of angiogenesis in myocardial regeneration was increasingly revealed. Copper critically participates in the regulation of hypoxia-inducible factor 1 (HIF-1) of angiogenic gene expression. Interestingly, myocardial ischemia causes copper efflux from the heart, leading to suppression of angiogenesis, although HIF-1α, the critical subunit of HIF-1, remains accumulated in the ischemic myocardium. Strategies targeting copper specific delivery to the ischemic myocardium lead to selective activation of HIF-1-regulated angiogenic gene expression. Vascularization of the ischemic myocardium re-establishes the tissue injury microenvironment, and rebuilds the conduit for communication between the tissue injury signals and the remote regenerative responses including stem cells. This process promotes myocardial regeneration. Thus, a simple and effective copper supplementation to the ischemic myocardium would become a novel therapeutic approach to the treatment of patients with ischemic heart diseases.