Angiopoietin-1 improves endothelial progenitor cell–dependent neovascularization in diabetic wounds

Abstract

Background The diabetic phenotype of wound healing is in part characterized by impaired neovascularization and deficient endothelial progenitor cell (EPC) recruitment. Angiopoietin-1 (Ang-1) is a potent mobilizer of EPCs from the bone marrow (BM). A suggested mechanism for EPC mobilization from the BM is mediated by matrix metalloproteinase 9 (MMP-9) and stem cell factor (SCF). Taken together, we hypothesized that overexpression of Ang-1 in diabetic wounds will recruit EPCs and improve neovascularization and wound healing. Methods An endothelial lineage BM-labeled murine model of diabetes was developed to track BM-derived EPCs. FVBN mice were lethally irradiated and then reconstituted with BM from syngeneic Tie2/LacZ donor mice. Diabetes was induced with streptozotocin. Dorsal wounds in BM-transplanted (BMT) mice were treated with Ad-Ang-1, Ad-GFP, or PBS. At day 7 post injury, wounds were harvested and analyzed. A similar experiment was conducted in EPC mobilization deficient MMP-9 −/− mice to determine whether the effects of Ang-1 were EPC-dependent. Results Overexpression of Ang-1 resulted in significantly improved re-epithelialization, neovascularization, and EPC recruitment in diabetic BMT wounds at day 7. Ang-1 treatment resulted in increased serum levels of proMMP-9 and SCF, but had no effect on vascular endothelial growth factor (VEGF) levels. According to our FACS results, peripheral blood EPC (CD34+/Cd133+/Flk1+) counts at day 3 post wounding showed impaired EPC mobilization in MMP-9 −/− mice, when compared with those of wild type controls. EPC mobilization was rescued by SCF administration, validating this model for EPC-mobilization deficient mechanistic studies. In MMP-9 −/− mice, Ad-Ang-1 accelerated re-epithelialization in a similar manner, but had no effect on neovascularization. Conclusion Our results show that Ang-1 administration results in improved neovascularization which is dependent on EPC recruitment and has direct effects on wound re-epithelialization. These data may represent a novel strategy to correct the phenotype of impaired diabetic neovascularization and may improve diabetic wound healing.

Stem cell therapy for abrogating stroke-induced neuroinflammation and relevant secondary cell death mechanisms

“…They also promote angiogenesis via in situ migration and proliferation of endogenous endothelial cells according to the release of intracellular signals including VEGF, HGF, angiopoietin-1 (ANG-1), SDF-1α, IGF-1, and eNOS (Aicher et al, 2003; Zhao et al, 2013; Peplow, 2014; Balaji et al, 2015; Bai et al, 2015). The body’s natural mobilization of EPCs from a quiescent to proliferative state following ischemic events and their subsequent homing to the site of cerebral injury along a gradient of SDF-1 strongly suggest these cells play a vital role in the maintenance of damaged endothelial tissue (Shen et al, 2012).…”

Diabetic microangiopathy: Pathogenetic insights and novel therapeutic approaches

“…EPCs have a therapeutic impact on cardiovascular tissue repair and regeneration by playing various roles in the formation of new blood vessels, including mobilization, migration, adhesion, differentiation of vascular cells, and the production of adequate circulating levels of growth factors and chemokines, necessary for tissue repair and regeneration [27][28][29][30]. In fact, experimental and clinical studies suggest that EPCs can home to sites of a pre-existing vessel, and from there form neovessels under the influence of VEGF, chemokines and integrins, including monocyte chemoattractant protein (MCP)-1, stromal cell derived factor-1 (SDF-1), angiopoietin (Ang-1) and the α4β1 integrin [31][32][33][34][35]. Dysregulated levels of these molecules may contribute to a decrease in the number and function of EPCs in diabetes [31][32][33][34]36].…”

“…In fact, experimental and clinical studies suggest that EPCs can home to sites of a pre-existing vessel, and from there form neovessels under the influence of VEGF, chemokines and integrins, including monocyte chemoattractant protein (MCP)-1, stromal cell derived factor-1 (SDF-1), angiopoietin (Ang-1) and the α4β1 integrin [31][32][33][34][35]. Dysregulated levels of these molecules may contribute to a decrease in the number and function of EPCs in diabetes [31][32][33][34]36]. These defects are associated with a more rapid progression of microvascular disease [37].…”

Matrix metalloproteinases in the wound microenvironment: therapeutic perspectives

“…In murine model of wound healing, mice lacking MMP-9 showed reduced endothelial progenitor cell mobilization and vasculogenesis in damaged tissue. 52 The maximal level of MMP-9 is observed at the edges of the wound at 24 hours after an injury and decreases significantly by 48 hours. 53 Although gelatinases are essential for proper wound healing, the increased levels of both MMP-2 and -9 in wound fluid correlate with severity of chronic ulcers.…”