Mechanism of angiopoietin-1 mediated endothelial progenitor cell recruitment in wound healing

Abstract

Abstract Introduction: Gene transfer of Angiopoietin-1(Ang-1) corrects diabetic impaired wound healing by recruiting endothelial progenitor cells(EPCs) and enhancing neovascularization. EPCs are thought to be mobilized from the bone marrow through MMP9 activation of stem cell factor(SCF). We hypothesize that Ang-1’s effects on EPC recruitment are mediated through an MMP9 dependant-SCF activation mechanism. Methods: 8mm wounds were made in MMP9-/- or control mice. Wounds were treated with either 108PFU Ad-Ang-1(n=12), AdControl(n=12) or PBS(n=12). Half of MMP-9 -/- mice received daily intravenous SCF. Wounds at 7 days were analyzed for epithelial gap, capillary density(CD31), and EPCs(GATA-2). Serum SCF levels were assessed by ELISA. Letters in parentheses correspond to Table 1. Data expressed as mean+/-SEM. Results: Results: In control mice, Ang-1 had no effect on wound closure(a), neovascularization(b), or EPC recruitment(c). In MMP9-/- mice, AdAng1 accelerates reepithelialization(d)(p ∗ . Control MMP9 −/− MMP9 −/− IV SCF Ang1 Ad CTRL PBS Ang1 Ad CTRL PBS Ang1 Ad CTRL PBS Epithelial gap (mm) 2.7 ± 0.1 (a) 3.4 ± 0.2 (a) 2.6 ± 0.1 (a) 3.2 ± 0.1 ∗ (d) 4.1 ± 0.2 (d) 3.8 ± 0.2 (d) 2.7 ± 0.2 ∗ ∗ (g) 4.6 ± 0.4 (g) 4.5 ± 0.1 (g) Cap density (Caps/HPF) 7.5 ± 0.4 (b) 7.0 ± 0.4 (b) 7.0 ± 0.3 (b) 4.1 ± 0.5 (e) 3.9 ± 0.4 (c) 3.9 ± 0.6 (e) 8.4 ± 0.7 ∗ ∗ (h) 4.4 ± 0.4 (h) 4.6 ± 0.4 (h) EPCs (EPCs/HPF) 8.3 ± 0.2 (c) 7.3 ± 0.3 (c) 7.2 ± 0.2 (c) 2.0 ± 0.3 (f) 1.5 ± 0.3 (f) 1.6 ± 0.2 (f) 6.4 ± 0.3 ∗ ∗ (i) 2.4 ± 0.3 (i) 2.6 ± 0.2 (i) ∗ Indicates statistically significant differences (p Conclusions: Ang-1 mediated EPC recruitment and neovascularization occurs via an MMP-9 dependant activation of SCF mechanism. Ang-1 effects on reepithelialization are independent of this pathway. While SCF mobilizes EPCs, it has no effect on wound healing. SCF in combination with Ang-1 results in site specific recruitment of EPCs and enhanced neovascularization. EPC recruitment by Ang-1 is a novel and potentially potent therapeutic strategy to enhance impaired wound healing.